hstore_op.c

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/*
 * contrib/hstore/hstore_op.c
 */
#include "postgres.h"

#include "access/htup_details.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "hstore.h"
#include "utils/builtins.h"
#include "utils/hashutils.h"
#include "utils/memutils.h"

/* old names for C functions */
HSTORE_POLLUTE(hstore_fetchval, fetchval);
HSTORE_POLLUTE(hstore_exists, exists);
HSTORE_POLLUTE(hstore_defined, defined);
HSTORE_POLLUTE(hstore_delete, delete);
HSTORE_POLLUTE(hstore_concat, hs_concat);
HSTORE_POLLUTE(hstore_contains, hs_contains);
HSTORE_POLLUTE(hstore_contained, hs_contained);
HSTORE_POLLUTE(hstore_akeys, akeys);
HSTORE_POLLUTE(hstore_avals, avals);
HSTORE_POLLUTE(hstore_skeys, skeys);
HSTORE_POLLUTE(hstore_svals, svals);
HSTORE_POLLUTE(hstore_each, each);


/*
 * We're often finding a sequence of keys in ascending order. The
 * "lowbound" parameter is used to cache lower bounds of searches
 * between calls, based on this assumption. Pass NULL for it for
 * one-off or unordered searches.
 */
int
hstoreFindKey(HStore *hs, int *lowbound, char *key, int keylen)
{
    HEntry     *entries = ARRPTR(hs);
    int         stopLow = lowbound ? *lowbound : 0;
    int         stopHigh = HS_COUNT(hs);
    int         stopMiddle;
    char       *base = STRPTR(hs);

    while (stopLow < stopHigh)
    {
        int         difference;

        stopMiddle = stopLow + (stopHigh - stopLow) / 2;

        if (HSTORE_KEYLEN(entries, stopMiddle) == keylen)
            difference = memcmp(HSTORE_KEY(entries, base, stopMiddle), key, keylen);
        else
            difference = (HSTORE_KEYLEN(entries, stopMiddle) > keylen) ? 1 : -1;

        if (difference == 0)
        {
            if (lowbound)
                *lowbound = stopMiddle + 1;
            return stopMiddle;
        }
        else if (difference < 0)
            stopLow = stopMiddle + 1;
        else
            stopHigh = stopMiddle;
    }

    if (lowbound)
        *lowbound = stopLow;
    return -1;
}

Pairs *
hstoreArrayToPairs(ArrayType *a, int *npairs)
{
    Datum      *key_datums;
    bool       *key_nulls;
    int         key_count;
    Pairs      *key_pairs;
    int         bufsiz;
    int         i,
                j;

    deconstruct_array(a,
                      TEXTOID, -1, false, 'i',
                      &key_datums, &key_nulls, &key_count);

    if (key_count == 0)
    {
        *npairs = 0;
        return NULL;
    }

    /*
     * A text array uses at least eight bytes per element, so any overflow in
     * "key_count * sizeof(Pairs)" is small enough for palloc() to catch.
     * However, credible improvements to the array format could invalidate
     * that assumption.  Therefore, use an explicit check rather than relying
     * on palloc() to complain.
     */
    if (key_count > MaxAllocSize / sizeof(Pairs))
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("number of pairs (%d) exceeds the maximum allowed (%d)",
                        key_count, (int) (MaxAllocSize / sizeof(Pairs)))));

    key_pairs = palloc(sizeof(Pairs) * key_count);

    for (i = 0, j = 0; i < key_count; i++)
    {
        if (!key_nulls[i])
        {
            key_pairs[j].key = VARDATA(key_datums[i]);
            key_pairs[j].keylen = VARSIZE(key_datums[i]) - VARHDRSZ;
            key_pairs[j].val = NULL;
            key_pairs[j].vallen = 0;
            key_pairs[j].needfree = 0;
            key_pairs[j].isnull = 1;
            j++;
        }
    }

    *npairs = hstoreUniquePairs(key_pairs, j, &bufsiz);

    return key_pairs;
}


PG_FUNCTION_INFO_V1(hstore_fetchval);
Datum
hstore_fetchval(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    text       *key = PG_GETARG_TEXT_PP(1);
    HEntry     *entries = ARRPTR(hs);
    text       *out;
    int         idx = hstoreFindKey(hs, NULL,
                                    VARDATA_ANY(key), VARSIZE_ANY_EXHDR(key));

    if (idx < 0 || HSTORE_VALISNULL(entries, idx))
        PG_RETURN_NULL();

    out = cstring_to_text_with_len(HSTORE_VAL(entries, STRPTR(hs), idx),
                                   HSTORE_VALLEN(entries, idx));

    PG_RETURN_TEXT_P(out);
}


PG_FUNCTION_INFO_V1(hstore_exists);
Datum
hstore_exists(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    text       *key = PG_GETARG_TEXT_PP(1);
    int         idx = hstoreFindKey(hs, NULL,
                                    VARDATA_ANY(key), VARSIZE_ANY_EXHDR(key));

