tuplesortvariants.c

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/*-------------------------------------------------------------------------
 *
 * tuplesortvariants.c
 *    Implementation of tuple sorting variants.
 *
 * This module handles the sorting of heap tuples, index tuples, or single
 * Datums.  The implementation is based on the generalized tuple sorting
 * facility given in tuplesort.c.  Support other kinds of sortable objects
 * could be easily added here, another module, or even an extension.
 *
 *
 * Copyright (c) 2022-2026, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    src/backend/utils/sort/tuplesortvariants.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "access/brin_tuple.h"
#include "access/gin.h"
#include "access/gin_tuple.h"
#include "access/hash.h"
#include "access/htup_details.h"
#include "access/nbtree.h"
#include "catalog/index.h"
#include "catalog/pg_collation.h"
#include "executor/executor.h"
#include "pg_trace.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/tuplesort.h"
 
 
/* sort-type codes for sort__start probes */
#define HEAP_SORT       0
#define INDEX_SORT      1
#define DATUM_SORT      2
#define CLUSTER_SORT    3
 
static void removeabbrev_heap(Tuplesortstate *state, SortTuple *stups,
                              int count);
static void removeabbrev_cluster(Tuplesortstate *state, SortTuple *stups,
                                 int count);
static void removeabbrev_index(Tuplesortstate *state, SortTuple *stups,
                               int count);
static void removeabbrev_index_brin(Tuplesortstate *state, SortTuple *stups,
                                    int count);
static void removeabbrev_index_gin(Tuplesortstate *state, SortTuple *stups,
                                   int count);
static void removeabbrev_datum(Tuplesortstate *state, SortTuple *stups,
                               int count);
static int  comparetup_heap(const SortTuple *a, const SortTuple *b,
                            Tuplesortstate *state);
static int  comparetup_heap_tiebreak(const SortTuple *a, const SortTuple *b,
                                     Tuplesortstate *state);
static void writetup_heap(Tuplesortstate *state, LogicalTape *tape,
                          SortTuple *stup);
static void readtup_heap(Tuplesortstate *state, SortTuple *stup,
                         LogicalTape *tape, unsigned int len);
static int  comparetup_cluster(const SortTuple *a, const SortTuple *b,
                               Tuplesortstate *state);
static int  comparetup_cluster_tiebreak(const SortTuple *a, const SortTuple *b,
                                        Tuplesortstate *state);
static void writetup_cluster(Tuplesortstate *state, LogicalTape *tape,
                             SortTuple *stup);
static void readtup_cluster(Tuplesortstate *state, SortTuple *stup,
                            LogicalTape *tape, unsigned int tuplen);
static int  comparetup_index_btree(const SortTuple *a, const SortTuple *b,
                                   Tuplesortstate *state);
static int  comparetup_index_btree_tiebreak(const SortTuple *a, const SortTuple *b,
                                            Tuplesortstate *state);
static int  comparetup_index_hash(const SortTuple *a, const SortTuple *b,
                                  Tuplesortstate *state);
static int  comparetup_index_hash_tiebreak(const SortTuple *a, const SortTuple *b,
                                           Tuplesortstate *state);
static int  comparetup_index_brin(const SortTuple *a, const SortTuple *b,
                                  Tuplesortstate *state);
static int  comparetup_index_gin(const SortTuple *a, const SortTuple *b,
                                 Tuplesortstate *state);
static void writetup_index(Tuplesortstate *state, LogicalTape *tape,
                           SortTuple *stup);
static void readtup_index(Tuplesortstate *state, SortTuple *stup,
                          LogicalTape *tape, unsigned int len);
static void writetup_index_brin(Tuplesortstate *state, LogicalTape *tape,
                                SortTuple *stup);
static void readtup_index_brin(Tuplesortstate *state, SortTuple *stup,
                               LogicalTape *tape, unsigned int len);
static void writetup_index_gin(Tuplesortstate *state, LogicalTape *tape,
                               SortTuple *stup);
static void readtup_index_gin(Tuplesortstate *state, SortTuple *stup,
                              LogicalTape *tape, unsigned int len);
static int  comparetup_datum(const SortTuple *a, const SortTuple *b,
                             Tuplesortstate *state);
static int  comparetup_datum_tiebreak(const SortTuple *a, const SortTuple *b,
                                      Tuplesortstate *state);
static void writetup_datum(Tuplesortstate *state, LogicalTape *tape,
                           SortTuple *stup);
static void readtup_datum(Tuplesortstate *state, SortTuple *stup,
                          LogicalTape *tape, unsigned int len);
static void freestate_cluster(Tuplesortstate *state);
 
/*
 * Data structure pointed by "TuplesortPublic.arg" for the CLUSTER case.  Set by
 * the tuplesort_begin_cluster.
 */
typedef struct
{
    TupleDesc   tupDesc;
 
    IndexInfo  *indexInfo;      /* info about index being used for reference */
    EState     *estate;         /* for evaluating index expressions */
} TuplesortClusterArg;
 
/*
 * Data structure pointed by "TuplesortPublic.arg" for the IndexTuple case.
 * Set by tuplesort_begin_index_xxx and used only by the IndexTuple routines.
 */
typedef struct
{
    Relation    heapRel;        /* table the index is being built on */
    Relation    indexRel;       /* index being built */
} TuplesortIndexArg;
 
/*
 * Data structure pointed by "TuplesortPublic.arg" for the index_btree subcase.
 */
typedef struct
{
    TuplesortIndexArg index;
 
    bool        enforceUnique;  /* complain if we find duplicate tuples */
    bool        uniqueNullsNotDistinct; /* unique constraint null treatment */
} TuplesortIndexBTreeArg;
 
/*
 * Data structure pointed by "TuplesortPublic.arg" for the index_hash subcase.
 */
typedef struct
{
    TuplesortIndexArg index;
 
    uint32      high_mask;      /* masks for sortable part of hash code */
    uint32      low_mask;
    uint32      max_buckets;
} TuplesortIndexHashArg;
 
/*
 * Data structure pointed by "TuplesortPublic.arg" for the Datum case.
 * Set by tuplesort_begin_datum and used only by the DatumTuple routines.
 */
typedef struct
{
    /* the datatype oid of Datum's to be sorted */
    Oid         datumType;
    /* we need typelen in order to know how to copy the Datums. */
    int         datumTypeLen;
} TuplesortDatumArg;
 
/*
 * Computing BrinTuple size with only the tuple is difficult, so we want to track
 * the length referenced by the SortTuple. That's what BrinSortTuple is meant
 * to do - it's essentially a BrinTuple prefixed by its length.
 */
typedef struct BrinSortTuple
{
    Size        tuplen;
    BrinTuple   tuple;
} BrinSortTuple;
 
/* Size of the BrinSortTuple, given length of the BrinTuple. */
#define BRINSORTTUPLE_SIZE(len)     (offsetof(BrinSortTuple, tuple) + (len))
 
 
Tuplesortstate *
tuplesort_begin_heap(TupleDesc tupDesc,
                     int nkeys, AttrNumber *attNums,
                     Oid *sortOperators, Oid *sortCollations,
                     bool *nullsFirstFlags,
                     int workMem, SortCoordinate coordinate, int sortopt)
{
    Tuplesortstate *state = tuplesort_begin_common(workMem, coordinate,
                                                   sortopt);
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext;
    int         i;
 
    oldcontext = MemoryContextSwitchTo(base->maincontext);
 
    Assert(nkeys > 0);
 
    if (trace_sort)
        elog(LOG,
             "begin tuple sort: nkeys = %d, workMem = %d, randomAccess = %c",
             nkeys, workMem, sortopt & TUPLESORT_RANDOMACCESS ? 't' : 'f');
 
    base->nKeys = nkeys;
 
    TRACE_POSTGRESQL_SORT_START(HEAP_SORT,
                                false,  /* no unique check */
                                nkeys,
                                workMem,
                                sortopt & TUPLESORT_RANDOMACCESS,
                                PARALLEL_SORT(coordinate));
 
    base->removeabbrev = removeabbrev_heap;
    base->comparetup = comparetup_heap;
    base->comparetup_tiebreak = comparetup_heap_tiebreak;
    base->writetup = writetup_heap;
    base->readtup = readtup_heap;
    base->haveDatum1 = true;
    base->arg = tupDesc;        /* assume we need not copy tupDesc */
 
    /* Prepare SortSupport data for each column */
    base->sortKeys = (SortSupport) palloc0(nkeys * sizeof(SortSupportData));
 
    for (i = 0; i < nkeys; i++)
    {
        SortSupport sortKey = base->sortKeys + i;
 
        Assert(attNums[i] != 0);
        Assert(sortOperators[i] != 0);
 
        sortKey->ssup_cxt = CurrentMemoryContext;
        sortKey->ssup_collation = sortCollations[i];
        sortKey->ssup_nulls_first = nullsFirstFlags[i];
        sortKey->ssup_attno = attNums[i];
        /* Convey if abbreviation optimization is applicable in principle */
        sortKey->abbreviate = (i == 0 && base->haveDatum1);
 
