timestamp.c

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/*-------------------------------------------------------------------------
 *
 * timestamp.c
 *    Functions for the built-in SQL types "timestamp" and "interval".
 *
 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/timestamp.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <ctype.h>
#include <math.h>
#include <limits.h>
#include <sys/time.h>

#include "access/xact.h"
#include "catalog/pg_type.h"
#include "common/int128.h"
#include "funcapi.h"
#include "libpq/pqformat.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "nodes/supportnodes.h"
#include "parser/scansup.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/date.h"
#include "utils/datetime.h"
#include "utils/float.h"

/*
 * gcc's -ffast-math switch breaks routines that expect exact results from
 * expressions like timeval / SECS_PER_HOUR, where timeval is double.
 */
#ifdef __FAST_MATH__
#error -ffast-math is known to break this code
#endif

#define SAMESIGN(a,b)   (((a) < 0) == ((b) < 0))

/* Set at postmaster start */
TimestampTz PgStartTime;

/* Set at configuration reload */
TimestampTz PgReloadTime;

typedef struct
{
    Timestamp   current;
    Timestamp   finish;
    Interval    step;
    int         step_sign;
} generate_series_timestamp_fctx;

typedef struct
{
    TimestampTz current;
    TimestampTz finish;
    Interval    step;
    int         step_sign;
} generate_series_timestamptz_fctx;


static TimeOffset time2t(const int hour, const int min, const int sec, const fsec_t fsec);
static Timestamp dt2local(Timestamp dt, int timezone);
static void AdjustIntervalForTypmod(Interval *interval, int32 typmod);
static TimestampTz timestamp2timestamptz(Timestamp timestamp);
static Timestamp timestamptz2timestamp(TimestampTz timestamp);


/* common code for timestamptypmodin and timestamptztypmodin */
static int32
anytimestamp_typmodin(bool istz, ArrayType *ta)
{
    int32      *tl;
    int         n;

    tl = ArrayGetIntegerTypmods(ta, &n);

    /*
     * we're not too tense about good error message here because grammar
     * shouldn't allow wrong number of modifiers for TIMESTAMP
     */
    if (n != 1)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("invalid type modifier")));

    return anytimestamp_typmod_check(istz, tl[0]);
}

/* exported so parse_expr.c can use it */
int32
anytimestamp_typmod_check(bool istz, int32 typmod)
{
    if (typmod < 0)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("TIMESTAMP(%d)%s precision must not be negative",
                        typmod, (istz ? " WITH TIME ZONE" : ""))));
    if (typmod > MAX_TIMESTAMP_PRECISION)
    {
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("TIMESTAMP(%d)%s precision reduced to maximum allowed, %d",
                        typmod, (istz ? " WITH TIME ZONE" : ""),
                        MAX_TIMESTAMP_PRECISION)));
        typmod = MAX_TIMESTAMP_PRECISION;
    }

    return typmod;
}

/* common code for timestamptypmodout and timestamptztypmodout */
static char *
anytimestamp_typmodout(bool istz, int32 typmod)
{
    const char *tz = istz ? " with time zone" : " without time zone";

    if (typmod >= 0)
        return psprintf("(%d)%s", (int) typmod, tz);
    else
        return psprintf("%s", tz);
}


/*****************************************************************************
 *   USER I/O ROUTINES                                                       *
 *****************************************************************************/

/* timestamp_in()
 * Convert a string to internal form.
 */
Datum
timestamp_in(PG_FUNCTION_ARGS)
{
    char       *str = PG_GETARG_CSTRING(0);

#ifdef NOT_USED
    Oid         typelem = PG_GETARG_OID(1);
#endif
    int32       typmod = PG_GETARG_INT32(2);
    Timestamp   result;
    fsec_t      fsec;
    struct pg_tm tt,
               *tm = &tt;
    int         tz;
    int         dtype;
    int         nf;
    int         dterr;
    char       *field[MAXDATEFIELDS];
    int         ftype[MAXDATEFIELDS];
    char        workbuf[MAXDATELEN + MAXDATEFIELDS];

    dterr = ParseDateTime(str, workbuf, sizeof(workbuf),
                          field, ftype, MAXDATEFIELDS, &nf);
    if (dterr == 0)
        dterr = DecodeDateTime(field, ftype, nf, &dtype, tm, &fsec, &tz);
    if (dterr != 0)
        DateTimeParseError(dterr, str, "timestamp");

    switch (dtype)
    {
        case DTK_DATE:
            if (tm2timestamp(tm, fsec, NULL, &result) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range: \"%s\"", str)));
            break;

        case DTK_EPOCH:
            result = SetEpochTimestamp();
            break;

        case DTK_LATE:
            TIMESTAMP_NOEND(result);
            break;

        case DTK_EARLY:
            TIMESTAMP_NOBEGIN(result);
            break;

        default:
            elog(ERROR, "unexpected dtype %d while parsing timestamp \"%s\"",
                 dtype, str);
            TIMESTAMP_NOEND(result);
    }

    AdjustTimestampForTypmod(&result, typmod);

    PG_RETURN_TIMESTAMP(result);
}

/* timestamp_out()
 * Convert a timestamp to external form.
 */
Datum
timestamp_out(PG_FUNCTION_ARGS)
{
    Timestamp   timestamp = PG_GETARG_TIMESTAMP(0);
    char       *result;
    struct pg_tm tt,
               *tm = &tt;
    fsec_t      fsec;
    char        buf[MAXDATELEN + 1];

    if (TIMESTAMP_NOT_FINITE(timestamp))
        EncodeSpecialTimestamp(timestamp, buf);
    else if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) == 0)
        EncodeDateTime(tm, fsec, false, 0, NULL, DateStyle, buf);
    else
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    result = pstrdup(buf);
    PG_RETURN_CSTRING(result);
}

/*
 *      timestamp_recv          - converts external binary format to timestamp
 */
Datum
timestamp_recv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);

#ifdef NOT_USED
    Oid         typelem = PG_GETARG_OID(1);
#endif
    int32       typmod = PG_GETARG_INT32(2);
    Timestamp   timestamp;
    struct pg_tm tt,
               *tm = &tt;
    fsec_t      fsec;

    timestamp = (Timestamp) pq_getmsgint64(buf);

    /* range check: see if timestamp_out would like it */
    if (TIMESTAMP_NOT_FINITE(timestamp))
         /* ok */ ;
    else if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0 ||
             !IS_VALID_TIMESTAMP(timestamp))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    AdjustTimestampForTypmod(&timestamp, typmod);

    PG_RETURN_TIMESTAMP(timestamp);
}

/*
 *      timestamp_send          - converts timestamp to binary format
 */
Datum
timestamp_send(PG_FUNCTION_ARGS)
{
    Timestamp   timestamp = PG_GETARG_TIMESTAMP(0);
    StringInfoData buf;

    pq_begintypsend(&buf);
    pq_sendint64(&buf, timestamp);
    PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}

Datum
timestamptypmodin(PG_FUNCTION_ARGS)
{
    ArrayType  *ta = PG_GETARG_ARRAYTYPE_P(0);

    PG_RETURN_INT32(anytimestamp_typmodin(false, ta));
}

Datum
timestamptypmodout(PG_FUNCTION_ARGS)
{
    int32       typmod = PG_GETARG_INT32(0);

    PG_RETURN_CSTRING(anytimestamp_typmodout(false, typmod));
}


/*
 * timestamp_support()
 *
 * Planner support function for the timestamp_scale() and timestamptz_scale()
 * length coercion functions (we need not distinguish them here).
 */
Datum
timestamp_support(PG_FUNCTION_ARGS)
{
    Node       *rawreq = (Node *) PG_GETARG_POINTER(0);
    Node       *ret = NULL;

    if (IsA(rawreq, SupportRequestSimplify))
    {
        SupportRequestSimplify *req = (SupportRequestSimplify *) rawreq;

        ret = TemporalSimplify(MAX_TIMESTAMP_PRECISION, (Node *) req->fcall);
    }

    PG_RETURN_POINTER(ret);
}

/* timestamp_scale()
 * Adjust time type for specified scale factor.
 * Used by PostgreSQL type system to stuff columns.
 */
Datum
timestamp_scale(PG_FUNCTION_ARGS)
{
    Timestamp   timestamp = PG_GETARG_TIMESTAMP(0);
    int32       typmod = PG_GETARG_INT32(1);
    Timestamp   result;

    result = timestamp;

    AdjustTimestampForTypmod(&result, typmod);

    PG_RETURN_TIMESTAMP(result);
}

/*
 * AdjustTimestampForTypmodError --- round off a timestamp to suit given typmod
 * Works for either timestamp or timestamptz.
 */
bool
AdjustTimestampForTypmodError(Timestamp *time, int32 typmod, bool *error)
{
    static const int64 TimestampScales[MAX_TIMESTAMP_PRECISION + 1] = {
        INT64CONST(1000000),
        INT64CONST(100000),
        INT64CONST(10000),
        INT64CONST(1000),
        INT64CONST(100),
        INT64CONST(10),
        INT64CONST(1)
    };

    static const int64 TimestampOffsets[MAX_TIMESTAMP_PRECISION + 1] = {
        INT64CONST(500000),
        INT64CONST(50000),
        INT64CONST(5000),
        INT64CONST(500),
        INT64CONST(50),
        INT64CONST(5),
        INT64CONST(0)
    };

    if (!TIMESTAMP_NOT_FINITE(*time)
        && (typmod != -1) && (typmod != MAX_TIMESTAMP_PRECISION))
    {
        if (typmod < 0 || typmod > MAX_TIMESTAMP_PRECISION)
        {
            if (error)
            {
                *error = true;
                return false;
            }

            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("timestamp(%d) precision must be between %d and %d",
                            typmod, 0, MAX_TIMESTAMP_PRECISION)));
        }

        if (*time >= INT64CONST(0))
        {
            *time = ((*time + TimestampOffsets[typmod]) / TimestampScales[typmod]) *
                TimestampScales[typmod];
        }
        else
        {
            *time = -((((-*time) + TimestampOffsets[typmod]) / TimestampScales[typmod])
                      * TimestampScales[typmod]);
        }
    }

    return true;
}

void
AdjustTimestampForTypmod(Timestamp *time, int32 typmod)
{
    (void) AdjustTimestampForTypmodError(time, typmod, NULL);
}

/* timestamptz_in()
 * Convert a string to internal form.
 */
Datum
timestamptz_in(PG_FUNCTION_ARGS)
{
    char       *str = PG_GETARG_CSTRING(0);

#ifdef NOT_USED
    Oid         typelem = PG_GETARG_OID(1);
#endif
    int32       typmod = PG_GETARG_INT32(2);
    TimestampTz result;
    fsec_t      fsec;
    struct pg_tm tt,
               *tm = &tt;
    int         tz;
    int         dtype;
    int         nf;
    int         dterr;
    char       *field[MAXDATEFIELDS];
    int         ftype[MAXDATEFIELDS];
    char        workbuf[MAXDATELEN + MAXDATEFIELDS];

    dterr = ParseDateTime(str, workbuf, sizeof(workbuf),
                          field, ftype, MAXDATEFIELDS, &nf);
    if (dterr == 0)
        dterr = DecodeDateTime(field, ftype, nf, &dtype, tm, &fsec, &tz);
    if (dterr != 0)
        DateTimeParseError(dterr, str, "timestamp with time zone");

    switch (dtype)
    {
        case DTK_DATE:
            if (tm2timestamp(tm, fsec, &tz, &result) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range: \"%s\"", str)));
            break;

        case DTK_EPOCH:
            result = SetEpochTimestamp();
            break;

        case DTK_LATE:
            TIMESTAMP_NOEND(result);
            break;

        case DTK_EARLY:
            TIMESTAMP_NOBEGIN(result);
            break;

        default:
            elog(ERROR, "unexpected dtype %d while parsing timestamptz \"%s\"",
                 dtype, str);
            TIMESTAMP_NOEND(result);
    }

    AdjustTimestampForTypmod(&result, typmod);

    PG_RETURN_TIMESTAMPTZ(result);
}

/*
 * Try to parse a timezone specification, and return its timezone offset value
 * if it's acceptable.  Otherwise, an error is thrown.
 *
 * Note: some code paths update tm->tm_isdst, and some don't; current callers
 * don't care, so we don't bother being consistent.
 */
static int
parse_sane_timezone(struct pg_tm *tm, text *zone)
{
    char        tzname[TZ_STRLEN_MAX + 1];
    int         rt;
    int         tz;

    text_to_cstring_buffer(zone, tzname, sizeof(tzname));

    /*
     * Look up the requested timezone.  First we try to interpret it as a
     * numeric timezone specification; if DecodeTimezone decides it doesn't
     * like the format, we look in the timezone abbreviation table (to handle
     * cases like "EST"), and if that also fails, we look in the timezone
     * database (to handle cases like "America/New_York").  (This matches the
     * order in which timestamp input checks the cases; it's important because
     * the timezone database unwisely uses a few zone names that are identical
     * to offset abbreviations.)
     *
     * Note pg_tzset happily parses numeric input that DecodeTimezone would
     * reject.  To avoid having it accept input that would otherwise be seen
     * as invalid, it's enough to disallow having a digit in the first
     * position of our input string.
     */
    if (isdigit((unsigned char) *tzname))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("invalid input syntax for type %s: \"%s\"",
                        "numeric time zone", tzname),
                 errhint("Numeric time zones must have \"-\" or \"+\" as first character.")));

    rt = DecodeTimezone(tzname, &tz);
    if (rt != 0)
    {
        char       *lowzone;
        int         type,
                    val;
        pg_tz      *tzp;

        if (rt == DTERR_TZDISP_OVERFLOW)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("numeric time zone \"%s\" out of range", tzname)));
        else if (rt != DTERR_BAD_FORMAT)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("time zone \"%s\" not recognized", tzname)));

        /* DecodeTimezoneAbbrev requires lowercase input */
        lowzone = downcase_truncate_identifier(tzname,
                                               strlen(tzname),
                                               false);
        type = DecodeTimezoneAbbrev(0, lowzone, &val, &tzp);

        if (type == TZ || type == DTZ)
        {
            /* fixed-offset abbreviation */
            tz = -val;
        }
        else if (type == DYNTZ)
        {
            /* dynamic-offset abbreviation, resolve using specified time */
            tz = DetermineTimeZoneAbbrevOffset(tm, tzname, tzp);
        }
        else
        {
            /* try it as a full zone name */
            tzp = pg_tzset(tzname);
            if (tzp)
                tz = DetermineTimeZoneOffset(tm, tzp);
            else
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("time zone \"%s\" not recognized", tzname)));
        }
    }

    return tz;
}

/*
 * make_timestamp_internal
 *      workhorse for make_timestamp and make_timestamptz
 */
static Timestamp
make_timestamp_internal(int year, int month, int day,
                        int hour, int min, double sec)
{
    struct pg_tm tm;
    TimeOffset  date;
    TimeOffset  time;
    int         dterr;
    bool        bc = false;
    Timestamp   result;

    tm.tm_year = year;
    tm.tm_mon = month;
    tm.tm_mday = day;

    /* Handle negative years as BC */
    if (tm.tm_year < 0)
    {
        bc = true;
        tm.tm_year = -tm.tm_year;
    }

    dterr = ValidateDate(DTK_DATE_M, false, false, bc, &tm);

    if (dterr != 0)
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_FIELD_OVERFLOW),
                 errmsg("date field value out of range: %d-%02d-%02d",
                        year, month, day)));

    if (!IS_VALID_JULIAN(tm.tm_year, tm.tm_mon, tm.tm_mday))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("date out of range: %d-%02d-%02d",
                        year, month, day)));

    date = date2j(tm.tm_year, tm.tm_mon, tm.tm_mday) - POSTGRES_EPOCH_JDATE;

    /* Check for time overflow */
    if (float_time_overflows(hour, min, sec))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_FIELD_OVERFLOW),
                 errmsg("time field value out of range: %d:%02d:%02g",
                        hour, min, sec)));

    /* This should match tm2time */
    time = (((hour * MINS_PER_HOUR + min) * SECS_PER_MINUTE)
            * USECS_PER_SEC) + (int64) rint(sec * USECS_PER_SEC);

    result = date * USECS_PER_DAY + time;
    /* check for major overflow */
    if ((result - time) / USECS_PER_DAY != date)
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range: %d-%02d-%02d %d:%02d:%02g",
                        year, month, day,
                        hour, min, sec)));

    /* check for just-barely overflow (okay except time-of-day wraps) */
    /* caution: we want to allow 1999-12-31 24:00:00 */
    if ((result < 0 && date > 0) ||
        (result > 0 && date < -1))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range: %d-%02d-%02d %d:%02d:%02g",
                        year, month, day,
                        hour, min, sec)));

    /* final range check catches just-out-of-range timestamps */
    if (!IS_VALID_TIMESTAMP(result))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range: %d-%02d-%02d %d:%02d:%02g",
                        year, month, day,
                        hour, min, sec)));

    return result;
}

/*
 * make_timestamp() - timestamp constructor
 */
Datum
make_timestamp(PG_FUNCTION_ARGS)
{
    int32       year = PG_GETARG_INT32(0);
    int32       month = PG_GETARG_INT32(1);
    int32       mday = PG_GETARG_INT32(2);
    int32       hour = PG_GETARG_INT32(3);
    int32       min = PG_GETARG_INT32(4);
    float8      sec = PG_GETARG_FLOAT8(5);
    Timestamp   result;

    result = make_timestamp_internal(year, month, mday,
                                     hour, min, sec);

    PG_RETURN_TIMESTAMP(result);
}

/*
 * make_timestamptz() - timestamp with time zone constructor
 */
Datum
make_timestamptz(PG_FUNCTION_ARGS)
{
    int32       year = PG_GETARG_INT32(0);
    int32       month = PG_GETARG_INT32(1);
    int32       mday = PG_GETARG_INT32(2);
    int32       hour = PG_GETARG_INT32(3);
    int32       min = PG_GETARG_INT32(4);
    float8      sec = PG_GETARG_FLOAT8(5);
    Timestamp   result;

    result = make_timestamp_internal(year, month, mday,
                                     hour, min, sec);

    PG_RETURN_TIMESTAMPTZ(timestamp2timestamptz(result));
}

/*
 * Construct a timestamp with time zone.
 *      As above, but the time zone is specified as seventh argument.
 */
Datum
make_timestamptz_at_timezone(PG_FUNCTION_ARGS)
{
    int32       year = PG_GETARG_INT32(0);
    int32       month = PG_GETARG_INT32(1);
    int32       mday = PG_GETARG_INT32(2);
    int32       hour = PG_GETARG_INT32(3);
    int32       min = PG_GETARG_INT32(4);
    float8      sec = PG_GETARG_FLOAT8(5);
    text       *zone = PG_GETARG_TEXT_PP(6);
    TimestampTz result;
    Timestamp   timestamp;
    struct pg_tm tt;
    int         tz;
    fsec_t      fsec;

    timestamp = make_timestamp_internal(year, month, mday,
                                        hour, min, sec);

    if (timestamp2tm(timestamp, NULL, &tt, &fsec, NULL, NULL) != 0)
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    tz = parse_sane_timezone(&tt, zone);

    result = dt2local(timestamp, -tz);

    if (!IS_VALID_TIMESTAMP(result))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    PG_RETURN_TIMESTAMPTZ(result);
}

/*
 * to_timestamp(double precision)
 * Convert UNIX epoch to timestamptz.
 */
Datum
float8_timestamptz(PG_FUNCTION_ARGS)
{
    float8      seconds = PG_GETARG_FLOAT8(0);
    TimestampTz result;

