format_type.c

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/*-------------------------------------------------------------------------
 *
 * format_type.c
 *    Display type names "nicely".
 *
 *
 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/format_type.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <ctype.h>

#include "access/htup_details.h"
#include "catalog/namespace.h"
#include "catalog/pg_type.h"
#include "mb/pg_wchar.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/numeric.h"
#include "utils/syscache.h"

static char *printTypmod(const char *typname, int32 typmod, Oid typmodout);


/*
 * SQL function: format_type(type_oid, typemod)
 *
 * `type_oid' is from pg_type.oid, `typemod' is from
 * pg_attribute.atttypmod. This function will get the type name and
 * format it and the modifier to canonical SQL format, if the type is
 * a standard type. Otherwise you just get pg_type.typname back,
 * double quoted if it contains funny characters or matches a keyword.
 *
 * If typemod is NULL then we are formatting a type name in a context where
 * no typemod is available, eg a function argument or result type.  This
 * yields a slightly different result from specifying typemod = -1 in some
 * cases.  Given typemod = -1 we feel compelled to produce an output that
 * the parser will interpret as having typemod -1, so that pg_dump will
 * produce CREATE TABLE commands that recreate the original state.  But
 * given NULL typemod, we assume that the parser's interpretation of
 * typemod doesn't matter, and so we are willing to output a slightly
 * "prettier" representation of the same type.  For example, type = bpchar
 * and typemod = NULL gets you "character", whereas typemod = -1 gets you
 * "bpchar" --- the former will be interpreted as character(1) by the
 * parser, which does not yield typemod -1.
 *
 * XXX encoding a meaning in typemod = NULL is ugly; it'd have been
 * cleaner to make two functions of one and two arguments respectively.
 * Not worth changing it now, however.
 */
Datum
format_type(PG_FUNCTION_ARGS)
{
    Oid         type_oid;
    int32       typemod;
    char       *result;
    bits16      flags = FORMAT_TYPE_ALLOW_INVALID;

    /* Since this function is not strict, we must test for null args */
    if (PG_ARGISNULL(0))
        PG_RETURN_NULL();

    type_oid = PG_GETARG_OID(0);

    if (PG_ARGISNULL(1))
        typemod = -1;
    else
    {
        typemod = PG_GETARG_INT32(1);
        flags |= FORMAT_TYPE_TYPEMOD_GIVEN;
    }

    result = format_type_extended(type_oid, typemod, flags);

    PG_RETURN_TEXT_P(cstring_to_text(result));
}

/*
 * format_type_extended
 *      Generate a possibly-qualified type name.
 *
 * The default behavior is to only qualify if the type is not in the search
 * path, to ignore the given typmod, and to raise an error if a non-existent
 * type_oid is given.
 *
 * The following bits in 'flags' modify the behavior:
 * - FORMAT_TYPE_TYPEMOD_GIVEN
 *          include the typmod in the output (typmod could still be -1 though)
 * - FORMAT_TYPE_ALLOW_INVALID
 *          if the type OID is invalid or unknown, return ??? or such instead
 *          of failing
 * - FORMAT_TYPE_FORCE_QUALIFY
 *          always schema-qualify type names, regardless of search_path
 *
 * Note that TYPEMOD_GIVEN is not interchangeable with "typemod == -1";
 * see the comments above for format_type().
 *
 * Returns a palloc'd string.
 */
char *
format_type_extended(Oid type_oid, int32 typemod, bits16 flags)
{
    HeapTuple   tuple;
    Form_pg_type typeform;
    Oid         array_base_type;
    bool        is_array;
    char       *buf;
    bool        with_typemod;

    if (type_oid == InvalidOid && (flags & FORMAT_TYPE_ALLOW_INVALID) != 0)
        return pstrdup("-");

    tuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(type_oid));
    if (!HeapTupleIsValid(tuple))
    {
        if ((flags & FORMAT_TYPE_ALLOW_INVALID) != 0)
            return pstrdup("???");
        else
            elog(ERROR, "cache lookup failed for type %u", type_oid);
    }
    typeform = (Form_pg_type) GETSTRUCT(tuple);