        PrepareSortSupportFromOrderingOp(sortOperators[i], sortKey);
    }
 
    /*
     * The "onlyKey" optimization cannot be used with abbreviated keys, since
     * tie-breaker comparisons may be required.  Typically, the optimization
     * is only of value to pass-by-value types anyway, whereas abbreviated
     * keys are typically only of value to pass-by-reference types.
     */
    if (nkeys == 1 && !base->sortKeys->abbrev_converter)
        base->onlyKey = base->sortKeys;
 
    MemoryContextSwitchTo(oldcontext);
 
    return state;
}
 
Tuplesortstate *
tuplesort_begin_cluster(TupleDesc tupDesc,
                        Relation indexRel,
                        int workMem,
                        SortCoordinate coordinate, int sortopt)
{
    Tuplesortstate *state = tuplesort_begin_common(workMem, coordinate,
                                                   sortopt);
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    BTScanInsert indexScanKey;
    MemoryContext oldcontext;
    TuplesortClusterArg *arg;
    int         i;
 
    Assert(indexRel->rd_rel->relam == BTREE_AM_OID);
 
    oldcontext = MemoryContextSwitchTo(base->maincontext);
    arg = palloc0_object(TuplesortClusterArg);
 
    if (trace_sort)
        elog(LOG,
             "begin tuple sort: nkeys = %d, workMem = %d, randomAccess = %c",
             RelationGetNumberOfAttributes(indexRel),
             workMem, sortopt & TUPLESORT_RANDOMACCESS ? 't' : 'f');
 
    base->nKeys = IndexRelationGetNumberOfKeyAttributes(indexRel);
 
    TRACE_POSTGRESQL_SORT_START(CLUSTER_SORT,
                                false,  /* no unique check */
                                base->nKeys,
                                workMem,
                                sortopt & TUPLESORT_RANDOMACCESS,
                                PARALLEL_SORT(coordinate));
 
    base->removeabbrev = removeabbrev_cluster;
    base->comparetup = comparetup_cluster;
    base->comparetup_tiebreak = comparetup_cluster_tiebreak;
    base->writetup = writetup_cluster;
    base->readtup = readtup_cluster;
    base->freestate = freestate_cluster;
    base->arg = arg;
 
    arg->indexInfo = BuildIndexInfo(indexRel);
 
    /*
     * If we don't have a simple leading attribute, we don't currently
     * initialize datum1, so disable optimizations that require it.
     */
    if (arg->indexInfo->ii_IndexAttrNumbers[0] == 0)
        base->haveDatum1 = false;
    else
        base->haveDatum1 = true;
 
    arg->tupDesc = tupDesc;     /* assume we need not copy tupDesc */
 
    indexScanKey = _bt_mkscankey(indexRel, NULL);
 
    if (arg->indexInfo->ii_Expressions != NULL)
    {
        TupleTableSlot *slot;
        ExprContext *econtext;
 
        /*
         * We will need to use FormIndexDatum to evaluate the index
         * expressions.  To do that, we need an EState, as well as a
         * TupleTableSlot to put the table tuples into.  The econtext's
         * scantuple has to point to that slot, too.
         */
        arg->estate = CreateExecutorState();
        slot = MakeSingleTupleTableSlot(tupDesc, &TTSOpsHeapTuple);
        econtext = GetPerTupleExprContext(arg->estate);
        econtext->ecxt_scantuple = slot;
    }
 
    /* Prepare SortSupport data for each column */
    base->sortKeys = (SortSupport) palloc0(base->nKeys *
                                           sizeof(SortSupportData));
 
    for (i = 0; i < base->nKeys; i++)
    {
        SortSupport sortKey = base->sortKeys + i;
        ScanKey     scanKey = indexScanKey->scankeys + i;
        bool        reverse;
 
        sortKey->ssup_cxt = CurrentMemoryContext;
        sortKey->ssup_collation = scanKey->sk_collation;
        sortKey->ssup_nulls_first =
            (scanKey->sk_flags & SK_BT_NULLS_FIRST) != 0;
        sortKey->ssup_attno = scanKey->sk_attno;
        /* Convey if abbreviation optimization is applicable in principle */
        sortKey->abbreviate = (i == 0 && base->haveDatum1);
 
        Assert(sortKey->ssup_attno != 0);
 
        reverse = (scanKey->sk_flags & SK_BT_DESC) != 0;
 
        PrepareSortSupportFromIndexRel(indexRel, reverse, sortKey);
    }
 
    pfree(indexScanKey);
 
    MemoryContextSwitchTo(oldcontext);
 
    return state;
}
 
Tuplesortstate *
tuplesort_begin_index_btree(Relation heapRel,
                            Relation indexRel,
                            bool enforceUnique,
                            bool uniqueNullsNotDistinct,
                            int workMem,
                            SortCoordinate coordinate,
                            int sortopt)
{
    Tuplesortstate *state = tuplesort_begin_common(workMem, coordinate,
                                                   sortopt);
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    BTScanInsert indexScanKey;
    TuplesortIndexBTreeArg *arg;
    MemoryContext oldcontext;
    int         i;
 
    oldcontext = MemoryContextSwitchTo(base->maincontext);
    arg = palloc_object(TuplesortIndexBTreeArg);
 
    if (trace_sort)
        elog(LOG,
             "begin index sort: unique = %c, workMem = %d, randomAccess = %c",
             enforceUnique ? 't' : 'f',
             workMem, sortopt & TUPLESORT_RANDOMACCESS ? 't' : 'f');
 
    base->nKeys = IndexRelationGetNumberOfKeyAttributes(indexRel);
 
    TRACE_POSTGRESQL_SORT_START(INDEX_SORT,
                                enforceUnique,
                                base->nKeys,
                                workMem,
                                sortopt & TUPLESORT_RANDOMACCESS,
                                PARALLEL_SORT(coordinate));
 
    base->removeabbrev = removeabbrev_index;
    base->comparetup = comparetup_index_btree;
    base->comparetup_tiebreak = comparetup_index_btree_tiebreak;
    base->writetup = writetup_index;
    base->readtup = readtup_index;
    base->haveDatum1 = true;
    base->arg = arg;
 
    arg->index.heapRel = heapRel;
    arg->index.indexRel = indexRel;
    arg->enforceUnique = enforceUnique;
    arg->uniqueNullsNotDistinct = uniqueNullsNotDistinct;
 
    indexScanKey = _bt_mkscankey(indexRel, NULL);
 
    /* Prepare SortSupport data for each column */
    base->sortKeys = (SortSupport) palloc0(base->nKeys *
                                           sizeof(SortSupportData));
 
    for (i = 0; i < base->nKeys; i++)
    {
        SortSupport sortKey = base->sortKeys + i;
        ScanKey     scanKey = indexScanKey->scankeys + i;
        bool        reverse;
 
        sortKey->ssup_cxt = CurrentMemoryContext;
        sortKey->ssup_collation = scanKey->sk_collation;
        sortKey->ssup_nulls_first =
            (scanKey->sk_flags & SK_BT_NULLS_FIRST) != 0;
        sortKey->ssup_attno = scanKey->sk_attno;
        /* Convey if abbreviation optimization is applicable in principle */
        sortKey->abbreviate = (i == 0 && base->haveDatum1);
 
        Assert(sortKey->ssup_attno != 0);
 
        reverse = (scanKey->sk_flags & SK_BT_DESC) != 0;
 
        PrepareSortSupportFromIndexRel(indexRel, reverse, sortKey);
    }
 
    pfree(indexScanKey);
 
    MemoryContextSwitchTo(oldcontext);
 
    return state;
}
 
Tuplesortstate *
tuplesort_begin_index_hash(Relation heapRel,
                           Relation indexRel,
                           uint32 high_mask,
                           uint32 low_mask,
                           uint32 max_buckets,
                           int workMem,
                           SortCoordinate coordinate,
                           int sortopt)
{
    Tuplesortstate *state = tuplesort_begin_common(workMem, coordinate,
                                                   sortopt);
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext;
    TuplesortIndexHashArg *arg;
 
    oldcontext = MemoryContextSwitchTo(base->maincontext);
    arg = palloc_object(TuplesortIndexHashArg);
 
    if (trace_sort)
        elog(LOG,
             "begin index sort: high_mask = 0x%x, low_mask = 0x%x, "
             "max_buckets = 0x%x, workMem = %d, randomAccess = %c",
             high_mask,
             low_mask,
             max_buckets,
             workMem,
             sortopt & TUPLESORT_RANDOMACCESS ? 't' : 'f');
 
    base->nKeys = 1;            /* Only one sort column, the hash code */
 
    base->removeabbrev = removeabbrev_index;
    base->comparetup = comparetup_index_hash;
    base->comparetup_tiebreak = comparetup_index_hash_tiebreak;
    base->writetup = writetup_index;
    base->readtup = readtup_index;
    base->haveDatum1 = true;
    base->arg = arg;
 
    arg->index.heapRel = heapRel;
    arg->index.indexRel = indexRel;
 
    arg->high_mask = high_mask;
    arg->low_mask = low_mask;
    arg->max_buckets = max_buckets;
 