    PG_RETURN_BOOL(idx >= 0);
}


PG_FUNCTION_INFO_V1(hstore_exists_any);
Datum
hstore_exists_any(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    ArrayType  *keys = PG_GETARG_ARRAYTYPE_P(1);
    int         nkeys;
    Pairs      *key_pairs = hstoreArrayToPairs(keys, &nkeys);
    int         i;
    int         lowbound = 0;
    bool        res = false;

    /*
     * we exploit the fact that the pairs list is already sorted into strictly
     * increasing order to narrow the hstoreFindKey search; each search can
     * start one entry past the previous "found" entry, or at the lower bound
     * of the last search.
     */
    for (i = 0; i < nkeys; i++)
    {
        int         idx = hstoreFindKey(hs, &lowbound,
                                        key_pairs[i].key, key_pairs[i].keylen);

        if (idx >= 0)
        {
            res = true;
            break;
        }
    }

    PG_RETURN_BOOL(res);
}


PG_FUNCTION_INFO_V1(hstore_exists_all);
Datum
hstore_exists_all(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    ArrayType  *keys = PG_GETARG_ARRAYTYPE_P(1);
    int         nkeys;
    Pairs      *key_pairs = hstoreArrayToPairs(keys, &nkeys);
    int         i;
    int         lowbound = 0;
    bool        res = true;

    /*
     * we exploit the fact that the pairs list is already sorted into strictly
     * increasing order to narrow the hstoreFindKey search; each search can
     * start one entry past the previous "found" entry, or at the lower bound
     * of the last search.
     */
    for (i = 0; i < nkeys; i++)
    {
        int         idx = hstoreFindKey(hs, &lowbound,
                                        key_pairs[i].key, key_pairs[i].keylen);

        if (idx < 0)
        {
            res = false;
            break;
        }
    }

    PG_RETURN_BOOL(res);
}


PG_FUNCTION_INFO_V1(hstore_defined);
Datum
hstore_defined(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    text       *key = PG_GETARG_TEXT_PP(1);
    HEntry     *entries = ARRPTR(hs);
    int         idx = hstoreFindKey(hs, NULL,
                                    VARDATA_ANY(key), VARSIZE_ANY_EXHDR(key));
    bool        res = (idx >= 0 && !HSTORE_VALISNULL(entries, idx));

    PG_RETURN_BOOL(res);
}


PG_FUNCTION_INFO_V1(hstore_delete);
Datum
hstore_delete(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    text       *key = PG_GETARG_TEXT_PP(1);
    char       *keyptr = VARDATA_ANY(key);
    int         keylen = VARSIZE_ANY_EXHDR(key);
    HStore     *out = palloc(VARSIZE(hs));
    char       *bufs,
               *bufd,
               *ptrd;
    HEntry     *es,
               *ed;
    int         i;
    int         count = HS_COUNT(hs);
    int         outcount = 0;

    SET_VARSIZE(out, VARSIZE(hs));
    HS_SETCOUNT(out, count);    /* temporary! */

    bufs = STRPTR(hs);
    es = ARRPTR(hs);
    bufd = ptrd = STRPTR(out);
    ed = ARRPTR(out);

    for (i = 0; i < count; ++i)
    {
        int         len = HSTORE_KEYLEN(es, i);
        char       *ptrs = HSTORE_KEY(es, bufs, i);

        if (!(len == keylen && memcmp(ptrs, keyptr, keylen) == 0))
        {
            int         vallen = HSTORE_VALLEN(es, i);

            HS_COPYITEM(ed, bufd, ptrd, ptrs, len, vallen,
                        HSTORE_VALISNULL(es, i));
            ++outcount;
        }
    }

    HS_FINALIZE(out, outcount, bufd, ptrd);

    PG_RETURN_POINTER(out);
}


PG_FUNCTION_INFO_V1(hstore_delete_array);
Datum
hstore_delete_array(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    HStore     *out = palloc(VARSIZE(hs));
    int         hs_count = HS_COUNT(hs);
    char       *ps,
               *bufd,
               *pd;
    HEntry     *es,
               *ed;
    int         i,
                j;
    int         outcount = 0;
    ArrayType  *key_array = PG_GETARG_ARRAYTYPE_P(1);
    int         nkeys;
    Pairs      *key_pairs = hstoreArrayToPairs(key_array, &nkeys);

    SET_VARSIZE(out, VARSIZE(hs));
    HS_SETCOUNT(out, hs_count); /* temporary! */

    ps = STRPTR(hs);
    es = ARRPTR(hs);
    bufd = pd = STRPTR(out);
    ed = ARRPTR(out);

    if (nkeys == 0)
    {
        /* return a copy of the input, unchanged */
        memcpy(out, hs, VARSIZE(hs));
        HS_FIXSIZE(out, hs_count);
        HS_SETCOUNT(out, hs_count);
        PG_RETURN_POINTER(out);
    }