    /* Deal with NaN and infinite inputs ... */
    if (isnan(seconds))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp cannot be NaN")));

    if (isinf(seconds))
    {
        if (seconds < 0)
            TIMESTAMP_NOBEGIN(result);
        else
            TIMESTAMP_NOEND(result);
    }
    else
    {
        /* Out of range? */
        if (seconds <
            (float8) SECS_PER_DAY * (DATETIME_MIN_JULIAN - UNIX_EPOCH_JDATE)
            || seconds >=
            (float8) SECS_PER_DAY * (TIMESTAMP_END_JULIAN - UNIX_EPOCH_JDATE))
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range: \"%g\"", seconds)));

        /* Convert UNIX epoch to Postgres epoch */
        seconds -= ((POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY);

        seconds = rint(seconds * USECS_PER_SEC);
        result = (int64) seconds;

        /* Recheck in case roundoff produces something just out of range */
        if (!IS_VALID_TIMESTAMP(result))
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range: \"%g\"",
                            PG_GETARG_FLOAT8(0))));
    }

    PG_RETURN_TIMESTAMP(result);
}

/* timestamptz_out()
 * Convert a timestamp to external form.
 */
Datum
timestamptz_out(PG_FUNCTION_ARGS)
{
    TimestampTz dt = PG_GETARG_TIMESTAMPTZ(0);
    char       *result;
    int         tz;
    struct pg_tm tt,
               *tm = &tt;
    fsec_t      fsec;
    const char *tzn;
    char        buf[MAXDATELEN + 1];

    if (TIMESTAMP_NOT_FINITE(dt))
        EncodeSpecialTimestamp(dt, buf);
    else if (timestamp2tm(dt, &tz, tm, &fsec, &tzn, NULL) == 0)
        EncodeDateTime(tm, fsec, true, tz, tzn, DateStyle, buf);
    else
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    result = pstrdup(buf);
    PG_RETURN_CSTRING(result);
}

/*
 *      timestamptz_recv            - converts external binary format to timestamptz
 */
Datum
timestamptz_recv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);

#ifdef NOT_USED
    Oid         typelem = PG_GETARG_OID(1);
#endif
    int32       typmod = PG_GETARG_INT32(2);
    TimestampTz timestamp;
    int         tz;
    struct pg_tm tt,
               *tm = &tt;
    fsec_t      fsec;

    timestamp = (TimestampTz) pq_getmsgint64(buf);

    /* range check: see if timestamptz_out would like it */
    if (TIMESTAMP_NOT_FINITE(timestamp))
         /* ok */ ;
    else if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0 ||
             !IS_VALID_TIMESTAMP(timestamp))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    AdjustTimestampForTypmod(&timestamp, typmod);

    PG_RETURN_TIMESTAMPTZ(timestamp);
}

/*
 *      timestamptz_send            - converts timestamptz to binary format
 */
Datum
timestamptz_send(PG_FUNCTION_ARGS)
{
    TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(0);
    StringInfoData buf;

    pq_begintypsend(&buf);
    pq_sendint64(&buf, timestamp);
    PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}

Datum
timestamptztypmodin(PG_FUNCTION_ARGS)
{
    ArrayType  *ta = PG_GETARG_ARRAYTYPE_P(0);

    PG_RETURN_INT32(anytimestamp_typmodin(true, ta));
}

Datum
timestamptztypmodout(PG_FUNCTION_ARGS)
{
    int32       typmod = PG_GETARG_INT32(0);

    PG_RETURN_CSTRING(anytimestamp_typmodout(true, typmod));
}


/* timestamptz_scale()
 * Adjust time type for specified scale factor.
 * Used by PostgreSQL type system to stuff columns.
 */
Datum
timestamptz_scale(PG_FUNCTION_ARGS)
{
    TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(0);
    int32       typmod = PG_GETARG_INT32(1);
    TimestampTz result;

    result = timestamp;

    AdjustTimestampForTypmod(&result, typmod);

    PG_RETURN_TIMESTAMPTZ(result);
}


/* interval_in()
 * Convert a string to internal form.
 *
 * External format(s):
 *  Uses the generic date/time parsing and decoding routines.
 */
Datum
interval_in(PG_FUNCTION_ARGS)
{
    char       *str = PG_GETARG_CSTRING(0);

#ifdef NOT_USED
    Oid         typelem = PG_GETARG_OID(1);
#endif
    int32       typmod = PG_GETARG_INT32(2);
    Interval   *result;
    fsec_t      fsec;
    struct pg_tm tt,
               *tm = &tt;
    int         dtype;
    int         nf;
    int         range;
    int         dterr;
    char       *field[MAXDATEFIELDS];
    int         ftype[MAXDATEFIELDS];
    char        workbuf[256];

    tm->tm_year = 0;
    tm->tm_mon = 0;
    tm->tm_mday = 0;
    tm->tm_hour = 0;
    tm->tm_min = 0;
    tm->tm_sec = 0;
    fsec = 0;

    if (typmod >= 0)
        range = INTERVAL_RANGE(typmod);
    else
        range = INTERVAL_FULL_RANGE;

    dterr = ParseDateTime(str, workbuf, sizeof(workbuf), field,
                          ftype, MAXDATEFIELDS, &nf);
    if (dterr == 0)
        dterr = DecodeInterval(field, ftype, nf, range,
                               &dtype, tm, &fsec);

    /* if those functions think it's a bad format, try ISO8601 style */
    if (dterr == DTERR_BAD_FORMAT)
        dterr = DecodeISO8601Interval(str,
                                      &dtype, tm, &fsec);

    if (dterr != 0)
    {
        if (dterr == DTERR_FIELD_OVERFLOW)
            dterr = DTERR_INTERVAL_OVERFLOW;
        DateTimeParseError(dterr, str, "interval");
    }

    result = (Interval *) palloc(sizeof(Interval));

    switch (dtype)
    {
        case DTK_DELTA:
            if (tm2interval(tm, fsec, result) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("interval out of range")));
            break;

        default:
            elog(ERROR, "unexpected dtype %d while parsing interval \"%s\"",
                 dtype, str);
    }

    AdjustIntervalForTypmod(result, typmod);

    PG_RETURN_INTERVAL_P(result);
}

/* interval_out()
 * Convert a time span to external form.
 */
Datum
interval_out(PG_FUNCTION_ARGS)
{
    Interval   *span = PG_GETARG_INTERVAL_P(0);
    char       *result;
    struct pg_tm tt,
               *tm = &tt;
    fsec_t      fsec;
    char        buf[MAXDATELEN + 1];

    if (interval2tm(*span, tm, &fsec) != 0)
        elog(ERROR, "could not convert interval to tm");

    EncodeInterval(tm, fsec, IntervalStyle, buf);

    result = pstrdup(buf);
    PG_RETURN_CSTRING(result);
}

/*
 *      interval_recv           - converts external binary format to interval
 */
Datum
interval_recv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);

#ifdef NOT_USED
    Oid         typelem = PG_GETARG_OID(1);
#endif
    int32       typmod = PG_GETARG_INT32(2);
    Interval   *interval;

    interval = (Interval *) palloc(sizeof(Interval));

    interval->time = pq_getmsgint64(buf);
    interval->day = pq_getmsgint(buf, sizeof(interval->day));
    interval->month = pq_getmsgint(buf, sizeof(interval->month));

    AdjustIntervalForTypmod(interval, typmod);

    PG_RETURN_INTERVAL_P(interval);
}

/*
 *      interval_send           - converts interval to binary format
 */
Datum
interval_send(PG_FUNCTION_ARGS)
{
    Interval   *interval = PG_GETARG_INTERVAL_P(0);
    StringInfoData buf;

    pq_begintypsend(&buf);
    pq_sendint64(&buf, interval->time);
    pq_sendint32(&buf, interval->day);
    pq_sendint32(&buf, interval->month);
    PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}

/*
 * The interval typmod stores a "range" in its high 16 bits and a "precision"
 * in its low 16 bits.  Both contribute to defining the resolution of the
 * type.  Range addresses resolution granules larger than one second, and
 * precision specifies resolution below one second.  This representation can
 * express all SQL standard resolutions, but we implement them all in terms of
 * truncating rightward from some position.  Range is a bitmap of permitted
 * fields, but only the temporally-smallest such field is significant to our
 * calculations.  Precision is a count of sub-second decimal places to retain.
 * Setting all bits (INTERVAL_FULL_PRECISION) gives the same truncation
 * semantics as choosing MAX_INTERVAL_PRECISION.
 */
Datum
intervaltypmodin(PG_FUNCTION_ARGS)
{
    ArrayType  *ta = PG_GETARG_ARRAYTYPE_P(0);
    int32      *tl;
    int         n;
    int32       typmod;

    tl = ArrayGetIntegerTypmods(ta, &n);

    /*
     * tl[0] - interval range (fields bitmask)  tl[1] - precision (optional)
     *
     * Note we must validate tl[0] even though it's normally guaranteed
     * correct by the grammar --- consider SELECT 'foo'::"interval"(1000).
     */
    if (n > 0)
    {
        switch (tl[0])
        {
            case INTERVAL_MASK(YEAR):
            case INTERVAL_MASK(MONTH):
            case INTERVAL_MASK(DAY):
            case INTERVAL_MASK(HOUR):
            case INTERVAL_MASK(MINUTE):
            case INTERVAL_MASK(SECOND):
            case INTERVAL_MASK(YEAR) | INTERVAL_MASK(MONTH):
            case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR):
            case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE):
            case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
            case INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE):
            case INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
            case INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
            case INTERVAL_FULL_RANGE:
                /* all OK */
                break;
            default:
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("invalid INTERVAL type modifier")));
        }
    }

    if (n == 1)
    {
        if (tl[0] != INTERVAL_FULL_RANGE)
            typmod = INTERVAL_TYPMOD(INTERVAL_FULL_PRECISION, tl[0]);
        else
            typmod = -1;
    }
    else if (n == 2)
    {
        if (tl[1] < 0)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("INTERVAL(%d) precision must not be negative",
                            tl[1])));
        if (tl[1] > MAX_INTERVAL_PRECISION)
        {
            ereport(WARNING,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("INTERVAL(%d) precision reduced to maximum allowed, %d",
                            tl[1], MAX_INTERVAL_PRECISION)));
            typmod = INTERVAL_TYPMOD(MAX_INTERVAL_PRECISION, tl[0]);
        }
        else
            typmod = INTERVAL_TYPMOD(tl[1], tl[0]);
    }
    else
    {
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("invalid INTERVAL type modifier")));
        typmod = 0;             /* keep compiler quiet */
    }

    PG_RETURN_INT32(typmod);
}

Datum
intervaltypmodout(PG_FUNCTION_ARGS)
{
    int32       typmod = PG_GETARG_INT32(0);
    char       *res = (char *) palloc(64);
    int         fields;
    int         precision;
    const char *fieldstr;

    if (typmod < 0)
    {
        *res = '\0';
        PG_RETURN_CSTRING(res);
    }

    fields = INTERVAL_RANGE(typmod);
    precision = INTERVAL_PRECISION(typmod);

    switch (fields)
    {
        case INTERVAL_MASK(YEAR):
            fieldstr = " year";
            break;
        case INTERVAL_MASK(MONTH):
            fieldstr = " month";
            break;
        case INTERVAL_MASK(DAY):
            fieldstr = " day";
            break;
        case INTERVAL_MASK(HOUR):
            fieldstr = " hour";
            break;
        case INTERVAL_MASK(MINUTE):
            fieldstr = " minute";
            break;
        case INTERVAL_MASK(SECOND):
            fieldstr = " second";
            break;
        case INTERVAL_MASK(YEAR) | INTERVAL_MASK(MONTH):
            fieldstr = " year to month";
            break;
        case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR):
            fieldstr = " day to hour";
            break;
        case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE):
            fieldstr = " day to minute";
            break;
        case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
            fieldstr = " day to second";
            break;
        case INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE):
            fieldstr = " hour to minute";
            break;
        case INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
            fieldstr = " hour to second";
            break;
        case INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
            fieldstr = " minute to second";
            break;
        case INTERVAL_FULL_RANGE:
            fieldstr = "";
            break;
        default:
            elog(ERROR, "invalid INTERVAL typmod: 0x%x", typmod);
            fieldstr = "";
            break;
    }

    if (precision != INTERVAL_FULL_PRECISION)
        snprintf(res, 64, "%s(%d)", fieldstr, precision);
    else
        snprintf(res, 64, "%s", fieldstr);

    PG_RETURN_CSTRING(res);
}

/*
 * Given an interval typmod value, return a code for the least-significant
 * field that the typmod allows to be nonzero, for instance given
 * INTERVAL DAY TO HOUR we want to identify "hour".
 *
 * The results should be ordered by field significance, which means
 * we can't use the dt.h macros YEAR etc, because for some odd reason
 * they aren't ordered that way.  Instead, arbitrarily represent
 * SECOND = 0, MINUTE = 1, HOUR = 2, DAY = 3, MONTH = 4, YEAR = 5.
 */
static int
intervaltypmodleastfield(int32 typmod)
{
    if (typmod < 0)
        return 0;               /* SECOND */

    switch (INTERVAL_RANGE(typmod))
    {
        case INTERVAL_MASK(YEAR):
            return 5;           /* YEAR */
        case INTERVAL_MASK(MONTH):
            return 4;           /* MONTH */
        case INTERVAL_MASK(DAY):
            return 3;           /* DAY */
        case INTERVAL_MASK(HOUR):
            return 2;           /* HOUR */
        case INTERVAL_MASK(MINUTE):
            return 1;           /* MINUTE */
        case INTERVAL_MASK(SECOND):
            return 0;           /* SECOND */
        case INTERVAL_MASK(YEAR) | INTERVAL_MASK(MONTH):
            return 4;           /* MONTH */
        case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR):
            return 2;           /* HOUR */
        case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE):
            return 1;           /* MINUTE */
        case INTERVAL_MASK(DAY) | INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
            return 0;           /* SECOND */
        case INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE):
            return 1;           /* MINUTE */
        case INTERVAL_MASK(HOUR) | INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
            return 0;           /* SECOND */
        case INTERVAL_MASK(MINUTE) | INTERVAL_MASK(SECOND):
            return 0;           /* SECOND */
        case INTERVAL_FULL_RANGE:
            return 0;           /* SECOND */
        default:
            elog(ERROR, "invalid INTERVAL typmod: 0x%x", typmod);
            break;
    }
    return 0;                   /* can't get here, but keep compiler quiet */
}


/*
 * interval_support()
 *
 * Planner support function for interval_scale().
 *
 * Flatten superfluous calls to interval_scale().  The interval typmod is
 * complex to permit accepting and regurgitating all SQL standard variations.
 * For truncation purposes, it boils down to a single, simple granularity.
 */
Datum
interval_support(PG_FUNCTION_ARGS)
{
    Node       *rawreq = (Node *) PG_GETARG_POINTER(0);
    Node       *ret = NULL;

    if (IsA(rawreq, SupportRequestSimplify))
    {
        SupportRequestSimplify *req = (SupportRequestSimplify *) rawreq;
        FuncExpr   *expr = req->fcall;
        Node       *typmod;

        Assert(list_length(expr->args) >= 2);

        typmod = (Node *) lsecond(expr->args);

        if (IsA(typmod, Const) && !((Const *) typmod)->constisnull)
        {
            Node       *source = (Node *) linitial(expr->args);
            int32       new_typmod = DatumGetInt32(((Const *) typmod)->constvalue);
            bool        noop;

            if (new_typmod < 0)
                noop = true;
            else
            {
                int32       old_typmod = exprTypmod(source);
                int         old_least_field;
                int         new_least_field;
                int         old_precis;
                int         new_precis;

                old_least_field = intervaltypmodleastfield(old_typmod);
                new_least_field = intervaltypmodleastfield(new_typmod);
                if (old_typmod < 0)
                    old_precis = INTERVAL_FULL_PRECISION;
                else
                    old_precis = INTERVAL_PRECISION(old_typmod);
                new_precis = INTERVAL_PRECISION(new_typmod);

                /*
                 * Cast is a no-op if least field stays the same or decreases
                 * while precision stays the same or increases.  But
                 * precision, which is to say, sub-second precision, only
                 * affects ranges that include SECOND.
                 */
                noop = (new_least_field <= old_least_field) &&
                    (old_least_field > 0 /* SECOND */ ||
                     new_precis >= MAX_INTERVAL_PRECISION ||
                     new_precis >= old_precis);
            }
            if (noop)
                ret = relabel_to_typmod(source, new_typmod);
        }
    }

    PG_RETURN_POINTER(ret);
}

/* interval_scale()
 * Adjust interval type for specified fields.
 * Used by PostgreSQL type system to stuff columns.
 */
Datum
interval_scale(PG_FUNCTION_ARGS)
{
    Interval   *interval = PG_GETARG_INTERVAL_P(0);
    int32       typmod = PG_GETARG_INT32(1);
    Interval   *result;

    result = palloc(sizeof(Interval));
    *result = *interval;

    AdjustIntervalForTypmod(result, typmod);

    PG_RETURN_INTERVAL_P(result);
}

/*
 *  Adjust interval for specified precision, in both YEAR to SECOND
 *  range and sub-second precision.
 */
static void
AdjustIntervalForTypmod(Interval *interval, int32 typmod)
{
    static const int64 IntervalScales[MAX_INTERVAL_PRECISION + 1] = {
        INT64CONST(1000000),
        INT64CONST(100000),
        INT64CONST(10000),
        INT64CONST(1000),
        INT64CONST(100),
        INT64CONST(10),
        INT64CONST(1)
    };

    static const int64 IntervalOffsets[MAX_INTERVAL_PRECISION + 1] = {
        INT64CONST(500000),
        INT64CONST(50000),
        INT64CONST(5000),
        INT64CONST(500),
        INT64CONST(50),
        INT64CONST(5),
        INT64CONST(0)
    };

    /*
     * Unspecified range and precision? Then not necessary to adjust. Setting
     * typmod to -1 is the convention for all data types.
     */
    if (typmod >= 0)
    {
        int         range = INTERVAL_RANGE(typmod);
        int         precision = INTERVAL_PRECISION(typmod);

        /*
         * Our interpretation of intervals with a limited set of fields is
         * that fields to the right of the last one specified are zeroed out,
         * but those to the left of it remain valid.  Thus for example there
         * is no operational difference between INTERVAL YEAR TO MONTH and
         * INTERVAL MONTH.  In some cases we could meaningfully enforce that
         * higher-order fields are zero; for example INTERVAL DAY could reject
         * nonzero "month" field.  However that seems a bit pointless when we
         * can't do it consistently.  (We cannot enforce a range limit on the
         * highest expected field, since we do not have any equivalent of
         * SQL's <interval leading field precision>.)  If we ever decide to
         * revisit this, interval_support will likely require adjusting.
         *
         * Note: before PG 8.4 we interpreted a limited set of fields as
         * actually causing a "modulo" operation on a given value, potentially
         * losing high-order as well as low-order information.  But there is
         * no support for such behavior in the standard, and it seems fairly
         * undesirable on data consistency grounds anyway.  Now we only
         * perform truncation or rounding of low-order fields.
         */
        if (range == INTERVAL_FULL_RANGE)
        {
            /* Do nothing... */
        }
        else if (range == INTERVAL_MASK(YEAR))
        {
            interval->month = (interval->month / MONTHS_PER_YEAR) * MONTHS_PER_YEAR;
            interval->day = 0;
            interval->time = 0;
        }
        else if (range == INTERVAL_MASK(MONTH))
        {
            interval->day = 0;
            interval->time = 0;
        }
        /* YEAR TO MONTH */
        else if (range == (INTERVAL_MASK(YEAR) | INTERVAL_MASK(MONTH)))
        {
            interval->day = 0;
            interval->time = 0;
        }
        else if (range == INTERVAL_MASK(DAY))
        {
            interval->time = 0;
        }
        else if (range == INTERVAL_MASK(HOUR))
        {
            interval->time = (interval->time / USECS_PER_HOUR) *
                USECS_PER_HOUR;
        }
        else if (range == INTERVAL_MASK(MINUTE))
        {
            interval->time = (interval->time / USECS_PER_MINUTE) *
                USECS_PER_MINUTE;
        }
        else if (range == INTERVAL_MASK(SECOND))
        {
            /* fractional-second rounding will be dealt with below */
        }
        /* DAY TO HOUR */
        else if (range == (INTERVAL_MASK(DAY) |
                           INTERVAL_MASK(HOUR)))
        {
            interval->time = (interval->time / USECS_PER_HOUR) *
                USECS_PER_HOUR;
        }
        /* DAY TO MINUTE */
        else if (range == (INTERVAL_MASK(DAY) |
                           INTERVAL_MASK(HOUR) |
                           INTERVAL_MASK(MINUTE)))
        {
            interval->time = (interval->time / USECS_PER_MINUTE) *
                USECS_PER_MINUTE;
        }
        /* DAY TO SECOND */
        else if (range == (INTERVAL_MASK(DAY) |
                           INTERVAL_MASK(HOUR) |
                           INTERVAL_MASK(MINUTE) |
                           INTERVAL_MASK(SECOND)))
        {
            /* fractional-second rounding will be dealt with below */
        }
        /* HOUR TO MINUTE */
        else if (range == (INTERVAL_MASK(HOUR) |
                           INTERVAL_MASK(MINUTE)))
        {
            interval->time = (interval->time / USECS_PER_MINUTE) *
                USECS_PER_MINUTE;
        }
        /* HOUR TO SECOND */
        else if (range == (INTERVAL_MASK(HOUR) |
                           INTERVAL_MASK(MINUTE) |
                           INTERVAL_MASK(SECOND)))
        {
            /* fractional-second rounding will be dealt with below */
        }
        /* MINUTE TO SECOND */
        else if (range == (INTERVAL_MASK(MINUTE) |
                           INTERVAL_MASK(SECOND)))
        {
            /* fractional-second rounding will be dealt with below */
        }
        else
            elog(ERROR, "unrecognized interval typmod: %d", typmod);