    /*
     * Check if it's a regular (variable length) array type.  Fixed-length
     * array types such as "name" shouldn't get deconstructed.  As of Postgres
     * 8.1, rather than checking typlen we check the toast property, and don't
     * deconstruct "plain storage" array types --- this is because we don't
     * want to show oidvector as oid[].
     */
    array_base_type = typeform->typelem;

    if (array_base_type != InvalidOid && typeform->typstorage != 'p')
    {
        /* Switch our attention to the array element type */
        ReleaseSysCache(tuple);
        tuple = SearchSysCache1(TYPEOID, ObjectIdGetDatum(array_base_type));
        if (!HeapTupleIsValid(tuple))
        {
            if ((flags & FORMAT_TYPE_ALLOW_INVALID) != 0)
                return pstrdup("???[]");
            else
                elog(ERROR, "cache lookup failed for type %u", type_oid);
        }
        typeform = (Form_pg_type) GETSTRUCT(tuple);
        type_oid = array_base_type;
        is_array = true;
    }
    else
        is_array = false;

    with_typemod = (flags & FORMAT_TYPE_TYPEMOD_GIVEN) != 0 && (typemod >= 0);

    /*
     * See if we want to special-case the output for certain built-in types.
     * Note that these special cases should all correspond to special
     * productions in gram.y, to ensure that the type name will be taken as a
     * system type, not a user type of the same name.
     *
     * If we do not provide a special-case output here, the type name will be
     * handled the same way as a user type name --- in particular, it will be
     * double-quoted if it matches any lexer keyword.  This behavior is
     * essential for some cases, such as types "bit" and "char".
     */
    buf = NULL;                 /* flag for no special case */

    switch (type_oid)
    {
        case BITOID:
            if (with_typemod)
                buf = printTypmod("bit", typemod, typeform->typmodout);
            else if ((flags & FORMAT_TYPE_TYPEMOD_GIVEN) != 0)
            {
                /*
                 * bit with typmod -1 is not the same as BIT, which means
                 * BIT(1) per SQL spec.  Report it as the quoted typename so
                 * that parser will not assign a bogus typmod.
                 */
            }
            else
                buf = pstrdup("bit");
            break;

        case BOOLOID:
            buf = pstrdup("boolean");
            break;

        case BPCHAROID:
            if (with_typemod)
                buf = printTypmod("character", typemod, typeform->typmodout);
            else if ((flags & FORMAT_TYPE_TYPEMOD_GIVEN) != 0)
            {
                /*
                 * bpchar with typmod -1 is not the same as CHARACTER, which
                 * means CHARACTER(1) per SQL spec.  Report it as bpchar so
                 * that parser will not assign a bogus typmod.
                 */
            }
            else
                buf = pstrdup("character");
            break;

        case FLOAT4OID:
            buf = pstrdup("real");
            break;

        case FLOAT8OID:
            buf = pstrdup("double precision");
            break;

        case INT2OID:
            buf = pstrdup("smallint");
            break;

        case INT4OID:
            buf = pstrdup("integer");
            break;

        case INT8OID:
            buf = pstrdup("bigint");
            break;

        case NUMERICOID:
            if (with_typemod)
                buf = printTypmod("numeric", typemod, typeform->typmodout);
            else
                buf = pstrdup("numeric");
            break;

        case INTERVALOID:
            if (with_typemod)
                buf = printTypmod("interval", typemod, typeform->typmodout);
            else
                buf = pstrdup("interval");
            break;

        case TIMEOID:
            if (with_typemod)
                buf = printTypmod("time", typemod, typeform->typmodout);
            else
                buf = pstrdup("time without time zone");
            break;

        case TIMETZOID:
            if (with_typemod)
                buf = printTypmod("time", typemod, typeform->typmodout);
            else
                buf = pstrdup("time with time zone");
            break;

        case TIMESTAMPOID:
            if (with_typemod)
                buf = printTypmod("timestamp", typemod, typeform->typmodout);
            else
                buf = pstrdup("timestamp without time zone");
            break;

        case TIMESTAMPTZOID:
            if (with_typemod)
                buf = printTypmod("timestamp", typemod, typeform->typmodout);
            else
                buf = pstrdup("timestamp with time zone");
            break;

        case VARBITOID:
            if (with_typemod)
                buf = printTypmod("bit varying", typemod, typeform->typmodout);
            else
                buf = pstrdup("bit varying");
            break;

        case VARCHAROID:
            if (with_typemod)
                buf = printTypmod("character varying", typemod, typeform->typmodout);
            else
                buf = pstrdup("character varying");
            break;
    }

    if (buf == NULL)
    {
        /*
         * Default handling: report the name as it appears in the catalog.
         * Here, we must qualify the name if it is not visible in the search
         * path or if caller requests it; and we must double-quote it if it's
         * not a standard identifier or if it matches any keyword.
         */
        char       *nspname;
        char       *typname;

        if ((flags & FORMAT_TYPE_FORCE_QUALIFY) == 0 &&
            TypeIsVisible(type_oid))
            nspname = NULL;
        else
            nspname = get_namespace_name_or_temp(typeform->typnamespace);

        typname = NameStr(typeform->typname);

        buf = quote_qualified_identifier(nspname, typname);

        if (with_typemod)
            buf = printTypmod(buf, typemod, typeform->typmodout);
    }

    if (is_array)
        buf = psprintf("%s[]", buf);

