array_userfuncs.c

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/*-------------------------------------------------------------------------
 *
 * array_userfuncs.c
 *    Misc user-visible array support functions
 *
 * Copyright (c) 2003-2024, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/array_userfuncs.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "catalog/pg_type.h"
#include "common/int.h"
#include "common/pg_prng.h"
#include "libpq/pqformat.h"
#include "port/pg_bitutils.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/lsyscache.h"
#include "utils/typcache.h"
 
/*
 * SerialIOData
 *      Used for caching element-type data in array_agg_serialize
 */
typedef struct SerialIOData
{
    FmgrInfo    typsend;
} SerialIOData;
 
/*
 * DeserialIOData
 *      Used for caching element-type data in array_agg_deserialize
 */
typedef struct DeserialIOData
{
    FmgrInfo    typreceive;
    Oid         typioparam;
} DeserialIOData;
 
static Datum array_position_common(FunctionCallInfo fcinfo);
 
 
/*
 * fetch_array_arg_replace_nulls
 *
 * Fetch an array-valued argument in expanded form; if it's null, construct an
 * empty array value of the proper data type.  Also cache basic element type
 * information in fn_extra.
 *
 * Caution: if the input is a read/write pointer, this returns the input
 * argument; so callers must be sure that their changes are "safe", that is
 * they cannot leave the array in a corrupt state.
 *
 * If we're being called as an aggregate function, make sure any newly-made
 * expanded array is allocated in the aggregate state context, so as to save
 * copying operations.
 */
static ExpandedArrayHeader *
fetch_array_arg_replace_nulls(FunctionCallInfo fcinfo, int argno)
{
    ExpandedArrayHeader *eah;
    Oid         element_type;
    ArrayMetaState *my_extra;
    MemoryContext resultcxt;
 
    /* If first time through, create datatype cache struct */
    my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
    if (my_extra == NULL)
    {
        my_extra = (ArrayMetaState *)
            MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
                               sizeof(ArrayMetaState));
        my_extra->element_type = InvalidOid;
        fcinfo->flinfo->fn_extra = my_extra;
    }
 
    /* Figure out which context we want the result in */
    if (!AggCheckCallContext(fcinfo, &resultcxt))
        resultcxt = CurrentMemoryContext;
 
    /* Now collect the array value */
    if (!PG_ARGISNULL(argno))
    {
        MemoryContext oldcxt = MemoryContextSwitchTo(resultcxt);
 
        eah = PG_GETARG_EXPANDED_ARRAYX(argno, my_extra);
        MemoryContextSwitchTo(oldcxt);
    }
    else
    {
        /* We have to look up the array type and element type */
        Oid         arr_typeid = get_fn_expr_argtype(fcinfo->flinfo, argno);
 
        if (!OidIsValid(arr_typeid))
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("could not determine input data type")));
        element_type = get_element_type(arr_typeid);
        if (!OidIsValid(element_type))
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("input data type is not an array")));
 
        eah = construct_empty_expanded_array(element_type,
                                             resultcxt,
                                             my_extra);
    }
 
    return eah;
}
 
/*-----------------------------------------------------------------------------
 * array_append :
 *      push an element onto the end of a one-dimensional array
 *----------------------------------------------------------------------------
 */
Datum
array_append(PG_FUNCTION_ARGS)
{
    ExpandedArrayHeader *eah;
    Datum       newelem;
    bool        isNull;
    Datum       result;
    int        *dimv,
               *lb;
    int         indx;
    ArrayMetaState *my_extra;
 
    eah = fetch_array_arg_replace_nulls(fcinfo, 0);
    isNull = PG_ARGISNULL(1);
    if (isNull)
        newelem = (Datum) 0;
    else
        newelem = PG_GETARG_DATUM(1);
 
    if (eah->ndims == 1)
    {
        /* append newelem */
        lb = eah->lbound;
        dimv = eah->dims;
 
        /* index of added elem is at lb[0] + (dimv[0] - 1) + 1 */
        if (pg_add_s32_overflow(lb[0], dimv[0], &indx))
            ereport(ERROR,
                    (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                     errmsg("integer out of range")));
    }
    else if (eah->ndims == 0)
        indx = 1;
    else
        ereport(ERROR,
                (errcode(ERRCODE_DATA_EXCEPTION),
                 errmsg("argument must be empty or one-dimensional array")));
 
    /* Perform element insertion */
    my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
 
    result = array_set_element(EOHPGetRWDatum(&eah->hdr),
                               1, &indx, newelem, isNull,
                               -1, my_extra->typlen, my_extra->typbyval, my_extra->typalign);
 
    PG_RETURN_DATUM(result);
}
 
/*-----------------------------------------------------------------------------
 * array_prepend :
 *      push an element onto the front of a one-dimensional array
 *----------------------------------------------------------------------------
 */
Datum
array_prepend(PG_FUNCTION_ARGS)
{
    ExpandedArrayHeader *eah;
    Datum       newelem;
    bool        isNull;
    Datum       result;
    int        *lb;
    int         indx;
    int         lb0;
    ArrayMetaState *my_extra;
 
    isNull = PG_ARGISNULL(0);
    if (isNull)
        newelem = (Datum) 0;
    else
        newelem = PG_GETARG_DATUM(0);
    eah = fetch_array_arg_replace_nulls(fcinfo, 1);
 
    if (eah->ndims == 1)
    {
        /* prepend newelem */
        lb = eah->lbound;
        lb0 = lb[0];
 
        if (pg_sub_s32_overflow(lb0, 1, &indx))
            ereport(ERROR,
                    (errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                     errmsg("integer out of range")));
    }
    else if (eah->ndims == 0)
    {
        indx = 1;
        lb0 = 1;
    }
    else
        ereport(ERROR,
                (errcode(ERRCODE_DATA_EXCEPTION),
                 errmsg("argument must be empty or one-dimensional array")));
 
    /* Perform element insertion */
    my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
 
    result = array_set_element(EOHPGetRWDatum(&eah->hdr),
                               1, &indx, newelem, isNull,
                               -1, my_extra->typlen, my_extra->typbyval, my_extra->typalign);
 
    /* Readjust result's LB to match the input's, as expected for prepend */
    Assert(result == EOHPGetRWDatum(&eah->hdr));
    if (eah->ndims == 1)
    {
        /* This is ok whether we've deconstructed or not */
        eah->lbound[0] = lb0;
    }
 
    PG_RETURN_DATUM(result);
}
 
/*-----------------------------------------------------------------------------
 * array_cat :
 *      concatenate two nD arrays to form an nD array, or
 *      push an (n-1)D array onto the end of an nD array
 *----------------------------------------------------------------------------
 */
Datum
array_cat(PG_FUNCTION_ARGS)
{
    ArrayType  *v1,
               *v2;
    ArrayType  *result;
    int        *dims,
               *lbs,
                ndims,
                nitems,
                ndatabytes,
                nbytes;
    int        *dims1,
               *lbs1,
                ndims1,
                nitems1,
                ndatabytes1;
    int        *dims2,
               *lbs2,
                ndims2,
                nitems2,
                ndatabytes2;
    int         i;
    char       *dat1,
               *dat2;
    bits8      *bitmap1,
               *bitmap2;
    Oid         element_type;
    Oid         element_type1;
    Oid         element_type2;
    int32       dataoffset;
 