        /* Need to adjust sub-second precision? */
        if (precision != INTERVAL_FULL_PRECISION)
        {
            if (precision < 0 || precision > MAX_INTERVAL_PRECISION)
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("interval(%d) precision must be between %d and %d",
                                precision, 0, MAX_INTERVAL_PRECISION)));

            if (interval->time >= INT64CONST(0))
            {
                interval->time = ((interval->time +
                                   IntervalOffsets[precision]) /
                                  IntervalScales[precision]) *
                    IntervalScales[precision];
            }
            else
            {
                interval->time = -(((-interval->time +
                                     IntervalOffsets[precision]) /
                                    IntervalScales[precision]) *
                                   IntervalScales[precision]);
            }
        }
    }
}

/*
 * make_interval - numeric Interval constructor
 */
Datum
make_interval(PG_FUNCTION_ARGS)
{
    int32       years = PG_GETARG_INT32(0);
    int32       months = PG_GETARG_INT32(1);
    int32       weeks = PG_GETARG_INT32(2);
    int32       days = PG_GETARG_INT32(3);
    int32       hours = PG_GETARG_INT32(4);
    int32       mins = PG_GETARG_INT32(5);
    double      secs = PG_GETARG_FLOAT8(6);
    Interval   *result;

    /*
     * Reject out-of-range inputs.  We really ought to check the integer
     * inputs as well, but it's not entirely clear what limits to apply.
     */
    if (isinf(secs) || isnan(secs))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));

    result = (Interval *) palloc(sizeof(Interval));
    result->month = years * MONTHS_PER_YEAR + months;
    result->day = weeks * 7 + days;

    secs = rint(secs * USECS_PER_SEC);
    result->time = hours * ((int64) SECS_PER_HOUR * USECS_PER_SEC) +
        mins * ((int64) SECS_PER_MINUTE * USECS_PER_SEC) +
        (int64) secs;

    PG_RETURN_INTERVAL_P(result);
}

/* EncodeSpecialTimestamp()
 * Convert reserved timestamp data type to string.
 */
void
EncodeSpecialTimestamp(Timestamp dt, char *str)
{
    if (TIMESTAMP_IS_NOBEGIN(dt))
        strcpy(str, EARLY);
    else if (TIMESTAMP_IS_NOEND(dt))
        strcpy(str, LATE);
    else                        /* shouldn't happen */
        elog(ERROR, "invalid argument for EncodeSpecialTimestamp");
}

Datum
now(PG_FUNCTION_ARGS)
{
    PG_RETURN_TIMESTAMPTZ(GetCurrentTransactionStartTimestamp());
}

Datum
statement_timestamp(PG_FUNCTION_ARGS)
{
    PG_RETURN_TIMESTAMPTZ(GetCurrentStatementStartTimestamp());
}

Datum
clock_timestamp(PG_FUNCTION_ARGS)
{
    PG_RETURN_TIMESTAMPTZ(GetCurrentTimestamp());
}

Datum
pg_postmaster_start_time(PG_FUNCTION_ARGS)
{
    PG_RETURN_TIMESTAMPTZ(PgStartTime);
}

Datum
pg_conf_load_time(PG_FUNCTION_ARGS)
{
    PG_RETURN_TIMESTAMPTZ(PgReloadTime);
}

/*
 * GetCurrentTimestamp -- get the current operating system time
 *
 * Result is in the form of a TimestampTz value, and is expressed to the
 * full precision of the gettimeofday() syscall
 */
TimestampTz
GetCurrentTimestamp(void)
{
    TimestampTz result;
    struct timeval tp;

    gettimeofday(&tp, NULL);

    result = (TimestampTz) tp.tv_sec -
        ((POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY);
    result = (result * USECS_PER_SEC) + tp.tv_usec;

    return result;
}

/*
 * GetSQLCurrentTimestamp -- implements CURRENT_TIMESTAMP, CURRENT_TIMESTAMP(n)
 */
TimestampTz
GetSQLCurrentTimestamp(int32 typmod)
{
    TimestampTz ts;

    ts = GetCurrentTransactionStartTimestamp();
    if (typmod >= 0)
        AdjustTimestampForTypmod(&ts, typmod);
    return ts;
}

/*
 * GetSQLLocalTimestamp -- implements LOCALTIMESTAMP, LOCALTIMESTAMP(n)
 */
Timestamp
GetSQLLocalTimestamp(int32 typmod)
{
    Timestamp   ts;

    ts = timestamptz2timestamp(GetCurrentTransactionStartTimestamp());
    if (typmod >= 0)
        AdjustTimestampForTypmod(&ts, typmod);
    return ts;
}

/*
 * timeofday(*) -- returns the current time as a text.
 */
Datum
timeofday(PG_FUNCTION_ARGS)
{
    struct timeval tp;
    char        templ[128];
    char        buf[128];
    pg_time_t   tt;

    gettimeofday(&tp, NULL);
    tt = (pg_time_t) tp.tv_sec;
    pg_strftime(templ, sizeof(templ), "%a %b %d %H:%M:%S.%%06d %Y %Z",
                pg_localtime(&tt, session_timezone));
    snprintf(buf, sizeof(buf), templ, tp.tv_usec);

    PG_RETURN_TEXT_P(cstring_to_text(buf));
}

/*
 * TimestampDifference -- convert the difference between two timestamps
 *      into integer seconds and microseconds
 *
 * Both inputs must be ordinary finite timestamps (in current usage,
 * they'll be results from GetCurrentTimestamp()).
 *
 * We expect start_time <= stop_time.  If not, we return zeros; for current
 * callers there is no need to be tense about which way division rounds on
 * negative inputs.
 */
void
TimestampDifference(TimestampTz start_time, TimestampTz stop_time,
                    long *secs, int *microsecs)
{
    TimestampTz diff = stop_time - start_time;

    if (diff <= 0)
    {
        *secs = 0;
        *microsecs = 0;
    }
    else
    {
        *secs = (long) (diff / USECS_PER_SEC);
        *microsecs = (int) (diff % USECS_PER_SEC);
    }
}

/*
 * TimestampDifferenceExceeds -- report whether the difference between two
 *      timestamps is >= a threshold (expressed in milliseconds)
 *
 * Both inputs must be ordinary finite timestamps (in current usage,
 * they'll be results from GetCurrentTimestamp()).
 */
bool
TimestampDifferenceExceeds(TimestampTz start_time,
                           TimestampTz stop_time,
                           int msec)
{
    TimestampTz diff = stop_time - start_time;

    return (diff >= msec * INT64CONST(1000));
}

/*
 * Convert a time_t to TimestampTz.
 *
 * We do not use time_t internally in Postgres, but this is provided for use
 * by functions that need to interpret, say, a stat(2) result.
 *
 * To avoid having the function's ABI vary depending on the width of time_t,
 * we declare the argument as pg_time_t, which is cast-compatible with
 * time_t but always 64 bits wide (unless the platform has no 64-bit type).
 * This detail should be invisible to callers, at least at source code level.
 */
TimestampTz
time_t_to_timestamptz(pg_time_t tm)
{
    TimestampTz result;

    result = (TimestampTz) tm -
        ((POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY);
    result *= USECS_PER_SEC;

    return result;
}

/*
 * Convert a TimestampTz to time_t.
 *
 * This too is just marginally useful, but some places need it.
 *
 * To avoid having the function's ABI vary depending on the width of time_t,
 * we declare the result as pg_time_t, which is cast-compatible with
 * time_t but always 64 bits wide (unless the platform has no 64-bit type).
 * This detail should be invisible to callers, at least at source code level.
 */
pg_time_t
timestamptz_to_time_t(TimestampTz t)
{
    pg_time_t   result;

    result = (pg_time_t) (t / USECS_PER_SEC +
                          ((POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY));

    return result;
}

/*
 * Produce a C-string representation of a TimestampTz.
 *
 * This is mostly for use in emitting messages.  The primary difference
 * from timestamptz_out is that we force the output format to ISO.  Note
 * also that the result is in a static buffer, not pstrdup'd.
 *
 * See also pg_strftime.
 */
const char *
timestamptz_to_str(TimestampTz t)
{
    static char buf[MAXDATELEN + 1];
    int         tz;
    struct pg_tm tt,
               *tm = &tt;
    fsec_t      fsec;
    const char *tzn;

    if (TIMESTAMP_NOT_FINITE(t))
        EncodeSpecialTimestamp(t, buf);
    else if (timestamp2tm(t, &tz, tm, &fsec, &tzn, NULL) == 0)
        EncodeDateTime(tm, fsec, true, tz, tzn, USE_ISO_DATES, buf);
    else
        strlcpy(buf, "(timestamp out of range)", sizeof(buf));

    return buf;
}


void
dt2time(Timestamp jd, int *hour, int *min, int *sec, fsec_t *fsec)
{
    TimeOffset  time;

    time = jd;

    *hour = time / USECS_PER_HOUR;
    time -= (*hour) * USECS_PER_HOUR;
    *min = time / USECS_PER_MINUTE;
    time -= (*min) * USECS_PER_MINUTE;
    *sec = time / USECS_PER_SEC;
    *fsec = time - (*sec * USECS_PER_SEC);
}                               /* dt2time() */


/*
 * timestamp2tm() - Convert timestamp data type to POSIX time structure.
 *
 * Note that year is _not_ 1900-based, but is an explicit full value.
 * Also, month is one-based, _not_ zero-based.
 * Returns:
 *   0 on success
 *  -1 on out of range
 *
 * If attimezone is NULL, the global timezone setting will be used.
 */
int
timestamp2tm(Timestamp dt, int *tzp, struct pg_tm *tm, fsec_t *fsec, const char **tzn, pg_tz *attimezone)
{
    Timestamp   date;
    Timestamp   time;
    pg_time_t   utime;

    /* Use session timezone if caller asks for default */
    if (attimezone == NULL)
        attimezone = session_timezone;

    time = dt;
    TMODULO(time, date, USECS_PER_DAY);

    if (time < INT64CONST(0))
    {
        time += USECS_PER_DAY;
        date -= 1;
    }

    /* add offset to go from J2000 back to standard Julian date */
    date += POSTGRES_EPOCH_JDATE;

    /* Julian day routine does not work for negative Julian days */
    if (date < 0 || date > (Timestamp) INT_MAX)
        return -1;

    j2date((int) date, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);
    dt2time(time, &tm->tm_hour, &tm->tm_min, &tm->tm_sec, fsec);

    /* Done if no TZ conversion wanted */
    if (tzp == NULL)
    {
        tm->tm_isdst = -1;
        tm->tm_gmtoff = 0;
        tm->tm_zone = NULL;
        if (tzn != NULL)
            *tzn = NULL;
        return 0;
    }

    /*
     * If the time falls within the range of pg_time_t, use pg_localtime() to
     * rotate to the local time zone.
     *
     * First, convert to an integral timestamp, avoiding possibly
     * platform-specific roundoff-in-wrong-direction errors, and adjust to
     * Unix epoch.  Then see if we can convert to pg_time_t without loss. This
     * coding avoids hardwiring any assumptions about the width of pg_time_t,
     * so it should behave sanely on machines without int64.
     */
    dt = (dt - *fsec) / USECS_PER_SEC +
        (POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY;
    utime = (pg_time_t) dt;
    if ((Timestamp) utime == dt)
    {
        struct pg_tm *tx = pg_localtime(&utime, attimezone);

        tm->tm_year = tx->tm_year + 1900;
        tm->tm_mon = tx->tm_mon + 1;
        tm->tm_mday = tx->tm_mday;
        tm->tm_hour = tx->tm_hour;
        tm->tm_min = tx->tm_min;
        tm->tm_sec = tx->tm_sec;
        tm->tm_isdst = tx->tm_isdst;
        tm->tm_gmtoff = tx->tm_gmtoff;
        tm->tm_zone = tx->tm_zone;
        *tzp = -tm->tm_gmtoff;
        if (tzn != NULL)
            *tzn = tm->tm_zone;
    }
    else
    {
        /*
         * When out of range of pg_time_t, treat as GMT
         */
        *tzp = 0;
        /* Mark this as *no* time zone available */
        tm->tm_isdst = -1;
        tm->tm_gmtoff = 0;
        tm->tm_zone = NULL;
        if (tzn != NULL)
            *tzn = NULL;
    }

    return 0;
}


/* tm2timestamp()
 * Convert a tm structure to a timestamp data type.
 * Note that year is _not_ 1900-based, but is an explicit full value.
 * Also, month is one-based, _not_ zero-based.
 *
 * Returns -1 on failure (value out of range).
 */
int
tm2timestamp(struct pg_tm *tm, fsec_t fsec, int *tzp, Timestamp *result)
{
    TimeOffset  date;
    TimeOffset  time;

    /* Prevent overflow in Julian-day routines */
    if (!IS_VALID_JULIAN(tm->tm_year, tm->tm_mon, tm->tm_mday))
    {
        *result = 0;            /* keep compiler quiet */
        return -1;
    }

    date = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - POSTGRES_EPOCH_JDATE;
    time = time2t(tm->tm_hour, tm->tm_min, tm->tm_sec, fsec);

    *result = date * USECS_PER_DAY + time;
    /* check for major overflow */
    if ((*result - time) / USECS_PER_DAY != date)
    {
        *result = 0;            /* keep compiler quiet */
        return -1;
    }
    /* check for just-barely overflow (okay except time-of-day wraps) */
    /* caution: we want to allow 1999-12-31 24:00:00 */
    if ((*result < 0 && date > 0) ||
        (*result > 0 && date < -1))
    {
        *result = 0;            /* keep compiler quiet */
        return -1;
    }
    if (tzp != NULL)
        *result = dt2local(*result, -(*tzp));

    /* final range check catches just-out-of-range timestamps */
    if (!IS_VALID_TIMESTAMP(*result))
    {
        *result = 0;            /* keep compiler quiet */
        return -1;
    }

    return 0;
}


/* interval2tm()
 * Convert an interval data type to a tm structure.
 */
int
interval2tm(Interval span, struct pg_tm *tm, fsec_t *fsec)
{
    TimeOffset  time;
    TimeOffset  tfrac;

    tm->tm_year = span.month / MONTHS_PER_YEAR;
    tm->tm_mon = span.month % MONTHS_PER_YEAR;
    tm->tm_mday = span.day;
    time = span.time;

    tfrac = time / USECS_PER_HOUR;
    time -= tfrac * USECS_PER_HOUR;
    tm->tm_hour = tfrac;
    if (!SAMESIGN(tm->tm_hour, tfrac))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));
    tfrac = time / USECS_PER_MINUTE;
    time -= tfrac * USECS_PER_MINUTE;
    tm->tm_min = tfrac;
    tfrac = time / USECS_PER_SEC;
    *fsec = time - (tfrac * USECS_PER_SEC);
    tm->tm_sec = tfrac;

    return 0;
}

int
tm2interval(struct pg_tm *tm, fsec_t fsec, Interval *span)
{
    double      total_months = (double) tm->tm_year * MONTHS_PER_YEAR + tm->tm_mon;

    if (total_months > INT_MAX || total_months < INT_MIN)
        return -1;
    span->month = total_months;
    span->day = tm->tm_mday;
    span->time = (((((tm->tm_hour * INT64CONST(60)) +
                     tm->tm_min) * INT64CONST(60)) +
                   tm->tm_sec) * USECS_PER_SEC) + fsec;

    return 0;
}

static TimeOffset
time2t(const int hour, const int min, const int sec, const fsec_t fsec)
{
    return (((((hour * MINS_PER_HOUR) + min) * SECS_PER_MINUTE) + sec) * USECS_PER_SEC) + fsec;
}

static Timestamp
dt2local(Timestamp dt, int tz)
{
    dt -= (tz * USECS_PER_SEC);
    return dt;
}


/*****************************************************************************
 *   PUBLIC ROUTINES                                                         *
 *****************************************************************************/


Datum
timestamp_finite(PG_FUNCTION_ARGS)
{
    Timestamp   timestamp = PG_GETARG_TIMESTAMP(0);

    PG_RETURN_BOOL(!TIMESTAMP_NOT_FINITE(timestamp));
}

Datum
interval_finite(PG_FUNCTION_ARGS)
{
    PG_RETURN_BOOL(true);
}


/*----------------------------------------------------------
 *  Relational operators for timestamp.
 *---------------------------------------------------------*/

void
GetEpochTime(struct pg_tm *tm)
{
    struct pg_tm *t0;
    pg_time_t   epoch = 0;

    t0 = pg_gmtime(&epoch);

    if (t0 == NULL)
        elog(ERROR, "could not convert epoch to timestamp: %m");

    tm->tm_year = t0->tm_year;
    tm->tm_mon = t0->tm_mon;
    tm->tm_mday = t0->tm_mday;
    tm->tm_hour = t0->tm_hour;
    tm->tm_min = t0->tm_min;
    tm->tm_sec = t0->tm_sec;

    tm->tm_year += 1900;
    tm->tm_mon++;
}

Timestamp
SetEpochTimestamp(void)
{
    Timestamp   dt;
    struct pg_tm tt,
               *tm = &tt;

    GetEpochTime(tm);
    /* we don't bother to test for failure ... */
    tm2timestamp(tm, 0, NULL, &dt);

    return dt;
}                               /* SetEpochTimestamp() */

/*
 * We are currently sharing some code between timestamp and timestamptz.
 * The comparison functions are among them. - thomas 2001-09-25
 *
 *      timestamp_relop - is timestamp1 relop timestamp2
 */
int
timestamp_cmp_internal(Timestamp dt1, Timestamp dt2)
{
    return (dt1 < dt2) ? -1 : ((dt1 > dt2) ? 1 : 0);
}

Datum
timestamp_eq(PG_FUNCTION_ARGS)
{
    Timestamp   dt1 = PG_GETARG_TIMESTAMP(0);
    Timestamp   dt2 = PG_GETARG_TIMESTAMP(1);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) == 0);
}

Datum
timestamp_ne(PG_FUNCTION_ARGS)
{
    Timestamp   dt1 = PG_GETARG_TIMESTAMP(0);
    Timestamp   dt2 = PG_GETARG_TIMESTAMP(1);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) != 0);
}

