enum.c

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/*-------------------------------------------------------------------------
 *
 * enum.c
 *    I/O functions, operators, aggregates etc for enum types
 *
 * Copyright (c) 2006-2024, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/enum.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/genam.h"
#include "access/htup_details.h"
#include "access/table.h"
#include "catalog/pg_enum.h"
#include "libpq/pqformat.h"
#include "storage/procarray.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/syscache.h"
#include "utils/typcache.h"
 
 
static Oid  enum_endpoint(Oid enumtypoid, ScanDirection direction);
static ArrayType *enum_range_internal(Oid enumtypoid, Oid lower, Oid upper);
 
 
/*
 * Disallow use of an uncommitted pg_enum tuple.
 *
 * We need to make sure that uncommitted enum values don't get into indexes.
 * If they did, and if we then rolled back the pg_enum addition, we'd have
 * broken the index because value comparisons will not work reliably without
 * an underlying pg_enum entry.  (Note that removal of the heap entry
 * containing an enum value is not sufficient to ensure that it doesn't appear
 * in upper levels of indexes.)  To do this we prevent an uncommitted row from
 * being used for any SQL-level purpose.  This is stronger than necessary,
 * since the value might not be getting inserted into a table or there might
 * be no index on its column, but it's easy to enforce centrally.
 *
 * However, it's okay to allow use of uncommitted values belonging to enum
 * types that were themselves created in the same transaction, because then
 * any such index would also be new and would go away altogether on rollback.
 * We don't implement that fully right now, but we do allow free use of enum
 * values created during CREATE TYPE AS ENUM, which are surely of the same
 * lifespan as the enum type.  (This case is required by "pg_restore -1".)
 * Values added by ALTER TYPE ADD VALUE are also allowed if the enum type
 * is known to have been created earlier in the same transaction.  (Note that
 * we have to track that explicitly; comparing tuple xmins is insufficient,
 * because the type tuple might have been updated in the current transaction.
 * Subtransactions also create hazards to be accounted for; currently,
 * pg_enum.c only handles ADD VALUE at the outermost transaction level.)
 *
 * This function needs to be called (directly or indirectly) in any of the
 * functions below that could return an enum value to SQL operations.
 */
static void
check_safe_enum_use(HeapTuple enumval_tup)
{
    TransactionId xmin;
    Form_pg_enum en = (Form_pg_enum) GETSTRUCT(enumval_tup);
 
    /*
     * If the row is hinted as committed, it's surely safe.  This provides a
     * fast path for all normal use-cases.
     */
    if (HeapTupleHeaderXminCommitted(enumval_tup->t_data))
        return;
 
    /*
     * Usually, a row would get hinted as committed when it's read or loaded
     * into syscache; but just in case not, let's check the xmin directly.
     */
    xmin = HeapTupleHeaderGetXmin(enumval_tup->t_data);
    if (!TransactionIdIsInProgress(xmin) &&
        TransactionIdDidCommit(xmin))
        return;
 
    /*
     * Check if the enum value is listed as uncommitted.  If not, it's safe,
     * because it can't be shorter-lived than its owning type.  (This'd also
     * be false for values made by other transactions; but the previous tests
     * should have handled all of those.)
     */
    if (!EnumUncommitted(en->oid))
        return;
 
    /*
     * There might well be other tests we could do here to narrow down the
     * unsafe conditions, but for now just raise an exception.
     */
    ereport(ERROR,
            (errcode(ERRCODE_UNSAFE_NEW_ENUM_VALUE_USAGE),
             errmsg("unsafe use of new value \"%s\" of enum type %s",
                    NameStr(en->enumlabel),
                    format_type_be(en->enumtypid)),
             errhint("New enum values must be committed before they can be used.")));
}
 
 
/* Basic I/O support */
 
Datum
enum_in(PG_FUNCTION_ARGS)
{
    char       *name = PG_GETARG_CSTRING(0);
    Oid         enumtypoid = PG_GETARG_OID(1);
    Node       *escontext = fcinfo->context;
    Oid         enumoid;
    HeapTuple   tup;
 