    /*
     * this is in effect a merge between hs and key_pairs, both of which are
     * already sorted by (keylen,key); we take keys from hs only
     */

    for (i = j = 0; i < hs_count;)
    {
        int         difference;

        if (j >= nkeys)
            difference = -1;
        else
        {
            int         skeylen = HSTORE_KEYLEN(es, i);

            if (skeylen == key_pairs[j].keylen)
                difference = memcmp(HSTORE_KEY(es, ps, i),
                                    key_pairs[j].key,
                                    key_pairs[j].keylen);
            else
                difference = (skeylen > key_pairs[j].keylen) ? 1 : -1;
        }

        if (difference > 0)
            ++j;
        else if (difference == 0)
            ++i, ++j;
        else
        {
            HS_COPYITEM(ed, bufd, pd,
                        HSTORE_KEY(es, ps, i), HSTORE_KEYLEN(es, i),
                        HSTORE_VALLEN(es, i), HSTORE_VALISNULL(es, i));
            ++outcount;
            ++i;
        }
    }

    HS_FINALIZE(out, outcount, bufd, pd);

    PG_RETURN_POINTER(out);
}


PG_FUNCTION_INFO_V1(hstore_delete_hstore);
Datum
hstore_delete_hstore(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    HStore     *hs2 = PG_GETARG_HSTORE_P(1);
    HStore     *out = palloc(VARSIZE(hs));
    int         hs_count = HS_COUNT(hs);
    int         hs2_count = HS_COUNT(hs2);
    char       *ps,
               *ps2,
               *bufd,
               *pd;
    HEntry     *es,
               *es2,
               *ed;
    int         i,
                j;
    int         outcount = 0;

    SET_VARSIZE(out, VARSIZE(hs));
    HS_SETCOUNT(out, hs_count); /* temporary! */

    ps = STRPTR(hs);
    es = ARRPTR(hs);
    ps2 = STRPTR(hs2);
    es2 = ARRPTR(hs2);
    bufd = pd = STRPTR(out);
    ed = ARRPTR(out);

    if (hs2_count == 0)
    {
        /* return a copy of the input, unchanged */
        memcpy(out, hs, VARSIZE(hs));
        HS_FIXSIZE(out, hs_count);
        HS_SETCOUNT(out, hs_count);
        PG_RETURN_POINTER(out);
    }

    /*
     * this is in effect a merge between hs and hs2, both of which are already
     * sorted by (keylen,key); we take keys from hs only; for equal keys, we
     * take the value from hs unless the values are equal
     */

    for (i = j = 0; i < hs_count;)
    {
        int         difference;

        if (j >= hs2_count)
            difference = -1;
        else
        {
            int         skeylen = HSTORE_KEYLEN(es, i);
            int         s2keylen = HSTORE_KEYLEN(es2, j);

            if (skeylen == s2keylen)
                difference = memcmp(HSTORE_KEY(es, ps, i),
                                    HSTORE_KEY(es2, ps2, j),
                                    skeylen);
            else
                difference = (skeylen > s2keylen) ? 1 : -1;
        }

        if (difference > 0)
            ++j;
        else if (difference == 0)
        {
            int         svallen = HSTORE_VALLEN(es, i);
            int         snullval = HSTORE_VALISNULL(es, i);

            if (snullval != HSTORE_VALISNULL(es2, j) ||
                (!snullval && (svallen != HSTORE_VALLEN(es2, j) ||
                               memcmp(HSTORE_VAL(es, ps, i),
                                      HSTORE_VAL(es2, ps2, j),
                                      svallen) != 0)))
            {
                HS_COPYITEM(ed, bufd, pd,
                            HSTORE_KEY(es, ps, i), HSTORE_KEYLEN(es, i),
                            svallen, snullval);
                ++outcount;
            }
            ++i, ++j;
        }
        else
        {
            HS_COPYITEM(ed, bufd, pd,
                        HSTORE_KEY(es, ps, i), HSTORE_KEYLEN(es, i),
                        HSTORE_VALLEN(es, i), HSTORE_VALISNULL(es, i));
            ++outcount;
            ++i;
        }
    }

    HS_FINALIZE(out, outcount, bufd, pd);

    PG_RETURN_POINTER(out);
}


PG_FUNCTION_INFO_V1(hstore_concat);
Datum
hstore_concat(PG_FUNCTION_ARGS)
{
    HStore     *s1 = PG_GETARG_HSTORE_P(0);
    HStore     *s2 = PG_GETARG_HSTORE_P(1);
    HStore     *out = palloc(VARSIZE(s1) + VARSIZE(s2));
    char       *ps1,
               *ps2,
               *bufd,
               *pd;
    HEntry     *es1,
               *es2,
               *ed;
    int         s1idx;
    int         s2idx;
    int         s1count = HS_COUNT(s1);
    int         s2count = HS_COUNT(s2);
    int         outcount = 0;

