Update copyright for 2022

[pgsql.git] / src / backend / access / hash / hashfunc.c

/*-------------------------------------------------------------------------
 *
 * hashfunc.c
 *        Support functions for hash access method.
 *
 * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *        src/backend/access/hash/hashfunc.c
 *
 * NOTES
 *        These functions are stored in pg_amproc.  For each operator class
 *        defined for hash indexes, they compute the hash value of the argument.
 *
 *        Additional hash functions appear in /utils/adt/ files for various
 *        specialized datatypes.
 *
 *        It is expected that every bit of a hash function's 32-bit result is
 *        as random as every other; failure to ensure this is likely to lead
 *        to poor performance of hash joins, for example.  In most cases a hash
 *        function should use hash_any() or its variant hash_uint32().
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/hash.h"
#include "catalog/pg_collation.h"
#include "common/hashfn.h"
#include "utils/builtins.h"
#include "utils/float.h"
#include "utils/pg_locale.h"

/*
 * Datatype-specific hash functions.
 *
 * These support both hash indexes and hash joins.
 *
 * NOTE: some of these are also used by catcache operations, without
 * any direct connection to hash indexes.  Also, the common hash_any
 * routine is also used by dynahash tables.
 */

/* Note: this is used for both "char" and boolean datatypes */
Datum
hashchar(PG_FUNCTION_ARGS)
{
        return hash_uint32((int32) PG_GETARG_CHAR(0));
}

Datum
hashcharextended(PG_FUNCTION_ARGS)
{
        return hash_uint32_extended((int32) PG_GETARG_CHAR(0), PG_GETARG_INT64(1));
}

Datum
hashint2(PG_FUNCTION_ARGS)
{
        return hash_uint32((int32) PG_GETARG_INT16(0));
}

Datum
hashint2extended(PG_FUNCTION_ARGS)
{
        return hash_uint32_extended((int32) PG_GETARG_INT16(0), PG_GETARG_INT64(1));
}

Datum
hashint4(PG_FUNCTION_ARGS)
{
        return hash_uint32(PG_GETARG_INT32(0));
}

Datum
hashint4extended(PG_FUNCTION_ARGS)
{
        return hash_uint32_extended(PG_GETARG_INT32(0), PG_GETARG_INT64(1));
}

Datum
hashint8(PG_FUNCTION_ARGS)
{
        /*
         * The idea here is to produce a hash value compatible with the values
         * produced by hashint4 and hashint2 for logically equal inputs; this is
         * necessary to support cross-type hash joins across these input types.
         * Since all three types are signed, we can xor the high half of the int8
         * value if the sign is positive, or the complement of the high half when
         * the sign is negative.
         */
        int64           val = PG_GETARG_INT64(0);
        uint32          lohalf = (uint32) val;
        uint32          hihalf = (uint32) (val >> 32);

        lohalf ^= (val >= 0) ? hihalf : ~hihalf;

        return hash_uint32(lohalf);
}

Datum
hashint8extended(PG_FUNCTION_ARGS)
{
        /* Same approach as hashint8 */
        int64           val = PG_GETARG_INT64(0);
        uint32          lohalf = (uint32) val;
        uint32          hihalf = (uint32) (val >> 32);

        lohalf ^= (val >= 0) ? hihalf : ~hihalf;

        return hash_uint32_extended(lohalf, PG_GETARG_INT64(1));
}

Datum
hashoid(PG_FUNCTION_ARGS)
{
        return hash_uint32((uint32) PG_GETARG_OID(0));
}

Datum
hashoidextended(PG_FUNCTION_ARGS)
{
        return hash_uint32_extended((uint32) PG_GETARG_OID(0), PG_GETARG_INT64(1));
}

Datum
hashenum(PG_FUNCTION_ARGS)
{
        return hash_uint32((uint32) PG_GETARG_OID(0));
}

Datum
hashenumextended(PG_FUNCTION_ARGS)
{
        return hash_uint32_extended((uint32) PG_GETARG_OID(0), PG_GETARG_INT64(1));
}

Datum
hashfloat4(PG_FUNCTION_ARGS)
{
        float4          key = PG_GETARG_FLOAT4(0);
        float8          key8;