    /* Concatenating a null array is a no-op, just return the other input */
    if (PG_ARGISNULL(0))
    {
        if (PG_ARGISNULL(1))
            PG_RETURN_NULL();
        result = PG_GETARG_ARRAYTYPE_P(1);
        PG_RETURN_ARRAYTYPE_P(result);
    }
    if (PG_ARGISNULL(1))
    {
        result = PG_GETARG_ARRAYTYPE_P(0);
        PG_RETURN_ARRAYTYPE_P(result);
    }
 
    v1 = PG_GETARG_ARRAYTYPE_P(0);
    v2 = PG_GETARG_ARRAYTYPE_P(1);
 
    element_type1 = ARR_ELEMTYPE(v1);
    element_type2 = ARR_ELEMTYPE(v2);
 
    /* Check we have matching element types */
    if (element_type1 != element_type2)
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
                 errmsg("cannot concatenate incompatible arrays"),
                 errdetail("Arrays with element types %s and %s are not "
                           "compatible for concatenation.",
                           format_type_be(element_type1),
                           format_type_be(element_type2))));
 
    /* OK, use it */
    element_type = element_type1;
 
    /*----------
     * We must have one of the following combinations of inputs:
     * 1) one empty array, and one non-empty array
     * 2) both arrays empty
     * 3) two arrays with ndims1 == ndims2
     * 4) ndims1 == ndims2 - 1
     * 5) ndims1 == ndims2 + 1
     *----------
     */
    ndims1 = ARR_NDIM(v1);
    ndims2 = ARR_NDIM(v2);
 
    /*
     * short circuit - if one input array is empty, and the other is not, we
     * return the non-empty one as the result
     *
     * if both are empty, return the first one
     */
    if (ndims1 == 0 && ndims2 > 0)
        PG_RETURN_ARRAYTYPE_P(v2);
 
    if (ndims2 == 0)
        PG_RETURN_ARRAYTYPE_P(v1);
 
    /* the rest fall under rule 3, 4, or 5 */
    if (ndims1 != ndims2 &&
        ndims1 != ndims2 - 1 &&
        ndims1 != ndims2 + 1)
        ereport(ERROR,
                (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                 errmsg("cannot concatenate incompatible arrays"),
                 errdetail("Arrays of %d and %d dimensions are not "
                           "compatible for concatenation.",
                           ndims1, ndims2)));
 
    /* get argument array details */
    lbs1 = ARR_LBOUND(v1);
    lbs2 = ARR_LBOUND(v2);
    dims1 = ARR_DIMS(v1);
    dims2 = ARR_DIMS(v2);
    dat1 = ARR_DATA_PTR(v1);
    dat2 = ARR_DATA_PTR(v2);
    bitmap1 = ARR_NULLBITMAP(v1);
    bitmap2 = ARR_NULLBITMAP(v2);
    nitems1 = ArrayGetNItems(ndims1, dims1);
    nitems2 = ArrayGetNItems(ndims2, dims2);
    ndatabytes1 = ARR_SIZE(v1) - ARR_DATA_OFFSET(v1);
    ndatabytes2 = ARR_SIZE(v2) - ARR_DATA_OFFSET(v2);
 
    if (ndims1 == ndims2)
    {
        /*
         * resulting array is made up of the elements (possibly arrays
         * themselves) of the input argument arrays
         */
        ndims = ndims1;
        dims = (int *) palloc(ndims * sizeof(int));
        lbs = (int *) palloc(ndims * sizeof(int));
 
        dims[0] = dims1[0] + dims2[0];
        lbs[0] = lbs1[0];
 
        for (i = 1; i < ndims; i++)
        {
            if (dims1[i] != dims2[i] || lbs1[i] != lbs2[i])
                ereport(ERROR,
                        (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                         errmsg("cannot concatenate incompatible arrays"),
                         errdetail("Arrays with differing element dimensions are "
                                   "not compatible for concatenation.")));
 
            dims[i] = dims1[i];
            lbs[i] = lbs1[i];
        }
    }
    else if (ndims1 == ndims2 - 1)
    {
        /*
         * resulting array has the second argument as the outer array, with
         * the first argument inserted at the front of the outer dimension
         */
        ndims = ndims2;
        dims = (int *) palloc(ndims * sizeof(int));
        lbs = (int *) palloc(ndims * sizeof(int));
        memcpy(dims, dims2, ndims * sizeof(int));
        memcpy(lbs, lbs2, ndims * sizeof(int));
 
        /* increment number of elements in outer array */
        dims[0] += 1;
 
        /* make sure the added element matches our existing elements */
        for (i = 0; i < ndims1; i++)
        {
            if (dims1[i] != dims[i + 1] || lbs1[i] != lbs[i + 1])
                ereport(ERROR,
                        (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                         errmsg("cannot concatenate incompatible arrays"),
                         errdetail("Arrays with differing dimensions are not "
                                   "compatible for concatenation.")));
        }
    }
    else
    {
        /*
         * (ndims1 == ndims2 + 1)
         *
         * resulting array has the first argument as the outer array, with the
         * second argument appended to the end of the outer dimension
         */
        ndims = ndims1;
        dims = (int *) palloc(ndims * sizeof(int));
        lbs = (int *) palloc(ndims * sizeof(int));
        memcpy(dims, dims1, ndims * sizeof(int));
        memcpy(lbs, lbs1, ndims * sizeof(int));
 
        /* increment number of elements in outer array */
        dims[0] += 1;
 
        /* make sure the added element matches our existing elements */
        for (i = 0; i < ndims2; i++)
        {
            if (dims2[i] != dims[i + 1] || lbs2[i] != lbs[i + 1])
                ereport(ERROR,
                        (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                         errmsg("cannot concatenate incompatible arrays"),
                         errdetail("Arrays with differing dimensions are not "
                                   "compatible for concatenation.")));
        }
    }
 
    /* Do this mainly for overflow checking */
    nitems = ArrayGetNItems(ndims, dims);
    ArrayCheckBounds(ndims, dims, lbs);
 
    /* build the result array */
    ndatabytes = ndatabytes1 + ndatabytes2;
    if (ARR_HASNULL(v1) || ARR_HASNULL(v2))
    {
        dataoffset = ARR_OVERHEAD_WITHNULLS(ndims, nitems);
        nbytes = ndatabytes + dataoffset;
    }
    else
    {
        dataoffset = 0;         /* marker for no null bitmap */
        nbytes = ndatabytes + ARR_OVERHEAD_NONULLS(ndims);
    }
    result = (ArrayType *) palloc0(nbytes);
    SET_VARSIZE(result, nbytes);
    result->ndim = ndims;
    result->dataoffset = dataoffset;
    result->elemtype = element_type;
    memcpy(ARR_DIMS(result), dims, ndims * sizeof(int));
    memcpy(ARR_LBOUND(result), lbs, ndims * sizeof(int));
    /* data area is arg1 then arg2 */
    memcpy(ARR_DATA_PTR(result), dat1, ndatabytes1);
    memcpy(ARR_DATA_PTR(result) + ndatabytes1, dat2, ndatabytes2);
    /* handle the null bitmap if needed */
    if (ARR_HASNULL(result))
    {
        array_bitmap_copy(ARR_NULLBITMAP(result), 0,
                          bitmap1, 0,
                          nitems1);
        array_bitmap_copy(ARR_NULLBITMAP(result), nitems1,
                          bitmap2, 0,
                          nitems2);
    }
 