    SET_VARSIZE(out, VARSIZE(s1) + VARSIZE(s2) - HSHRDSIZE);
    HS_SETCOUNT(out, s1count + s2count);

    if (s1count == 0)
    {
        /* return a copy of the input, unchanged */
        memcpy(out, s2, VARSIZE(s2));
        HS_FIXSIZE(out, s2count);
        HS_SETCOUNT(out, s2count);
        PG_RETURN_POINTER(out);
    }

    if (s2count == 0)
    {
        /* return a copy of the input, unchanged */
        memcpy(out, s1, VARSIZE(s1));
        HS_FIXSIZE(out, s1count);
        HS_SETCOUNT(out, s1count);
        PG_RETURN_POINTER(out);
    }

    ps1 = STRPTR(s1);
    ps2 = STRPTR(s2);
    bufd = pd = STRPTR(out);
    es1 = ARRPTR(s1);
    es2 = ARRPTR(s2);
    ed = ARRPTR(out);

    /*
     * this is in effect a merge between s1 and s2, both of which are already
     * sorted by (keylen,key); we take s2 for equal keys
     */

    for (s1idx = s2idx = 0; s1idx < s1count || s2idx < s2count; ++outcount)
    {
        int         difference;

        if (s1idx >= s1count)
            difference = 1;
        else if (s2idx >= s2count)
            difference = -1;
        else
        {
            int         s1keylen = HSTORE_KEYLEN(es1, s1idx);
            int         s2keylen = HSTORE_KEYLEN(es2, s2idx);

            if (s1keylen == s2keylen)
                difference = memcmp(HSTORE_KEY(es1, ps1, s1idx),
                                    HSTORE_KEY(es2, ps2, s2idx),
                                    s1keylen);
            else
                difference = (s1keylen > s2keylen) ? 1 : -1;
        }

        if (difference >= 0)
        {
            HS_COPYITEM(ed, bufd, pd,
                        HSTORE_KEY(es2, ps2, s2idx), HSTORE_KEYLEN(es2, s2idx),
                        HSTORE_VALLEN(es2, s2idx), HSTORE_VALISNULL(es2, s2idx));
            ++s2idx;
            if (difference == 0)
                ++s1idx;
        }
        else
        {
            HS_COPYITEM(ed, bufd, pd,
                        HSTORE_KEY(es1, ps1, s1idx), HSTORE_KEYLEN(es1, s1idx),
                        HSTORE_VALLEN(es1, s1idx), HSTORE_VALISNULL(es1, s1idx));
            ++s1idx;
        }
    }

    HS_FINALIZE(out, outcount, bufd, pd);

    PG_RETURN_POINTER(out);
}


PG_FUNCTION_INFO_V1(hstore_slice_to_array);
Datum
hstore_slice_to_array(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    HEntry     *entries = ARRPTR(hs);
    char       *ptr = STRPTR(hs);
    ArrayType  *key_array = PG_GETARG_ARRAYTYPE_P(1);
    ArrayType  *aout;
    Datum      *key_datums;
    bool       *key_nulls;
    Datum      *out_datums;
    bool       *out_nulls;
    int         key_count;
    int         i;

    deconstruct_array(key_array,
                      TEXTOID, -1, false, 'i',
                      &key_datums, &key_nulls, &key_count);

    if (key_count == 0)
    {
        aout = construct_empty_array(TEXTOID);
        PG_RETURN_POINTER(aout);
    }

    out_datums = palloc(sizeof(Datum) * key_count);
    out_nulls = palloc(sizeof(bool) * key_count);

    for (i = 0; i < key_count; ++i)
    {
        text       *key = (text *) DatumGetPointer(key_datums[i]);
        int         idx;

        if (key_nulls[i])
            idx = -1;
        else
            idx = hstoreFindKey(hs, NULL, VARDATA(key), VARSIZE(key) - VARHDRSZ);

        if (idx < 0 || HSTORE_VALISNULL(entries, idx))
        {
            out_nulls[i] = true;
            out_datums[i] = (Datum) 0;
        }
        else
        {
            out_datums[i] = PointerGetDatum(
                                            cstring_to_text_with_len(HSTORE_VAL(entries, ptr, idx),
                                                                     HSTORE_VALLEN(entries, idx)));
            out_nulls[i] = false;
        }
    }

    aout = construct_md_array(out_datums, out_nulls,
                              ARR_NDIM(key_array),
                              ARR_DIMS(key_array),
                              ARR_LBOUND(key_array),
                              TEXTOID, -1, false, 'i');