    MemoryContextSwitchTo(oldcontext);
 
    return state;
}
 
Tuplesortstate *
tuplesort_begin_index_gist(Relation heapRel,
                           Relation indexRel,
                           int workMem,
                           SortCoordinate coordinate,
                           int sortopt)
{
    Tuplesortstate *state = tuplesort_begin_common(workMem, coordinate,
                                                   sortopt);
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext;
    TuplesortIndexBTreeArg *arg;
    int         i;
 
    oldcontext = MemoryContextSwitchTo(base->maincontext);
    arg = palloc_object(TuplesortIndexBTreeArg);
 
    if (trace_sort)
        elog(LOG,
             "begin index sort: workMem = %d, randomAccess = %c",
             workMem, sortopt & TUPLESORT_RANDOMACCESS ? 't' : 'f');
 
    base->nKeys = IndexRelationGetNumberOfKeyAttributes(indexRel);
 
    base->removeabbrev = removeabbrev_index;
    base->comparetup = comparetup_index_btree;
    base->comparetup_tiebreak = comparetup_index_btree_tiebreak;
    base->writetup = writetup_index;
    base->readtup = readtup_index;
    base->haveDatum1 = true;
    base->arg = arg;
 
    arg->index.heapRel = heapRel;
    arg->index.indexRel = indexRel;
    arg->enforceUnique = false;
    arg->uniqueNullsNotDistinct = false;
 
    /* Prepare SortSupport data for each column */
    base->sortKeys = (SortSupport) palloc0(base->nKeys *
                                           sizeof(SortSupportData));
 
    for (i = 0; i < base->nKeys; i++)
    {
        SortSupport sortKey = base->sortKeys + i;
 
        sortKey->ssup_cxt = CurrentMemoryContext;
        sortKey->ssup_collation = indexRel->rd_indcollation[i];
        sortKey->ssup_nulls_first = false;
        sortKey->ssup_attno = i + 1;
        /* Convey if abbreviation optimization is applicable in principle */
        sortKey->abbreviate = (i == 0 && base->haveDatum1);
 
        Assert(sortKey->ssup_attno != 0);
 
        /* Look for a sort support function */
        PrepareSortSupportFromGistIndexRel(indexRel, sortKey);
    }
 
    MemoryContextSwitchTo(oldcontext);
 
    return state;
}
 
Tuplesortstate *
tuplesort_begin_index_brin(int workMem,
                           SortCoordinate coordinate,
                           int sortopt)
{
    Tuplesortstate *state = tuplesort_begin_common(workMem, coordinate,
                                                   sortopt);
    TuplesortPublic *base = TuplesortstateGetPublic(state);
 
    if (trace_sort)
        elog(LOG,
             "begin index sort: workMem = %d, randomAccess = %c",
             workMem,
             sortopt & TUPLESORT_RANDOMACCESS ? 't' : 'f');
 
    base->nKeys = 1;            /* Only one sort column, the block number */
 
    base->removeabbrev = removeabbrev_index_brin;
    base->comparetup = comparetup_index_brin;
    base->writetup = writetup_index_brin;
    base->readtup = readtup_index_brin;
    base->haveDatum1 = true;
    base->arg = NULL;
 
    return state;
}
 
Tuplesortstate *
tuplesort_begin_index_gin(Relation heapRel,
                          Relation indexRel,
                          int workMem, SortCoordinate coordinate,
                          int sortopt)
{
    Tuplesortstate *state = tuplesort_begin_common(workMem, coordinate,
                                                   sortopt);
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext;
    int         i;
    TupleDesc   desc = RelationGetDescr(indexRel);
 
    oldcontext = MemoryContextSwitchTo(base->maincontext);
 
#ifdef TRACE_SORT
    if (trace_sort)
        elog(LOG,
             "begin index sort: workMem = %d, randomAccess = %c",
             workMem,
             sortopt & TUPLESORT_RANDOMACCESS ? 't' : 'f');
#endif
 
    /*
     * Multi-column GIN indexes expand the row into a separate index entry for
     * attribute, and that's what we write into the tuplesort. But we still
     * need to initialize sortsupport for all the attributes.
     */
    base->nKeys = IndexRelationGetNumberOfKeyAttributes(indexRel);
 
    /* Prepare SortSupport data for each column */
    base->sortKeys = (SortSupport) palloc0(base->nKeys *
                                           sizeof(SortSupportData));
 
    for (i = 0; i < base->nKeys; i++)
    {
        SortSupport sortKey = base->sortKeys + i;
        Form_pg_attribute att = TupleDescAttr(desc, i);
        Oid         cmpFunc;
 
        sortKey->ssup_cxt = CurrentMemoryContext;
        sortKey->ssup_collation = indexRel->rd_indcollation[i];
        sortKey->ssup_nulls_first = false;
        sortKey->ssup_attno = i + 1;
        sortKey->abbreviate = false;
 
        Assert(sortKey->ssup_attno != 0);
 
        if (!OidIsValid(sortKey->ssup_collation))
            sortKey->ssup_collation = DEFAULT_COLLATION_OID;
 
        /*
         * If the compare proc isn't specified in the opclass definition, look
         * up the index key type's default btree comparator.
         */
        cmpFunc = index_getprocid(indexRel, i + 1, GIN_COMPARE_PROC);
        if (cmpFunc == InvalidOid)
        {
            TypeCacheEntry *typentry;
 
            typentry = lookup_type_cache(att->atttypid,
                                         TYPECACHE_CMP_PROC_FINFO);
            if (!OidIsValid(typentry->cmp_proc_finfo.fn_oid))
                ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_FUNCTION),
                         errmsg("could not identify a comparison function for type %s",
                                format_type_be(att->atttypid))));
 
            cmpFunc = typentry->cmp_proc_finfo.fn_oid;
        }
 
        PrepareSortSupportComparisonShim(cmpFunc, sortKey);
    }
 
    base->removeabbrev = removeabbrev_index_gin;
    base->comparetup = comparetup_index_gin;
    base->writetup = writetup_index_gin;
    base->readtup = readtup_index_gin;
    base->haveDatum1 = false;
    base->arg = NULL;
 
    MemoryContextSwitchTo(oldcontext);
 
    return state;
}
 
Tuplesortstate *
tuplesort_begin_datum(Oid datumType, Oid sortOperator, Oid sortCollation,
                      bool nullsFirstFlag, int workMem,
                      SortCoordinate coordinate, int sortopt)
{
    Tuplesortstate *state = tuplesort_begin_common(workMem, coordinate,
                                                   sortopt);
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    TuplesortDatumArg *arg;
    MemoryContext oldcontext;
    int16       typlen;
    bool        typbyval;
 
    oldcontext = MemoryContextSwitchTo(base->maincontext);
    arg = palloc_object(TuplesortDatumArg);
 
    if (trace_sort)
        elog(LOG,
             "begin datum sort: workMem = %d, randomAccess = %c",
             workMem, sortopt & TUPLESORT_RANDOMACCESS ? 't' : 'f');
 
    base->nKeys = 1;            /* always a one-column sort */
 
    TRACE_POSTGRESQL_SORT_START(DATUM_SORT,
                                false,  /* no unique check */
                                1,
                                workMem,
                                sortopt & TUPLESORT_RANDOMACCESS,
                                PARALLEL_SORT(coordinate));
 
    base->removeabbrev = removeabbrev_datum;
    base->comparetup = comparetup_datum;
    base->comparetup_tiebreak = comparetup_datum_tiebreak;
    base->writetup = writetup_datum;
    base->readtup = readtup_datum;
    base->haveDatum1 = true;
    base->arg = arg;
 
    arg->datumType = datumType;
 
    /* lookup necessary attributes of the datum type */
    get_typlenbyval(datumType, &typlen, &typbyval);
    arg->datumTypeLen = typlen;
    base->tuples = !typbyval;
 
    /* Prepare SortSupport data */
    base->sortKeys = palloc0_object(SortSupportData);
 
    base->sortKeys->ssup_cxt = CurrentMemoryContext;
    base->sortKeys->ssup_collation = sortCollation;
    base->sortKeys->ssup_nulls_first = nullsFirstFlag;
 
    /*
     * Abbreviation is possible here only for by-reference types.  In theory,
     * a pass-by-value datatype could have an abbreviated form that is cheaper
     * to compare.  In a tuple sort, we could support that, because we can
     * always extract the original datum from the tuple as needed.  Here, we
     * can't, because a datum sort only stores a single copy of the datum; the
     * "tuple" field of each SortTuple is NULL.
     */
    base->sortKeys->abbreviate = !typbyval;
 
    PrepareSortSupportFromOrderingOp(sortOperator, base->sortKeys);
 
    /*
     * The "onlyKey" optimization cannot be used with abbreviated keys, since
     * tie-breaker comparisons may be required.  Typically, the optimization
     * is only of value to pass-by-value types anyway, whereas abbreviated
     * keys are typically only of value to pass-by-reference types.
     */
    if (!base->sortKeys->abbrev_converter)
        base->onlyKey = base->sortKeys;
 
    MemoryContextSwitchTo(oldcontext);
 
    return state;
}
 
/*
 * Accept one tuple while collecting input data for sort.
 *
 * Note that the input data is always copied; the caller need not save it.
 */
void
tuplesort_puttupleslot(Tuplesortstate *state, TupleTableSlot *slot)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext = MemoryContextSwitchTo(base->tuplecontext);
    TupleDesc   tupDesc = (TupleDesc) base->arg;
    SortTuple   stup;
    MinimalTuple tuple;
    HeapTupleData htup;
    Size        tuplen;
 
