tuplesort.h

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/*-------------------------------------------------------------------------
 *
 * tuplesort.h
 *    Generalized tuple sorting routines.
 *
 * This module handles sorting of heap tuples, index tuples, or single
 * Datums (and could easily support other kinds of sortable objects,
 * if necessary).  It works efficiently for both small and large amounts
 * of data.  Small amounts are sorted in-memory using qsort().  Large
 * amounts are sorted using temporary files and a standard external sort
 * algorithm.
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/utils/tuplesort.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef TUPLESORT_H
#define TUPLESORT_H

#include "access/itup.h"
#include "executor/tuptable.h"
#include "fmgr.h"
#include "utils/relcache.h"


/* Tuplesortstate is an opaque type whose details are not known outside
 * tuplesort.c.
 */
typedef struct Tuplesortstate Tuplesortstate;

/*
 * We provide multiple interfaces to what is essentially the same code,
 * since different callers have different data to be sorted and want to
 * specify the sort key information differently.  There are two APIs for
 * sorting HeapTuples and two more for sorting IndexTuples.  Yet another
 * API supports sorting bare Datums.
 *
 * The "heap" API actually stores/sorts MinimalTuples, which means it doesn't
 * preserve the system columns (tuple identity and transaction visibility
 * info).  The sort keys are specified by column numbers within the tuples
 * and sort operator OIDs.  We save some cycles by passing and returning the
 * tuples in TupleTableSlots, rather than forming actual HeapTuples (which'd
 * have to be converted to MinimalTuples).  This API works well for sorts
 * executed as parts of plan trees.
 *
 * The "cluster" API stores/sorts full HeapTuples including all visibility
 * info. The sort keys are specified by reference to a btree index that is
 * defined on the relation to be sorted.  Note that putheaptuple/getheaptuple
 * go with this API, not the "begin_heap" one!
 *
 * The "index_btree" API stores/sorts IndexTuples (preserving all their
 * header fields).  The sort keys are specified by a btree index definition.
 *
 * The "index_hash" API is similar to index_btree, but the tuples are
 * actually sorted by their hash codes not the raw data.
 */

extern Tuplesortstate *tuplesort_begin_heap(TupleDesc tupDesc,
                     int nkeys, AttrNumber *attNums,
                     Oid *sortOperators, Oid *sortCollations,
                     bool *nullsFirstFlags,
                     int workMem, bool randomAccess);
extern Tuplesortstate *tuplesort_begin_cluster(TupleDesc tupDesc,
                        Relation indexRel,
                        int workMem, bool randomAccess);
extern Tuplesortstate *tuplesort_begin_index_btree(Relation heapRel,
                            Relation indexRel,
                            bool enforceUnique,
                            int workMem, bool randomAccess);
extern Tuplesortstate *tuplesort_begin_index_hash(Relation heapRel,
                           Relation indexRel,
                           uint32 high_mask,
                           uint32 low_mask,
                           uint32 max_buckets,
                           int workMem, bool randomAccess);
extern Tuplesortstate *tuplesort_begin_datum(Oid datumType,
                      Oid sortOperator, Oid sortCollation,
                      bool nullsFirstFlag,
                      int workMem, bool randomAccess);

extern void tuplesort_set_bound(Tuplesortstate *state, int64 bound);

extern void tuplesort_puttupleslot(Tuplesortstate *state,
                       TupleTableSlot *slot);
extern void tuplesort_putheaptuple(Tuplesortstate *state, HeapTuple tup);
extern void tuplesort_putindextuplevalues(Tuplesortstate *state,
                              Relation rel, ItemPointer self,
                              Datum *values, bool *isnull);
extern void tuplesort_putdatum(Tuplesortstate *state, Datum val,
                   bool isNull);

extern void tuplesort_performsort(Tuplesortstate *state);

extern bool tuplesort_gettupleslot(Tuplesortstate *state, bool forward,
                       bool copy, TupleTableSlot *slot, Datum *abbrev);
extern HeapTuple tuplesort_getheaptuple(Tuplesortstate *state, bool forward);
extern IndexTuple tuplesort_getindextuple(Tuplesortstate *state, bool forward);
extern bool tuplesort_getdatum(Tuplesortstate *state, bool forward,
                   Datum *val, bool *isNull, Datum *abbrev);

extern bool tuplesort_skiptuples(Tuplesortstate *state, int64 ntuples,
                     bool forward);

extern void tuplesort_end(Tuplesortstate *state);

extern void tuplesort_get_stats(Tuplesortstate *state,
                    const char **sortMethod,
                    const char **spaceType,
                    long *spaceUsed);

extern int  tuplesort_merge_order(int64 allowedMem);

/*
 * These routines may only be called if randomAccess was specified 'true'.
 * Likewise, backwards scan in gettuple/getdatum is only allowed if
 * randomAccess was specified.
 */

extern void tuplesort_rescan(Tuplesortstate *state);
extern void tuplesort_markpos(Tuplesortstate *state);
extern void tuplesort_restorepos(Tuplesortstate *state);

#endif                          /* TUPLESORT_H */