Datum
timestamp_lt(PG_FUNCTION_ARGS)
{
    Timestamp   dt1 = PG_GETARG_TIMESTAMP(0);
    Timestamp   dt2 = PG_GETARG_TIMESTAMP(1);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) < 0);
}

Datum
timestamp_gt(PG_FUNCTION_ARGS)
{
    Timestamp   dt1 = PG_GETARG_TIMESTAMP(0);
    Timestamp   dt2 = PG_GETARG_TIMESTAMP(1);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) > 0);
}

Datum
timestamp_le(PG_FUNCTION_ARGS)
{
    Timestamp   dt1 = PG_GETARG_TIMESTAMP(0);
    Timestamp   dt2 = PG_GETARG_TIMESTAMP(1);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) <= 0);
}

Datum
timestamp_ge(PG_FUNCTION_ARGS)
{
    Timestamp   dt1 = PG_GETARG_TIMESTAMP(0);
    Timestamp   dt2 = PG_GETARG_TIMESTAMP(1);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) >= 0);
}

Datum
timestamp_cmp(PG_FUNCTION_ARGS)
{
    Timestamp   dt1 = PG_GETARG_TIMESTAMP(0);
    Timestamp   dt2 = PG_GETARG_TIMESTAMP(1);

    PG_RETURN_INT32(timestamp_cmp_internal(dt1, dt2));
}

/* note: this is used for timestamptz also */
static int
timestamp_fastcmp(Datum x, Datum y, SortSupport ssup)
{
    Timestamp   a = DatumGetTimestamp(x);
    Timestamp   b = DatumGetTimestamp(y);

    return timestamp_cmp_internal(a, b);
}

Datum
timestamp_sortsupport(PG_FUNCTION_ARGS)
{
    SortSupport ssup = (SortSupport) PG_GETARG_POINTER(0);

    ssup->comparator = timestamp_fastcmp;
    PG_RETURN_VOID();
}

Datum
timestamp_hash(PG_FUNCTION_ARGS)
{
    return hashint8(fcinfo);
}

Datum
timestamp_hash_extended(PG_FUNCTION_ARGS)
{
    return hashint8extended(fcinfo);
}

/*
 * Cross-type comparison functions for timestamp vs timestamptz
 */

Datum
timestamp_eq_timestamptz(PG_FUNCTION_ARGS)
{
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(0);
    TimestampTz dt2 = PG_GETARG_TIMESTAMPTZ(1);
    TimestampTz dt1;

    dt1 = timestamp2timestamptz(timestampVal);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) == 0);
}

Datum
timestamp_ne_timestamptz(PG_FUNCTION_ARGS)
{
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(0);
    TimestampTz dt2 = PG_GETARG_TIMESTAMPTZ(1);
    TimestampTz dt1;

    dt1 = timestamp2timestamptz(timestampVal);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) != 0);
}

Datum
timestamp_lt_timestamptz(PG_FUNCTION_ARGS)
{
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(0);
    TimestampTz dt2 = PG_GETARG_TIMESTAMPTZ(1);
    TimestampTz dt1;

    dt1 = timestamp2timestamptz(timestampVal);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) < 0);
}

Datum
timestamp_gt_timestamptz(PG_FUNCTION_ARGS)
{
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(0);
    TimestampTz dt2 = PG_GETARG_TIMESTAMPTZ(1);
    TimestampTz dt1;

    dt1 = timestamp2timestamptz(timestampVal);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) > 0);
}

Datum
timestamp_le_timestamptz(PG_FUNCTION_ARGS)
{
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(0);
    TimestampTz dt2 = PG_GETARG_TIMESTAMPTZ(1);
    TimestampTz dt1;

    dt1 = timestamp2timestamptz(timestampVal);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) <= 0);
}

Datum
timestamp_ge_timestamptz(PG_FUNCTION_ARGS)
{
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(0);
    TimestampTz dt2 = PG_GETARG_TIMESTAMPTZ(1);
    TimestampTz dt1;

    dt1 = timestamp2timestamptz(timestampVal);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) >= 0);
}

Datum
timestamp_cmp_timestamptz(PG_FUNCTION_ARGS)
{
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(0);
    TimestampTz dt2 = PG_GETARG_TIMESTAMPTZ(1);
    TimestampTz dt1;

    dt1 = timestamp2timestamptz(timestampVal);

    PG_RETURN_INT32(timestamp_cmp_internal(dt1, dt2));
}

Datum
timestamptz_eq_timestamp(PG_FUNCTION_ARGS)
{
    TimestampTz dt1 = PG_GETARG_TIMESTAMPTZ(0);
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(1);
    TimestampTz dt2;

    dt2 = timestamp2timestamptz(timestampVal);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) == 0);
}

Datum
timestamptz_ne_timestamp(PG_FUNCTION_ARGS)
{
    TimestampTz dt1 = PG_GETARG_TIMESTAMPTZ(0);
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(1);
    TimestampTz dt2;

    dt2 = timestamp2timestamptz(timestampVal);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) != 0);
}

Datum
timestamptz_lt_timestamp(PG_FUNCTION_ARGS)
{
    TimestampTz dt1 = PG_GETARG_TIMESTAMPTZ(0);
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(1);
    TimestampTz dt2;

    dt2 = timestamp2timestamptz(timestampVal);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) < 0);
}

Datum
timestamptz_gt_timestamp(PG_FUNCTION_ARGS)
{
    TimestampTz dt1 = PG_GETARG_TIMESTAMPTZ(0);
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(1);
    TimestampTz dt2;

    dt2 = timestamp2timestamptz(timestampVal);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) > 0);
}

Datum
timestamptz_le_timestamp(PG_FUNCTION_ARGS)
{
    TimestampTz dt1 = PG_GETARG_TIMESTAMPTZ(0);
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(1);
    TimestampTz dt2;

    dt2 = timestamp2timestamptz(timestampVal);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) <= 0);
}

Datum
timestamptz_ge_timestamp(PG_FUNCTION_ARGS)
{
    TimestampTz dt1 = PG_GETARG_TIMESTAMPTZ(0);
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(1);
    TimestampTz dt2;

    dt2 = timestamp2timestamptz(timestampVal);

    PG_RETURN_BOOL(timestamp_cmp_internal(dt1, dt2) >= 0);
}

Datum
timestamptz_cmp_timestamp(PG_FUNCTION_ARGS)
{
    TimestampTz dt1 = PG_GETARG_TIMESTAMPTZ(0);
    Timestamp   timestampVal = PG_GETARG_TIMESTAMP(1);
    TimestampTz dt2;

    dt2 = timestamp2timestamptz(timestampVal);

    PG_RETURN_INT32(timestamp_cmp_internal(dt1, dt2));
}


/*
 *      interval_relop  - is interval1 relop interval2
 *
 * Interval comparison is based on converting interval values to a linear
 * representation expressed in the units of the time field (microseconds,
 * in the case of integer timestamps) with days assumed to be always 24 hours
 * and months assumed to be always 30 days.  To avoid overflow, we need a
 * wider-than-int64 datatype for the linear representation, so use INT128.
 */

static inline INT128
interval_cmp_value(const Interval *interval)
{
    INT128      span;
    int64       dayfraction;
    int64       days;

    /*
     * Separate time field into days and dayfraction, then add the month and
     * day fields to the days part.  We cannot overflow int64 days here.
     */
    dayfraction = interval->time % USECS_PER_DAY;
    days = interval->time / USECS_PER_DAY;
    days += interval->month * INT64CONST(30);
    days += interval->day;

    /* Widen dayfraction to 128 bits */
    span = int64_to_int128(dayfraction);

    /* Scale up days to microseconds, forming a 128-bit product */
    int128_add_int64_mul_int64(&span, days, USECS_PER_DAY);

    return span;
}

static int
interval_cmp_internal(Interval *interval1, Interval *interval2)
{
    INT128      span1 = interval_cmp_value(interval1);
    INT128      span2 = interval_cmp_value(interval2);

    return int128_compare(span1, span2);
}

Datum
interval_eq(PG_FUNCTION_ARGS)
{
    Interval   *interval1 = PG_GETARG_INTERVAL_P(0);
    Interval   *interval2 = PG_GETARG_INTERVAL_P(1);

    PG_RETURN_BOOL(interval_cmp_internal(interval1, interval2) == 0);
}

Datum
interval_ne(PG_FUNCTION_ARGS)
{
    Interval   *interval1 = PG_GETARG_INTERVAL_P(0);
    Interval   *interval2 = PG_GETARG_INTERVAL_P(1);

    PG_RETURN_BOOL(interval_cmp_internal(interval1, interval2) != 0);
}

Datum
interval_lt(PG_FUNCTION_ARGS)
{
    Interval   *interval1 = PG_GETARG_INTERVAL_P(0);
    Interval   *interval2 = PG_GETARG_INTERVAL_P(1);

    PG_RETURN_BOOL(interval_cmp_internal(interval1, interval2) < 0);
}

Datum
interval_gt(PG_FUNCTION_ARGS)
{
    Interval   *interval1 = PG_GETARG_INTERVAL_P(0);
    Interval   *interval2 = PG_GETARG_INTERVAL_P(1);

    PG_RETURN_BOOL(interval_cmp_internal(interval1, interval2) > 0);
}

Datum
interval_le(PG_FUNCTION_ARGS)
{
    Interval   *interval1 = PG_GETARG_INTERVAL_P(0);
    Interval   *interval2 = PG_GETARG_INTERVAL_P(1);

    PG_RETURN_BOOL(interval_cmp_internal(interval1, interval2) <= 0);
}

Datum
interval_ge(PG_FUNCTION_ARGS)
{
    Interval   *interval1 = PG_GETARG_INTERVAL_P(0);
    Interval   *interval2 = PG_GETARG_INTERVAL_P(1);

    PG_RETURN_BOOL(interval_cmp_internal(interval1, interval2) >= 0);
}

Datum
interval_cmp(PG_FUNCTION_ARGS)
{
    Interval   *interval1 = PG_GETARG_INTERVAL_P(0);
    Interval   *interval2 = PG_GETARG_INTERVAL_P(1);

    PG_RETURN_INT32(interval_cmp_internal(interval1, interval2));
}

/*
 * Hashing for intervals
 *
 * We must produce equal hashvals for values that interval_cmp_internal()
 * considers equal.  So, compute the net span the same way it does,
 * and then hash that.
 */
Datum
interval_hash(PG_FUNCTION_ARGS)
{
    Interval   *interval = PG_GETARG_INTERVAL_P(0);
    INT128      span = interval_cmp_value(interval);
    int64       span64;

    /*
     * Use only the least significant 64 bits for hashing.  The upper 64 bits
     * seldom add any useful information, and besides we must do it like this
     * for compatibility with hashes calculated before use of INT128 was
     * introduced.
     */
    span64 = int128_to_int64(span);

    return DirectFunctionCall1(hashint8, Int64GetDatumFast(span64));
}

Datum
interval_hash_extended(PG_FUNCTION_ARGS)
{
    Interval   *interval = PG_GETARG_INTERVAL_P(0);
    INT128      span = interval_cmp_value(interval);
    int64       span64;

    /* Same approach as interval_hash */
    span64 = int128_to_int64(span);

    return DirectFunctionCall2(hashint8extended, Int64GetDatumFast(span64),
                               PG_GETARG_DATUM(1));
}

/* overlaps_timestamp() --- implements the SQL OVERLAPS operator.
 *
 * Algorithm is per SQL spec.  This is much harder than you'd think
 * because the spec requires us to deliver a non-null answer in some cases
 * where some of the inputs are null.
 */
Datum
overlaps_timestamp(PG_FUNCTION_ARGS)
{
    /*
     * The arguments are Timestamps, but we leave them as generic Datums to
     * avoid unnecessary conversions between value and reference forms --- not
     * to mention possible dereferences of null pointers.
     */
    Datum       ts1 = PG_GETARG_DATUM(0);
    Datum       te1 = PG_GETARG_DATUM(1);
    Datum       ts2 = PG_GETARG_DATUM(2);
    Datum       te2 = PG_GETARG_DATUM(3);
    bool        ts1IsNull = PG_ARGISNULL(0);
    bool        te1IsNull = PG_ARGISNULL(1);
    bool        ts2IsNull = PG_ARGISNULL(2);
    bool        te2IsNull = PG_ARGISNULL(3);

#define TIMESTAMP_GT(t1,t2) \
    DatumGetBool(DirectFunctionCall2(timestamp_gt,t1,t2))
#define TIMESTAMP_LT(t1,t2) \
    DatumGetBool(DirectFunctionCall2(timestamp_lt,t1,t2))

    /*
     * If both endpoints of interval 1 are null, the result is null (unknown).
     * If just one endpoint is null, take ts1 as the non-null one. Otherwise,
     * take ts1 as the lesser endpoint.
     */
    if (ts1IsNull)
    {
        if (te1IsNull)
            PG_RETURN_NULL();
        /* swap null for non-null */
        ts1 = te1;
        te1IsNull = true;
    }
    else if (!te1IsNull)
    {
        if (TIMESTAMP_GT(ts1, te1))
        {
            Datum       tt = ts1;

            ts1 = te1;
            te1 = tt;
        }
    }

    /* Likewise for interval 2. */
    if (ts2IsNull)
    {
        if (te2IsNull)
            PG_RETURN_NULL();
        /* swap null for non-null */
        ts2 = te2;
        te2IsNull = true;
    }
    else if (!te2IsNull)
    {
        if (TIMESTAMP_GT(ts2, te2))
        {
            Datum       tt = ts2;

            ts2 = te2;
            te2 = tt;
        }
    }

    /*
     * At this point neither ts1 nor ts2 is null, so we can consider three
     * cases: ts1 > ts2, ts1 < ts2, ts1 = ts2
     */
    if (TIMESTAMP_GT(ts1, ts2))
    {
        /*
         * This case is ts1 < te2 OR te1 < te2, which may look redundant but
         * in the presence of nulls it's not quite completely so.
         */
        if (te2IsNull)
            PG_RETURN_NULL();
        if (TIMESTAMP_LT(ts1, te2))
            PG_RETURN_BOOL(true);
        if (te1IsNull)
            PG_RETURN_NULL();

        /*
         * If te1 is not null then we had ts1 <= te1 above, and we just found
         * ts1 >= te2, hence te1 >= te2.
         */
        PG_RETURN_BOOL(false);
    }
    else if (TIMESTAMP_LT(ts1, ts2))
    {
        /* This case is ts2 < te1 OR te2 < te1 */
        if (te1IsNull)
            PG_RETURN_NULL();
        if (TIMESTAMP_LT(ts2, te1))
            PG_RETURN_BOOL(true);
        if (te2IsNull)
            PG_RETURN_NULL();

        /*
         * If te2 is not null then we had ts2 <= te2 above, and we just found
         * ts2 >= te1, hence te2 >= te1.
         */
        PG_RETURN_BOOL(false);
    }
    else
    {
        /*
         * For ts1 = ts2 the spec says te1 <> te2 OR te1 = te2, which is a
         * rather silly way of saying "true if both are non-null, else null".
         */
        if (te1IsNull || te2IsNull)
            PG_RETURN_NULL();
        PG_RETURN_BOOL(true);
    }

#undef TIMESTAMP_GT
#undef TIMESTAMP_LT
}


/*----------------------------------------------------------
 *  "Arithmetic" operators on date/times.
 *---------------------------------------------------------*/

Datum
timestamp_smaller(PG_FUNCTION_ARGS)
{
    Timestamp   dt1 = PG_GETARG_TIMESTAMP(0);
    Timestamp   dt2 = PG_GETARG_TIMESTAMP(1);
    Timestamp   result;

    /* use timestamp_cmp_internal to be sure this agrees with comparisons */
    if (timestamp_cmp_internal(dt1, dt2) < 0)
        result = dt1;
    else
        result = dt2;
    PG_RETURN_TIMESTAMP(result);
}

Datum
timestamp_larger(PG_FUNCTION_ARGS)
{
    Timestamp   dt1 = PG_GETARG_TIMESTAMP(0);
    Timestamp   dt2 = PG_GETARG_TIMESTAMP(1);
    Timestamp   result;

    if (timestamp_cmp_internal(dt1, dt2) > 0)
        result = dt1;
    else
        result = dt2;
    PG_RETURN_TIMESTAMP(result);
}


Datum
timestamp_mi(PG_FUNCTION_ARGS)
{
    Timestamp   dt1 = PG_GETARG_TIMESTAMP(0);
    Timestamp   dt2 = PG_GETARG_TIMESTAMP(1);
    Interval   *result;

    result = (Interval *) palloc(sizeof(Interval));

    if (TIMESTAMP_NOT_FINITE(dt1) || TIMESTAMP_NOT_FINITE(dt2))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("cannot subtract infinite timestamps")));

    result->time = dt1 - dt2;

    result->month = 0;
    result->day = 0;

    /*----------
     *  This is wrong, but removing it breaks a lot of regression tests.
     *  For example:
     *
     *  test=> SET timezone = 'EST5EDT';
     *  test=> SELECT
     *  test-> ('2005-10-30 13:22:00-05'::timestamptz -
     *  test(>  '2005-10-29 13:22:00-04'::timestamptz);
     *  ?column?
     *  ----------------
     *   1 day 01:00:00
     *   (1 row)
     *
     *  so adding that to the first timestamp gets:
     *
     *   test=> SELECT
     *   test-> ('2005-10-29 13:22:00-04'::timestamptz +
     *   test(> ('2005-10-30 13:22:00-05'::timestamptz -
     *   test(>  '2005-10-29 13:22:00-04'::timestamptz)) at time zone 'EST';
     *      timezone
     *  --------------------
     *  2005-10-30 14:22:00
     *  (1 row)
     *----------
     */
    result = DatumGetIntervalP(DirectFunctionCall1(interval_justify_hours,
                                                   IntervalPGetDatum(result)));

    PG_RETURN_INTERVAL_P(result);
}

/*
 *  interval_justify_interval()
 *
 *  Adjust interval so 'month', 'day', and 'time' portions are within
 *  customary bounds.  Specifically:
 *
 *      0 <= abs(time) < 24 hours
 *      0 <= abs(day)  < 30 days
 *
 *  Also, the sign bit on all three fields is made equal, so either
 *  all three fields are negative or all are positive.
 */
Datum
interval_justify_interval(PG_FUNCTION_ARGS)
{
    Interval   *span = PG_GETARG_INTERVAL_P(0);
    Interval   *result;
    TimeOffset  wholeday;
    int32       wholemonth;

    result = (Interval *) palloc(sizeof(Interval));
    result->month = span->month;
    result->day = span->day;
    result->time = span->time;

    TMODULO(result->time, wholeday, USECS_PER_DAY);
    result->day += wholeday;    /* could overflow... */

    wholemonth = result->day / DAYS_PER_MONTH;
    result->day -= wholemonth * DAYS_PER_MONTH;
    result->month += wholemonth;

    if (result->month > 0 &&
        (result->day < 0 || (result->day == 0 && result->time < 0)))
    {
        result->day += DAYS_PER_MONTH;
        result->month--;
    }
    else if (result->month < 0 &&
             (result->day > 0 || (result->day == 0 && result->time > 0)))
    {
        result->day -= DAYS_PER_MONTH;
        result->month++;
    }

    if (result->day > 0 && result->time < 0)
    {
        result->time += USECS_PER_DAY;
        result->day--;
    }
    else if (result->day < 0 && result->time > 0)
    {
        result->time -= USECS_PER_DAY;
        result->day++;
    }