    PG_RETURN_ARRAYTYPE_P(result);
}
 
 
/*
 * ARRAY_AGG(anynonarray) aggregate function
 */
Datum
array_agg_transfn(PG_FUNCTION_ARGS)
{
    Oid         arg1_typeid = get_fn_expr_argtype(fcinfo->flinfo, 1);
    MemoryContext aggcontext;
    ArrayBuildState *state;
    Datum       elem;
 
    if (arg1_typeid == InvalidOid)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("could not determine input data type")));
 
    /*
     * Note: we do not need a run-time check about whether arg1_typeid is a
     * valid array element type, because the parser would have verified that
     * while resolving the input/result types of this polymorphic aggregate.
     */
 
    if (!AggCheckCallContext(fcinfo, &aggcontext))
    {
        /* cannot be called directly because of internal-type argument */
        elog(ERROR, "array_agg_transfn called in non-aggregate context");
    }
 
    if (PG_ARGISNULL(0))
        state = initArrayResult(arg1_typeid, aggcontext, false);
    else
        state = (ArrayBuildState *) PG_GETARG_POINTER(0);
 
    elem = PG_ARGISNULL(1) ? (Datum) 0 : PG_GETARG_DATUM(1);
 
    state = accumArrayResult(state,
                             elem,
                             PG_ARGISNULL(1),
                             arg1_typeid,
                             aggcontext);
 
    /*
     * The transition type for array_agg() is declared to be "internal", which
     * is a pass-by-value type the same size as a pointer.  So we can safely
     * pass the ArrayBuildState pointer through nodeAgg.c's machinations.
     */
    PG_RETURN_POINTER(state);
}
 
Datum
array_agg_combine(PG_FUNCTION_ARGS)
{
    ArrayBuildState *state1;
    ArrayBuildState *state2;
    MemoryContext agg_context;
    MemoryContext old_context;
 
    if (!AggCheckCallContext(fcinfo, &agg_context))
        elog(ERROR, "aggregate function called in non-aggregate context");
 
    state1 = PG_ARGISNULL(0) ? NULL : (ArrayBuildState *) PG_GETARG_POINTER(0);
    state2 = PG_ARGISNULL(1) ? NULL : (ArrayBuildState *) PG_GETARG_POINTER(1);
 
    if (state2 == NULL)
    {
        /*
         * NULL state2 is easy, just return state1, which we know is already
         * in the agg_context
         */
        if (state1 == NULL)
            PG_RETURN_NULL();
        PG_RETURN_POINTER(state1);
    }
 
    if (state1 == NULL)
    {
        /* We must copy state2's data into the agg_context */
        state1 = initArrayResultWithSize(state2->element_type, agg_context,
                                         false, state2->alen);
 
        old_context = MemoryContextSwitchTo(agg_context);
 
        for (int i = 0; i < state2->nelems; i++)
        {
            if (!state2->dnulls[i])
                state1->dvalues[i] = datumCopy(state2->dvalues[i],
                                               state1->typbyval,
                                               state1->typlen);
            else
                state1->dvalues[i] = (Datum) 0;
        }
 
        MemoryContextSwitchTo(old_context);
 
        memcpy(state1->dnulls, state2->dnulls, sizeof(bool) * state2->nelems);
 
        state1->nelems = state2->nelems;
 
        PG_RETURN_POINTER(state1);
    }
    else if (state2->nelems > 0)
    {
        /* We only need to combine the two states if state2 has any elements */
        int         reqsize = state1->nelems + state2->nelems;
        MemoryContext oldContext = MemoryContextSwitchTo(state1->mcontext);
 
        Assert(state1->element_type == state2->element_type);
 
        /* Enlarge state1 arrays if needed */
        if (state1->alen < reqsize)
        {
            /* Use a power of 2 size rather than allocating just reqsize */
            state1->alen = pg_nextpower2_32(reqsize);
            state1->dvalues = (Datum *) repalloc(state1->dvalues,
                                                 state1->alen * sizeof(Datum));
            state1->dnulls = (bool *) repalloc(state1->dnulls,
                                               state1->alen * sizeof(bool));
        }
 
        /* Copy in the state2 elements to the end of the state1 arrays */
        for (int i = 0; i < state2->nelems; i++)
        {
            if (!state2->dnulls[i])
                state1->dvalues[i + state1->nelems] =
                    datumCopy(state2->dvalues[i],
                              state1->typbyval,
                              state1->typlen);
            else
                state1->dvalues[i + state1->nelems] = (Datum) 0;
        }
 
        memcpy(&state1->dnulls[state1->nelems], state2->dnulls,
               sizeof(bool) * state2->nelems);
 
        state1->nelems = reqsize;
 
        MemoryContextSwitchTo(oldContext);
    }
 
    PG_RETURN_POINTER(state1);
}
 
/*
 * array_agg_serialize
 *      Serialize ArrayBuildState into bytea.
 */
Datum
array_agg_serialize(PG_FUNCTION_ARGS)
{
    ArrayBuildState *state;
    StringInfoData buf;
    bytea      *result;
 
    /* cannot be called directly because of internal-type argument */
    Assert(AggCheckCallContext(fcinfo, NULL));
 
    state = (ArrayBuildState *) PG_GETARG_POINTER(0);
 
    pq_begintypsend(&buf);
 
    /*
     * element_type. Putting this first is more convenient in deserialization
     */
    pq_sendint32(&buf, state->element_type);
 
    /*
     * nelems -- send first so we know how large to make the dvalues and
     * dnulls array during deserialization.
     */
    pq_sendint64(&buf, state->nelems);
 
    /* alen can be decided during deserialization */
 
    /* typlen */
    pq_sendint16(&buf, state->typlen);
 
    /* typbyval */
    pq_sendbyte(&buf, state->typbyval);
 
    /* typalign */
    pq_sendbyte(&buf, state->typalign);
 
    /* dnulls */
    pq_sendbytes(&buf, state->dnulls, sizeof(bool) * state->nelems);
 
    /*
     * dvalues.  By agreement with array_agg_deserialize, when the element
     * type is byval, we just transmit the Datum array as-is, including any
     * null elements.  For by-ref types, we must invoke the element type's
     * send function, and we skip null elements (which is why the nulls flags
     * must be sent first).
     */
    if (state->typbyval)
        pq_sendbytes(&buf, state->dvalues, sizeof(Datum) * state->nelems);
    else
    {
        SerialIOData *iodata;
        int         i;
 