        /*
         * On IEEE-float machines, minus zero and zero have different bit patterns
         * but should compare as equal.  We must ensure that they have the same
         * hash value, which is most reliably done this way:
         */
        if (key == (float4) 0)
                PG_RETURN_UINT32(0);

        /*
         * To support cross-type hashing of float8 and float4, we want to return
         * the same hash value hashfloat8 would produce for an equal float8 value.
         * So, widen the value to float8 and hash that.  (We must do this rather
         * than have hashfloat8 try to narrow its value to float4; that could fail
         * on overflow.)
         */
        key8 = key;

        /*
         * Similarly, NaNs can have different bit patterns but they should all
         * compare as equal.  For backwards-compatibility reasons we force them to
         * have the hash value of a standard float8 NaN.  (You'd think we could
         * replace key with a float4 NaN and then widen it; but on some old
         * platforms, that way produces a different bit pattern.)
         */
        if (isnan(key8))
                key8 = get_float8_nan();

        return hash_any((unsigned char *) &key8, sizeof(key8));
}

Datum
hashfloat4extended(PG_FUNCTION_ARGS)
{
        float4          key = PG_GETARG_FLOAT4(0);
        uint64          seed = PG_GETARG_INT64(1);
        float8          key8;

        /* Same approach as hashfloat4 */
        if (key == (float4) 0)
                PG_RETURN_UINT64(seed);
        key8 = key;
        if (isnan(key8))
                key8 = get_float8_nan();

        return hash_any_extended((unsigned char *) &key8, sizeof(key8), seed);
}

Datum
hashfloat8(PG_FUNCTION_ARGS)
{
        float8          key = PG_GETARG_FLOAT8(0);

        /*
         * On IEEE-float machines, minus zero and zero have different bit patterns
         * but should compare as equal.  We must ensure that they have the same
         * hash value, which is most reliably done this way:
         */
        if (key == (float8) 0)
                PG_RETURN_UINT32(0);

        /*
         * Similarly, NaNs can have different bit patterns but they should all
         * compare as equal.  For backwards-compatibility reasons we force them to
         * have the hash value of a standard NaN.
         */
        if (isnan(key))
                key = get_float8_nan();

        return hash_any((unsigned char *) &key, sizeof(key));
}

Datum
hashfloat8extended(PG_FUNCTION_ARGS)
{
        float8          key = PG_GETARG_FLOAT8(0);
        uint64          seed = PG_GETARG_INT64(1);

        /* Same approach as hashfloat8 */
        if (key == (float8) 0)
                PG_RETURN_UINT64(seed);
        if (isnan(key))
                key = get_float8_nan();

        return hash_any_extended((unsigned char *) &key, sizeof(key), seed);
}

Datum
hashoidvector(PG_FUNCTION_ARGS)
{
        oidvector  *key = (oidvector *) PG_GETARG_POINTER(0);

        return hash_any((unsigned char *) key->values, key->dim1 * sizeof(Oid));
}

Datum
hashoidvectorextended(PG_FUNCTION_ARGS)
{
        oidvector  *key = (oidvector *) PG_GETARG_POINTER(0);

        return hash_any_extended((unsigned char *) key->values,
                                                         key->dim1 * sizeof(Oid),
                                                         PG_GETARG_INT64(1));
}

Datum
hashname(PG_FUNCTION_ARGS)
{
        char       *key = NameStr(*PG_GETARG_NAME(0));

        return hash_any((unsigned char *) key, strlen(key));
}

Datum
hashnameextended(PG_FUNCTION_ARGS)
{
        char       *key = NameStr(*PG_GETARG_NAME(0));

        return hash_any_extended((unsigned char *) key, strlen(key),
                                                         PG_GETARG_INT64(1));
}

Datum
hashtext(PG_FUNCTION_ARGS)
{
        text       *key = PG_GETARG_TEXT_PP(0);
        Oid                     collid = PG_GET_COLLATION();
        pg_locale_t mylocale = 0;
        Datum           result;

        if (!collid)
                ereport(ERROR,
                                (errcode(ERRCODE_INDETERMINATE_COLLATION),
                                 errmsg("could not determine which collation to use for string hashing"),
                                 errhint("Use the COLLATE clause to set the collation explicitly.")));

        if (!lc_collate_is_c(collid) && collid != DEFAULT_COLLATION_OID)
                mylocale = pg_newlocale_from_collation(collid);

        if (!mylocale || mylocale->deterministic)
        {
                result = hash_any((unsigned char *) VARDATA_ANY(key),
                                                  VARSIZE_ANY_EXHDR(key));
        }
        else
        {
#ifdef USE_ICU
                if (mylocale->provider == COLLPROVIDER_ICU)
                {
                        int32_t         ulen = -1;
                        UChar      *uchar = NULL;
                        Size            bsize;
                        uint8_t    *buf;