    /* copy the tuple into sort storage */
    tuple = ExecCopySlotMinimalTuple(slot);
    stup.tuple = tuple;
    /* set up first-column key value */
    htup.t_len = tuple->t_len + MINIMAL_TUPLE_OFFSET;
    htup.t_data = (HeapTupleHeader) ((char *) tuple - MINIMAL_TUPLE_OFFSET);
    stup.datum1 = heap_getattr(&htup,
                               base->sortKeys[0].ssup_attno,
                               tupDesc,
                               &stup.isnull1);
 
    /* GetMemoryChunkSpace is not supported for bump contexts */
    if (TupleSortUseBumpTupleCxt(base->sortopt))
        tuplen = MAXALIGN(tuple->t_len);
    else
        tuplen = GetMemoryChunkSpace(tuple);
 
    tuplesort_puttuple_common(state, &stup,
                              base->sortKeys->abbrev_converter &&
                              !stup.isnull1, tuplen);
 
    MemoryContextSwitchTo(oldcontext);
}
 
/*
 * Accept one tuple while collecting input data for sort.
 *
 * Note that the input data is always copied; the caller need not save it.
 */
void
tuplesort_putheaptuple(Tuplesortstate *state, HeapTuple tup)
{
    SortTuple   stup;
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext = MemoryContextSwitchTo(base->tuplecontext);
    TuplesortClusterArg *arg = (TuplesortClusterArg *) base->arg;
    Size        tuplen;
 
    /* copy the tuple into sort storage */
    tup = heap_copytuple(tup);
    stup.tuple = tup;
 
    /*
     * set up first-column key value, and potentially abbreviate, if it's a
     * simple column
     */
    if (base->haveDatum1)
    {
        stup.datum1 = heap_getattr(tup,
                                   arg->indexInfo->ii_IndexAttrNumbers[0],
                                   arg->tupDesc,
                                   &stup.isnull1);
    }
 
    /* GetMemoryChunkSpace is not supported for bump contexts */
    if (TupleSortUseBumpTupleCxt(base->sortopt))
        tuplen = MAXALIGN(HEAPTUPLESIZE + tup->t_len);
    else
        tuplen = GetMemoryChunkSpace(tup);
 
    tuplesort_puttuple_common(state, &stup,
                              base->haveDatum1 &&
                              base->sortKeys->abbrev_converter &&
                              !stup.isnull1, tuplen);
 
    MemoryContextSwitchTo(oldcontext);
}
 
/*
 * Collect one index tuple while collecting input data for sort, building
 * it from caller-supplied values.
 */
void
tuplesort_putindextuplevalues(Tuplesortstate *state, Relation rel,
                              const ItemPointerData *self, const Datum *values,
                              const bool *isnull)
{
    SortTuple   stup;
    IndexTuple  tuple;
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    TuplesortIndexArg *arg = (TuplesortIndexArg *) base->arg;
    Size        tuplen;
 
    stup.tuple = index_form_tuple_context(RelationGetDescr(rel), values,
                                          isnull, base->tuplecontext);
    tuple = ((IndexTuple) stup.tuple);
    tuple->t_tid = *self;
    /* set up first-column key value */
    stup.datum1 = index_getattr(tuple,
                                1,
                                RelationGetDescr(arg->indexRel),
                                &stup.isnull1);
 
    /* GetMemoryChunkSpace is not supported for bump contexts */
    if (TupleSortUseBumpTupleCxt(base->sortopt))
        tuplen = MAXALIGN(tuple->t_info & INDEX_SIZE_MASK);
    else
        tuplen = GetMemoryChunkSpace(tuple);
 
    tuplesort_puttuple_common(state, &stup,
                              base->sortKeys &&
                              base->sortKeys->abbrev_converter &&
                              !stup.isnull1, tuplen);
}
 
/*
 * Collect one BRIN tuple while collecting input data for sort.
 */
void
tuplesort_putbrintuple(Tuplesortstate *state, BrinTuple *tuple, Size size)
{
    SortTuple   stup;
    BrinSortTuple *bstup;
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext = MemoryContextSwitchTo(base->tuplecontext);
    Size        tuplen;
 
    /* allocate space for the whole BRIN sort tuple */
    bstup = palloc(BRINSORTTUPLE_SIZE(size));
 
    bstup->tuplen = size;
    memcpy(&bstup->tuple, tuple, size);
 
    stup.tuple = bstup;
    stup.datum1 = UInt32GetDatum(tuple->bt_blkno);
    stup.isnull1 = false;
 
    /* GetMemoryChunkSpace is not supported for bump contexts */
    if (TupleSortUseBumpTupleCxt(base->sortopt))
        tuplen = MAXALIGN(BRINSORTTUPLE_SIZE(size));
    else
        tuplen = GetMemoryChunkSpace(bstup);
 
    tuplesort_puttuple_common(state, &stup,
                              base->sortKeys &&
                              base->sortKeys->abbrev_converter &&
                              !stup.isnull1, tuplen);
 
    MemoryContextSwitchTo(oldcontext);
}
 
void
tuplesort_putgintuple(Tuplesortstate *state, GinTuple *tuple, Size size)
{
    SortTuple   stup;
    GinTuple   *ctup;
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext = MemoryContextSwitchTo(base->tuplecontext);
    Size        tuplen;
 
    /* copy the GinTuple into the right memory context */
    ctup = palloc(size);
    memcpy(ctup, tuple, size);
 
    stup.tuple = ctup;
    stup.datum1 = (Datum) 0;
    stup.isnull1 = false;
 
    /* GetMemoryChunkSpace is not supported for bump contexts */
    if (TupleSortUseBumpTupleCxt(base->sortopt))
        tuplen = MAXALIGN(size);
    else
        tuplen = GetMemoryChunkSpace(ctup);
 
    tuplesort_puttuple_common(state, &stup,
                              base->sortKeys &&
                              base->sortKeys->abbrev_converter &&
                              !stup.isnull1, tuplen);
 
    MemoryContextSwitchTo(oldcontext);
}
 
/*
 * Accept one Datum while collecting input data for sort.
 *
 * If the Datum is pass-by-ref type, the value will be copied.
 */
void
tuplesort_putdatum(Tuplesortstate *state, Datum val, bool isNull)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext = MemoryContextSwitchTo(base->tuplecontext);
    TuplesortDatumArg *arg = (TuplesortDatumArg *) base->arg;
    SortTuple   stup;
 
    /*
     * Pass-by-value types or null values are just stored directly in
     * stup.datum1 (and stup.tuple is not used and set to NULL).
     *
     * Non-null pass-by-reference values need to be copied into memory we
     * control, and possibly abbreviated. The copied value is pointed to by
     * stup.tuple and is treated as the canonical copy (e.g. to return via
     * tuplesort_getdatum or when writing to tape); stup.datum1 gets the
     * abbreviated value if abbreviation is happening, otherwise it's
     * identical to stup.tuple.
     */
 
    if (isNull || !base->tuples)
    {
        /*
         * Set datum1 to zeroed representation for NULLs (to be consistent,
         * and to support cheap inequality tests for NULL abbreviated keys).
         */
        stup.datum1 = !isNull ? val : (Datum) 0;
        stup.isnull1 = isNull;
        stup.tuple = NULL;      /* no separate storage */
    }
    else
    {
        stup.isnull1 = false;
        stup.datum1 = datumCopy(val, false, arg->datumTypeLen);
        stup.tuple = DatumGetPointer(stup.datum1);
    }
 
    tuplesort_puttuple_common(state, &stup,
                              base->tuples &&
                              base->sortKeys->abbrev_converter && !isNull, 0);
 
    MemoryContextSwitchTo(oldcontext);
}
 
/*
 * Fetch the next tuple in either forward or back direction.
 * If successful, put tuple in slot and return true; else, clear the slot
 * and return false.
 *
 * Caller may optionally be passed back abbreviated value (on true return
 * value) when abbreviation was used, which can be used to cheaply avoid
 * equality checks that might otherwise be required.  Caller can safely make a
 * determination of "non-equal tuple" based on simple binary inequality.  A
 * NULL value in leading attribute will set abbreviated value to zeroed
 * representation, which caller may rely on in abbreviated inequality check.
 *
 * If copy is true, the slot receives a tuple that's been copied into the
 * caller's memory context, so that it will stay valid regardless of future
 * manipulations of the tuplesort's state (up to and including deleting the
 * tuplesort).  If copy is false, the slot will just receive a pointer to a
 * tuple held within the tuplesort, which is more efficient, but only safe for
 * callers that are prepared to have any subsequent manipulation of the
 * tuplesort's state invalidate slot contents.
 */
bool
tuplesort_gettupleslot(Tuplesortstate *state, bool forward, bool copy,
                       TupleTableSlot *slot, Datum *abbrev)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext = MemoryContextSwitchTo(base->sortcontext);
    SortTuple   stup;
 
    if (!tuplesort_gettuple_common(state, forward, &stup))
        stup.tuple = NULL;
 