    /* must check length to prevent Assert failure within SearchSysCache */
    if (strlen(name) >= NAMEDATALEN)
        ereturn(escontext, (Datum) 0,
                (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                 errmsg("invalid input value for enum %s: \"%s\"",
                        format_type_be(enumtypoid),
                        name)));
 
    tup = SearchSysCache2(ENUMTYPOIDNAME,
                          ObjectIdGetDatum(enumtypoid),
                          CStringGetDatum(name));
    if (!HeapTupleIsValid(tup))
        ereturn(escontext, (Datum) 0,
                (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                 errmsg("invalid input value for enum %s: \"%s\"",
                        format_type_be(enumtypoid),
                        name)));
 
    /*
     * Check it's safe to use in SQL.  Perhaps we should take the trouble to
     * report "unsafe use" softly; but it's unclear that it's worth the
     * trouble, or indeed that that is a legitimate bad-input case at all
     * rather than an implementation shortcoming.
     */
    check_safe_enum_use(tup);
 
    /*
     * This comes from pg_enum.oid and stores system oids in user tables. This
     * oid must be preserved by binary upgrades.
     */
    enumoid = ((Form_pg_enum) GETSTRUCT(tup))->oid;
 
    ReleaseSysCache(tup);
 
    PG_RETURN_OID(enumoid);
}
 
Datum
enum_out(PG_FUNCTION_ARGS)
{
    Oid         enumval = PG_GETARG_OID(0);
    char       *result;
    HeapTuple   tup;
    Form_pg_enum en;
 
    tup = SearchSysCache1(ENUMOID, ObjectIdGetDatum(enumval));
    if (!HeapTupleIsValid(tup))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
                 errmsg("invalid internal value for enum: %u",
                        enumval)));
    en = (Form_pg_enum) GETSTRUCT(tup);
 
    result = pstrdup(NameStr(en->enumlabel));
 
    ReleaseSysCache(tup);
 
    PG_RETURN_CSTRING(result);
}
 
/* Binary I/O support */
Datum
enum_recv(PG_FUNCTION_ARGS)
{
    StringInfo  buf = (StringInfo) PG_GETARG_POINTER(0);
    Oid         enumtypoid = PG_GETARG_OID(1);
    Oid         enumoid;
    HeapTuple   tup;
    char       *name;
    int         nbytes;
 
    name = pq_getmsgtext(buf, buf->len - buf->cursor, &nbytes);
 
    /* must check length to prevent Assert failure within SearchSysCache */
    if (strlen(name) >= NAMEDATALEN)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                 errmsg("invalid input value for enum %s: \"%s\"",
                        format_type_be(enumtypoid),
                        name)));
 
    tup = SearchSysCache2(ENUMTYPOIDNAME,
                          ObjectIdGetDatum(enumtypoid),
                          CStringGetDatum(name));
    if (!HeapTupleIsValid(tup))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
                 errmsg("invalid input value for enum %s: \"%s\"",
                        format_type_be(enumtypoid),
                        name)));
 
    /* check it's safe to use in SQL */
    check_safe_enum_use(tup);
 
    enumoid = ((Form_pg_enum) GETSTRUCT(tup))->oid;
 
    ReleaseSysCache(tup);
 
    pfree(name);
 
    PG_RETURN_OID(enumoid);
}
 
Datum
enum_send(PG_FUNCTION_ARGS)
{
    Oid         enumval = PG_GETARG_OID(0);
    StringInfoData buf;
    HeapTuple   tup;
    Form_pg_enum en;
 
    tup = SearchSysCache1(ENUMOID, ObjectIdGetDatum(enumval));
    if (!HeapTupleIsValid(tup))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
                 errmsg("invalid internal value for enum: %u",
                        enumval)));
    en = (Form_pg_enum) GETSTRUCT(tup);
 
    pq_begintypsend(&buf);
    pq_sendtext(&buf, NameStr(en->enumlabel), strlen(NameStr(en->enumlabel)));
 