                        ulen = icu_to_uchar(&uchar, VARDATA_ANY(key), VARSIZE_ANY_EXHDR(key));

                        bsize = ucol_getSortKey(mylocale->info.icu.ucol,
                                                                        uchar, ulen, NULL, 0);
                        buf = palloc(bsize);
                        ucol_getSortKey(mylocale->info.icu.ucol,
                                                        uchar, ulen, buf, bsize);

                        result = hash_any(buf, bsize);

                        pfree(buf);
                }
                else
#endif
                        /* shouldn't happen */
                        elog(ERROR, "unsupported collprovider: %c", mylocale->provider);
        }

        /* Avoid leaking memory for toasted inputs */
        PG_FREE_IF_COPY(key, 0);

        return result;
}

Datum
hashtextextended(PG_FUNCTION_ARGS)
{
        text       *key = PG_GETARG_TEXT_PP(0);
        Oid                     collid = PG_GET_COLLATION();
        pg_locale_t mylocale = 0;
        Datum           result;

        if (!collid)
                ereport(ERROR,
                                (errcode(ERRCODE_INDETERMINATE_COLLATION),
                                 errmsg("could not determine which collation to use for string hashing"),
                                 errhint("Use the COLLATE clause to set the collation explicitly.")));

        if (!lc_collate_is_c(collid) && collid != DEFAULT_COLLATION_OID)
                mylocale = pg_newlocale_from_collation(collid);

        if (!mylocale || mylocale->deterministic)
        {
                result = hash_any_extended((unsigned char *) VARDATA_ANY(key),
                                                                   VARSIZE_ANY_EXHDR(key),
                                                                   PG_GETARG_INT64(1));
        }
        else
        {
#ifdef USE_ICU
                if (mylocale->provider == COLLPROVIDER_ICU)
                {
                        int32_t         ulen = -1;
                        UChar      *uchar = NULL;
                        Size            bsize;
                        uint8_t    *buf;

                        ulen = icu_to_uchar(&uchar, VARDATA_ANY(key), VARSIZE_ANY_EXHDR(key));

                        bsize = ucol_getSortKey(mylocale->info.icu.ucol,
                                                                        uchar, ulen, NULL, 0);
                        buf = palloc(bsize);
                        ucol_getSortKey(mylocale->info.icu.ucol,
                                                        uchar, ulen, buf, bsize);

                        result = hash_any_extended(buf, bsize, PG_GETARG_INT64(1));

                        pfree(buf);
                }
                else
#endif
                        /* shouldn't happen */
                        elog(ERROR, "unsupported collprovider: %c", mylocale->provider);
        }

        PG_FREE_IF_COPY(key, 0);

        return result;
}

/*
 * hashvarlena() can be used for any varlena datatype in which there are
 * no non-significant bits, ie, distinct bitpatterns never compare as equal.
 */
Datum
hashvarlena(PG_FUNCTION_ARGS)
{
        struct varlena *key = PG_GETARG_VARLENA_PP(0);
        Datum           result;

        result = hash_any((unsigned char *) VARDATA_ANY(key),
                                          VARSIZE_ANY_EXHDR(key));

        /* Avoid leaking memory for toasted inputs */
        PG_FREE_IF_COPY(key, 0);

        return result;
}

Datum
hashvarlenaextended(PG_FUNCTION_ARGS)
{
        struct varlena *key = PG_GETARG_VARLENA_PP(0);
        Datum           result;

        result = hash_any_extended((unsigned char *) VARDATA_ANY(key),
                                                           VARSIZE_ANY_EXHDR(key),
                                                           PG_GETARG_INT64(1));

        PG_FREE_IF_COPY(key, 0);

        return result;
}