        /* Avoid repeat catalog lookups for typsend function */
        iodata = (SerialIOData *) fcinfo->flinfo->fn_extra;
        if (iodata == NULL)
        {
            Oid         typsend;
            bool        typisvarlena;
 
            iodata = (SerialIOData *)
                MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
                                   sizeof(SerialIOData));
            getTypeBinaryOutputInfo(state->element_type, &typsend,
                                    &typisvarlena);
            fmgr_info_cxt(typsend, &iodata->typsend,
                          fcinfo->flinfo->fn_mcxt);
            fcinfo->flinfo->fn_extra = iodata;
        }
 
        for (i = 0; i < state->nelems; i++)
        {
            bytea      *outputbytes;
 
            if (state->dnulls[i])
                continue;
            outputbytes = SendFunctionCall(&iodata->typsend,
                                           state->dvalues[i]);
            pq_sendint32(&buf, VARSIZE(outputbytes) - VARHDRSZ);
            pq_sendbytes(&buf, VARDATA(outputbytes),
                         VARSIZE(outputbytes) - VARHDRSZ);
        }
    }
 
    result = pq_endtypsend(&buf);
 
    PG_RETURN_BYTEA_P(result);
}
 
Datum
array_agg_deserialize(PG_FUNCTION_ARGS)
{
    bytea      *sstate;
    ArrayBuildState *result;
    StringInfoData buf;
    Oid         element_type;
    int64       nelems;
    const char *temp;
 
    if (!AggCheckCallContext(fcinfo, NULL))
        elog(ERROR, "aggregate function called in non-aggregate context");
 
    sstate = PG_GETARG_BYTEA_PP(0);
 
    /*
     * Initialize a StringInfo so that we can "receive" it using the standard
     * recv-function infrastructure.
     */
    initReadOnlyStringInfo(&buf, VARDATA_ANY(sstate),
                           VARSIZE_ANY_EXHDR(sstate));
 
    /* element_type */
    element_type = pq_getmsgint(&buf, 4);
 
    /* nelems */
    nelems = pq_getmsgint64(&buf);
 
    /* Create output ArrayBuildState with the needed number of elements */
    result = initArrayResultWithSize(element_type, CurrentMemoryContext,
                                     false, nelems);
    result->nelems = nelems;
 
    /* typlen */
    result->typlen = pq_getmsgint(&buf, 2);
 
    /* typbyval */
    result->typbyval = pq_getmsgbyte(&buf);
 
    /* typalign */
    result->typalign = pq_getmsgbyte(&buf);
 
    /* dnulls */
    temp = pq_getmsgbytes(&buf, sizeof(bool) * nelems);
    memcpy(result->dnulls, temp, sizeof(bool) * nelems);
 
    /* dvalues --- see comment in array_agg_serialize */
    if (result->typbyval)
    {
        temp = pq_getmsgbytes(&buf, sizeof(Datum) * nelems);
        memcpy(result->dvalues, temp, sizeof(Datum) * nelems);
    }
    else
    {
        DeserialIOData *iodata;
 
        /* Avoid repeat catalog lookups for typreceive function */
        iodata = (DeserialIOData *) fcinfo->flinfo->fn_extra;
        if (iodata == NULL)
        {
            Oid         typreceive;
 
            iodata = (DeserialIOData *)
                MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
                                   sizeof(DeserialIOData));
            getTypeBinaryInputInfo(element_type, &typreceive,
                                   &iodata->typioparam);
            fmgr_info_cxt(typreceive, &iodata->typreceive,
                          fcinfo->flinfo->fn_mcxt);
            fcinfo->flinfo->fn_extra = iodata;
        }
 
        for (int i = 0; i < nelems; i++)
        {
            int         itemlen;
            StringInfoData elem_buf;
 
            if (result->dnulls[i])
            {
                result->dvalues[i] = (Datum) 0;
                continue;
            }
 
            itemlen = pq_getmsgint(&buf, 4);
            if (itemlen < 0 || itemlen > (buf.len - buf.cursor))
                ereport(ERROR,
                        (errcode(ERRCODE_INVALID_BINARY_REPRESENTATION),
                         errmsg("insufficient data left in message")));
 
            /*
             * Rather than copying data around, we just initialize a
             * StringInfo pointing to the correct portion of the message
             * buffer.
             */
            initReadOnlyStringInfo(&elem_buf, &buf.data[buf.cursor], itemlen);
 
            buf.cursor += itemlen;
 
            /* Now call the element's receiveproc */
            result->dvalues[i] = ReceiveFunctionCall(&iodata->typreceive,
                                                     &elem_buf,
                                                     iodata->typioparam,
                                                     -1);
        }
    }
 
    pq_getmsgend(&buf);
 
    PG_RETURN_POINTER(result);
}
 
Datum
array_agg_finalfn(PG_FUNCTION_ARGS)
{
    Datum       result;
    ArrayBuildState *state;
    int         dims[1];
    int         lbs[1];
 
    /* cannot be called directly because of internal-type argument */
    Assert(AggCheckCallContext(fcinfo, NULL));
 
    state = PG_ARGISNULL(0) ? NULL : (ArrayBuildState *) PG_GETARG_POINTER(0);
 
    if (state == NULL)
        PG_RETURN_NULL();       /* returns null iff no input values */
 
    dims[0] = state->nelems;
    lbs[0] = 1;
 
    /*
     * Make the result.  We cannot release the ArrayBuildState because
     * sometimes aggregate final functions are re-executed.  Rather, it is
     * nodeAgg.c's responsibility to reset the aggcontext when it's safe to do
     * so.
     */
    result = makeMdArrayResult(state, 1, dims, lbs,
                               CurrentMemoryContext,
                               false);
 
    PG_RETURN_DATUM(result);
}
 
/*
 * ARRAY_AGG(anyarray) aggregate function
 */
Datum
array_agg_array_transfn(PG_FUNCTION_ARGS)
{
    Oid         arg1_typeid = get_fn_expr_argtype(fcinfo->flinfo, 1);
    MemoryContext aggcontext;
    ArrayBuildStateArr *state;
 
    if (arg1_typeid == InvalidOid)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("could not determine input data type")));
 
    /*
     * Note: we do not need a run-time check about whether arg1_typeid is a
     * valid array type, because the parser would have verified that while
     * resolving the input/result types of this polymorphic aggregate.
     */
 
    if (!AggCheckCallContext(fcinfo, &aggcontext))
    {
        /* cannot be called directly because of internal-type argument */
        elog(ERROR, "array_agg_array_transfn called in non-aggregate context");
    }
 
 
    if (PG_ARGISNULL(0))
        state = initArrayResultArr(arg1_typeid, InvalidOid, aggcontext, false);
    else
        state = (ArrayBuildStateArr *) PG_GETARG_POINTER(0);
 
    state = accumArrayResultArr(state,
                                PG_GETARG_DATUM(1),
                                PG_ARGISNULL(1),
                                arg1_typeid,
                                aggcontext);
 