    PG_RETURN_INTERVAL_P(result);
}

/*
 *  interval_justify_hours()
 *
 *  Adjust interval so 'time' contains less than a whole day, adding
 *  the excess to 'day'.  This is useful for
 *  situations (such as non-TZ) where '1 day' = '24 hours' is valid,
 *  e.g. interval subtraction and division.
 */
Datum
interval_justify_hours(PG_FUNCTION_ARGS)
{
    Interval   *span = PG_GETARG_INTERVAL_P(0);
    Interval   *result;
    TimeOffset  wholeday;

    result = (Interval *) palloc(sizeof(Interval));
    result->month = span->month;
    result->day = span->day;
    result->time = span->time;

    TMODULO(result->time, wholeday, USECS_PER_DAY);
    result->day += wholeday;    /* could overflow... */

    if (result->day > 0 && result->time < 0)
    {
        result->time += USECS_PER_DAY;
        result->day--;
    }
    else if (result->day < 0 && result->time > 0)
    {
        result->time -= USECS_PER_DAY;
        result->day++;
    }

    PG_RETURN_INTERVAL_P(result);
}

/*
 *  interval_justify_days()
 *
 *  Adjust interval so 'day' contains less than 30 days, adding
 *  the excess to 'month'.
 */
Datum
interval_justify_days(PG_FUNCTION_ARGS)
{
    Interval   *span = PG_GETARG_INTERVAL_P(0);
    Interval   *result;
    int32       wholemonth;

    result = (Interval *) palloc(sizeof(Interval));
    result->month = span->month;
    result->day = span->day;
    result->time = span->time;

    wholemonth = result->day / DAYS_PER_MONTH;
    result->day -= wholemonth * DAYS_PER_MONTH;
    result->month += wholemonth;

    if (result->month > 0 && result->day < 0)
    {
        result->day += DAYS_PER_MONTH;
        result->month--;
    }
    else if (result->month < 0 && result->day > 0)
    {
        result->day -= DAYS_PER_MONTH;
        result->month++;
    }

    PG_RETURN_INTERVAL_P(result);
}

/* timestamp_pl_interval()
 * Add an interval to a timestamp data type.
 * Note that interval has provisions for qualitative year/month and day
 *  units, so try to do the right thing with them.
 * To add a month, increment the month, and use the same day of month.
 * Then, if the next month has fewer days, set the day of month
 *  to the last day of month.
 * To add a day, increment the mday, and use the same time of day.
 * Lastly, add in the "quantitative time".
 */
Datum
timestamp_pl_interval(PG_FUNCTION_ARGS)
{
    Timestamp   timestamp = PG_GETARG_TIMESTAMP(0);
    Interval   *span = PG_GETARG_INTERVAL_P(1);
    Timestamp   result;

    if (TIMESTAMP_NOT_FINITE(timestamp))
        result = timestamp;
    else
    {
        if (span->month != 0)
        {
            struct pg_tm tt,
                       *tm = &tt;
            fsec_t      fsec;

            if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range")));

            tm->tm_mon += span->month;
            if (tm->tm_mon > MONTHS_PER_YEAR)
            {
                tm->tm_year += (tm->tm_mon - 1) / MONTHS_PER_YEAR;
                tm->tm_mon = ((tm->tm_mon - 1) % MONTHS_PER_YEAR) + 1;
            }
            else if (tm->tm_mon < 1)
            {
                tm->tm_year += tm->tm_mon / MONTHS_PER_YEAR - 1;
                tm->tm_mon = tm->tm_mon % MONTHS_PER_YEAR + MONTHS_PER_YEAR;
            }

            /* adjust for end of month boundary problems... */
            if (tm->tm_mday > day_tab[isleap(tm->tm_year)][tm->tm_mon - 1])
                tm->tm_mday = (day_tab[isleap(tm->tm_year)][tm->tm_mon - 1]);

            if (tm2timestamp(tm, fsec, NULL, &timestamp) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range")));
        }

        if (span->day != 0)
        {
            struct pg_tm tt,
                       *tm = &tt;
            fsec_t      fsec;
            int         julian;

            if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range")));

            /* Add days by converting to and from Julian */
            julian = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) + span->day;
            j2date(julian, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);

            if (tm2timestamp(tm, fsec, NULL, &timestamp) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range")));
        }

        timestamp += span->time;

        if (!IS_VALID_TIMESTAMP(timestamp))
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range")));

        result = timestamp;
    }

    PG_RETURN_TIMESTAMP(result);
}

Datum
timestamp_mi_interval(PG_FUNCTION_ARGS)
{
    Timestamp   timestamp = PG_GETARG_TIMESTAMP(0);
    Interval   *span = PG_GETARG_INTERVAL_P(1);
    Interval    tspan;

    tspan.month = -span->month;
    tspan.day = -span->day;
    tspan.time = -span->time;

    return DirectFunctionCall2(timestamp_pl_interval,
                               TimestampGetDatum(timestamp),
                               PointerGetDatum(&tspan));
}


/* timestamptz_pl_interval()
 * Add an interval to a timestamp with time zone data type.
 * Note that interval has provisions for qualitative year/month
 *  units, so try to do the right thing with them.
 * To add a month, increment the month, and use the same day of month.
 * Then, if the next month has fewer days, set the day of month
 *  to the last day of month.
 * Lastly, add in the "quantitative time".
 */
Datum
timestamptz_pl_interval(PG_FUNCTION_ARGS)
{
    TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(0);
    Interval   *span = PG_GETARG_INTERVAL_P(1);
    TimestampTz result;
    int         tz;

    if (TIMESTAMP_NOT_FINITE(timestamp))
        result = timestamp;
    else
    {
        if (span->month != 0)
        {
            struct pg_tm tt,
                       *tm = &tt;
            fsec_t      fsec;

            if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range")));

            tm->tm_mon += span->month;
            if (tm->tm_mon > MONTHS_PER_YEAR)
            {
                tm->tm_year += (tm->tm_mon - 1) / MONTHS_PER_YEAR;
                tm->tm_mon = ((tm->tm_mon - 1) % MONTHS_PER_YEAR) + 1;
            }
            else if (tm->tm_mon < 1)
            {
                tm->tm_year += tm->tm_mon / MONTHS_PER_YEAR - 1;
                tm->tm_mon = tm->tm_mon % MONTHS_PER_YEAR + MONTHS_PER_YEAR;
            }

            /* adjust for end of month boundary problems... */
            if (tm->tm_mday > day_tab[isleap(tm->tm_year)][tm->tm_mon - 1])
                tm->tm_mday = (day_tab[isleap(tm->tm_year)][tm->tm_mon - 1]);

            tz = DetermineTimeZoneOffset(tm, session_timezone);

            if (tm2timestamp(tm, fsec, &tz, &timestamp) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range")));
        }

        if (span->day != 0)
        {
            struct pg_tm tt,
                       *tm = &tt;
            fsec_t      fsec;
            int         julian;

            if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range")));

            /* Add days by converting to and from Julian */
            julian = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) + span->day;
            j2date(julian, &tm->tm_year, &tm->tm_mon, &tm->tm_mday);

            tz = DetermineTimeZoneOffset(tm, session_timezone);

            if (tm2timestamp(tm, fsec, &tz, &timestamp) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range")));
        }

        timestamp += span->time;

        if (!IS_VALID_TIMESTAMP(timestamp))
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range")));

        result = timestamp;
    }

    PG_RETURN_TIMESTAMP(result);
}

Datum
timestamptz_mi_interval(PG_FUNCTION_ARGS)
{
    TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(0);
    Interval   *span = PG_GETARG_INTERVAL_P(1);
    Interval    tspan;

    tspan.month = -span->month;
    tspan.day = -span->day;
    tspan.time = -span->time;

    return DirectFunctionCall2(timestamptz_pl_interval,
                               TimestampGetDatum(timestamp),
                               PointerGetDatum(&tspan));
}


Datum
interval_um(PG_FUNCTION_ARGS)
{
    Interval   *interval = PG_GETARG_INTERVAL_P(0);
    Interval   *result;

    result = (Interval *) palloc(sizeof(Interval));

    result->time = -interval->time;
    /* overflow check copied from int4um */
    if (interval->time != 0 && SAMESIGN(result->time, interval->time))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));
    result->day = -interval->day;
    if (interval->day != 0 && SAMESIGN(result->day, interval->day))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));
    result->month = -interval->month;
    if (interval->month != 0 && SAMESIGN(result->month, interval->month))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));

    PG_RETURN_INTERVAL_P(result);
}


Datum
interval_smaller(PG_FUNCTION_ARGS)
{
    Interval   *interval1 = PG_GETARG_INTERVAL_P(0);
    Interval   *interval2 = PG_GETARG_INTERVAL_P(1);
    Interval   *result;

    /* use interval_cmp_internal to be sure this agrees with comparisons */
    if (interval_cmp_internal(interval1, interval2) < 0)
        result = interval1;
    else
        result = interval2;
    PG_RETURN_INTERVAL_P(result);
}

Datum
interval_larger(PG_FUNCTION_ARGS)
{
    Interval   *interval1 = PG_GETARG_INTERVAL_P(0);
    Interval   *interval2 = PG_GETARG_INTERVAL_P(1);
    Interval   *result;

    if (interval_cmp_internal(interval1, interval2) > 0)
        result = interval1;
    else
        result = interval2;
    PG_RETURN_INTERVAL_P(result);
}

Datum
interval_pl(PG_FUNCTION_ARGS)
{
    Interval   *span1 = PG_GETARG_INTERVAL_P(0);
    Interval   *span2 = PG_GETARG_INTERVAL_P(1);
    Interval   *result;

    result = (Interval *) palloc(sizeof(Interval));

    result->month = span1->month + span2->month;
    /* overflow check copied from int4pl */
    if (SAMESIGN(span1->month, span2->month) &&
        !SAMESIGN(result->month, span1->month))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));

    result->day = span1->day + span2->day;
    if (SAMESIGN(span1->day, span2->day) &&
        !SAMESIGN(result->day, span1->day))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));

    result->time = span1->time + span2->time;
    if (SAMESIGN(span1->time, span2->time) &&
        !SAMESIGN(result->time, span1->time))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));

    PG_RETURN_INTERVAL_P(result);
}

Datum
interval_mi(PG_FUNCTION_ARGS)
{
    Interval   *span1 = PG_GETARG_INTERVAL_P(0);
    Interval   *span2 = PG_GETARG_INTERVAL_P(1);
    Interval   *result;

    result = (Interval *) palloc(sizeof(Interval));

    result->month = span1->month - span2->month;
    /* overflow check copied from int4mi */
    if (!SAMESIGN(span1->month, span2->month) &&
        !SAMESIGN(result->month, span1->month))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));

    result->day = span1->day - span2->day;
    if (!SAMESIGN(span1->day, span2->day) &&
        !SAMESIGN(result->day, span1->day))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));

    result->time = span1->time - span2->time;
    if (!SAMESIGN(span1->time, span2->time) &&
        !SAMESIGN(result->time, span1->time))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));

    PG_RETURN_INTERVAL_P(result);
}

/*
 *  There is no interval_abs():  it is unclear what value to return:
 *    http://archives.postgresql.org/pgsql-general/2009-10/msg01031.php
 *    http://archives.postgresql.org/pgsql-general/2009-11/msg00041.php
 */

Datum
interval_mul(PG_FUNCTION_ARGS)
{
    Interval   *span = PG_GETARG_INTERVAL_P(0);
    float8      factor = PG_GETARG_FLOAT8(1);
    double      month_remainder_days,
                sec_remainder,
                result_double;
    int32       orig_month = span->month,
                orig_day = span->day;
    Interval   *result;

    result = (Interval *) palloc(sizeof(Interval));

    result_double = span->month * factor;
    if (isnan(result_double) ||
        result_double > INT_MAX || result_double < INT_MIN)
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));
    result->month = (int32) result_double;

    result_double = span->day * factor;
    if (isnan(result_double) ||
        result_double > INT_MAX || result_double < INT_MIN)
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));
    result->day = (int32) result_double;

    /*
     * The above correctly handles the whole-number part of the month and day
     * products, but we have to do something with any fractional part
     * resulting when the factor is non-integral.  We cascade the fractions
     * down to lower units using the conversion factors DAYS_PER_MONTH and
     * SECS_PER_DAY.  Note we do NOT cascade up, since we are not forced to do
     * so by the representation.  The user can choose to cascade up later,
     * using justify_hours and/or justify_days.
     */

    /*
     * Fractional months full days into days.
     *
     * Floating point calculation are inherently imprecise, so these
     * calculations are crafted to produce the most reliable result possible.
     * TSROUND() is needed to more accurately produce whole numbers where
     * appropriate.
     */
    month_remainder_days = (orig_month * factor - result->month) * DAYS_PER_MONTH;
    month_remainder_days = TSROUND(month_remainder_days);
    sec_remainder = (orig_day * factor - result->day +
                     month_remainder_days - (int) month_remainder_days) * SECS_PER_DAY;
    sec_remainder = TSROUND(sec_remainder);

    /*
     * Might have 24:00:00 hours due to rounding, or >24 hours because of time
     * cascade from months and days.  It might still be >24 if the combination
     * of cascade and the seconds factor operation itself.
     */
    if (Abs(sec_remainder) >= SECS_PER_DAY)
    {
        result->day += (int) (sec_remainder / SECS_PER_DAY);
        sec_remainder -= (int) (sec_remainder / SECS_PER_DAY) * SECS_PER_DAY;
    }

    /* cascade units down */
    result->day += (int32) month_remainder_days;
    result_double = rint(span->time * factor + sec_remainder * USECS_PER_SEC);
    if (isnan(result_double) || !FLOAT8_FITS_IN_INT64(result_double))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("interval out of range")));
    result->time = (int64) result_double;

    PG_RETURN_INTERVAL_P(result);
}

Datum
mul_d_interval(PG_FUNCTION_ARGS)
{
    /* Args are float8 and Interval *, but leave them as generic Datum */
    Datum       factor = PG_GETARG_DATUM(0);
    Datum       span = PG_GETARG_DATUM(1);

    return DirectFunctionCall2(interval_mul, span, factor);
}

Datum
interval_div(PG_FUNCTION_ARGS)
{
    Interval   *span = PG_GETARG_INTERVAL_P(0);
    float8      factor = PG_GETARG_FLOAT8(1);
    double      month_remainder_days,
                sec_remainder;
    int32       orig_month = span->month,
                orig_day = span->day;
    Interval   *result;

    result = (Interval *) palloc(sizeof(Interval));

    if (factor == 0.0)
        ereport(ERROR,
                (errcode(ERRCODE_DIVISION_BY_ZERO),
                 errmsg("division by zero")));

    result->month = (int32) (span->month / factor);
    result->day = (int32) (span->day / factor);

    /*
     * Fractional months full days into days.  See comment in interval_mul().
     */
    month_remainder_days = (orig_month / factor - result->month) * DAYS_PER_MONTH;
    month_remainder_days = TSROUND(month_remainder_days);
    sec_remainder = (orig_day / factor - result->day +
                     month_remainder_days - (int) month_remainder_days) * SECS_PER_DAY;
    sec_remainder = TSROUND(sec_remainder);
    if (Abs(sec_remainder) >= SECS_PER_DAY)
    {
        result->day += (int) (sec_remainder / SECS_PER_DAY);
        sec_remainder -= (int) (sec_remainder / SECS_PER_DAY) * SECS_PER_DAY;
    }

    /* cascade units down */
    result->day += (int32) month_remainder_days;
    result->time = rint(span->time / factor + sec_remainder * USECS_PER_SEC);

    PG_RETURN_INTERVAL_P(result);
}


/*
 * in_range support functions for timestamps and intervals.
 *
 * Per SQL spec, we support these with interval as the offset type.
 * The spec's restriction that the offset not be negative is a bit hard to
 * decipher for intervals, but we choose to interpret it the same as our
 * interval comparison operators would.
 */

Datum
in_range_timestamptz_interval(PG_FUNCTION_ARGS)
{
    TimestampTz val = PG_GETARG_TIMESTAMPTZ(0);
    TimestampTz base = PG_GETARG_TIMESTAMPTZ(1);
    Interval   *offset = PG_GETARG_INTERVAL_P(2);
    bool        sub = PG_GETARG_BOOL(3);
    bool        less = PG_GETARG_BOOL(4);
    TimestampTz sum;

    if (int128_compare(interval_cmp_value(offset), int64_to_int128(0)) < 0)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PRECEDING_OR_FOLLOWING_SIZE),
                 errmsg("invalid preceding or following size in window function")));

    /* We don't currently bother to avoid overflow hazards here */
    if (sub)
        sum = DatumGetTimestampTz(DirectFunctionCall2(timestamptz_mi_interval,
                                                      TimestampTzGetDatum(base),
                                                      IntervalPGetDatum(offset)));
    else
        sum = DatumGetTimestampTz(DirectFunctionCall2(timestamptz_pl_interval,
                                                      TimestampTzGetDatum(base),
                                                      IntervalPGetDatum(offset)));

    if (less)
        PG_RETURN_BOOL(val <= sum);
    else
        PG_RETURN_BOOL(val >= sum);
}

Datum
in_range_timestamp_interval(PG_FUNCTION_ARGS)
{
    Timestamp   val = PG_GETARG_TIMESTAMP(0);
    Timestamp   base = PG_GETARG_TIMESTAMP(1);
    Interval   *offset = PG_GETARG_INTERVAL_P(2);
    bool        sub = PG_GETARG_BOOL(3);
    bool        less = PG_GETARG_BOOL(4);
    Timestamp   sum;

    if (int128_compare(interval_cmp_value(offset), int64_to_int128(0)) < 0)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PRECEDING_OR_FOLLOWING_SIZE),
                 errmsg("invalid preceding or following size in window function")));

    /* We don't currently bother to avoid overflow hazards here */
    if (sub)
        sum = DatumGetTimestamp(DirectFunctionCall2(timestamp_mi_interval,
                                                    TimestampGetDatum(base),
                                                    IntervalPGetDatum(offset)));
    else
        sum = DatumGetTimestamp(DirectFunctionCall2(timestamp_pl_interval,
                                                    TimestampGetDatum(base),
                                                    IntervalPGetDatum(offset)));

    if (less)
        PG_RETURN_BOOL(val <= sum);
    else
        PG_RETURN_BOOL(val >= sum);
}

Datum
in_range_interval_interval(PG_FUNCTION_ARGS)
{
    Interval   *val = PG_GETARG_INTERVAL_P(0);
    Interval   *base = PG_GETARG_INTERVAL_P(1);
    Interval   *offset = PG_GETARG_INTERVAL_P(2);
    bool        sub = PG_GETARG_BOOL(3);
    bool        less = PG_GETARG_BOOL(4);
    Interval   *sum;

    if (int128_compare(interval_cmp_value(offset), int64_to_int128(0)) < 0)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PRECEDING_OR_FOLLOWING_SIZE),
                 errmsg("invalid preceding or following size in window function")));

    /* We don't currently bother to avoid overflow hazards here */
    if (sub)
        sum = DatumGetIntervalP(DirectFunctionCall2(interval_mi,
                                                    IntervalPGetDatum(base),
                                                    IntervalPGetDatum(offset)));
    else
        sum = DatumGetIntervalP(DirectFunctionCall2(interval_pl,
                                                    IntervalPGetDatum(base),
                                                    IntervalPGetDatum(offset)));

    if (less)
        PG_RETURN_BOOL(interval_cmp_internal(val, sum) <= 0);
    else
        PG_RETURN_BOOL(interval_cmp_internal(val, sum) >= 0);
}


/*
 * interval_accum, interval_accum_inv, and interval_avg implement the
 * AVG(interval) aggregate.
 *
 * The transition datatype for this aggregate is a 2-element array of
 * intervals, where the first is the running sum and the second contains
 * the number of values so far in its 'time' field.  This is a bit ugly
 * but it beats inventing a specialized datatype for the purpose.
 */