    ReleaseSysCache(tup);
 
    PG_RETURN_BYTEA_P(pq_endtypsend(&buf));
}
 
/* Comparison functions and related */
 
/*
 * enum_cmp_internal is the common engine for all the visible comparison
 * functions, except for enum_eq and enum_ne which can just check for OID
 * equality directly.
 */
static int
enum_cmp_internal(Oid arg1, Oid arg2, FunctionCallInfo fcinfo)
{
    TypeCacheEntry *tcache;
 
    /*
     * We don't need the typcache except in the hopefully-uncommon case that
     * one or both Oids are odd.  This means that cursory testing of code that
     * fails to pass flinfo to an enum comparison function might not disclose
     * the oversight.  To make such errors more obvious, Assert that we have a
     * place to cache even when we take a fast-path exit.
     */
    Assert(fcinfo->flinfo != NULL);
 
    /* Equal OIDs are equal no matter what */
    if (arg1 == arg2)
        return 0;
 
    /* Fast path: even-numbered Oids are known to compare correctly */
    if ((arg1 & 1) == 0 && (arg2 & 1) == 0)
    {
        if (arg1 < arg2)
            return -1;
        else
            return 1;
    }
 
    /* Locate the typcache entry for the enum type */
    tcache = (TypeCacheEntry *) fcinfo->flinfo->fn_extra;
    if (tcache == NULL)
    {
        HeapTuple   enum_tup;
        Form_pg_enum en;
        Oid         typeoid;
 
        /* Get the OID of the enum type containing arg1 */
        enum_tup = SearchSysCache1(ENUMOID, ObjectIdGetDatum(arg1));
        if (!HeapTupleIsValid(enum_tup))
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
                     errmsg("invalid internal value for enum: %u",
                            arg1)));
        en = (Form_pg_enum) GETSTRUCT(enum_tup);
        typeoid = en->enumtypid;
        ReleaseSysCache(enum_tup);
        /* Now locate and remember the typcache entry */
        tcache = lookup_type_cache(typeoid, 0);
        fcinfo->flinfo->fn_extra = (void *) tcache;
    }
 
    /* The remaining comparison logic is in typcache.c */
    return compare_values_of_enum(tcache, arg1, arg2);
}
 
Datum
enum_lt(PG_FUNCTION_ARGS)
{
    Oid         a = PG_GETARG_OID(0);
    Oid         b = PG_GETARG_OID(1);
 
    PG_RETURN_BOOL(enum_cmp_internal(a, b, fcinfo) < 0);
}
 
Datum
enum_le(PG_FUNCTION_ARGS)
{
    Oid         a = PG_GETARG_OID(0);
    Oid         b = PG_GETARG_OID(1);
 
    PG_RETURN_BOOL(enum_cmp_internal(a, b, fcinfo) <= 0);
}
 
Datum
enum_eq(PG_FUNCTION_ARGS)
{
    Oid         a = PG_GETARG_OID(0);
    Oid         b = PG_GETARG_OID(1);
 
    PG_RETURN_BOOL(a == b);
}
 
Datum
enum_ne(PG_FUNCTION_ARGS)
{
    Oid         a = PG_GETARG_OID(0);
    Oid         b = PG_GETARG_OID(1);
 
    PG_RETURN_BOOL(a != b);
}
 
Datum
enum_ge(PG_FUNCTION_ARGS)
{
    Oid         a = PG_GETARG_OID(0);
    Oid         b = PG_GETARG_OID(1);
 
    PG_RETURN_BOOL(enum_cmp_internal(a, b, fcinfo) >= 0);
}
 
Datum
enum_gt(PG_FUNCTION_ARGS)
{
    Oid         a = PG_GETARG_OID(0);
    Oid         b = PG_GETARG_OID(1);
 