    MemoryContextSwitchTo(oldcontext);
 
    if (stup.tuple)
    {
        /* Record abbreviated key for caller */
        if (base->sortKeys->abbrev_converter && abbrev)
            *abbrev = stup.datum1;
 
        if (copy)
            stup.tuple = heap_copy_minimal_tuple((MinimalTuple) stup.tuple, 0);
 
        ExecStoreMinimalTuple((MinimalTuple) stup.tuple, slot, copy);
        return true;
    }
    else
    {
        ExecClearTuple(slot);
        return false;
    }
}
 
/*
 * Fetch the next tuple in either forward or back direction.
 * Returns NULL if no more tuples.  Returned tuple belongs to tuplesort memory
 * context, and must not be freed by caller.  Caller may not rely on tuple
 * remaining valid after any further manipulation of tuplesort.
 */
HeapTuple
tuplesort_getheaptuple(Tuplesortstate *state, bool forward)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext = MemoryContextSwitchTo(base->sortcontext);
    SortTuple   stup;
 
    if (!tuplesort_gettuple_common(state, forward, &stup))
        stup.tuple = NULL;
 
    MemoryContextSwitchTo(oldcontext);
 
    return stup.tuple;
}
 
/*
 * Fetch the next index tuple in either forward or back direction.
 * Returns NULL if no more tuples.  Returned tuple belongs to tuplesort memory
 * context, and must not be freed by caller.  Caller may not rely on tuple
 * remaining valid after any further manipulation of tuplesort.
 */
IndexTuple
tuplesort_getindextuple(Tuplesortstate *state, bool forward)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext = MemoryContextSwitchTo(base->sortcontext);
    SortTuple   stup;
 
    if (!tuplesort_gettuple_common(state, forward, &stup))
        stup.tuple = NULL;
 
    MemoryContextSwitchTo(oldcontext);
 
    return (IndexTuple) stup.tuple;
}
 
/*
 * Fetch the next BRIN tuple in either forward or back direction.
 * Returns NULL if no more tuples.  Returned tuple belongs to tuplesort memory
 * context, and must not be freed by caller.  Caller may not rely on tuple
 * remaining valid after any further manipulation of tuplesort.
 */
BrinTuple *
tuplesort_getbrintuple(Tuplesortstate *state, Size *len, bool forward)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext = MemoryContextSwitchTo(base->sortcontext);
    SortTuple   stup;
    BrinSortTuple *btup;
 
    if (!tuplesort_gettuple_common(state, forward, &stup))
        stup.tuple = NULL;
 
    MemoryContextSwitchTo(oldcontext);
 
    if (!stup.tuple)
        return NULL;
 
    btup = (BrinSortTuple *) stup.tuple;
 
    *len = btup->tuplen;
 
    return &btup->tuple;
}
 
GinTuple *
tuplesort_getgintuple(Tuplesortstate *state, Size *len, bool forward)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext = MemoryContextSwitchTo(base->sortcontext);
    SortTuple   stup;
    GinTuple   *tup;
 
    if (!tuplesort_gettuple_common(state, forward, &stup))
        stup.tuple = NULL;
 
    MemoryContextSwitchTo(oldcontext);
 
    if (!stup.tuple)
        return NULL;
 
    tup = (GinTuple *) stup.tuple;
 
    *len = tup->tuplen;
 
    return tup;
}
 
/*
 * Fetch the next Datum in either forward or back direction.
 * Returns false if no more datums.
 *
 * If the Datum is pass-by-ref type, the returned value is freshly palloc'd
 * in caller's context, and is now owned by the caller (this differs from
 * similar routines for other types of tuplesorts).
 *
 * Caller may optionally be passed back abbreviated value (on true return
 * value) when abbreviation was used, which can be used to cheaply avoid
 * equality checks that might otherwise be required.  Caller can safely make a
 * determination of "non-equal tuple" based on simple binary inequality.  A
 * NULL value will have a zeroed abbreviated value representation, which caller
 * may rely on in abbreviated inequality check.
 *
 * For byref Datums, if copy is true, *val is set to a copy of the Datum
 * copied into the caller's memory context, so that it will stay valid
 * regardless of future manipulations of the tuplesort's state (up to and
 * including deleting the tuplesort).  If copy is false, *val will just be
 * set to a pointer to the Datum held within the tuplesort, which is more
 * efficient, but only safe for callers that are prepared to have any
 * subsequent manipulation of the tuplesort's state invalidate slot contents.
 * For byval Datums, the value of the 'copy' parameter has no effect.
 */
bool
tuplesort_getdatum(Tuplesortstate *state, bool forward, bool copy,
                   Datum *val, bool *isNull, Datum *abbrev)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MemoryContext oldcontext = MemoryContextSwitchTo(base->sortcontext);
    TuplesortDatumArg *arg = (TuplesortDatumArg *) base->arg;
    SortTuple   stup;
 
    if (!tuplesort_gettuple_common(state, forward, &stup))
    {
        MemoryContextSwitchTo(oldcontext);
        return false;
    }
 
    /* Ensure we copy into caller's memory context */
    MemoryContextSwitchTo(oldcontext);
 
    /* Record abbreviated key for caller */
    if (base->sortKeys->abbrev_converter && abbrev)
        *abbrev = stup.datum1;
 
    if (stup.isnull1 || !base->tuples)
    {
        *val = stup.datum1;
        *isNull = stup.isnull1;
    }
    else
    {
        /* use stup.tuple because stup.datum1 may be an abbreviation */
        if (copy)
            *val = datumCopy(PointerGetDatum(stup.tuple), false,
                             arg->datumTypeLen);
        else
            *val = PointerGetDatum(stup.tuple);
        *isNull = false;
    }
 
    return true;
}
 
 
/*
 * Routines specialized for HeapTuple (actually MinimalTuple) case
 */
 
static void
removeabbrev_heap(Tuplesortstate *state, SortTuple *stups, int count)
{
    int         i;
    TuplesortPublic *base = TuplesortstateGetPublic(state);
 
    for (i = 0; i < count; i++)
    {
        HeapTupleData htup;
 
        htup.t_len = ((MinimalTuple) stups[i].tuple)->t_len +
            MINIMAL_TUPLE_OFFSET;
        htup.t_data = (HeapTupleHeader) ((char *) stups[i].tuple -
                                         MINIMAL_TUPLE_OFFSET);
        stups[i].datum1 = heap_getattr(&htup,
                                       base->sortKeys[0].ssup_attno,
                                       (TupleDesc) base->arg,
                                       &stups[i].isnull1);
    }
}
 
static int
comparetup_heap(const SortTuple *a, const SortTuple *b, Tuplesortstate *state)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    SortSupport sortKey = base->sortKeys;
    int32       compare;
 
 
    /* Compare the leading sort key */
    compare = ApplySortComparator(a->datum1, a->isnull1,
                                  b->datum1, b->isnull1,
                                  sortKey);
    if (compare != 0)
        return compare;
 
    /* Compare additional sort keys */
    return comparetup_heap_tiebreak(a, b, state);
}
 
static int
comparetup_heap_tiebreak(const SortTuple *a, const SortTuple *b, Tuplesortstate *state)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    SortSupport sortKey = base->sortKeys;
    HeapTupleData ltup;
    HeapTupleData rtup;
    TupleDesc   tupDesc;
    int         nkey;
    int32       compare;
    AttrNumber  attno;
    Datum       datum1,
                datum2;
    bool        isnull1,
                isnull2;
 
    ltup.t_len = ((MinimalTuple) a->tuple)->t_len + MINIMAL_TUPLE_OFFSET;
    ltup.t_data = (HeapTupleHeader) ((char *) a->tuple - MINIMAL_TUPLE_OFFSET);
    rtup.t_len = ((MinimalTuple) b->tuple)->t_len + MINIMAL_TUPLE_OFFSET;
    rtup.t_data = (HeapTupleHeader) ((char *) b->tuple - MINIMAL_TUPLE_OFFSET);
    tupDesc = (TupleDesc) base->arg;
 
    if (sortKey->abbrev_converter)
    {
        attno = sortKey->ssup_attno;
 
        datum1 = heap_getattr(&ltup, attno, tupDesc, &isnull1);
        datum2 = heap_getattr(&rtup, attno, tupDesc, &isnull2);
 
        compare = ApplySortAbbrevFullComparator(datum1, isnull1,
                                                datum2, isnull2,
                                                sortKey);
        if (compare != 0)
            return compare;
    }
 
    sortKey++;
    for (nkey = 1; nkey < base->nKeys; nkey++, sortKey++)
    {
        attno = sortKey->ssup_attno;
 
        datum1 = heap_getattr(&ltup, attno, tupDesc, &isnull1);
        datum2 = heap_getattr(&rtup, attno, tupDesc, &isnull2);
 
        compare = ApplySortComparator(datum1, isnull1,
                                      datum2, isnull2,
                                      sortKey);
        if (compare != 0)
            return compare;
    }
 
    return 0;
}
 
static void
writetup_heap(Tuplesortstate *state, LogicalTape *tape, SortTuple *stup)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    MinimalTuple tuple = (MinimalTuple) stup->tuple;
 