Datum
interval_accum(PG_FUNCTION_ARGS)
{
    ArrayType  *transarray = PG_GETARG_ARRAYTYPE_P(0);
    Interval   *newval = PG_GETARG_INTERVAL_P(1);
    Datum      *transdatums;
    int         ndatums;
    Interval    sumX,
                N;
    Interval   *newsum;
    ArrayType  *result;

    deconstruct_array(transarray,
                      INTERVALOID, sizeof(Interval), false, TYPALIGN_DOUBLE,
                      &transdatums, NULL, &ndatums);
    if (ndatums != 2)
        elog(ERROR, "expected 2-element interval array");

    sumX = *(DatumGetIntervalP(transdatums[0]));
    N = *(DatumGetIntervalP(transdatums[1]));

    newsum = DatumGetIntervalP(DirectFunctionCall2(interval_pl,
                                                   IntervalPGetDatum(&sumX),
                                                   IntervalPGetDatum(newval)));
    N.time += 1;

    transdatums[0] = IntervalPGetDatum(newsum);
    transdatums[1] = IntervalPGetDatum(&N);

    result = construct_array(transdatums, 2,
                             INTERVALOID, sizeof(Interval), false, TYPALIGN_DOUBLE);

    PG_RETURN_ARRAYTYPE_P(result);
}

Datum
interval_combine(PG_FUNCTION_ARGS)
{
    ArrayType  *transarray1 = PG_GETARG_ARRAYTYPE_P(0);
    ArrayType  *transarray2 = PG_GETARG_ARRAYTYPE_P(1);
    Datum      *transdatums1;
    Datum      *transdatums2;
    int         ndatums1;
    int         ndatums2;
    Interval    sum1,
                N1;
    Interval    sum2,
                N2;

    Interval   *newsum;
    ArrayType  *result;

    deconstruct_array(transarray1,
                      INTERVALOID, sizeof(Interval), false, TYPALIGN_DOUBLE,
                      &transdatums1, NULL, &ndatums1);
    if (ndatums1 != 2)
        elog(ERROR, "expected 2-element interval array");

    sum1 = *(DatumGetIntervalP(transdatums1[0]));
    N1 = *(DatumGetIntervalP(transdatums1[1]));

    deconstruct_array(transarray2,
                      INTERVALOID, sizeof(Interval), false, TYPALIGN_DOUBLE,
                      &transdatums2, NULL, &ndatums2);
    if (ndatums2 != 2)
        elog(ERROR, "expected 2-element interval array");

    sum2 = *(DatumGetIntervalP(transdatums2[0]));
    N2 = *(DatumGetIntervalP(transdatums2[1]));

    newsum = DatumGetIntervalP(DirectFunctionCall2(interval_pl,
                                                   IntervalPGetDatum(&sum1),
                                                   IntervalPGetDatum(&sum2)));
    N1.time += N2.time;

    transdatums1[0] = IntervalPGetDatum(newsum);
    transdatums1[1] = IntervalPGetDatum(&N1);

    result = construct_array(transdatums1, 2,
                             INTERVALOID, sizeof(Interval), false, TYPALIGN_DOUBLE);

    PG_RETURN_ARRAYTYPE_P(result);
}

Datum
interval_accum_inv(PG_FUNCTION_ARGS)
{
    ArrayType  *transarray = PG_GETARG_ARRAYTYPE_P(0);
    Interval   *newval = PG_GETARG_INTERVAL_P(1);
    Datum      *transdatums;
    int         ndatums;
    Interval    sumX,
                N;
    Interval   *newsum;
    ArrayType  *result;

    deconstruct_array(transarray,
                      INTERVALOID, sizeof(Interval), false, TYPALIGN_DOUBLE,
                      &transdatums, NULL, &ndatums);
    if (ndatums != 2)
        elog(ERROR, "expected 2-element interval array");

    sumX = *(DatumGetIntervalP(transdatums[0]));
    N = *(DatumGetIntervalP(transdatums[1]));

    newsum = DatumGetIntervalP(DirectFunctionCall2(interval_mi,
                                                   IntervalPGetDatum(&sumX),
                                                   IntervalPGetDatum(newval)));
    N.time -= 1;

    transdatums[0] = IntervalPGetDatum(newsum);
    transdatums[1] = IntervalPGetDatum(&N);

    result = construct_array(transdatums, 2,
                             INTERVALOID, sizeof(Interval), false, TYPALIGN_DOUBLE);

    PG_RETURN_ARRAYTYPE_P(result);
}

Datum
interval_avg(PG_FUNCTION_ARGS)
{
    ArrayType  *transarray = PG_GETARG_ARRAYTYPE_P(0);
    Datum      *transdatums;
    int         ndatums;
    Interval    sumX,
                N;

    deconstruct_array(transarray,
                      INTERVALOID, sizeof(Interval), false, TYPALIGN_DOUBLE,
                      &transdatums, NULL, &ndatums);
    if (ndatums != 2)
        elog(ERROR, "expected 2-element interval array");

    sumX = *(DatumGetIntervalP(transdatums[0]));
    N = *(DatumGetIntervalP(transdatums[1]));

    /* SQL defines AVG of no values to be NULL */
    if (N.time == 0)
        PG_RETURN_NULL();

    return DirectFunctionCall2(interval_div,
                               IntervalPGetDatum(&sumX),
                               Float8GetDatum((double) N.time));
}


/* timestamp_age()
 * Calculate time difference while retaining year/month fields.
 * Note that this does not result in an accurate absolute time span
 *  since year and month are out of context once the arithmetic
 *  is done.
 */
Datum
timestamp_age(PG_FUNCTION_ARGS)
{
    Timestamp   dt1 = PG_GETARG_TIMESTAMP(0);
    Timestamp   dt2 = PG_GETARG_TIMESTAMP(1);
    Interval   *result;
    fsec_t      fsec,
                fsec1,
                fsec2;
    struct pg_tm tt,
               *tm = &tt;
    struct pg_tm tt1,
               *tm1 = &tt1;
    struct pg_tm tt2,
               *tm2 = &tt2;

    result = (Interval *) palloc(sizeof(Interval));

    if (timestamp2tm(dt1, NULL, tm1, &fsec1, NULL, NULL) == 0 &&
        timestamp2tm(dt2, NULL, tm2, &fsec2, NULL, NULL) == 0)
    {
        /* form the symbolic difference */
        fsec = fsec1 - fsec2;
        tm->tm_sec = tm1->tm_sec - tm2->tm_sec;
        tm->tm_min = tm1->tm_min - tm2->tm_min;
        tm->tm_hour = tm1->tm_hour - tm2->tm_hour;
        tm->tm_mday = tm1->tm_mday - tm2->tm_mday;
        tm->tm_mon = tm1->tm_mon - tm2->tm_mon;
        tm->tm_year = tm1->tm_year - tm2->tm_year;

        /* flip sign if necessary... */
        if (dt1 < dt2)
        {
            fsec = -fsec;
            tm->tm_sec = -tm->tm_sec;
            tm->tm_min = -tm->tm_min;
            tm->tm_hour = -tm->tm_hour;
            tm->tm_mday = -tm->tm_mday;
            tm->tm_mon = -tm->tm_mon;
            tm->tm_year = -tm->tm_year;
        }

        /* propagate any negative fields into the next higher field */
        while (fsec < 0)
        {
            fsec += USECS_PER_SEC;
            tm->tm_sec--;
        }

        while (tm->tm_sec < 0)
        {
            tm->tm_sec += SECS_PER_MINUTE;
            tm->tm_min--;
        }

        while (tm->tm_min < 0)
        {
            tm->tm_min += MINS_PER_HOUR;
            tm->tm_hour--;
        }

        while (tm->tm_hour < 0)
        {
            tm->tm_hour += HOURS_PER_DAY;
            tm->tm_mday--;
        }

        while (tm->tm_mday < 0)
        {
            if (dt1 < dt2)
            {
                tm->tm_mday += day_tab[isleap(tm1->tm_year)][tm1->tm_mon - 1];
                tm->tm_mon--;
            }
            else
            {
                tm->tm_mday += day_tab[isleap(tm2->tm_year)][tm2->tm_mon - 1];
                tm->tm_mon--;
            }
        }

        while (tm->tm_mon < 0)
        {
            tm->tm_mon += MONTHS_PER_YEAR;
            tm->tm_year--;
        }

        /* recover sign if necessary... */
        if (dt1 < dt2)
        {
            fsec = -fsec;
            tm->tm_sec = -tm->tm_sec;
            tm->tm_min = -tm->tm_min;
            tm->tm_hour = -tm->tm_hour;
            tm->tm_mday = -tm->tm_mday;
            tm->tm_mon = -tm->tm_mon;
            tm->tm_year = -tm->tm_year;
        }

        if (tm2interval(tm, fsec, result) != 0)
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("interval out of range")));
    }
    else
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    PG_RETURN_INTERVAL_P(result);
}


/* timestamptz_age()
 * Calculate time difference while retaining year/month fields.
 * Note that this does not result in an accurate absolute time span
 *  since year and month are out of context once the arithmetic
 *  is done.
 */
Datum
timestamptz_age(PG_FUNCTION_ARGS)
{
    TimestampTz dt1 = PG_GETARG_TIMESTAMPTZ(0);
    TimestampTz dt2 = PG_GETARG_TIMESTAMPTZ(1);
    Interval   *result;
    fsec_t      fsec,
                fsec1,
                fsec2;
    struct pg_tm tt,
               *tm = &tt;
    struct pg_tm tt1,
               *tm1 = &tt1;
    struct pg_tm tt2,
               *tm2 = &tt2;
    int         tz1;
    int         tz2;

    result = (Interval *) palloc(sizeof(Interval));

    if (timestamp2tm(dt1, &tz1, tm1, &fsec1, NULL, NULL) == 0 &&
        timestamp2tm(dt2, &tz2, tm2, &fsec2, NULL, NULL) == 0)
    {
        /* form the symbolic difference */
        fsec = fsec1 - fsec2;
        tm->tm_sec = tm1->tm_sec - tm2->tm_sec;
        tm->tm_min = tm1->tm_min - tm2->tm_min;
        tm->tm_hour = tm1->tm_hour - tm2->tm_hour;
        tm->tm_mday = tm1->tm_mday - tm2->tm_mday;
        tm->tm_mon = tm1->tm_mon - tm2->tm_mon;
        tm->tm_year = tm1->tm_year - tm2->tm_year;

        /* flip sign if necessary... */
        if (dt1 < dt2)
        {
            fsec = -fsec;
            tm->tm_sec = -tm->tm_sec;
            tm->tm_min = -tm->tm_min;
            tm->tm_hour = -tm->tm_hour;
            tm->tm_mday = -tm->tm_mday;
            tm->tm_mon = -tm->tm_mon;
            tm->tm_year = -tm->tm_year;
        }

        /* propagate any negative fields into the next higher field */
        while (fsec < 0)
        {
            fsec += USECS_PER_SEC;
            tm->tm_sec--;
        }

        while (tm->tm_sec < 0)
        {
            tm->tm_sec += SECS_PER_MINUTE;
            tm->tm_min--;
        }

        while (tm->tm_min < 0)
        {
            tm->tm_min += MINS_PER_HOUR;
            tm->tm_hour--;
        }

        while (tm->tm_hour < 0)
        {
            tm->tm_hour += HOURS_PER_DAY;
            tm->tm_mday--;
        }

        while (tm->tm_mday < 0)
        {
            if (dt1 < dt2)
            {
                tm->tm_mday += day_tab[isleap(tm1->tm_year)][tm1->tm_mon - 1];
                tm->tm_mon--;
            }
            else
            {
                tm->tm_mday += day_tab[isleap(tm2->tm_year)][tm2->tm_mon - 1];
                tm->tm_mon--;
            }
        }

        while (tm->tm_mon < 0)
        {
            tm->tm_mon += MONTHS_PER_YEAR;
            tm->tm_year--;
        }

        /*
         * Note: we deliberately ignore any difference between tz1 and tz2.
         */

        /* recover sign if necessary... */
        if (dt1 < dt2)
        {
            fsec = -fsec;
            tm->tm_sec = -tm->tm_sec;
            tm->tm_min = -tm->tm_min;
            tm->tm_hour = -tm->tm_hour;
            tm->tm_mday = -tm->tm_mday;
            tm->tm_mon = -tm->tm_mon;
            tm->tm_year = -tm->tm_year;
        }

        if (tm2interval(tm, fsec, result) != 0)
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("interval out of range")));
    }
    else
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    PG_RETURN_INTERVAL_P(result);
}


/*----------------------------------------------------------
 *  Conversion operators.
 *---------------------------------------------------------*/


/* timestamp_trunc()
 * Truncate timestamp to specified units.
 */
Datum
timestamp_trunc(PG_FUNCTION_ARGS)
{
    text       *units = PG_GETARG_TEXT_PP(0);
    Timestamp   timestamp = PG_GETARG_TIMESTAMP(1);
    Timestamp   result;
    int         type,
                val;
    char       *lowunits;
    fsec_t      fsec;
    struct pg_tm tt,
               *tm = &tt;

    if (TIMESTAMP_NOT_FINITE(timestamp))
        PG_RETURN_TIMESTAMP(timestamp);

    lowunits = downcase_truncate_identifier(VARDATA_ANY(units),
                                            VARSIZE_ANY_EXHDR(units),
                                            false);

    type = DecodeUnits(0, lowunits, &val);

    if (type == UNITS)
    {
        if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range")));

        switch (val)
        {
            case DTK_WEEK:
                {
                    int         woy;

                    woy = date2isoweek(tm->tm_year, tm->tm_mon, tm->tm_mday);

                    /*
                     * If it is week 52/53 and the month is January, then the
                     * week must belong to the previous year. Also, some
                     * December dates belong to the next year.
                     */
                    if (woy >= 52 && tm->tm_mon == 1)
                        --tm->tm_year;
                    if (woy <= 1 && tm->tm_mon == MONTHS_PER_YEAR)
                        ++tm->tm_year;
                    isoweek2date(woy, &(tm->tm_year), &(tm->tm_mon), &(tm->tm_mday));
                    tm->tm_hour = 0;
                    tm->tm_min = 0;
                    tm->tm_sec = 0;
                    fsec = 0;
                    break;
                }
            case DTK_MILLENNIUM:
                /* see comments in timestamptz_trunc */
                if (tm->tm_year > 0)
                    tm->tm_year = ((tm->tm_year + 999) / 1000) * 1000 - 999;
                else
                    tm->tm_year = -((999 - (tm->tm_year - 1)) / 1000) * 1000 + 1;
                /* FALL THRU */
            case DTK_CENTURY:
                /* see comments in timestamptz_trunc */
                if (tm->tm_year > 0)
                    tm->tm_year = ((tm->tm_year + 99) / 100) * 100 - 99;
                else
                    tm->tm_year = -((99 - (tm->tm_year - 1)) / 100) * 100 + 1;
                /* FALL THRU */
            case DTK_DECADE:
                /* see comments in timestamptz_trunc */
                if (val != DTK_MILLENNIUM && val != DTK_CENTURY)
                {
                    if (tm->tm_year > 0)
                        tm->tm_year = (tm->tm_year / 10) * 10;
                    else
                        tm->tm_year = -((8 - (tm->tm_year - 1)) / 10) * 10;
                }
                /* FALL THRU */
            case DTK_YEAR:
                tm->tm_mon = 1;
                /* FALL THRU */
            case DTK_QUARTER:
                tm->tm_mon = (3 * ((tm->tm_mon - 1) / 3)) + 1;
                /* FALL THRU */
            case DTK_MONTH:
                tm->tm_mday = 1;
                /* FALL THRU */
            case DTK_DAY:
                tm->tm_hour = 0;
                /* FALL THRU */
            case DTK_HOUR:
                tm->tm_min = 0;
                /* FALL THRU */
            case DTK_MINUTE:
                tm->tm_sec = 0;
                /* FALL THRU */
            case DTK_SECOND:
                fsec = 0;
                break;

            case DTK_MILLISEC:
                fsec = (fsec / 1000) * 1000;
                break;

            case DTK_MICROSEC:
                break;

            default:
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("timestamp units \"%s\" not supported",
                                lowunits)));
                result = 0;
        }

        if (tm2timestamp(tm, fsec, NULL, &result) != 0)
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range")));
    }
    else
    {
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("timestamp units \"%s\" not recognized",
                        lowunits)));
        result = 0;
    }

    PG_RETURN_TIMESTAMP(result);
}

/*
 * Common code for timestamptz_trunc() and timestamptz_trunc_zone().
 *
 * tzp identifies the zone to truncate with respect to.  We assume
 * infinite timestamps have already been rejected.
 */
static TimestampTz
timestamptz_trunc_internal(text *units, TimestampTz timestamp, pg_tz *tzp)
{
    TimestampTz result;
    int         tz;
    int         type,
                val;
    bool        redotz = false;
    char       *lowunits;
    fsec_t      fsec;
    struct pg_tm tt,
               *tm = &tt;

    lowunits = downcase_truncate_identifier(VARDATA_ANY(units),
                                            VARSIZE_ANY_EXHDR(units),
                                            false);

    type = DecodeUnits(0, lowunits, &val);

    if (type == UNITS)
    {
        if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, tzp) != 0)
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range")));

        switch (val)
        {
            case DTK_WEEK:
                {
                    int         woy;

                    woy = date2isoweek(tm->tm_year, tm->tm_mon, tm->tm_mday);

                    /*
                     * If it is week 52/53 and the month is January, then the
                     * week must belong to the previous year. Also, some
                     * December dates belong to the next year.
                     */
                    if (woy >= 52 && tm->tm_mon == 1)
                        --tm->tm_year;
                    if (woy <= 1 && tm->tm_mon == MONTHS_PER_YEAR)
                        ++tm->tm_year;
                    isoweek2date(woy, &(tm->tm_year), &(tm->tm_mon), &(tm->tm_mday));
                    tm->tm_hour = 0;
                    tm->tm_min = 0;
                    tm->tm_sec = 0;
                    fsec = 0;
                    redotz = true;
                    break;
                }
                /* one may consider DTK_THOUSAND and DTK_HUNDRED... */
            case DTK_MILLENNIUM:

                /*
                 * truncating to the millennium? what is this supposed to
                 * mean? let us put the first year of the millennium... i.e.
                 * -1000, 1, 1001, 2001...
                 */
                if (tm->tm_year > 0)
                    tm->tm_year = ((tm->tm_year + 999) / 1000) * 1000 - 999;
                else
                    tm->tm_year = -((999 - (tm->tm_year - 1)) / 1000) * 1000 + 1;
                /* FALL THRU */
            case DTK_CENTURY:
                /* truncating to the century? as above: -100, 1, 101... */
                if (tm->tm_year > 0)
                    tm->tm_year = ((tm->tm_year + 99) / 100) * 100 - 99;
                else
                    tm->tm_year = -((99 - (tm->tm_year - 1)) / 100) * 100 + 1;
                /* FALL THRU */
            case DTK_DECADE:

                /*
                 * truncating to the decade? first year of the decade. must
                 * not be applied if year was truncated before!
                 */
                if (val != DTK_MILLENNIUM && val != DTK_CENTURY)
                {
                    if (tm->tm_year > 0)
                        tm->tm_year = (tm->tm_year / 10) * 10;
                    else
                        tm->tm_year = -((8 - (tm->tm_year - 1)) / 10) * 10;
                }
                /* FALL THRU */
            case DTK_YEAR:
                tm->tm_mon = 1;
                /* FALL THRU */
            case DTK_QUARTER:
                tm->tm_mon = (3 * ((tm->tm_mon - 1) / 3)) + 1;
                /* FALL THRU */
            case DTK_MONTH:
                tm->tm_mday = 1;
                /* FALL THRU */
            case DTK_DAY:
                tm->tm_hour = 0;
                redotz = true;  /* for all cases >= DAY */
                /* FALL THRU */
            case DTK_HOUR:
                tm->tm_min = 0;
                /* FALL THRU */
            case DTK_MINUTE:
                tm->tm_sec = 0;
                /* FALL THRU */
            case DTK_SECOND:
                fsec = 0;
                break;
            case DTK_MILLISEC:
                fsec = (fsec / 1000) * 1000;
                break;
            case DTK_MICROSEC:
                break;

            default:
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("timestamp with time zone units \"%s\" not "
                                "supported", lowunits)));
                result = 0;
        }

        if (redotz)
            tz = DetermineTimeZoneOffset(tm, tzp);

        if (tm2timestamp(tm, fsec, &tz, &result) != 0)
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range")));
    }
    else
    {
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("timestamp with time zone units \"%s\" not recognized",
                        lowunits)));
        result = 0;
    }

    return result;
}

/* timestamptz_trunc()
 * Truncate timestamptz to specified units in session timezone.
 */
Datum
timestamptz_trunc(PG_FUNCTION_ARGS)
{
    text       *units = PG_GETARG_TEXT_PP(0);
    TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(1);
    TimestampTz result;

    if (TIMESTAMP_NOT_FINITE(timestamp))
        PG_RETURN_TIMESTAMPTZ(timestamp);

    result = timestamptz_trunc_internal(units, timestamp, session_timezone);