    /*
     * The transition type for array_agg() is declared to be "internal", which
     * is a pass-by-value type the same size as a pointer.  So we can safely
     * pass the ArrayBuildStateArr pointer through nodeAgg.c's machinations.
     */
    PG_RETURN_POINTER(state);
}
 
Datum
array_agg_array_combine(PG_FUNCTION_ARGS)
{
    ArrayBuildStateArr *state1;
    ArrayBuildStateArr *state2;
    MemoryContext agg_context;
    MemoryContext old_context;
 
    if (!AggCheckCallContext(fcinfo, &agg_context))
        elog(ERROR, "aggregate function called in non-aggregate context");
 
    state1 = PG_ARGISNULL(0) ? NULL : (ArrayBuildStateArr *) PG_GETARG_POINTER(0);
    state2 = PG_ARGISNULL(1) ? NULL : (ArrayBuildStateArr *) PG_GETARG_POINTER(1);
 
    if (state2 == NULL)
    {
        /*
         * NULL state2 is easy, just return state1, which we know is already
         * in the agg_context
         */
        if (state1 == NULL)
            PG_RETURN_NULL();
        PG_RETURN_POINTER(state1);
    }
 
    if (state1 == NULL)
    {
        /* We must copy state2's data into the agg_context */
        old_context = MemoryContextSwitchTo(agg_context);
 
        state1 = initArrayResultArr(state2->array_type, InvalidOid,
                                    agg_context, false);
 
        state1->abytes = state2->abytes;
        state1->data = (char *) palloc(state1->abytes);
 
        if (state2->nullbitmap)
        {
            int         size = (state2->aitems + 7) / 8;
 
            state1->nullbitmap = (bits8 *) palloc(size);
            memcpy(state1->nullbitmap, state2->nullbitmap, size);
        }
 
        memcpy(state1->data, state2->data, state2->nbytes);
        state1->nbytes = state2->nbytes;
        state1->aitems = state2->aitems;
        state1->nitems = state2->nitems;
        state1->ndims = state2->ndims;
        memcpy(state1->dims, state2->dims, sizeof(state2->dims));
        memcpy(state1->lbs, state2->lbs, sizeof(state2->lbs));
        state1->array_type = state2->array_type;
        state1->element_type = state2->element_type;
 
        MemoryContextSwitchTo(old_context);
 
        PG_RETURN_POINTER(state1);
    }
 
    /* We only need to combine the two states if state2 has any items */
    else if (state2->nitems > 0)
    {
        MemoryContext oldContext;
        int         reqsize = state1->nbytes + state2->nbytes;
        int         i;
 
        /*
         * Check the states are compatible with each other.  Ensure we use the
         * same error messages that are listed in accumArrayResultArr so that
         * the same error is shown as would have been if we'd not used the
         * combine function for the aggregation.
         */
        if (state1->ndims != state2->ndims)
            ereport(ERROR,
                    (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                     errmsg("cannot accumulate arrays of different dimensionality")));
 
        /* Check dimensions match ignoring the first dimension. */
        for (i = 1; i < state1->ndims; i++)
        {
            if (state1->dims[i] != state2->dims[i] || state1->lbs[i] != state2->lbs[i])
                ereport(ERROR,
                        (errcode(ERRCODE_ARRAY_SUBSCRIPT_ERROR),
                         errmsg("cannot accumulate arrays of different dimensionality")));
        }
 
 
        oldContext = MemoryContextSwitchTo(state1->mcontext);
 
        /*
         * If there's not enough space in state1 then we'll need to reallocate
         * more.
         */
        if (state1->abytes < reqsize)
        {
            /* use a power of 2 size rather than allocating just reqsize */
            state1->abytes = pg_nextpower2_32(reqsize);
            state1->data = (char *) repalloc(state1->data, state1->abytes);
        }
 
        if (state2->nullbitmap)
        {
            int         newnitems = state1->nitems + state2->nitems;
 
            if (state1->nullbitmap == NULL)
            {
                /*
                 * First input with nulls; we must retrospectively handle any
                 * previous inputs by marking all their items non-null.
                 */
                state1->aitems = pg_nextpower2_32(Max(256, newnitems + 1));
                state1->nullbitmap = (bits8 *) palloc((state1->aitems + 7) / 8);
                array_bitmap_copy(state1->nullbitmap, 0,
                                  NULL, 0,
                                  state1->nitems);
            }
            else if (newnitems > state1->aitems)
            {
                int         newaitems = state1->aitems + state2->aitems;
 
                state1->aitems = pg_nextpower2_32(newaitems);
                state1->nullbitmap = (bits8 *)
                    repalloc(state1->nullbitmap, (state1->aitems + 7) / 8);
            }
            array_bitmap_copy(state1->nullbitmap, state1->nitems,
                              state2->nullbitmap, 0,
                              state2->nitems);
        }
 
        memcpy(state1->data + state1->nbytes, state2->data, state2->nbytes);
        state1->nbytes += state2->nbytes;
        state1->nitems += state2->nitems;
 
        state1->dims[0] += state2->dims[0];
        /* remaining dims already match, per test above */
 
        Assert(state1->array_type == state2->array_type);
        Assert(state1->element_type == state2->element_type);
 
        MemoryContextSwitchTo(oldContext);
    }
 
    PG_RETURN_POINTER(state1);
}
 
/*
 * array_agg_array_serialize
 *      Serialize ArrayBuildStateArr into bytea.
 */
Datum
array_agg_array_serialize(PG_FUNCTION_ARGS)
{
    ArrayBuildStateArr *state;
    StringInfoData buf;
    bytea      *result;
 
    /* cannot be called directly because of internal-type argument */
    Assert(AggCheckCallContext(fcinfo, NULL));
 
    state = (ArrayBuildStateArr *) PG_GETARG_POINTER(0);
 
    pq_begintypsend(&buf);
 
    /*
     * element_type. Putting this first is more convenient in deserialization
     * so that we can init the new state sooner.
     */
    pq_sendint32(&buf, state->element_type);
 
    /* array_type */
    pq_sendint32(&buf, state->array_type);
 
    /* nbytes */
    pq_sendint32(&buf, state->nbytes);
 
    /* data */
    pq_sendbytes(&buf, state->data, state->nbytes);
 
    /* abytes */
    pq_sendint32(&buf, state->abytes);
 
    /* aitems */
    pq_sendint32(&buf, state->aitems);
 
    /* nullbitmap */
    if (state->nullbitmap)
    {
        Assert(state->aitems > 0);
        pq_sendbytes(&buf, state->nullbitmap, (state->aitems + 7) / 8);
    }
 
    /* nitems */
    pq_sendint32(&buf, state->nitems);
 
    /* ndims */
    pq_sendint32(&buf, state->ndims);
 
    /* dims: XXX should we just send ndims elements? */
    pq_sendbytes(&buf, state->dims, sizeof(state->dims));
 
    /* lbs */
    pq_sendbytes(&buf, state->lbs, sizeof(state->lbs));
 
    result = pq_endtypsend(&buf);
 
