postgresql/src/include/utils/tuplesort.h

/*-------------------------------------------------------------------------
 *
 * 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;

/*
 * Data structures for reporting sort statistics.  Note that
 * TuplesortInstrumentation can't contain any pointers because we
 * sometimes put it in shared memory.
 */
typedef enum
{
	SORT_TYPE_STILL_IN_PROGRESS = 0,
	SORT_TYPE_TOP_N_HEAPSORT,
	SORT_TYPE_QUICKSORT,
	SORT_TYPE_EXTERNAL_SORT,
	SORT_TYPE_EXTERNAL_MERGE
} TuplesortMethod;

typedef enum
{
	SORT_SPACE_TYPE_DISK,
	SORT_SPACE_TYPE_MEMORY
} TuplesortSpaceType;

typedef struct TuplesortInstrumentation
{
	TuplesortMethod sortMethod; /* sort algorithm used */
	TuplesortSpaceType spaceType;	/* type of space spaceUsed represents */
	long		spaceUsed;		/* space consumption, in kB */
} TuplesortInstrumentation;


/*
 * 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,
					TuplesortInstrumentation *stats);
extern const char *tuplesort_method_name(TuplesortMethod m);
extern const char *tuplesort_space_type_name(TuplesortSpaceType t);

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 */