    PG_RETURN_TIMESTAMPTZ(result);
}

/* timestamptz_trunc_zone()
 * Truncate timestamptz to specified units in specified timezone.
 */
Datum
timestamptz_trunc_zone(PG_FUNCTION_ARGS)
{
    text       *units = PG_GETARG_TEXT_PP(0);
    TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(1);
    text       *zone = PG_GETARG_TEXT_PP(2);
    TimestampTz result;
    char        tzname[TZ_STRLEN_MAX + 1];
    char       *lowzone;
    int         type,
                val;
    pg_tz      *tzp;

    /*
     * timestamptz_zone() doesn't look up the zone for infinite inputs, so we
     * don't do so here either.
     */
    if (TIMESTAMP_NOT_FINITE(timestamp))
        PG_RETURN_TIMESTAMP(timestamp);

    /*
     * Look up the requested timezone (see notes in timestamptz_zone()).
     */
    text_to_cstring_buffer(zone, tzname, sizeof(tzname));

    /* DecodeTimezoneAbbrev requires lowercase input */
    lowzone = downcase_truncate_identifier(tzname,
                                           strlen(tzname),
                                           false);

    type = DecodeTimezoneAbbrev(0, lowzone, &val, &tzp);

    if (type == TZ || type == DTZ)
    {
        /* fixed-offset abbreviation, get a pg_tz descriptor for that */
        tzp = pg_tzset_offset(-val);
    }
    else if (type == DYNTZ)
    {
        /* dynamic-offset abbreviation, use its referenced timezone */
    }
    else
    {
        /* try it as a full zone name */
        tzp = pg_tzset(tzname);
        if (!tzp)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("time zone \"%s\" not recognized", tzname)));
    }

    result = timestamptz_trunc_internal(units, timestamp, tzp);

    PG_RETURN_TIMESTAMPTZ(result);
}

/* interval_trunc()
 * Extract specified field from interval.
 */
Datum
interval_trunc(PG_FUNCTION_ARGS)
{
    text       *units = PG_GETARG_TEXT_PP(0);
    Interval   *interval = PG_GETARG_INTERVAL_P(1);
    Interval   *result;
    int         type,
                val;
    char       *lowunits;
    fsec_t      fsec;
    struct pg_tm tt,
               *tm = &tt;

    result = (Interval *) palloc(sizeof(Interval));

    lowunits = downcase_truncate_identifier(VARDATA_ANY(units),
                                            VARSIZE_ANY_EXHDR(units),
                                            false);

    type = DecodeUnits(0, lowunits, &val);

    if (type == UNITS)
    {
        if (interval2tm(*interval, tm, &fsec) == 0)
        {
            switch (val)
            {
                case DTK_MILLENNIUM:
                    /* caution: C division may have negative remainder */
                    tm->tm_year = (tm->tm_year / 1000) * 1000;
                    /* FALL THRU */
                case DTK_CENTURY:
                    /* caution: C division may have negative remainder */
                    tm->tm_year = (tm->tm_year / 100) * 100;
                    /* FALL THRU */
                case DTK_DECADE:
                    /* caution: C division may have negative remainder */
                    tm->tm_year = (tm->tm_year / 10) * 10;
                    /* FALL THRU */
                case DTK_YEAR:
                    tm->tm_mon = 0;
                    /* FALL THRU */
                case DTK_QUARTER:
                    tm->tm_mon = 3 * (tm->tm_mon / 3);
                    /* FALL THRU */
                case DTK_MONTH:
                    tm->tm_mday = 0;
                    /* FALL THRU */
                case DTK_DAY:
                    tm->tm_hour = 0;
                    /* FALL THRU */
                case DTK_HOUR:
                    tm->tm_min = 0;
                    /* FALL THRU */
                case DTK_MINUTE:
                    tm->tm_sec = 0;
                    /* FALL THRU */
                case DTK_SECOND:
                    fsec = 0;
                    break;
                case DTK_MILLISEC:
                    fsec = (fsec / 1000) * 1000;
                    break;
                case DTK_MICROSEC:
                    break;

                default:
                    if (val == DTK_WEEK)
                        ereport(ERROR,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("interval units \"%s\" not supported "
                                        "because months usually have fractional weeks",
                                        lowunits)));
                    else
                        ereport(ERROR,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("interval units \"%s\" not supported",
                                        lowunits)));
            }

            if (tm2interval(tm, fsec, result) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("interval out of range")));
        }
        else
            elog(ERROR, "could not convert interval to tm");
    }
    else
    {
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("interval units \"%s\" not recognized",
                        lowunits)));
    }

    PG_RETURN_INTERVAL_P(result);
}

/* isoweek2j()
 *
 *  Return the Julian day which corresponds to the first day (Monday) of the given ISO 8601 year and week.
 *  Julian days are used to convert between ISO week dates and Gregorian dates.
 */
int
isoweek2j(int year, int week)
{
    int         day0,
                day4;

    /* fourth day of current year */
    day4 = date2j(year, 1, 4);

    /* day0 == offset to first day of week (Monday) */
    day0 = j2day(day4 - 1);

    return ((week - 1) * 7) + (day4 - day0);
}

/* isoweek2date()
 * Convert ISO week of year number to date.
 * The year field must be specified with the ISO year!
 * karel 2000/08/07
 */
void
isoweek2date(int woy, int *year, int *mon, int *mday)
{
    j2date(isoweek2j(*year, woy), year, mon, mday);
}

/* isoweekdate2date()
 *
 *  Convert an ISO 8601 week date (ISO year, ISO week) into a Gregorian date.
 *  Gregorian day of week sent so weekday strings can be supplied.
 *  Populates year, mon, and mday with the correct Gregorian values.
 *  year must be passed in as the ISO year.
 */
void
isoweekdate2date(int isoweek, int wday, int *year, int *mon, int *mday)
{
    int         jday;

    jday = isoweek2j(*year, isoweek);
    /* convert Gregorian week start (Sunday=1) to ISO week start (Monday=1) */
    if (wday > 1)
        jday += wday - 2;
    else
        jday += 6;
    j2date(jday, year, mon, mday);
}

/* date2isoweek()
 *
 *  Returns ISO week number of year.
 */
int
date2isoweek(int year, int mon, int mday)
{
    float8      result;
    int         day0,
                day4,
                dayn;

    /* current day */
    dayn = date2j(year, mon, mday);

    /* fourth day of current year */
    day4 = date2j(year, 1, 4);

    /* day0 == offset to first day of week (Monday) */
    day0 = j2day(day4 - 1);

    /*
     * We need the first week containing a Thursday, otherwise this day falls
     * into the previous year for purposes of counting weeks
     */
    if (dayn < day4 - day0)
    {
        day4 = date2j(year - 1, 1, 4);

        /* day0 == offset to first day of week (Monday) */
        day0 = j2day(day4 - 1);
    }

    result = (dayn - (day4 - day0)) / 7 + 1;

    /*
     * Sometimes the last few days in a year will fall into the first week of
     * the next year, so check for this.
     */
    if (result >= 52)
    {
        day4 = date2j(year + 1, 1, 4);

        /* day0 == offset to first day of week (Monday) */
        day0 = j2day(day4 - 1);

        if (dayn >= day4 - day0)
            result = (dayn - (day4 - day0)) / 7 + 1;
    }

    return (int) result;
}


/* date2isoyear()
 *
 *  Returns ISO 8601 year number.
 *  Note: zero or negative results follow the year-zero-exists convention.
 */
int
date2isoyear(int year, int mon, int mday)
{
    float8      result;
    int         day0,
                day4,
                dayn;

    /* current day */
    dayn = date2j(year, mon, mday);

    /* fourth day of current year */
    day4 = date2j(year, 1, 4);

    /* day0 == offset to first day of week (Monday) */
    day0 = j2day(day4 - 1);

    /*
     * We need the first week containing a Thursday, otherwise this day falls
     * into the previous year for purposes of counting weeks
     */
    if (dayn < day4 - day0)
    {
        day4 = date2j(year - 1, 1, 4);

        /* day0 == offset to first day of week (Monday) */
        day0 = j2day(day4 - 1);

        year--;
    }

    result = (dayn - (day4 - day0)) / 7 + 1;

    /*
     * Sometimes the last few days in a year will fall into the first week of
     * the next year, so check for this.
     */
    if (result >= 52)
    {
        day4 = date2j(year + 1, 1, 4);

        /* day0 == offset to first day of week (Monday) */
        day0 = j2day(day4 - 1);

        if (dayn >= day4 - day0)
            year++;
    }

    return year;
}


/* date2isoyearday()
 *
 *  Returns the ISO 8601 day-of-year, given a Gregorian year, month and day.
 *  Possible return values are 1 through 371 (364 in non-leap years).
 */
int
date2isoyearday(int year, int mon, int mday)
{
    return date2j(year, mon, mday) - isoweek2j(date2isoyear(year, mon, mday), 1) + 1;
}

/*
 * NonFiniteTimestampTzPart
 *
 *  Used by timestamp_part and timestamptz_part when extracting from infinite
 *  timestamp[tz].  Returns +/-Infinity if that is the appropriate result,
 *  otherwise returns zero (which should be taken as meaning to return NULL).
 *
 *  Errors thrown here for invalid units should exactly match those that
 *  would be thrown in the calling functions, else there will be unexpected
 *  discrepancies between finite- and infinite-input cases.
 */
static float8
NonFiniteTimestampTzPart(int type, int unit, char *lowunits,
                         bool isNegative, bool isTz)
{
    if ((type != UNITS) && (type != RESERV))
    {
        if (isTz)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("timestamp with time zone units \"%s\" not recognized",
                            lowunits)));
        else
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("timestamp units \"%s\" not recognized",
                            lowunits)));
    }

    switch (unit)
    {
            /* Oscillating units */
        case DTK_MICROSEC:
        case DTK_MILLISEC:
        case DTK_SECOND:
        case DTK_MINUTE:
        case DTK_HOUR:
        case DTK_DAY:
        case DTK_MONTH:
        case DTK_QUARTER:
        case DTK_WEEK:
        case DTK_DOW:
        case DTK_ISODOW:
        case DTK_DOY:
        case DTK_TZ:
        case DTK_TZ_MINUTE:
        case DTK_TZ_HOUR:
            return 0.0;

            /* Monotonically-increasing units */
        case DTK_YEAR:
        case DTK_DECADE:
        case DTK_CENTURY:
        case DTK_MILLENNIUM:
        case DTK_JULIAN:
        case DTK_ISOYEAR:
        case DTK_EPOCH:
            if (isNegative)
                return -get_float8_infinity();
            else
                return get_float8_infinity();

        default:
            if (isTz)
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("timestamp with time zone units \"%s\" not supported",
                                lowunits)));
            else
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("timestamp units \"%s\" not supported",
                                lowunits)));
            return 0.0;         /* keep compiler quiet */
    }
}

/* timestamp_part()
 * Extract specified field from timestamp.
 */
Datum
timestamp_part(PG_FUNCTION_ARGS)
{
    text       *units = PG_GETARG_TEXT_PP(0);
    Timestamp   timestamp = PG_GETARG_TIMESTAMP(1);
    float8      result;
    Timestamp   epoch;
    int         type,
                val;
    char       *lowunits;
    fsec_t      fsec;
    struct pg_tm tt,
               *tm = &tt;

    lowunits = downcase_truncate_identifier(VARDATA_ANY(units),
                                            VARSIZE_ANY_EXHDR(units),
                                            false);

    type = DecodeUnits(0, lowunits, &val);
    if (type == UNKNOWN_FIELD)
        type = DecodeSpecial(0, lowunits, &val);

    if (TIMESTAMP_NOT_FINITE(timestamp))
    {
        result = NonFiniteTimestampTzPart(type, val, lowunits,
                                          TIMESTAMP_IS_NOBEGIN(timestamp),
                                          false);
        if (result)
            PG_RETURN_FLOAT8(result);
        else
            PG_RETURN_NULL();
    }

    if (type == UNITS)
    {
        if (timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL) != 0)
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range")));

        switch (val)
        {
            case DTK_MICROSEC:
                result = tm->tm_sec * 1000000.0 + fsec;
                break;

            case DTK_MILLISEC:
                result = tm->tm_sec * 1000.0 + fsec / 1000.0;
                break;

            case DTK_SECOND:
                result = tm->tm_sec + fsec / 1000000.0;
                break;

            case DTK_MINUTE:
                result = tm->tm_min;
                break;

            case DTK_HOUR:
                result = tm->tm_hour;
                break;

            case DTK_DAY:
                result = tm->tm_mday;
                break;

            case DTK_MONTH:
                result = tm->tm_mon;
                break;

            case DTK_QUARTER:
                result = (tm->tm_mon - 1) / 3 + 1;
                break;

            case DTK_WEEK:
                result = (float8) date2isoweek(tm->tm_year, tm->tm_mon, tm->tm_mday);
                break;

            case DTK_YEAR:
                if (tm->tm_year > 0)
                    result = tm->tm_year;
                else
                    /* there is no year 0, just 1 BC and 1 AD */
                    result = tm->tm_year - 1;
                break;

            case DTK_DECADE:

                /*
                 * what is a decade wrt dates? let us assume that decade 199
                 * is 1990 thru 1999... decade 0 starts on year 1 BC, and -1
                 * is 11 BC thru 2 BC...
                 */
                if (tm->tm_year >= 0)
                    result = tm->tm_year / 10;
                else
                    result = -((8 - (tm->tm_year - 1)) / 10);
                break;

            case DTK_CENTURY:

                /* ----
                 * centuries AD, c>0: year in [ (c-1)* 100 + 1 : c*100 ]
                 * centuries BC, c<0: year in [ c*100 : (c+1) * 100 - 1]
                 * there is no number 0 century.
                 * ----
                 */
                if (tm->tm_year > 0)
                    result = (tm->tm_year + 99) / 100;
                else
                    /* caution: C division may have negative remainder */
                    result = -((99 - (tm->tm_year - 1)) / 100);
                break;

            case DTK_MILLENNIUM:
                /* see comments above. */
                if (tm->tm_year > 0)
                    result = (tm->tm_year + 999) / 1000;
                else
                    result = -((999 - (tm->tm_year - 1)) / 1000);
                break;

            case DTK_JULIAN:
                result = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
                result += ((((tm->tm_hour * MINS_PER_HOUR) + tm->tm_min) * SECS_PER_MINUTE) +
                           tm->tm_sec + (fsec / 1000000.0)) / (double) SECS_PER_DAY;
                break;

            case DTK_ISOYEAR:
                result = date2isoyear(tm->tm_year, tm->tm_mon, tm->tm_mday);
                /* Adjust BC years */
                if (result <= 0)
                    result -= 1;
                break;

            case DTK_DOW:
            case DTK_ISODOW:
                result = j2day(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday));
                if (val == DTK_ISODOW && result == 0)
                    result = 7;
                break;

            case DTK_DOY:
                result = (date2j(tm->tm_year, tm->tm_mon, tm->tm_mday)
                          - date2j(tm->tm_year, 1, 1) + 1);
                break;

            case DTK_TZ:
            case DTK_TZ_MINUTE:
            case DTK_TZ_HOUR:
            default:
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("timestamp units \"%s\" not supported",
                                lowunits)));
                result = 0;
        }
    }
    else if (type == RESERV)
    {
        switch (val)
        {
            case DTK_EPOCH:
                epoch = SetEpochTimestamp();
                /* try to avoid precision loss in subtraction */
                if (timestamp < (PG_INT64_MAX + epoch))
                    result = (timestamp - epoch) / 1000000.0;
                else
                    result = ((float8) timestamp - epoch) / 1000000.0;
                break;

            default:
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("timestamp units \"%s\" not supported",
                                lowunits)));
                result = 0;
        }

    }
    else
    {
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("timestamp units \"%s\" not recognized", lowunits)));
        result = 0;
    }

    PG_RETURN_FLOAT8(result);
}

/* timestamptz_part()
 * Extract specified field from timestamp with time zone.
 */
Datum
timestamptz_part(PG_FUNCTION_ARGS)
{
    text       *units = PG_GETARG_TEXT_PP(0);
    TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(1);
    float8      result;
    Timestamp   epoch;
    int         tz;
    int         type,
                val;
    char       *lowunits;
    double      dummy;
    fsec_t      fsec;
    struct pg_tm tt,
               *tm = &tt;

    lowunits = downcase_truncate_identifier(VARDATA_ANY(units),
                                            VARSIZE_ANY_EXHDR(units),
                                            false);

    type = DecodeUnits(0, lowunits, &val);
    if (type == UNKNOWN_FIELD)
        type = DecodeSpecial(0, lowunits, &val);

    if (TIMESTAMP_NOT_FINITE(timestamp))
    {
        result = NonFiniteTimestampTzPart(type, val, lowunits,
                                          TIMESTAMP_IS_NOBEGIN(timestamp),
                                          true);
        if (result)
            PG_RETURN_FLOAT8(result);
        else
            PG_RETURN_NULL();
    }

    if (type == UNITS)
    {
        if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range")));

        switch (val)
        {
            case DTK_TZ:
                result = -tz;
                break;

            case DTK_TZ_MINUTE:
                result = -tz;
                result /= MINS_PER_HOUR;
                FMODULO(result, dummy, (double) MINS_PER_HOUR);
                break;

            case DTK_TZ_HOUR:
                dummy = -tz;
                FMODULO(dummy, result, (double) SECS_PER_HOUR);
                break;

            case DTK_MICROSEC:
                result = tm->tm_sec * 1000000.0 + fsec;
                break;

            case DTK_MILLISEC:
                result = tm->tm_sec * 1000.0 + fsec / 1000.0;
                break;

            case DTK_SECOND:
                result = tm->tm_sec + fsec / 1000000.0;
                break;

            case DTK_MINUTE:
                result = tm->tm_min;
                break;

            case DTK_HOUR:
                result = tm->tm_hour;
                break;

            case DTK_DAY:
                result = tm->tm_mday;
                break;

            case DTK_MONTH:
                result = tm->tm_mon;
                break;

            case DTK_QUARTER:
                result = (tm->tm_mon - 1) / 3 + 1;
                break;

            case DTK_WEEK:
                result = (float8) date2isoweek(tm->tm_year, tm->tm_mon, tm->tm_mday);
                break;

            case DTK_YEAR:
                if (tm->tm_year > 0)
                    result = tm->tm_year;
                else
                    /* there is no year 0, just 1 BC and 1 AD */
                    result = tm->tm_year - 1;
                break;

            case DTK_DECADE:
                /* see comments in timestamp_part */
                if (tm->tm_year > 0)
                    result = tm->tm_year / 10;
                else
                    result = -((8 - (tm->tm_year - 1)) / 10);
                break;

            case DTK_CENTURY:
                /* see comments in timestamp_part */
                if (tm->tm_year > 0)
                    result = (tm->tm_year + 99) / 100;
                else
                    result = -((99 - (tm->tm_year - 1)) / 100);
                break;

            case DTK_MILLENNIUM:
                /* see comments in timestamp_part */
                if (tm->tm_year > 0)
                    result = (tm->tm_year + 999) / 1000;
                else
                    result = -((999 - (tm->tm_year - 1)) / 1000);
                break;

            case DTK_JULIAN:
                result = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
                result += ((((tm->tm_hour * MINS_PER_HOUR) + tm->tm_min) * SECS_PER_MINUTE) +
                           tm->tm_sec + (fsec / 1000000.0)) / (double) SECS_PER_DAY;
                break;

            case DTK_ISOYEAR:
                result = date2isoyear(tm->tm_year, tm->tm_mon, tm->tm_mday);
                /* Adjust BC years */
                if (result <= 0)
                    result -= 1;
                break;

            case DTK_DOW:
            case DTK_ISODOW:
                result = j2day(date2j(tm->tm_year, tm->tm_mon, tm->tm_mday));
                if (val == DTK_ISODOW && result == 0)
                    result = 7;
                break;

            case DTK_DOY:
                result = (date2j(tm->tm_year, tm->tm_mon, tm->tm_mday)
                          - date2j(tm->tm_year, 1, 1) + 1);
                break;

            default:
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("timestamp with time zone units \"%s\" not supported",
                                lowunits)));
                result = 0;
        }