    PG_RETURN_POINTER(aout);
}


PG_FUNCTION_INFO_V1(hstore_slice_to_hstore);
Datum
hstore_slice_to_hstore(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    HEntry     *entries = ARRPTR(hs);
    char       *ptr = STRPTR(hs);
    ArrayType  *key_array = PG_GETARG_ARRAYTYPE_P(1);
    HStore     *out;
    int         nkeys;
    Pairs      *key_pairs = hstoreArrayToPairs(key_array, &nkeys);
    Pairs      *out_pairs;
    int         bufsiz;
    int         lastidx = 0;
    int         i;
    int         out_count = 0;

    if (nkeys == 0)
    {
        out = hstorePairs(NULL, 0, 0);
        PG_RETURN_POINTER(out);
    }

    /* hstoreArrayToPairs() checked overflow */
    out_pairs = palloc(sizeof(Pairs) * nkeys);
    bufsiz = 0;

    /*
     * we exploit the fact that the pairs list is already sorted into strictly
     * increasing order to narrow the hstoreFindKey search; each search can
     * start one entry past the previous "found" entry, or at the lower bound
     * of the last search.
     */

    for (i = 0; i < nkeys; ++i)
    {
        int         idx = hstoreFindKey(hs, &lastidx,
                                        key_pairs[i].key, key_pairs[i].keylen);

        if (idx >= 0)
        {
            out_pairs[out_count].key = key_pairs[i].key;
            bufsiz += (out_pairs[out_count].keylen = key_pairs[i].keylen);
            out_pairs[out_count].val = HSTORE_VAL(entries, ptr, idx);
            bufsiz += (out_pairs[out_count].vallen = HSTORE_VALLEN(entries, idx));
            out_pairs[out_count].isnull = HSTORE_VALISNULL(entries, idx);
            out_pairs[out_count].needfree = false;
            ++out_count;
        }
    }

    /*
     * we don't use hstoreUniquePairs here because we know that the pairs list
     * is already sorted and uniq'ed.
     */

    out = hstorePairs(out_pairs, out_count, bufsiz);

    PG_RETURN_POINTER(out);
}


PG_FUNCTION_INFO_V1(hstore_akeys);
Datum
hstore_akeys(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    Datum      *d;
    ArrayType  *a;
    HEntry     *entries = ARRPTR(hs);
    char       *base = STRPTR(hs);
    int         count = HS_COUNT(hs);
    int         i;

    if (count == 0)
    {
        a = construct_empty_array(TEXTOID);
        PG_RETURN_POINTER(a);
    }

    d = (Datum *) palloc(sizeof(Datum) * count);

    for (i = 0; i < count; ++i)
    {
        text       *t = cstring_to_text_with_len(HSTORE_KEY(entries, base, i),
                                                 HSTORE_KEYLEN(entries, i));

        d[i] = PointerGetDatum(t);
    }

    a = construct_array(d, count,
                        TEXTOID, -1, false, 'i');

    PG_RETURN_POINTER(a);
}


PG_FUNCTION_INFO_V1(hstore_avals);
Datum
hstore_avals(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    Datum      *d;
    bool       *nulls;
    ArrayType  *a;
    HEntry     *entries = ARRPTR(hs);
    char       *base = STRPTR(hs);
    int         count = HS_COUNT(hs);
    int         lb = 1;
    int         i;

    if (count == 0)
    {
        a = construct_empty_array(TEXTOID);
        PG_RETURN_POINTER(a);
    }

    d = (Datum *) palloc(sizeof(Datum) * count);
    nulls = (bool *) palloc(sizeof(bool) * count);

    for (i = 0; i < count; ++i)
    {
        if (HSTORE_VALISNULL(entries, i))
        {
            d[i] = (Datum) 0;
            nulls[i] = true;
        }
        else
        {
            text       *item = cstring_to_text_with_len(HSTORE_VAL(entries, base, i),
                                                        HSTORE_VALLEN(entries, i));

            d[i] = PointerGetDatum(item);
            nulls[i] = false;
        }
    }

    a = construct_md_array(d, nulls, 1, &count, &lb,
                           TEXTOID, -1, false, 'i');

    PG_RETURN_POINTER(a);
}


static ArrayType *
hstore_to_array_internal(HStore *hs, int ndims)
{
    HEntry     *entries = ARRPTR(hs);
    char       *base = STRPTR(hs);
    int         count = HS_COUNT(hs);
    int         out_size[2] = {0, 2};
    int         lb[2] = {1, 1};
    Datum      *out_datums;
    bool       *out_nulls;
    int         i;

    Assert(ndims < 3);

    if (count == 0 || ndims == 0)
        return construct_empty_array(TEXTOID);

    out_size[0] = count * 2 / ndims;
    out_datums = palloc(sizeof(Datum) * count * 2);
    out_nulls = palloc(sizeof(bool) * count * 2);

    for (i = 0; i < count; ++i)
    {
        text       *key = cstring_to_text_with_len(HSTORE_KEY(entries, base, i),
                                                   HSTORE_KEYLEN(entries, i));

        out_datums[i * 2] = PointerGetDatum(key);
        out_nulls[i * 2] = false;

        if (HSTORE_VALISNULL(entries, i))
        {
            out_datums[i * 2 + 1] = (Datum) 0;
            out_nulls[i * 2 + 1] = true;
        }
        else
        {
            text       *item = cstring_to_text_with_len(HSTORE_VAL(entries, base, i),
                                                        HSTORE_VALLEN(entries, i));

            out_datums[i * 2 + 1] = PointerGetDatum(item);
            out_nulls[i * 2 + 1] = false;
        }
    }

    return construct_md_array(out_datums, out_nulls,
                              ndims, out_size, lb,
                              TEXTOID, -1, false, 'i');
}