    PG_RETURN_BOOL(enum_cmp_internal(a, b, fcinfo) > 0);
}
 
Datum
enum_smaller(PG_FUNCTION_ARGS)
{
    Oid         a = PG_GETARG_OID(0);
    Oid         b = PG_GETARG_OID(1);
 
    PG_RETURN_OID(enum_cmp_internal(a, b, fcinfo) < 0 ? a : b);
}
 
Datum
enum_larger(PG_FUNCTION_ARGS)
{
    Oid         a = PG_GETARG_OID(0);
    Oid         b = PG_GETARG_OID(1);
 
    PG_RETURN_OID(enum_cmp_internal(a, b, fcinfo) > 0 ? a : b);
}
 
Datum
enum_cmp(PG_FUNCTION_ARGS)
{
    Oid         a = PG_GETARG_OID(0);
    Oid         b = PG_GETARG_OID(1);
 
    PG_RETURN_INT32(enum_cmp_internal(a, b, fcinfo));
}
 
/* Enum programming support functions */
 
/*
 * enum_endpoint: common code for enum_first/enum_last
 */
static Oid
enum_endpoint(Oid enumtypoid, ScanDirection direction)
{
    Relation    enum_rel;
    Relation    enum_idx;
    SysScanDesc enum_scan;
    HeapTuple   enum_tuple;
    ScanKeyData skey;
    Oid         minmax;
 
    /*
     * Find the first/last enum member using pg_enum_typid_sortorder_index.
     * Note we must not use the syscache.  See comments for RenumberEnumType
     * in catalog/pg_enum.c for more info.
     */
    ScanKeyInit(&skey,
                Anum_pg_enum_enumtypid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(enumtypoid));
 
    enum_rel = table_open(EnumRelationId, AccessShareLock);
    enum_idx = index_open(EnumTypIdSortOrderIndexId, AccessShareLock);
    enum_scan = systable_beginscan_ordered(enum_rel, enum_idx, NULL,
                                           1, &skey);
 
    enum_tuple = systable_getnext_ordered(enum_scan, direction);
    if (HeapTupleIsValid(enum_tuple))
    {
        /* check it's safe to use in SQL */
        check_safe_enum_use(enum_tuple);
        minmax = ((Form_pg_enum) GETSTRUCT(enum_tuple))->oid;
    }
    else
    {
        /* should only happen with an empty enum */
        minmax = InvalidOid;
    }
 
    systable_endscan_ordered(enum_scan);
    index_close(enum_idx, AccessShareLock);
    table_close(enum_rel, AccessShareLock);
 
    return minmax;
}
 
Datum
enum_first(PG_FUNCTION_ARGS)
{
    Oid         enumtypoid;
    Oid         min;
 
    /*
     * We rely on being able to get the specific enum type from the calling
     * expression tree.  Notice that the actual value of the argument isn't
     * examined at all; in particular it might be NULL.
     */
    enumtypoid = get_fn_expr_argtype(fcinfo->flinfo, 0);
    if (enumtypoid == InvalidOid)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("could not determine actual enum type")));
 
    /* Get the OID using the index */
    min = enum_endpoint(enumtypoid, ForwardScanDirection);
 
    if (!OidIsValid(min))
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("enum %s contains no values",
                        format_type_be(enumtypoid))));
 
    PG_RETURN_OID(min);
}
 
Datum
enum_last(PG_FUNCTION_ARGS)
{
    Oid         enumtypoid;
    Oid         max;
 
    /*
     * We rely on being able to get the specific enum type from the calling
     * expression tree.  Notice that the actual value of the argument isn't
     * examined at all; in particular it might be NULL.
     */
    enumtypoid = get_fn_expr_argtype(fcinfo->flinfo, 0);
    if (enumtypoid == InvalidOid)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("could not determine actual enum type")));
 
    /* Get the OID using the index */
    max = enum_endpoint(enumtypoid, BackwardScanDirection);
 
    if (!OidIsValid(max))
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("enum %s contains no values",
                        format_type_be(enumtypoid))));
 