    }
    else if (type == RESERV)
    {
        switch (val)
        {
            case DTK_EPOCH:
                epoch = SetEpochTimestamp();
                /* try to avoid precision loss in subtraction */
                if (timestamp < (PG_INT64_MAX + epoch))
                    result = (timestamp - epoch) / 1000000.0;
                else
                    result = ((float8) timestamp - epoch) / 1000000.0;
                break;

            default:
                ereport(ERROR,
                        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                         errmsg("timestamp with time zone units \"%s\" not supported",
                                lowunits)));
                result = 0;
        }
    }
    else
    {
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("timestamp with time zone units \"%s\" not recognized",
                        lowunits)));

        result = 0;
    }

    PG_RETURN_FLOAT8(result);
}


/* interval_part()
 * Extract specified field from interval.
 */
Datum
interval_part(PG_FUNCTION_ARGS)
{
    text       *units = PG_GETARG_TEXT_PP(0);
    Interval   *interval = PG_GETARG_INTERVAL_P(1);
    float8      result;
    int         type,
                val;
    char       *lowunits;
    fsec_t      fsec;
    struct pg_tm tt,
               *tm = &tt;

    lowunits = downcase_truncate_identifier(VARDATA_ANY(units),
                                            VARSIZE_ANY_EXHDR(units),
                                            false);

    type = DecodeUnits(0, lowunits, &val);
    if (type == UNKNOWN_FIELD)
        type = DecodeSpecial(0, lowunits, &val);

    if (type == UNITS)
    {
        if (interval2tm(*interval, tm, &fsec) == 0)
        {
            switch (val)
            {
                case DTK_MICROSEC:
                    result = tm->tm_sec * 1000000.0 + fsec;
                    break;

                case DTK_MILLISEC:
                    result = tm->tm_sec * 1000.0 + fsec / 1000.0;
                    break;

                case DTK_SECOND:
                    result = tm->tm_sec + fsec / 1000000.0;
                    break;

                case DTK_MINUTE:
                    result = tm->tm_min;
                    break;

                case DTK_HOUR:
                    result = tm->tm_hour;
                    break;

                case DTK_DAY:
                    result = tm->tm_mday;
                    break;

                case DTK_MONTH:
                    result = tm->tm_mon;
                    break;

                case DTK_QUARTER:
                    result = (tm->tm_mon / 3) + 1;
                    break;

                case DTK_YEAR:
                    result = tm->tm_year;
                    break;

                case DTK_DECADE:
                    /* caution: C division may have negative remainder */
                    result = tm->tm_year / 10;
                    break;

                case DTK_CENTURY:
                    /* caution: C division may have negative remainder */
                    result = tm->tm_year / 100;
                    break;

                case DTK_MILLENNIUM:
                    /* caution: C division may have negative remainder */
                    result = tm->tm_year / 1000;
                    break;

                default:
                    ereport(ERROR,
                            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                             errmsg("interval units \"%s\" not supported",
                                    lowunits)));
                    result = 0;
            }

        }
        else
        {
            elog(ERROR, "could not convert interval to tm");
            result = 0;
        }
    }
    else if (type == RESERV && val == DTK_EPOCH)
    {
        result = interval->time / 1000000.0;
        result += ((double) DAYS_PER_YEAR * SECS_PER_DAY) * (interval->month / MONTHS_PER_YEAR);
        result += ((double) DAYS_PER_MONTH * SECS_PER_DAY) * (interval->month % MONTHS_PER_YEAR);
        result += ((double) SECS_PER_DAY) * interval->day;
    }
    else
    {
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("interval units \"%s\" not recognized",
                        lowunits)));
        result = 0;
    }

    PG_RETURN_FLOAT8(result);
}


/*  timestamp_zone()
 *  Encode timestamp type with specified time zone.
 *  This function is just timestamp2timestamptz() except instead of
 *  shifting to the global timezone, we shift to the specified timezone.
 *  This is different from the other AT TIME ZONE cases because instead
 *  of shifting _to_ a new time zone, it sets the time to _be_ the
 *  specified timezone.
 */
Datum
timestamp_zone(PG_FUNCTION_ARGS)
{
    text       *zone = PG_GETARG_TEXT_PP(0);
    Timestamp   timestamp = PG_GETARG_TIMESTAMP(1);
    TimestampTz result;
    int         tz;
    char        tzname[TZ_STRLEN_MAX + 1];
    char       *lowzone;
    int         type,
                val;
    pg_tz      *tzp;
    struct pg_tm tm;
    fsec_t      fsec;

    if (TIMESTAMP_NOT_FINITE(timestamp))
        PG_RETURN_TIMESTAMPTZ(timestamp);

    /*
     * Look up the requested timezone.  First we look in the timezone
     * abbreviation table (to handle cases like "EST"), and if that fails, we
     * look in the timezone database (to handle cases like
     * "America/New_York").  (This matches the order in which timestamp input
     * checks the cases; it's important because the timezone database unwisely
     * uses a few zone names that are identical to offset abbreviations.)
     */
    text_to_cstring_buffer(zone, tzname, sizeof(tzname));

    /* DecodeTimezoneAbbrev requires lowercase input */
    lowzone = downcase_truncate_identifier(tzname,
                                           strlen(tzname),
                                           false);

    type = DecodeTimezoneAbbrev(0, lowzone, &val, &tzp);

    if (type == TZ || type == DTZ)
    {
        /* fixed-offset abbreviation */
        tz = val;
        result = dt2local(timestamp, tz);
    }
    else if (type == DYNTZ)
    {
        /* dynamic-offset abbreviation, resolve using specified time */
        if (timestamp2tm(timestamp, NULL, &tm, &fsec, NULL, tzp) != 0)
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range")));
        tz = -DetermineTimeZoneAbbrevOffset(&tm, tzname, tzp);
        result = dt2local(timestamp, tz);
    }
    else
    {
        /* try it as a full zone name */
        tzp = pg_tzset(tzname);
        if (tzp)
        {
            /* Apply the timezone change */
            if (timestamp2tm(timestamp, NULL, &tm, &fsec, NULL, tzp) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range")));
            tz = DetermineTimeZoneOffset(&tm, tzp);
            if (tm2timestamp(&tm, fsec, &tz, &result) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range")));
        }
        else
        {
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("time zone \"%s\" not recognized", tzname)));
            result = 0;         /* keep compiler quiet */
        }
    }

    if (!IS_VALID_TIMESTAMP(result))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    PG_RETURN_TIMESTAMPTZ(result);
}

/* timestamp_izone()
 * Encode timestamp type with specified time interval as time zone.
 */
Datum
timestamp_izone(PG_FUNCTION_ARGS)
{
    Interval   *zone = PG_GETARG_INTERVAL_P(0);
    Timestamp   timestamp = PG_GETARG_TIMESTAMP(1);
    TimestampTz result;
    int         tz;

    if (TIMESTAMP_NOT_FINITE(timestamp))
        PG_RETURN_TIMESTAMPTZ(timestamp);

    if (zone->month != 0 || zone->day != 0)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("interval time zone \"%s\" must not include months or days",
                        DatumGetCString(DirectFunctionCall1(interval_out,
                                                            PointerGetDatum(zone))))));

    tz = zone->time / USECS_PER_SEC;

    result = dt2local(timestamp, tz);

    if (!IS_VALID_TIMESTAMP(result))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    PG_RETURN_TIMESTAMPTZ(result);
}                               /* timestamp_izone() */

/* TimestampTimestampTzRequiresRewrite()
 *
 * Returns false if the TimeZone GUC setting causes timestamp_timestamptz and
 * timestamptz_timestamp to be no-ops, where the return value has the same
 * bits as the argument.  Since project convention is to assume a GUC changes
 * no more often than STABLE functions change, the answer is valid that long.
 */
bool
TimestampTimestampTzRequiresRewrite(void)
{
    long        offset;

    if (pg_get_timezone_offset(session_timezone, &offset) && offset == 0)
        return false;
    return true;
}

/* timestamp_timestamptz()
 * Convert local timestamp to timestamp at GMT
 */
Datum
timestamp_timestamptz(PG_FUNCTION_ARGS)
{
    Timestamp   timestamp = PG_GETARG_TIMESTAMP(0);

    PG_RETURN_TIMESTAMPTZ(timestamp2timestamptz(timestamp));
}

/*
 * Convert timestamp to timestamp with time zone.
 *
 * On overflow error is thrown if 'overflow' is NULL.  Otherwise, '*overflow'
 * is set to -1 (+1) when result value exceed lower (upper) boundary and zero
 * returned.
 */
TimestampTz
timestamp2timestamptz_opt_overflow(Timestamp timestamp, int *overflow)
{
    TimestampTz result;
    struct pg_tm tt,
               *tm = &tt;
    fsec_t      fsec;
    int         tz;

    if (TIMESTAMP_NOT_FINITE(timestamp))
        return timestamp;

    if (!timestamp2tm(timestamp, NULL, tm, &fsec, NULL, NULL))
    {
        tz = DetermineTimeZoneOffset(tm, session_timezone);

        result = dt2local(timestamp, -tz);

        if (IS_VALID_TIMESTAMP(result))
        {
            return result;
        }
        else if (overflow)
        {
            if (result < MIN_TIMESTAMP)
                *overflow = -1;
            else
            {
                Assert(result >= END_TIMESTAMP);
                *overflow = 1;
            }
            return (TimestampTz) 0;
        }
    }

    ereport(ERROR,
            (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
             errmsg("timestamp out of range")));

    return 0;
}

/*
 * Single-argument version of timestamp2timestamptz_opt_overflow().
 */
static TimestampTz
timestamp2timestamptz(Timestamp timestamp)
{
    return timestamp2timestamptz_opt_overflow(timestamp, NULL);
}

/* timestamptz_timestamp()
 * Convert timestamp at GMT to local timestamp
 */
Datum
timestamptz_timestamp(PG_FUNCTION_ARGS)
{
    TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(0);

    PG_RETURN_TIMESTAMP(timestamptz2timestamp(timestamp));
}

static Timestamp
timestamptz2timestamp(TimestampTz timestamp)
{
    Timestamp   result;
    struct pg_tm tt,
               *tm = &tt;
    fsec_t      fsec;
    int         tz;

    if (TIMESTAMP_NOT_FINITE(timestamp))
        result = timestamp;
    else
    {
        if (timestamp2tm(timestamp, &tz, tm, &fsec, NULL, NULL) != 0)
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range")));
        if (tm2timestamp(tm, fsec, NULL, &result) != 0)
            ereport(ERROR,
                    (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                     errmsg("timestamp out of range")));
    }
    return result;
}

/* timestamptz_zone()
 * Evaluate timestamp with time zone type at the specified time zone.
 * Returns a timestamp without time zone.
 */
Datum
timestamptz_zone(PG_FUNCTION_ARGS)
{
    text       *zone = PG_GETARG_TEXT_PP(0);
    TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(1);
    Timestamp   result;
    int         tz;
    char        tzname[TZ_STRLEN_MAX + 1];
    char       *lowzone;
    int         type,
                val;
    pg_tz      *tzp;

    if (TIMESTAMP_NOT_FINITE(timestamp))
        PG_RETURN_TIMESTAMP(timestamp);

    /*
     * Look up the requested timezone.  First we look in the timezone
     * abbreviation table (to handle cases like "EST"), and if that fails, we
     * look in the timezone database (to handle cases like
     * "America/New_York").  (This matches the order in which timestamp input
     * checks the cases; it's important because the timezone database unwisely
     * uses a few zone names that are identical to offset abbreviations.)
     */
    text_to_cstring_buffer(zone, tzname, sizeof(tzname));

    /* DecodeTimezoneAbbrev requires lowercase input */
    lowzone = downcase_truncate_identifier(tzname,
                                           strlen(tzname),
                                           false);

    type = DecodeTimezoneAbbrev(0, lowzone, &val, &tzp);

    if (type == TZ || type == DTZ)
    {
        /* fixed-offset abbreviation */
        tz = -val;
        result = dt2local(timestamp, tz);
    }
    else if (type == DYNTZ)
    {
        /* dynamic-offset abbreviation, resolve using specified time */
        int         isdst;

        tz = DetermineTimeZoneAbbrevOffsetTS(timestamp, tzname, tzp, &isdst);
        result = dt2local(timestamp, tz);
    }
    else
    {
        /* try it as a full zone name */
        tzp = pg_tzset(tzname);
        if (tzp)
        {
            /* Apply the timezone change */
            struct pg_tm tm;
            fsec_t      fsec;

            if (timestamp2tm(timestamp, &tz, &tm, &fsec, NULL, tzp) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range")));
            if (tm2timestamp(&tm, fsec, NULL, &result) != 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                         errmsg("timestamp out of range")));
        }
        else
        {
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("time zone \"%s\" not recognized", tzname)));
            result = 0;         /* keep compiler quiet */
        }
    }

    if (!IS_VALID_TIMESTAMP(result))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    PG_RETURN_TIMESTAMP(result);
}

/* timestamptz_izone()
 * Encode timestamp with time zone type with specified time interval as time zone.
 * Returns a timestamp without time zone.
 */
Datum
timestamptz_izone(PG_FUNCTION_ARGS)
{
    Interval   *zone = PG_GETARG_INTERVAL_P(0);
    TimestampTz timestamp = PG_GETARG_TIMESTAMPTZ(1);
    Timestamp   result;
    int         tz;

    if (TIMESTAMP_NOT_FINITE(timestamp))
        PG_RETURN_TIMESTAMP(timestamp);

    if (zone->month != 0 || zone->day != 0)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("interval time zone \"%s\" must not include months or days",
                        DatumGetCString(DirectFunctionCall1(interval_out,
                                                            PointerGetDatum(zone))))));

    tz = -(zone->time / USECS_PER_SEC);

    result = dt2local(timestamp, tz);

    if (!IS_VALID_TIMESTAMP(result))
        ereport(ERROR,
                (errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
                 errmsg("timestamp out of range")));

    PG_RETURN_TIMESTAMP(result);
}

/* generate_series_timestamp()
 * Generate the set of timestamps from start to finish by step
 */
Datum
generate_series_timestamp(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx;
    generate_series_timestamp_fctx *fctx;
    Timestamp   result;

    /* stuff done only on the first call of the function */
    if (SRF_IS_FIRSTCALL())
    {
        Timestamp   start = PG_GETARG_TIMESTAMP(0);
        Timestamp   finish = PG_GETARG_TIMESTAMP(1);
        Interval   *step = PG_GETARG_INTERVAL_P(2);
        MemoryContext oldcontext;
        Interval    interval_zero;

        /* create a function context for cross-call persistence */
        funcctx = SRF_FIRSTCALL_INIT();

        /*
         * switch to memory context appropriate for multiple function calls
         */
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

        /* allocate memory for user context */
        fctx = (generate_series_timestamp_fctx *)
            palloc(sizeof(generate_series_timestamp_fctx));

        /*
         * Use fctx to keep state from call to call. Seed current with the
         * original start value
         */
        fctx->current = start;
        fctx->finish = finish;
        fctx->step = *step;

        /* Determine sign of the interval */
        MemSet(&interval_zero, 0, sizeof(Interval));
        fctx->step_sign = interval_cmp_internal(&fctx->step, &interval_zero);

        if (fctx->step_sign == 0)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("step size cannot equal zero")));

        funcctx->user_fctx = fctx;
        MemoryContextSwitchTo(oldcontext);
    }

    /* stuff done on every call of the function */
    funcctx = SRF_PERCALL_SETUP();

    /*
     * get the saved state and use current as the result for this iteration
     */
    fctx = funcctx->user_fctx;
    result = fctx->current;

    if (fctx->step_sign > 0 ?
        timestamp_cmp_internal(result, fctx->finish) <= 0 :
        timestamp_cmp_internal(result, fctx->finish) >= 0)
    {
        /* increment current in preparation for next iteration */
        fctx->current = DatumGetTimestamp(DirectFunctionCall2(timestamp_pl_interval,
                                                              TimestampGetDatum(fctx->current),
                                                              PointerGetDatum(&fctx->step)));

        /* do when there is more left to send */
        SRF_RETURN_NEXT(funcctx, TimestampGetDatum(result));
    }
    else
    {
        /* do when there is no more left */
        SRF_RETURN_DONE(funcctx);
    }
}

/* generate_series_timestamptz()
 * Generate the set of timestamps from start to finish by step
 */
Datum
generate_series_timestamptz(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx;
    generate_series_timestamptz_fctx *fctx;
    TimestampTz result;

    /* stuff done only on the first call of the function */
    if (SRF_IS_FIRSTCALL())
    {
        TimestampTz start = PG_GETARG_TIMESTAMPTZ(0);
        TimestampTz finish = PG_GETARG_TIMESTAMPTZ(1);
        Interval   *step = PG_GETARG_INTERVAL_P(2);
        MemoryContext oldcontext;
        Interval    interval_zero;

        /* create a function context for cross-call persistence */
        funcctx = SRF_FIRSTCALL_INIT();

        /*
         * switch to memory context appropriate for multiple function calls
         */
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

        /* allocate memory for user context */
        fctx = (generate_series_timestamptz_fctx *)
            palloc(sizeof(generate_series_timestamptz_fctx));

        /*
         * Use fctx to keep state from call to call. Seed current with the
         * original start value
         */
        fctx->current = start;
        fctx->finish = finish;
        fctx->step = *step;

        /* Determine sign of the interval */
        MemSet(&interval_zero, 0, sizeof(Interval));
        fctx->step_sign = interval_cmp_internal(&fctx->step, &interval_zero);

        if (fctx->step_sign == 0)
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("step size cannot equal zero")));

        funcctx->user_fctx = fctx;
        MemoryContextSwitchTo(oldcontext);
    }

    /* stuff done on every call of the function */
    funcctx = SRF_PERCALL_SETUP();

    /*
     * get the saved state and use current as the result for this iteration
     */
    fctx = funcctx->user_fctx;
    result = fctx->current;

    if (fctx->step_sign > 0 ?
        timestamp_cmp_internal(result, fctx->finish) <= 0 :
        timestamp_cmp_internal(result, fctx->finish) >= 0)
    {
        /* increment current in preparation for next iteration */
        fctx->current = DatumGetTimestampTz(DirectFunctionCall2(timestamptz_pl_interval,
                                                                TimestampTzGetDatum(fctx->current),
                                                                PointerGetDatum(&fctx->step)));

        /* do when there is more left to send */
        SRF_RETURN_NEXT(funcctx, TimestampTzGetDatum(result));
    }
    else
    {
        /* do when there is no more left */
        SRF_RETURN_DONE(funcctx);
    }
}