PG_FUNCTION_INFO_V1(hstore_to_array);
Datum
hstore_to_array(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    ArrayType  *out = hstore_to_array_internal(hs, 1);

    PG_RETURN_POINTER(out);
}

PG_FUNCTION_INFO_V1(hstore_to_matrix);
Datum
hstore_to_matrix(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    ArrayType  *out = hstore_to_array_internal(hs, 2);

    PG_RETURN_POINTER(out);
}

/*
 * Common initialization function for the various set-returning
 * funcs. fcinfo is only passed if the function is to return a
 * composite; it will be used to look up the return tupledesc.
 * we stash a copy of the hstore in the multi-call context in
 * case it was originally toasted. (At least I assume that's why;
 * there was no explanatory comment in the original code. --AG)
 */

static void
setup_firstcall(FuncCallContext *funcctx, HStore *hs,
                FunctionCallInfo fcinfo)
{
    MemoryContext oldcontext;
    HStore     *st;

    oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

    st = (HStore *) palloc(VARSIZE(hs));
    memcpy(st, hs, VARSIZE(hs));

    funcctx->user_fctx = (void *) st;

    if (fcinfo)
    {
        TupleDesc   tupdesc;

        /* Build a tuple descriptor for our result type */
        if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
            elog(ERROR, "return type must be a row type");

        funcctx->tuple_desc = BlessTupleDesc(tupdesc);
    }

    MemoryContextSwitchTo(oldcontext);
}


PG_FUNCTION_INFO_V1(hstore_skeys);
Datum
hstore_skeys(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx;
    HStore     *hs;
    int         i;

    if (SRF_IS_FIRSTCALL())
    {
        hs = PG_GETARG_HSTORE_P(0);
        funcctx = SRF_FIRSTCALL_INIT();
        setup_firstcall(funcctx, hs, NULL);
    }

    funcctx = SRF_PERCALL_SETUP();
    hs = (HStore *) funcctx->user_fctx;
    i = funcctx->call_cntr;

    if (i < HS_COUNT(hs))
    {
        HEntry     *entries = ARRPTR(hs);
        text       *item;

        item = cstring_to_text_with_len(HSTORE_KEY(entries, STRPTR(hs), i),
                                        HSTORE_KEYLEN(entries, i));

        SRF_RETURN_NEXT(funcctx, PointerGetDatum(item));
    }

    SRF_RETURN_DONE(funcctx);
}


PG_FUNCTION_INFO_V1(hstore_svals);
Datum
hstore_svals(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx;
    HStore     *hs;
    int         i;

    if (SRF_IS_FIRSTCALL())
    {
        hs = PG_GETARG_HSTORE_P(0);
        funcctx = SRF_FIRSTCALL_INIT();
        setup_firstcall(funcctx, hs, NULL);
    }

    funcctx = SRF_PERCALL_SETUP();
    hs = (HStore *) funcctx->user_fctx;
    i = funcctx->call_cntr;

    if (i < HS_COUNT(hs))
    {
        HEntry     *entries = ARRPTR(hs);

        if (HSTORE_VALISNULL(entries, i))
        {
            ReturnSetInfo *rsi;

            /* ugly ugly ugly. why no macro for this? */
            (funcctx)->call_cntr++;
            rsi = (ReturnSetInfo *) fcinfo->resultinfo;
            rsi->isDone = ExprMultipleResult;
            PG_RETURN_NULL();
        }
        else
        {
            text       *item;

            item = cstring_to_text_with_len(HSTORE_VAL(entries, STRPTR(hs), i),
                                            HSTORE_VALLEN(entries, i));

            SRF_RETURN_NEXT(funcctx, PointerGetDatum(item));
        }
    }

    SRF_RETURN_DONE(funcctx);
}


PG_FUNCTION_INFO_V1(hstore_contains);
Datum
hstore_contains(PG_FUNCTION_ARGS)
{
    HStore     *val = PG_GETARG_HSTORE_P(0);
    HStore     *tmpl = PG_GETARG_HSTORE_P(1);
    bool        res = true;
    HEntry     *te = ARRPTR(tmpl);
    char       *tstr = STRPTR(tmpl);
    HEntry     *ve = ARRPTR(val);
    char       *vstr = STRPTR(val);
    int         tcount = HS_COUNT(tmpl);
    int         lastidx = 0;
    int         i;