    PG_RETURN_BYTEA_P(result);
}
 
Datum
array_agg_array_deserialize(PG_FUNCTION_ARGS)
{
    bytea      *sstate;
    ArrayBuildStateArr *result;
    StringInfoData buf;
    Oid         element_type;
    Oid         array_type;
    int         nbytes;
    const char *temp;
 
    /* cannot be called directly because of internal-type argument */
    Assert(AggCheckCallContext(fcinfo, NULL));
 
    sstate = PG_GETARG_BYTEA_PP(0);
 
    /*
     * Initialize a StringInfo so that we can "receive" it using the standard
     * recv-function infrastructure.
     */
    initReadOnlyStringInfo(&buf, VARDATA_ANY(sstate),
                           VARSIZE_ANY_EXHDR(sstate));
 
    /* element_type */
    element_type = pq_getmsgint(&buf, 4);
 
    /* array_type */
    array_type = pq_getmsgint(&buf, 4);
 
    /* nbytes */
    nbytes = pq_getmsgint(&buf, 4);
 
    result = initArrayResultArr(array_type, element_type,
                                CurrentMemoryContext, false);
 
    result->abytes = 1024;
    while (result->abytes < nbytes)
        result->abytes *= 2;
 
    result->data = (char *) palloc(result->abytes);
 
    /* data */
    temp = pq_getmsgbytes(&buf, nbytes);
    memcpy(result->data, temp, nbytes);
    result->nbytes = nbytes;
 
    /* abytes */
    result->abytes = pq_getmsgint(&buf, 4);
 
    /* aitems: might be 0 */
    result->aitems = pq_getmsgint(&buf, 4);
 
    /* nullbitmap */
    if (result->aitems > 0)
    {
        int         size = (result->aitems + 7) / 8;
 
        result->nullbitmap = (bits8 *) palloc(size);
        temp = pq_getmsgbytes(&buf, size);
        memcpy(result->nullbitmap, temp, size);
    }
    else
        result->nullbitmap = NULL;
 
    /* nitems */
    result->nitems = pq_getmsgint(&buf, 4);
 
    /* ndims */
    result->ndims = pq_getmsgint(&buf, 4);
 
    /* dims */
    temp = pq_getmsgbytes(&buf, sizeof(result->dims));
    memcpy(result->dims, temp, sizeof(result->dims));
 
    /* lbs */
    temp = pq_getmsgbytes(&buf, sizeof(result->lbs));
    memcpy(result->lbs, temp, sizeof(result->lbs));
 
    pq_getmsgend(&buf);
 
    PG_RETURN_POINTER(result);
}
 
Datum
array_agg_array_finalfn(PG_FUNCTION_ARGS)
{
    Datum       result;
    ArrayBuildStateArr *state;
 
    /* cannot be called directly because of internal-type argument */
    Assert(AggCheckCallContext(fcinfo, NULL));
 
    state = PG_ARGISNULL(0) ? NULL : (ArrayBuildStateArr *) PG_GETARG_POINTER(0);
 
    if (state == NULL)
        PG_RETURN_NULL();       /* returns null iff no input values */
 
    /*
     * Make the result.  We cannot release the ArrayBuildStateArr because
     * sometimes aggregate final functions are re-executed.  Rather, it is
     * nodeAgg.c's responsibility to reset the aggcontext when it's safe to do
     * so.
     */
    result = makeArrayResultArr(state, CurrentMemoryContext, false);
 
    PG_RETURN_DATUM(result);
}
 
/*-----------------------------------------------------------------------------
 * array_position, array_position_start :
 *          return the offset of a value in an array.
 *
 * IS NOT DISTINCT FROM semantics are used for comparisons.  Return NULL when
 * the value is not found.
 *-----------------------------------------------------------------------------
 */
Datum
array_position(PG_FUNCTION_ARGS)
{
    return array_position_common(fcinfo);
}
 
Datum
array_position_start(PG_FUNCTION_ARGS)
{
    return array_position_common(fcinfo);
}
 
/*
 * array_position_common
 *      Common code for array_position and array_position_start
 *
 * These are separate wrappers for the sake of opr_sanity regression test.
 * They are not strict so we have to test for null inputs explicitly.
 */
static Datum
array_position_common(FunctionCallInfo fcinfo)
{
    ArrayType  *array;
    Oid         collation = PG_GET_COLLATION();
    Oid         element_type;
    Datum       searched_element,
                value;
    bool        isnull;
    int         position,
                position_min;
    bool        found = false;
    TypeCacheEntry *typentry;
    ArrayMetaState *my_extra;
    bool        null_search;
    ArrayIterator array_iterator;
 
    if (PG_ARGISNULL(0))
        PG_RETURN_NULL();
 
    array = PG_GETARG_ARRAYTYPE_P(0);
 
    /*
     * We refuse to search for elements in multi-dimensional arrays, since we
     * have no good way to report the element's location in the array.
     */
    if (ARR_NDIM(array) > 1)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("searching for elements in multidimensional arrays is not supported")));
 
    /* Searching in an empty array is well-defined, though: it always fails */
    if (ARR_NDIM(array) < 1)
        PG_RETURN_NULL();
 
    if (PG_ARGISNULL(1))
    {
        /* fast return when the array doesn't have nulls */
        if (!array_contains_nulls(array))
            PG_RETURN_NULL();
        searched_element = (Datum) 0;
        null_search = true;
    }
    else
    {
        searched_element = PG_GETARG_DATUM(1);
        null_search = false;
    }
 
    element_type = ARR_ELEMTYPE(array);
    position = (ARR_LBOUND(array))[0] - 1;
 
    /* figure out where to start */
    if (PG_NARGS() == 3)
    {
        if (PG_ARGISNULL(2))
            ereport(ERROR,
                    (errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
                     errmsg("initial position must not be null")));
 
        position_min = PG_GETARG_INT32(2);
    }
    else
        position_min = (ARR_LBOUND(array))[0];
 
    /*
     * We arrange to look up type info for array_create_iterator only once per
     * series of calls, assuming the element type doesn't change underneath
     * us.
     */
    my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
    if (my_extra == NULL)
    {
        fcinfo->flinfo->fn_extra = MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
                                                      sizeof(ArrayMetaState));
        my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
        my_extra->element_type = ~element_type;
    }
 
    if (my_extra->element_type != element_type)
    {
        get_typlenbyvalalign(element_type,
                             &my_extra->typlen,
                             &my_extra->typbyval,
                             &my_extra->typalign);
 
        typentry = lookup_type_cache(element_type, TYPECACHE_EQ_OPR_FINFO);
 
        if (!OidIsValid(typentry->eq_opr_finfo.fn_oid))
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_FUNCTION),
                     errmsg("could not identify an equality operator for type %s",
                            format_type_be(element_type))));
 
        my_extra->element_type = element_type;
        fmgr_info_cxt(typentry->eq_opr_finfo.fn_oid, &my_extra->proc,
                      fcinfo->flinfo->fn_mcxt);
    }
 
    /* Examine each array element until we find a match. */
    array_iterator = array_create_iterator(array, 0, my_extra);
    while (array_iterate(array_iterator, &value, &isnull))
    {
        position++;
 