    /* the part of the MinimalTuple we'll write: */
    char       *tupbody = (char *) tuple + MINIMAL_TUPLE_DATA_OFFSET;
    unsigned int tupbodylen = tuple->t_len - MINIMAL_TUPLE_DATA_OFFSET;
 
    /* total on-disk footprint: */
    unsigned int tuplen = tupbodylen + sizeof(int);
 
    LogicalTapeWrite(tape, &tuplen, sizeof(tuplen));
    LogicalTapeWrite(tape, tupbody, tupbodylen);
    if (base->sortopt & TUPLESORT_RANDOMACCESS) /* need trailing length word? */
        LogicalTapeWrite(tape, &tuplen, sizeof(tuplen));
}
 
static void
readtup_heap(Tuplesortstate *state, SortTuple *stup,
             LogicalTape *tape, unsigned int len)
{
    unsigned int tupbodylen = len - sizeof(int);
    unsigned int tuplen = tupbodylen + MINIMAL_TUPLE_DATA_OFFSET;
    MinimalTuple tuple = (MinimalTuple) tuplesort_readtup_alloc(state, tuplen);
    char       *tupbody = (char *) tuple + MINIMAL_TUPLE_DATA_OFFSET;
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    HeapTupleData htup;
 
    /* read in the tuple proper */
    tuple->t_len = tuplen;
    LogicalTapeReadExact(tape, tupbody, tupbodylen);
    if (base->sortopt & TUPLESORT_RANDOMACCESS) /* need trailing length word? */
        LogicalTapeReadExact(tape, &tuplen, sizeof(tuplen));
    stup->tuple = tuple;
    /* set up first-column key value */
    htup.t_len = tuple->t_len + MINIMAL_TUPLE_OFFSET;
    htup.t_data = (HeapTupleHeader) ((char *) tuple - MINIMAL_TUPLE_OFFSET);
    stup->datum1 = heap_getattr(&htup,
                                base->sortKeys[0].ssup_attno,
                                (TupleDesc) base->arg,
                                &stup->isnull1);
}
 
/*
 * Routines specialized for the CLUSTER case (HeapTuple data, with
 * comparisons per a btree index definition)
 */
 
static void
removeabbrev_cluster(Tuplesortstate *state, SortTuple *stups, int count)
{
    int         i;
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    TuplesortClusterArg *arg = (TuplesortClusterArg *) base->arg;
 
    for (i = 0; i < count; i++)
    {
        HeapTuple   tup;
 
        tup = (HeapTuple) stups[i].tuple;
        stups[i].datum1 = heap_getattr(tup,
                                       arg->indexInfo->ii_IndexAttrNumbers[0],
                                       arg->tupDesc,
                                       &stups[i].isnull1);
    }
}
 
static int
comparetup_cluster(const SortTuple *a, const SortTuple *b,
                   Tuplesortstate *state)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    SortSupport sortKey = base->sortKeys;
    int32       compare;
 
    /* Compare the leading sort key, if it's simple */
    if (base->haveDatum1)
    {
        compare = ApplySortComparator(a->datum1, a->isnull1,
                                      b->datum1, b->isnull1,
                                      sortKey);
        if (compare != 0)
            return compare;
    }
 
    return comparetup_cluster_tiebreak(a, b, state);
}
 
static int
comparetup_cluster_tiebreak(const SortTuple *a, const SortTuple *b,
                            Tuplesortstate *state)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    TuplesortClusterArg *arg = (TuplesortClusterArg *) base->arg;
    SortSupport sortKey = base->sortKeys;
    HeapTuple   ltup;
    HeapTuple   rtup;
    TupleDesc   tupDesc;
    int         nkey;
    int32       compare = 0;
    Datum       datum1,
                datum2;
    bool        isnull1,
                isnull2;
 
    ltup = (HeapTuple) a->tuple;
    rtup = (HeapTuple) b->tuple;
    tupDesc = arg->tupDesc;
 
    /* Compare the leading sort key, if it's simple */
    if (base->haveDatum1)
    {
        if (sortKey->abbrev_converter)
        {
            AttrNumber  leading = arg->indexInfo->ii_IndexAttrNumbers[0];
 
            datum1 = heap_getattr(ltup, leading, tupDesc, &isnull1);
            datum2 = heap_getattr(rtup, leading, tupDesc, &isnull2);
 
            compare = ApplySortAbbrevFullComparator(datum1, isnull1,
                                                    datum2, isnull2,
                                                    sortKey);
        }
        if (compare != 0 || base->nKeys == 1)
            return compare;
        /* Compare additional columns the hard way */
        sortKey++;
        nkey = 1;
    }
    else
    {
        /* Must compare all keys the hard way */
        nkey = 0;
    }
 
    if (arg->indexInfo->ii_Expressions == NULL)
    {
        /* If not expression index, just compare the proper heap attrs */
 
        for (; nkey < base->nKeys; nkey++, sortKey++)
        {
            AttrNumber  attno = arg->indexInfo->ii_IndexAttrNumbers[nkey];
 
            datum1 = heap_getattr(ltup, attno, tupDesc, &isnull1);
            datum2 = heap_getattr(rtup, attno, tupDesc, &isnull2);
 
            compare = ApplySortComparator(datum1, isnull1,
                                          datum2, isnull2,
                                          sortKey);
            if (compare != 0)
                return compare;
        }
    }
    else
    {
        /*
         * In the expression index case, compute the whole index tuple and
         * then compare values.  It would perhaps be faster to compute only as
         * many columns as we need to compare, but that would require
         * duplicating all the logic in FormIndexDatum.
         */
        Datum       l_index_values[INDEX_MAX_KEYS];
        bool        l_index_isnull[INDEX_MAX_KEYS];
        Datum       r_index_values[INDEX_MAX_KEYS];
        bool        r_index_isnull[INDEX_MAX_KEYS];
        TupleTableSlot *ecxt_scantuple;
 
        /* Reset context each time to prevent memory leakage */
        ResetPerTupleExprContext(arg->estate);
 
        ecxt_scantuple = GetPerTupleExprContext(arg->estate)->ecxt_scantuple;
 
        ExecStoreHeapTuple(ltup, ecxt_scantuple, false);
        FormIndexDatum(arg->indexInfo, ecxt_scantuple, arg->estate,
                       l_index_values, l_index_isnull);
 
        ExecStoreHeapTuple(rtup, ecxt_scantuple, false);
        FormIndexDatum(arg->indexInfo, ecxt_scantuple, arg->estate,
                       r_index_values, r_index_isnull);
 
        for (; nkey < base->nKeys; nkey++, sortKey++)
        {
            compare = ApplySortComparator(l_index_values[nkey],
                                          l_index_isnull[nkey],
                                          r_index_values[nkey],
                                          r_index_isnull[nkey],
                                          sortKey);
            if (compare != 0)
                return compare;
        }
    }
 
    return 0;
}
 
static void
writetup_cluster(Tuplesortstate *state, LogicalTape *tape, SortTuple *stup)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    HeapTuple   tuple = (HeapTuple) stup->tuple;
    unsigned int tuplen = tuple->t_len + sizeof(ItemPointerData) + sizeof(int);
 
    /* We need to store t_self, but not other fields of HeapTupleData */
    LogicalTapeWrite(tape, &tuplen, sizeof(tuplen));
    LogicalTapeWrite(tape, &tuple->t_self, sizeof(ItemPointerData));
    LogicalTapeWrite(tape, tuple->t_data, tuple->t_len);
    if (base->sortopt & TUPLESORT_RANDOMACCESS) /* need trailing length word? */
        LogicalTapeWrite(tape, &tuplen, sizeof(tuplen));
}
 
static void
readtup_cluster(Tuplesortstate *state, SortTuple *stup,
                LogicalTape *tape, unsigned int tuplen)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    TuplesortClusterArg *arg = (TuplesortClusterArg *) base->arg;
    unsigned int t_len = tuplen - sizeof(ItemPointerData) - sizeof(int);
    HeapTuple   tuple = (HeapTuple) tuplesort_readtup_alloc(state,
                                                            t_len + HEAPTUPLESIZE);
 
    /* Reconstruct the HeapTupleData header */
    tuple->t_data = (HeapTupleHeader) ((char *) tuple + HEAPTUPLESIZE);
    tuple->t_len = t_len;
    LogicalTapeReadExact(tape, &tuple->t_self, sizeof(ItemPointerData));
    /* We don't currently bother to reconstruct t_tableOid */
    tuple->t_tableOid = InvalidOid;
    /* Read in the tuple body */
    LogicalTapeReadExact(tape, tuple->t_data, tuple->t_len);
    if (base->sortopt & TUPLESORT_RANDOMACCESS) /* need trailing length word? */
        LogicalTapeReadExact(tape, &tuplen, sizeof(tuplen));
    stup->tuple = tuple;
    /* set up first-column key value, if it's a simple column */
    if (base->haveDatum1)
        stup->datum1 = heap_getattr(tuple,
                                    arg->indexInfo->ii_IndexAttrNumbers[0],
                                    arg->tupDesc,
                                    &stup->isnull1);
}
 
static void
freestate_cluster(Tuplesortstate *state)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    TuplesortClusterArg *arg = (TuplesortClusterArg *) base->arg;
 