    /*
     * we exploit the fact that keys in "tmpl" are in strictly increasing
     * order to narrow the hstoreFindKey search; each search can start one
     * entry past the previous "found" entry, or at the lower bound of the
     * search
     */

    for (i = 0; res && i < tcount; ++i)
    {
        int         idx = hstoreFindKey(val, &lastidx,
                                        HSTORE_KEY(te, tstr, i),
                                        HSTORE_KEYLEN(te, i));

        if (idx >= 0)
        {
            bool        nullval = HSTORE_VALISNULL(te, i);
            int         vallen = HSTORE_VALLEN(te, i);

            if (nullval != HSTORE_VALISNULL(ve, idx) ||
                (!nullval && (vallen != HSTORE_VALLEN(ve, idx) ||
                              memcmp(HSTORE_VAL(te, tstr, i),
                                     HSTORE_VAL(ve, vstr, idx),
                                     vallen) != 0)))
                res = false;
        }
        else
            res = false;
    }

    PG_RETURN_BOOL(res);
}


PG_FUNCTION_INFO_V1(hstore_contained);
Datum
hstore_contained(PG_FUNCTION_ARGS)
{
    PG_RETURN_DATUM(DirectFunctionCall2(hstore_contains,
                                        PG_GETARG_DATUM(1),
                                        PG_GETARG_DATUM(0)
                                        ));
}


PG_FUNCTION_INFO_V1(hstore_each);
Datum
hstore_each(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx;
    HStore     *hs;
    int         i;

    if (SRF_IS_FIRSTCALL())
    {
        hs = PG_GETARG_HSTORE_P(0);
        funcctx = SRF_FIRSTCALL_INIT();
        setup_firstcall(funcctx, hs, fcinfo);
    }

    funcctx = SRF_PERCALL_SETUP();
    hs = (HStore *) funcctx->user_fctx;
    i = funcctx->call_cntr;

    if (i < HS_COUNT(hs))
    {
        HEntry     *entries = ARRPTR(hs);
        char       *ptr = STRPTR(hs);
        Datum       res,
                    dvalues[2];
        bool        nulls[2] = {false, false};
        text       *item;
        HeapTuple   tuple;

        item = cstring_to_text_with_len(HSTORE_KEY(entries, ptr, i),
                                        HSTORE_KEYLEN(entries, i));
        dvalues[0] = PointerGetDatum(item);

        if (HSTORE_VALISNULL(entries, i))
        {
            dvalues[1] = (Datum) 0;
            nulls[1] = true;
        }
        else
        {
            item = cstring_to_text_with_len(HSTORE_VAL(entries, ptr, i),
                                            HSTORE_VALLEN(entries, i));
            dvalues[1] = PointerGetDatum(item);
        }

        tuple = heap_form_tuple(funcctx->tuple_desc, dvalues, nulls);
        res = HeapTupleGetDatum(tuple);

        SRF_RETURN_NEXT(funcctx, PointerGetDatum(res));
    }

    SRF_RETURN_DONE(funcctx);
}


/*
 * btree sort order for hstores isn't intended to be useful; we really only
 * care about equality versus non-equality.  we compare the entire string
 * buffer first, then the entry pos array.
 */

PG_FUNCTION_INFO_V1(hstore_cmp);
Datum
hstore_cmp(PG_FUNCTION_ARGS)
{
    HStore     *hs1 = PG_GETARG_HSTORE_P(0);
    HStore     *hs2 = PG_GETARG_HSTORE_P(1);
    int         hcount1 = HS_COUNT(hs1);
    int         hcount2 = HS_COUNT(hs2);
    int         res = 0;

    if (hcount1 == 0 || hcount2 == 0)
    {
        /*
         * if either operand is empty, and the other is nonempty, the nonempty
         * one is larger. If both are empty they are equal.
         */
        if (hcount1 > 0)
            res = 1;
        else if (hcount2 > 0)
            res = -1;
    }
    else
    {
        /* here we know both operands are nonempty */
        char       *str1 = STRPTR(hs1);
        char       *str2 = STRPTR(hs2);
        HEntry     *ent1 = ARRPTR(hs1);
        HEntry     *ent2 = ARRPTR(hs2);
        size_t      len1 = HSE_ENDPOS(ent1[2 * hcount1 - 1]);
        size_t      len2 = HSE_ENDPOS(ent2[2 * hcount2 - 1]);

        res = memcmp(str1, str2, Min(len1, len2));

        if (res == 0)
        {
            if (len1 > len2)
                res = 1;
            else if (len1 < len2)
                res = -1;
            else if (hcount1 > hcount2)
                res = 1;
            else if (hcount2 > hcount1)
                res = -1;
            else
            {
                int         count = hcount1 * 2;
                int         i;

                for (i = 0; i < count; ++i)
                    if (HSE_ENDPOS(ent1[i]) != HSE_ENDPOS(ent2[i]) ||
                        HSE_ISNULL(ent1[i]) != HSE_ISNULL(ent2[i]))
                        break;
                if (i < count)
                {
                    if (HSE_ENDPOS(ent1[i]) < HSE_ENDPOS(ent2[i]))
                        res = -1;
                    else if (HSE_ENDPOS(ent1[i]) > HSE_ENDPOS(ent2[i]))
                        res = 1;
                    else if (HSE_ISNULL(ent1[i]))
                        res = 1;
                    else if (HSE_ISNULL(ent2[i]))
                        res = -1;
                }
            }
        }
        else
        {
            res = (res > 0) ? 1 : -1;
        }
    }