        /* skip initial elements if caller requested so */
        if (position < position_min)
            continue;
 
        /*
         * Can't look at the array element's value if it's null; but if we
         * search for null, we have a hit and are done.
         */
        if (isnull || null_search)
        {
            if (isnull && null_search)
            {
                found = true;
                break;
            }
            else
                continue;
        }
 
        /* not nulls, so run the operator */
        if (DatumGetBool(FunctionCall2Coll(&my_extra->proc, collation,
                                           searched_element, value)))
        {
            found = true;
            break;
        }
    }
 
    array_free_iterator(array_iterator);
 
    /* Avoid leaking memory when handed toasted input */
    PG_FREE_IF_COPY(array, 0);
 
    if (!found)
        PG_RETURN_NULL();
 
    PG_RETURN_INT32(position);
}
 
/*-----------------------------------------------------------------------------
 * array_positions :
 *          return an array of positions of a value in an array.
 *
 * IS NOT DISTINCT FROM semantics are used for comparisons.  Returns NULL when
 * the input array is NULL.  When the value is not found in the array, returns
 * an empty array.
 *
 * This is not strict so we have to test for null inputs explicitly.
 *-----------------------------------------------------------------------------
 */
Datum
array_positions(PG_FUNCTION_ARGS)
{
    ArrayType  *array;
    Oid         collation = PG_GET_COLLATION();
    Oid         element_type;
    Datum       searched_element,
                value;
    bool        isnull;
    int         position;
    TypeCacheEntry *typentry;
    ArrayMetaState *my_extra;
    bool        null_search;
    ArrayIterator array_iterator;
    ArrayBuildState *astate = NULL;
 
    if (PG_ARGISNULL(0))
        PG_RETURN_NULL();
 
    array = PG_GETARG_ARRAYTYPE_P(0);
 
    /*
     * We refuse to search for elements in multi-dimensional arrays, since we
     * have no good way to report the element's location in the array.
     */
    if (ARR_NDIM(array) > 1)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("searching for elements in multidimensional arrays is not supported")));
 
    astate = initArrayResult(INT4OID, CurrentMemoryContext, false);
 
    /* Searching in an empty array is well-defined, though: it always fails */
    if (ARR_NDIM(array) < 1)
        PG_RETURN_DATUM(makeArrayResult(astate, CurrentMemoryContext));
 
    if (PG_ARGISNULL(1))
    {
        /* fast return when the array doesn't have nulls */
        if (!array_contains_nulls(array))
            PG_RETURN_DATUM(makeArrayResult(astate, CurrentMemoryContext));
        searched_element = (Datum) 0;
        null_search = true;
    }
    else
    {
        searched_element = PG_GETARG_DATUM(1);
        null_search = false;
    }
 
    element_type = ARR_ELEMTYPE(array);
    position = (ARR_LBOUND(array))[0] - 1;
 
    /*
     * We arrange to look up type info for array_create_iterator only once per
     * series of calls, assuming the element type doesn't change underneath
     * us.
     */
    my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
    if (my_extra == NULL)
    {
        fcinfo->flinfo->fn_extra = MemoryContextAlloc(fcinfo->flinfo->fn_mcxt,
                                                      sizeof(ArrayMetaState));
        my_extra = (ArrayMetaState *) fcinfo->flinfo->fn_extra;
        my_extra->element_type = ~element_type;
    }
 
    if (my_extra->element_type != element_type)
    {
        get_typlenbyvalalign(element_type,
                             &my_extra->typlen,
                             &my_extra->typbyval,
                             &my_extra->typalign);
 
        typentry = lookup_type_cache(element_type, TYPECACHE_EQ_OPR_FINFO);
 
        if (!OidIsValid(typentry->eq_opr_finfo.fn_oid))
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_FUNCTION),
                     errmsg("could not identify an equality operator for type %s",
                            format_type_be(element_type))));
 
        my_extra->element_type = element_type;
        fmgr_info_cxt(typentry->eq_opr_finfo.fn_oid, &my_extra->proc,
                      fcinfo->flinfo->fn_mcxt);
    }
 
    /*
     * Accumulate each array position iff the element matches the given
     * element.
     */
    array_iterator = array_create_iterator(array, 0, my_extra);
    while (array_iterate(array_iterator, &value, &isnull))
    {
        position += 1;
 
        /*
         * Can't look at the array element's value if it's null; but if we
         * search for null, we have a hit.
         */
        if (isnull || null_search)
        {
            if (isnull && null_search)
                astate =
                    accumArrayResult(astate, Int32GetDatum(position), false,
                                     INT4OID, CurrentMemoryContext);
 
            continue;
        }
 
        /* not nulls, so run the operator */
        if (DatumGetBool(FunctionCall2Coll(&my_extra->proc, collation,
                                           searched_element, value)))
            astate =
                accumArrayResult(astate, Int32GetDatum(position), false,
                                 INT4OID, CurrentMemoryContext);
    }
 
    array_free_iterator(array_iterator);
 
    /* Avoid leaking memory when handed toasted input */
    PG_FREE_IF_COPY(array, 0);
 
    PG_RETURN_DATUM(makeArrayResult(astate, CurrentMemoryContext));
}
 
/*
 * array_shuffle_n
 *      Return a copy of array with n randomly chosen items.
 *
 * The number of items must not exceed the size of the first dimension of the
 * array.  We preserve the first dimension's lower bound if keep_lb,
 * else it's set to 1.  Lower-order dimensions are preserved in any case.
 *
 * NOTE: it would be cleaner to look up the elmlen/elmbval/elmalign info
 * from the system catalogs, given only the elmtyp. However, the caller is
 * in a better position to cache this info across multiple calls.
 */
static ArrayType *
array_shuffle_n(ArrayType *array, int n, bool keep_lb,
                Oid elmtyp, TypeCacheEntry *typentry)
{
    ArrayType  *result;
    int         ndim,
               *dims,
               *lbs,
                nelm,
                nitem,
                rdims[MAXDIM],
                rlbs[MAXDIM];
    int16       elmlen;
    bool        elmbyval;
    char        elmalign;
    Datum      *elms,
               *ielms;
    bool       *nuls,
               *inuls;
 
    ndim = ARR_NDIM(array);
    dims = ARR_DIMS(array);
    lbs = ARR_LBOUND(array);
 
    elmlen = typentry->typlen;
    elmbyval = typentry->typbyval;
    elmalign = typentry->typalign;
 
    /* If the target array is empty, exit fast */
    if (ndim < 1 || dims[0] < 1 || n < 1)
        return construct_empty_array(elmtyp);
 
    deconstruct_array(array, elmtyp, elmlen, elmbyval, elmalign,
                      &elms, &nuls, &nelm);
 
    nitem = dims[0];            /* total number of items */
    nelm /= nitem;              /* number of elements per item */
 