    PG_RETURN_OID(max);
}
 
/* 2-argument variant of enum_range */
Datum
enum_range_bounds(PG_FUNCTION_ARGS)
{
    Oid         lower;
    Oid         upper;
    Oid         enumtypoid;
 
    if (PG_ARGISNULL(0))
        lower = InvalidOid;
    else
        lower = PG_GETARG_OID(0);
    if (PG_ARGISNULL(1))
        upper = InvalidOid;
    else
        upper = PG_GETARG_OID(1);
 
    /*
     * We rely on being able to get the specific enum type from the calling
     * expression tree.  The generic type mechanism should have ensured that
     * both are of the same type.
     */
    enumtypoid = get_fn_expr_argtype(fcinfo->flinfo, 0);
    if (enumtypoid == InvalidOid)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("could not determine actual enum type")));
 
    PG_RETURN_ARRAYTYPE_P(enum_range_internal(enumtypoid, lower, upper));
}
 
/* 1-argument variant of enum_range */
Datum
enum_range_all(PG_FUNCTION_ARGS)
{
    Oid         enumtypoid;
 
    /*
     * We rely on being able to get the specific enum type from the calling
     * expression tree.  Notice that the actual value of the argument isn't
     * examined at all; in particular it might be NULL.
     */
    enumtypoid = get_fn_expr_argtype(fcinfo->flinfo, 0);
    if (enumtypoid == InvalidOid)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("could not determine actual enum type")));
 
    PG_RETURN_ARRAYTYPE_P(enum_range_internal(enumtypoid,
                                              InvalidOid, InvalidOid));
}
 
static ArrayType *
enum_range_internal(Oid enumtypoid, Oid lower, Oid upper)
{
    ArrayType  *result;
    Relation    enum_rel;
    Relation    enum_idx;
    SysScanDesc enum_scan;
    HeapTuple   enum_tuple;
    ScanKeyData skey;
    Datum      *elems;
    int         max,
                cnt;
    bool        left_found;
 
    /*
     * Scan the enum members in order using pg_enum_typid_sortorder_index.
     * Note we must not use the syscache.  See comments for RenumberEnumType
     * in catalog/pg_enum.c for more info.
     */
    ScanKeyInit(&skey,
                Anum_pg_enum_enumtypid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(enumtypoid));
 
    enum_rel = table_open(EnumRelationId, AccessShareLock);
    enum_idx = index_open(EnumTypIdSortOrderIndexId, AccessShareLock);
    enum_scan = systable_beginscan_ordered(enum_rel, enum_idx, NULL, 1, &skey);
 
    max = 64;
    elems = (Datum *) palloc(max * sizeof(Datum));
    cnt = 0;
    left_found = !OidIsValid(lower);
 
    while (HeapTupleIsValid(enum_tuple = systable_getnext_ordered(enum_scan, ForwardScanDirection)))
    {
        Oid         enum_oid = ((Form_pg_enum) GETSTRUCT(enum_tuple))->oid;
 
        if (!left_found && lower == enum_oid)
            left_found = true;
 
        if (left_found)
        {
            /* check it's safe to use in SQL */
            check_safe_enum_use(enum_tuple);
 
            if (cnt >= max)
            {
                max *= 2;
                elems = (Datum *) repalloc(elems, max * sizeof(Datum));
            }
 
            elems[cnt++] = ObjectIdGetDatum(enum_oid);
        }
 
        if (OidIsValid(upper) && upper == enum_oid)
            break;
    }
 
    systable_endscan_ordered(enum_scan);
    index_close(enum_idx, AccessShareLock);
    table_close(enum_rel, AccessShareLock);
 
    /* and build the result array */
    /* note this hardwires some details about the representation of Oid */
    result = construct_array(elems, cnt, enumtypoid,
                             sizeof(Oid), true, TYPALIGN_INT);
 
    pfree(elems);
 
    return result;
}