    ReleaseSysCache(tuple);

    return buf;
}

/*
 * This version is for use within the backend in error messages, etc.
 * One difference is that it will fail for an invalid type.
 *
 * The result is always a palloc'd string.
 */
char *
format_type_be(Oid type_oid)
{
    return format_type_extended(type_oid, -1, 0);
}

/*
 * This version returns a name that is always qualified (unless it's one
 * of the SQL-keyword type names, such as TIMESTAMP WITH TIME ZONE).
 */
char *
format_type_be_qualified(Oid type_oid)
{
    return format_type_extended(type_oid, -1, FORMAT_TYPE_FORCE_QUALIFY);
}

/*
 * This version allows a nondefault typemod to be specified.
 */
char *
format_type_with_typemod(Oid type_oid, int32 typemod)
{
    return format_type_extended(type_oid, typemod, FORMAT_TYPE_TYPEMOD_GIVEN);
}

/*
 * Add typmod decoration to the basic type name
 */
static char *
printTypmod(const char *typname, int32 typmod, Oid typmodout)
{
    char       *res;

    /* Shouldn't be called if typmod is -1 */
    Assert(typmod >= 0);

    if (typmodout == InvalidOid)
    {
        /* Default behavior: just print the integer typmod with parens */
        res = psprintf("%s(%d)", typname, (int) typmod);
    }
    else
    {
        /* Use the type-specific typmodout procedure */
        char       *tmstr;

        tmstr = DatumGetCString(OidFunctionCall1(typmodout,
                                                 Int32GetDatum(typmod)));
        res = psprintf("%s%s", typname, tmstr);
    }

    return res;
}


/*
 * type_maximum_size --- determine maximum width of a variable-width column
 *
 * If the max width is indeterminate, return -1.  In particular, we return
 * -1 for any type not known to this routine.  We assume the caller has
 * already determined that the type is a variable-width type, so it's not
 * necessary to look up the type's pg_type tuple here.
 *
 * This may appear unrelated to format_type(), but in fact the two routines
 * share knowledge of the encoding of typmod for different types, so it's
 * convenient to keep them together.  (XXX now that most of this knowledge
 * has been pushed out of format_type into the typmodout functions, it's
 * interesting to wonder if it's worth trying to factor this code too...)
 */
int32
type_maximum_size(Oid type_oid, int32 typemod)
{
    if (typemod < 0)
        return -1;

    switch (type_oid)
    {
        case BPCHAROID:
        case VARCHAROID:
            /* typemod includes varlena header */

            /* typemod is in characters not bytes */
            return (typemod - VARHDRSZ) *
                pg_encoding_max_length(GetDatabaseEncoding())
                + VARHDRSZ;

        case NUMERICOID:
            return numeric_maximum_size(typemod);

        case VARBITOID:
        case BITOID:
            /* typemod is the (max) number of bits */
            return (typemod + (BITS_PER_BYTE - 1)) / BITS_PER_BYTE
                + 2 * sizeof(int32);
    }

    /* Unknown type, or unlimited-width type such as 'text' */
    return -1;
}


/*
 * oidvectortypes           - converts a vector of type OIDs to "typname" list
 */
Datum
oidvectortypes(PG_FUNCTION_ARGS)
{
    oidvector  *oidArray = (oidvector *) PG_GETARG_POINTER(0);
    char       *result;
    int         numargs = oidArray->dim1;
    int         num;
    size_t      total;
    size_t      left;

    total = 20 * numargs + 1;
    result = palloc(total);
    result[0] = '\0';
    left = total - 1;

    for (num = 0; num < numargs; num++)
    {
        char       *typename = format_type_extended(oidArray->values[num], -1,
                                                    FORMAT_TYPE_ALLOW_INVALID);
        size_t      slen = strlen(typename);

        if (left < (slen + 2))
        {
            total += slen + 2;
            result = repalloc(result, total);
            left += slen + 2;
        }

        if (num > 0)
        {
            strcat(result, ", ");
            left -= 2;
        }
        strcat(result, typename);
        left -= slen;
    }

    PG_RETURN_TEXT_P(cstring_to_text(result));
}