    /*
     * this is a btree support function; this is one of the few places where
     * memory needs to be explicitly freed.
     */
    PG_FREE_IF_COPY(hs1, 0);
    PG_FREE_IF_COPY(hs2, 1);
    PG_RETURN_INT32(res);
}


PG_FUNCTION_INFO_V1(hstore_eq);
Datum
hstore_eq(PG_FUNCTION_ARGS)
{
    int         res = DatumGetInt32(DirectFunctionCall2(hstore_cmp,
                                                        PG_GETARG_DATUM(0),
                                                        PG_GETARG_DATUM(1)));

    PG_RETURN_BOOL(res == 0);
}

PG_FUNCTION_INFO_V1(hstore_ne);
Datum
hstore_ne(PG_FUNCTION_ARGS)
{
    int         res = DatumGetInt32(DirectFunctionCall2(hstore_cmp,
                                                        PG_GETARG_DATUM(0),
                                                        PG_GETARG_DATUM(1)));

    PG_RETURN_BOOL(res != 0);
}

PG_FUNCTION_INFO_V1(hstore_gt);
Datum
hstore_gt(PG_FUNCTION_ARGS)
{
    int         res = DatumGetInt32(DirectFunctionCall2(hstore_cmp,
                                                        PG_GETARG_DATUM(0),
                                                        PG_GETARG_DATUM(1)));

    PG_RETURN_BOOL(res > 0);
}

PG_FUNCTION_INFO_V1(hstore_ge);
Datum
hstore_ge(PG_FUNCTION_ARGS)
{
    int         res = DatumGetInt32(DirectFunctionCall2(hstore_cmp,
                                                        PG_GETARG_DATUM(0),
                                                        PG_GETARG_DATUM(1)));

    PG_RETURN_BOOL(res >= 0);
}

PG_FUNCTION_INFO_V1(hstore_lt);
Datum
hstore_lt(PG_FUNCTION_ARGS)
{
    int         res = DatumGetInt32(DirectFunctionCall2(hstore_cmp,
                                                        PG_GETARG_DATUM(0),
                                                        PG_GETARG_DATUM(1)));

    PG_RETURN_BOOL(res < 0);
}

PG_FUNCTION_INFO_V1(hstore_le);
Datum
hstore_le(PG_FUNCTION_ARGS)
{
    int         res = DatumGetInt32(DirectFunctionCall2(hstore_cmp,
                                                        PG_GETARG_DATUM(0),
                                                        PG_GETARG_DATUM(1)));

    PG_RETURN_BOOL(res <= 0);
}


PG_FUNCTION_INFO_V1(hstore_hash);
Datum
hstore_hash(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    Datum       hval = hash_any((unsigned char *) VARDATA(hs),
                                VARSIZE(hs) - VARHDRSZ);

    /*
     * This (along with hstore_hash_extended) is the only place in the code
     * that cares whether the overall varlena size exactly matches the true
     * data size; this assertion should be maintained by all the other code,
     * but we make it explicit here.
     */
    Assert(VARSIZE(hs) ==
           (HS_COUNT(hs) != 0 ?
            CALCDATASIZE(HS_COUNT(hs),
                         HSE_ENDPOS(ARRPTR(hs)[2 * HS_COUNT(hs) - 1])) :
            HSHRDSIZE));

    PG_FREE_IF_COPY(hs, 0);
    PG_RETURN_DATUM(hval);
}

PG_FUNCTION_INFO_V1(hstore_hash_extended);
Datum
hstore_hash_extended(PG_FUNCTION_ARGS)
{
    HStore     *hs = PG_GETARG_HSTORE_P(0);
    uint64      seed = PG_GETARG_INT64(1);
    Datum       hval;

    hval = hash_any_extended((unsigned char *) VARDATA(hs),
                             VARSIZE(hs) - VARHDRSZ,
                             seed);

    /* See comment in hstore_hash */
    Assert(VARSIZE(hs) ==
           (HS_COUNT(hs) != 0 ?
            CALCDATASIZE(HS_COUNT(hs),
                         HSE_ENDPOS(ARRPTR(hs)[2 * HS_COUNT(hs) - 1])) :
            HSHRDSIZE));

    PG_FREE_IF_COPY(hs, 0);
    PG_RETURN_DATUM(hval);
}