    Assert(n <= nitem);         /* else it's caller error */
 
    /*
     * Shuffle array using Fisher-Yates algorithm.  Scan the array and swap
     * current item (nelm datums starting at ielms) with a randomly chosen
     * later item (nelm datums starting at jelms) in each iteration.  We can
     * stop once we've done n iterations; then first n items are the result.
     */
    ielms = elms;
    inuls = nuls;
    for (int i = 0; i < n; i++)
    {
        int         j = (int) pg_prng_uint64_range(&pg_global_prng_state, i, nitem - 1) * nelm;
        Datum      *jelms = elms + j;
        bool       *jnuls = nuls + j;
 
        /* Swap i'th and j'th items; advance ielms/inuls to next item */
        for (int k = 0; k < nelm; k++)
        {
            Datum       elm = *ielms;
            bool        nul = *inuls;
 
            *ielms++ = *jelms;
            *inuls++ = *jnuls;
            *jelms++ = elm;
            *jnuls++ = nul;
        }
    }
 
    /* Set up dimensions of the result */
    memcpy(rdims, dims, ndim * sizeof(int));
    memcpy(rlbs, lbs, ndim * sizeof(int));
    rdims[0] = n;
    if (!keep_lb)
        rlbs[0] = 1;
 
    result = construct_md_array(elms, nuls, ndim, rdims, rlbs,
                                elmtyp, elmlen, elmbyval, elmalign);
 
    pfree(elms);
    pfree(nuls);
 
    return result;
}
 
/*
 * array_shuffle
 *
 * Returns an array with the same dimensions as the input array, with its
 * first-dimension elements in random order.
 */
Datum
array_shuffle(PG_FUNCTION_ARGS)
{
    ArrayType  *array = PG_GETARG_ARRAYTYPE_P(0);
    ArrayType  *result;
    Oid         elmtyp;
    TypeCacheEntry *typentry;
 
    /*
     * There is no point in shuffling empty arrays or arrays with less than
     * two items.
     */
    if (ARR_NDIM(array) < 1 || ARR_DIMS(array)[0] < 2)
        PG_RETURN_ARRAYTYPE_P(array);
 
    elmtyp = ARR_ELEMTYPE(array);
    typentry = (TypeCacheEntry *) fcinfo->flinfo->fn_extra;
    if (typentry == NULL || typentry->type_id != elmtyp)
    {
        typentry = lookup_type_cache(elmtyp, 0);
        fcinfo->flinfo->fn_extra = typentry;
    }
 
    result = array_shuffle_n(array, ARR_DIMS(array)[0], true, elmtyp, typentry);
 
    PG_RETURN_ARRAYTYPE_P(result);
}
 
/*
 * array_sample
 *
 * Returns an array of n randomly chosen first-dimension elements
 * from the input array.
 */
Datum
array_sample(PG_FUNCTION_ARGS)
{
    ArrayType  *array = PG_GETARG_ARRAYTYPE_P(0);
    int         n = PG_GETARG_INT32(1);
    ArrayType  *result;
    Oid         elmtyp;
    TypeCacheEntry *typentry;
    int         nitem;
 
    nitem = (ARR_NDIM(array) < 1) ? 0 : ARR_DIMS(array)[0];
 
    if (n < 0 || n > nitem)
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("sample size must be between 0 and %d", nitem)));
 
    elmtyp = ARR_ELEMTYPE(array);
    typentry = (TypeCacheEntry *) fcinfo->flinfo->fn_extra;
    if (typentry == NULL || typentry->type_id != elmtyp)
    {
        typentry = lookup_type_cache(elmtyp, 0);
        fcinfo->flinfo->fn_extra = typentry;
    }
 
    result = array_shuffle_n(array, n, false, elmtyp, typentry);
 
    PG_RETURN_ARRAYTYPE_P(result);
}
 
 
/*
 * array_reverse_n
 *      Return a copy of array with reversed items.
 *
 * NOTE: it would be cleaner to look up the elmlen/elmbval/elmalign info
 * from the system catalogs, given only the elmtyp. However, the caller is
 * in a better position to cache this info across multiple calls.
 */
static ArrayType *
array_reverse_n(ArrayType *array, Oid elmtyp, TypeCacheEntry *typentry)
{
    ArrayType  *result;
    int         ndim,
               *dims,
               *lbs,
                nelm,
                nitem,
                rdims[MAXDIM],
                rlbs[MAXDIM];
    int16       elmlen;
    bool        elmbyval;
    char        elmalign;
    Datum      *elms,
               *ielms;
    bool       *nuls,
               *inuls;
 
    ndim = ARR_NDIM(array);
    dims = ARR_DIMS(array);
    lbs = ARR_LBOUND(array);
 
    elmlen = typentry->typlen;
    elmbyval = typentry->typbyval;
    elmalign = typentry->typalign;
 
    deconstruct_array(array, elmtyp, elmlen, elmbyval, elmalign,
                      &elms, &nuls, &nelm);
 
    nitem = dims[0];            /* total number of items */
    nelm /= nitem;              /* number of elements per item */
 
    /* Reverse the array */
    ielms = elms;
    inuls = nuls;
    for (int i = 0; i < nitem / 2; i++)
    {
        int         j = (nitem - i - 1) * nelm;
        Datum      *jelms = elms + j;
        bool       *jnuls = nuls + j;
 
        /* Swap i'th and j'th items; advance ielms/inuls to next item */
        for (int k = 0; k < nelm; k++)
        {
            Datum       elm = *ielms;
            bool        nul = *inuls;
 
            *ielms++ = *jelms;
            *inuls++ = *jnuls;
            *jelms++ = elm;
            *jnuls++ = nul;
        }
    }
 
    /* Set up dimensions of the result */
    memcpy(rdims, dims, ndim * sizeof(int));
    memcpy(rlbs, lbs, ndim * sizeof(int));
    rdims[0] = nitem;
 
    result = construct_md_array(elms, nuls, ndim, rdims, rlbs,
                                elmtyp, elmlen, elmbyval, elmalign);
 
    pfree(elms);
    pfree(nuls);
 
    return result;
}
 
/*
 * array_reverse
 *
 * Returns an array with the same dimensions as the input array, with its
 * first-dimension elements in reverse order.
 */
Datum
array_reverse(PG_FUNCTION_ARGS)
{
    ArrayType  *array = PG_GETARG_ARRAYTYPE_P(0);
    ArrayType  *result;
    Oid         elmtyp;
    TypeCacheEntry *typentry;
 
    /*
     * There is no point in reversing empty arrays or arrays with less than
     * two items.
     */
    if (ARR_NDIM(array) < 1 || ARR_DIMS(array)[0] < 2)
        PG_RETURN_ARRAYTYPE_P(array);
 
    elmtyp = ARR_ELEMTYPE(array);
    typentry = (TypeCacheEntry *) fcinfo->flinfo->fn_extra;
    if (typentry == NULL || typentry->type_id != elmtyp)
    {
        typentry = lookup_type_cache(elmtyp, 0);
        fcinfo->flinfo->fn_extra = (void *) typentry;
    }
 
    result = array_reverse_n(array, elmtyp, typentry);
 
    PG_RETURN_ARRAYTYPE_P(result);
}