    /* Free any execution state created for CLUSTER case */
    if (arg->estate != NULL)
    {
        ExprContext *econtext = GetPerTupleExprContext(arg->estate);
 
        ExecDropSingleTupleTableSlot(econtext->ecxt_scantuple);
        FreeExecutorState(arg->estate);
    }
}
 
/*
 * Routines specialized for IndexTuple case
 *
 * The btree and hash cases require separate comparison functions, but the
 * IndexTuple representation is the same so the copy/write/read support
 * functions can be shared.
 */
 
static void
removeabbrev_index(Tuplesortstate *state, SortTuple *stups, int count)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    TuplesortIndexArg *arg = (TuplesortIndexArg *) base->arg;
    int         i;
 
    for (i = 0; i < count; i++)
    {
        IndexTuple  tuple;
 
        tuple = stups[i].tuple;
        stups[i].datum1 = index_getattr(tuple,
                                        1,
                                        RelationGetDescr(arg->indexRel),
                                        &stups[i].isnull1);
    }
}
 
static int
comparetup_index_btree(const SortTuple *a, const SortTuple *b,
                       Tuplesortstate *state)
{
    /*
     * This is similar to comparetup_heap(), but expects index tuples.  There
     * is also special handling for enforcing uniqueness, and special
     * treatment for equal keys at the end.
     */
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    SortSupport sortKey = base->sortKeys;
    int32       compare;
 
    /* Compare the leading sort key */
    compare = ApplySortComparator(a->datum1, a->isnull1,
                                  b->datum1, b->isnull1,
                                  sortKey);
    if (compare != 0)
        return compare;
 
    /* Compare additional sort keys */
    return comparetup_index_btree_tiebreak(a, b, state);
}
 
static int
comparetup_index_btree_tiebreak(const SortTuple *a, const SortTuple *b,
                                Tuplesortstate *state)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    TuplesortIndexBTreeArg *arg = (TuplesortIndexBTreeArg *) base->arg;
    SortSupport sortKey = base->sortKeys;
    IndexTuple  tuple1;
    IndexTuple  tuple2;
    int         keysz;
    TupleDesc   tupDes;
    bool        equal_hasnull = false;
    int         nkey;
    int32       compare;
    Datum       datum1,
                datum2;
    bool        isnull1,
                isnull2;
 
    tuple1 = (IndexTuple) a->tuple;
    tuple2 = (IndexTuple) b->tuple;
    keysz = base->nKeys;
    tupDes = RelationGetDescr(arg->index.indexRel);
 
    if (sortKey->abbrev_converter)
    {
        datum1 = index_getattr(tuple1, 1, tupDes, &isnull1);
        datum2 = index_getattr(tuple2, 1, tupDes, &isnull2);
 
        compare = ApplySortAbbrevFullComparator(datum1, isnull1,
                                                datum2, isnull2,
                                                sortKey);
        if (compare != 0)
            return compare;
    }
 
    /* they are equal, so we only need to examine one null flag */
    if (a->isnull1)
        equal_hasnull = true;
 
    sortKey++;
    for (nkey = 2; nkey <= keysz; nkey++, sortKey++)
    {
        datum1 = index_getattr(tuple1, nkey, tupDes, &isnull1);
        datum2 = index_getattr(tuple2, nkey, tupDes, &isnull2);
 
        compare = ApplySortComparator(datum1, isnull1,
                                      datum2, isnull2,
                                      sortKey);
        if (compare != 0)
            return compare;     /* done when we find unequal attributes */
 
        /* they are equal, so we only need to examine one null flag */
        if (isnull1)
            equal_hasnull = true;
    }
 
    /*
     * If btree has asked us to enforce uniqueness, complain if two equal
     * tuples are detected (unless there was at least one NULL field and NULLS
     * NOT DISTINCT was not set).
     *
     * It is sufficient to make the test here, because if two tuples are equal
     * they *must* get compared at some stage of the sort --- otherwise the
     * sort algorithm wouldn't have checked whether one must appear before the
     * other.
     */
    if (arg->enforceUnique && !(!arg->uniqueNullsNotDistinct && equal_hasnull))
    {
        Datum       values[INDEX_MAX_KEYS];
        bool        isnull[INDEX_MAX_KEYS];
        char       *key_desc;
 
        /*
         * Some rather brain-dead implementations of qsort (such as the one in
         * QNX 4) will sometimes call the comparison routine to compare a
         * value to itself, but we always use our own implementation, which
         * does not.
         */
        Assert(tuple1 != tuple2);
 
        index_deform_tuple(tuple1, tupDes, values, isnull);
 
        key_desc = BuildIndexValueDescription(arg->index.indexRel, values, isnull);
 
        ereport(ERROR,
                (errcode(ERRCODE_UNIQUE_VIOLATION),
                 errmsg("could not create unique index \"%s\"",
                        RelationGetRelationName(arg->index.indexRel)),
                 key_desc ? errdetail("Key %s is duplicated.", key_desc) :
                 errdetail("Duplicate keys exist."),
                 errtableconstraint(arg->index.heapRel,
                                    RelationGetRelationName(arg->index.indexRel))));
    }
 
    /*
     * If key values are equal, we sort on ItemPointer.  This is required for
     * btree indexes, since heap TID is treated as an implicit last key
     * attribute in order to ensure that all keys in the index are physically
     * unique.
     */
    {
        BlockNumber blk1 = ItemPointerGetBlockNumber(&tuple1->t_tid);
        BlockNumber blk2 = ItemPointerGetBlockNumber(&tuple2->t_tid);
 
        if (blk1 != blk2)
            return (blk1 < blk2) ? -1 : 1;
    }
    {
        OffsetNumber pos1 = ItemPointerGetOffsetNumber(&tuple1->t_tid);
        OffsetNumber pos2 = ItemPointerGetOffsetNumber(&tuple2->t_tid);
 
        if (pos1 != pos2)
            return (pos1 < pos2) ? -1 : 1;
    }
 
    /* ItemPointer values should never be equal */
    Assert(false);
 
    return 0;
}
 
static int
comparetup_index_hash(const SortTuple *a, const SortTuple *b,
                      Tuplesortstate *state)
{
    Bucket      bucket1;
    Bucket      bucket2;
    uint32      hash1;
    uint32      hash2;
    IndexTuple  tuple1;
    IndexTuple  tuple2;
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    TuplesortIndexHashArg *arg = (TuplesortIndexHashArg *) base->arg;
 
    /*
     * Fetch hash keys and mask off bits we don't want to sort by, so that the
     * initial sort is just on the bucket number.  We know that the first
     * column of the index tuple is the hash key.
     */
    Assert(!a->isnull1);
    bucket1 = _hash_hashkey2bucket(DatumGetUInt32(a->datum1),
                                   arg->max_buckets, arg->high_mask,
                                   arg->low_mask);
    Assert(!b->isnull1);
    bucket2 = _hash_hashkey2bucket(DatumGetUInt32(b->datum1),
                                   arg->max_buckets, arg->high_mask,
                                   arg->low_mask);
    if (bucket1 > bucket2)
        return 1;
    else if (bucket1 < bucket2)
        return -1;
 
    /*
     * If bucket values are equal, sort by hash values.  This allows us to
     * insert directly onto bucket/overflow pages, where the index tuples are
     * stored in hash order to allow fast binary search within each page.
     */
    hash1 = DatumGetUInt32(a->datum1);
    hash2 = DatumGetUInt32(b->datum1);
    if (hash1 > hash2)
        return 1;
    else if (hash1 < hash2)
        return -1;
 
    /*
     * If hash values are equal, we sort on ItemPointer.  This does not affect
     * validity of the finished index, but it may be useful to have index
     * scans in physical order.
     */
    tuple1 = (IndexTuple) a->tuple;
    tuple2 = (IndexTuple) b->tuple;
 
    {
        BlockNumber blk1 = ItemPointerGetBlockNumber(&tuple1->t_tid);
        BlockNumber blk2 = ItemPointerGetBlockNumber(&tuple2->t_tid);
 
        if (blk1 != blk2)
            return (blk1 < blk2) ? -1 : 1;
    }
    {
        OffsetNumber pos1 = ItemPointerGetOffsetNumber(&tuple1->t_tid);
        OffsetNumber pos2 = ItemPointerGetOffsetNumber(&tuple2->t_tid);
 
        if (pos1 != pos2)
            return (pos1 < pos2) ? -1 : 1;
    }
 
    /* ItemPointer values should never be equal */
    Assert(false);
 
    return 0;
}
 
/*
 * Sorting for hash indexes only uses one sort key, so this shouldn't ever be
 * called. It's only here for consistency.
 */
static int
comparetup_index_hash_tiebreak(const SortTuple *a, const SortTuple *b,
                               Tuplesortstate *state)
{
    Assert(false);
 
    return 0;
}
 
static void
writetup_index(Tuplesortstate *state, LogicalTape *tape, SortTuple *stup)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    IndexTuple  tuple = (IndexTuple) stup->tuple;
    unsigned int tuplen;
 
    tuplen = IndexTupleSize(tuple) + sizeof(tuplen);
    LogicalTapeWrite(tape, &tuplen, sizeof(tuplen));
    LogicalTapeWrite(tape, tuple, IndexTupleSize(tuple));
    if (base->sortopt & TUPLESORT_RANDOMACCESS) /* need trailing length word? */
        LogicalTapeWrite(tape, &tuplen, sizeof(tuplen));
}
 
static void
readtup_index(Tuplesortstate *state, SortTuple *stup,
              LogicalTape *tape, unsigned int len)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    TuplesortIndexArg *arg = (TuplesortIndexArg *) base->arg;
    unsigned int tuplen = len - sizeof(unsigned int);
    IndexTuple  tuple = (IndexTuple) tuplesort_readtup_alloc(state, tuplen);
 
    LogicalTapeReadExact(tape, tuple, tuplen);
    if (base->sortopt & TUPLESORT_RANDOMACCESS) /* need trailing length word? */
        LogicalTapeReadExact(tape, &tuplen, sizeof(tuplen));
    stup->tuple = tuple;
    /* set up first-column key value */
    stup->datum1 = index_getattr(tuple,
                                 1,
                                 RelationGetDescr(arg->indexRel),
                                 &stup->isnull1);
}
 
/*
 * Routines specialized for BrinTuple case
 */
 
static void
removeabbrev_index_brin(Tuplesortstate *state, SortTuple *stups, int count)
{
    int         i;
 
    for (i = 0; i < count; i++)
    {
        BrinSortTuple *tuple;
 
        tuple = stups[i].tuple;
        stups[i].datum1 = UInt32GetDatum(tuple->tuple.bt_blkno);
    }
}
 
static int
comparetup_index_brin(const SortTuple *a, const SortTuple *b,
                      Tuplesortstate *state)
{
    Assert(TuplesortstateGetPublic(state)->haveDatum1);
 
    if (DatumGetUInt32(a->datum1) > DatumGetUInt32(b->datum1))
        return 1;
 
    if (DatumGetUInt32(a->datum1) < DatumGetUInt32(b->datum1))
        return -1;
 
    /* silence compilers */
    return 0;
}
 
static void
writetup_index_brin(Tuplesortstate *state, LogicalTape *tape, SortTuple *stup)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    BrinSortTuple *tuple = (BrinSortTuple *) stup->tuple;
    unsigned int tuplen = tuple->tuplen;
 
    tuplen = tuplen + sizeof(tuplen);
    LogicalTapeWrite(tape, &tuplen, sizeof(tuplen));
    LogicalTapeWrite(tape, &tuple->tuple, tuple->tuplen);
    if (base->sortopt & TUPLESORT_RANDOMACCESS) /* need trailing length word? */
        LogicalTapeWrite(tape, &tuplen, sizeof(tuplen));
}
 
static void
readtup_index_brin(Tuplesortstate *state, SortTuple *stup,
                   LogicalTape *tape, unsigned int len)
{
    BrinSortTuple *tuple;
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    unsigned int tuplen = len - sizeof(unsigned int);
 
    /*
     * Allocate space for the BRIN sort tuple, which is BrinTuple with an
     * extra length field.
     */
    tuple = (BrinSortTuple *) tuplesort_readtup_alloc(state,
                                                      BRINSORTTUPLE_SIZE(tuplen));
 
    tuple->tuplen = tuplen;
 
    LogicalTapeReadExact(tape, &tuple->tuple, tuplen);
    if (base->sortopt & TUPLESORT_RANDOMACCESS) /* need trailing length word? */
        LogicalTapeReadExact(tape, &tuplen, sizeof(tuplen));
    stup->tuple = tuple;
 
    /* set up first-column key value, which is block number */
    stup->datum1 = UInt32GetDatum(tuple->tuple.bt_blkno);
}
 
/*
 * Routines specialized for GIN case
 */
 
static void
removeabbrev_index_gin(Tuplesortstate *state, SortTuple *stups, int count)
{
    Assert(false);
    elog(ERROR, "removeabbrev_index_gin not implemented");
}
 
static int
comparetup_index_gin(const SortTuple *a, const SortTuple *b,
                     Tuplesortstate *state)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
 
    Assert(!TuplesortstateGetPublic(state)->haveDatum1);
 
    return _gin_compare_tuples((GinTuple *) a->tuple,
                               (GinTuple *) b->tuple,
                               base->sortKeys);
}
 
static void
writetup_index_gin(Tuplesortstate *state, LogicalTape *tape, SortTuple *stup)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    GinTuple   *tuple = (GinTuple *) stup->tuple;
    unsigned int tuplen = tuple->tuplen;
 
    tuplen = tuplen + sizeof(tuplen);
    LogicalTapeWrite(tape, &tuplen, sizeof(tuplen));
    LogicalTapeWrite(tape, tuple, tuple->tuplen);
    if (base->sortopt & TUPLESORT_RANDOMACCESS) /* need trailing length word? */
        LogicalTapeWrite(tape, &tuplen, sizeof(tuplen));
}
 
static void
readtup_index_gin(Tuplesortstate *state, SortTuple *stup,
                  LogicalTape *tape, unsigned int len)
{
    GinTuple   *tuple;
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    unsigned int tuplen = len - sizeof(unsigned int);
 
    /*
     * Allocate space for the GIN sort tuple, which already has the proper
     * length included in the header.
     */
    tuple = (GinTuple *) tuplesort_readtup_alloc(state, tuplen);
 
    tuple->tuplen = tuplen;
 
    LogicalTapeReadExact(tape, tuple, tuplen);
    if (base->sortopt & TUPLESORT_RANDOMACCESS) /* need trailing length word? */
        LogicalTapeReadExact(tape, &tuplen, sizeof(tuplen));
    stup->tuple = tuple;
 
    /* no abbreviations (FIXME maybe use attrnum for this?) */
    stup->datum1 = (Datum) 0;
}
 
/*
 * Routines specialized for DatumTuple case
 */
 
static void
removeabbrev_datum(Tuplesortstate *state, SortTuple *stups, int count)
{
    int         i;
 
    for (i = 0; i < count; i++)
        stups[i].datum1 = PointerGetDatum(stups[i].tuple);
}
 
static int
comparetup_datum(const SortTuple *a, const SortTuple *b, Tuplesortstate *state)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    int         compare;
 
    compare = ApplySortComparator(a->datum1, a->isnull1,
                                  b->datum1, b->isnull1,
                                  base->sortKeys);
    if (compare != 0)
        return compare;
 
    return comparetup_datum_tiebreak(a, b, state);
}
 
static int
comparetup_datum_tiebreak(const SortTuple *a, const SortTuple *b, Tuplesortstate *state)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    int32       compare = 0;
 
    /* if we have abbreviations, then "tuple" has the original value */
    if (base->sortKeys->abbrev_converter)
        compare = ApplySortAbbrevFullComparator(PointerGetDatum(a->tuple), a->isnull1,
                                                PointerGetDatum(b->tuple), b->isnull1,
                                                base->sortKeys);
 
    return compare;
}
 
static void
writetup_datum(Tuplesortstate *state, LogicalTape *tape, SortTuple *stup)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    TuplesortDatumArg *arg = (TuplesortDatumArg *) base->arg;
    void       *waddr;
    unsigned int tuplen;
    unsigned int writtenlen;
 
    if (stup->isnull1)
    {
        waddr = NULL;
        tuplen = 0;
    }
    else if (!base->tuples)
    {
        waddr = &stup->datum1;
        tuplen = sizeof(Datum);
    }
    else
    {
        waddr = stup->tuple;
        tuplen = datumGetSize(PointerGetDatum(stup->tuple), false, arg->datumTypeLen);
        Assert(tuplen != 0);
    }
 
    writtenlen = tuplen + sizeof(unsigned int);
 
    LogicalTapeWrite(tape, &writtenlen, sizeof(writtenlen));
    LogicalTapeWrite(tape, waddr, tuplen);
    if (base->sortopt & TUPLESORT_RANDOMACCESS) /* need trailing length word? */
        LogicalTapeWrite(tape, &writtenlen, sizeof(writtenlen));
}
 
static void
readtup_datum(Tuplesortstate *state, SortTuple *stup,
              LogicalTape *tape, unsigned int len)
{
    TuplesortPublic *base = TuplesortstateGetPublic(state);
    unsigned int tuplen = len - sizeof(unsigned int);
 
    if (tuplen == 0)
    {
        /* it's NULL */
        stup->datum1 = (Datum) 0;
        stup->isnull1 = true;
        stup->tuple = NULL;
    }
    else if (!base->tuples)
    {
        Assert(tuplen == sizeof(Datum));
        LogicalTapeReadExact(tape, &stup->datum1, tuplen);
        stup->isnull1 = false;
        stup->tuple = NULL;
    }
    else
    {
        void       *raddr = tuplesort_readtup_alloc(state, tuplen);
 
        LogicalTapeReadExact(tape, raddr, tuplen);
        stup->datum1 = PointerGetDatum(raddr);
        stup->isnull1 = false;
        stup->tuple = raddr;
    }
 
    if (base->sortopt & TUPLESORT_RANDOMACCESS) /* need trailing length word? */
        LogicalTapeReadExact(tape, &tuplen, sizeof(tuplen));
}