When creating a large hash index, pre-sort the index entries by estimated
bucket number, so as to ensure locality of access to the index during the insertion step. Without this, building an index significantly larger than available RAM takes a very long time because of thrashing. On the other hand, sorting is just useless overhead when the index does fit in RAM. We choose to sort when the initial index size exceeds effective_cache_size. This is a revised version of work by Tom Raney and Shreya Bhargava.
This commit is contained in:
Tom Lane
parent
ec6550c6c0
commit
787eba734b
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@ -4,7 +4,7 @@
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# Makefile for access/hash
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#
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# IDENTIFICATION
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# $PostgreSQL: pgsql/src/backend/access/hash/Makefile,v 1.14 2008/02/19 10:30:06 petere Exp $
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# $PostgreSQL: pgsql/src/backend/access/hash/Makefile,v 1.15 2008/03/16 23:15:08 tgl Exp $
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#
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#-------------------------------------------------------------------------
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@ -13,6 +13,6 @@ top_builddir = ../../../..
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include $(top_builddir)/src/Makefile.global
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OBJS = hash.o hashfunc.o hashinsert.o hashovfl.o hashpage.o hashscan.o \
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hashsearch.o hashutil.o
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hashsearch.o hashsort.o hashutil.o
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include $(top_srcdir)/src/backend/common.mk
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|
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.99 2008/03/15 20:46:31 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.100 2008/03/16 23:15:08 tgl Exp $
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*
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* NOTES
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* This file contains only the public interface routines.
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@ -22,13 +22,15 @@
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#include "access/hash.h"
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#include "catalog/index.h"
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#include "commands/vacuum.h"
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#include "optimizer/cost.h"
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#include "optimizer/plancat.h"
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/* Working state for hashbuild and its callback */
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typedef struct
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{
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double indtuples;
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HSpool *spool; /* NULL if not using spooling */
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double indtuples; /* # tuples accepted into index */
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} HashBuildState;
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static void hashbuildCallback(Relation index,
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@ -51,6 +53,7 @@ hashbuild(PG_FUNCTION_ARGS)
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IndexBuildResult *result;
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BlockNumber relpages;
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double reltuples;
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uint32 num_buckets;
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HashBuildState buildstate;
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/*
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@ -61,19 +64,43 @@ hashbuild(PG_FUNCTION_ARGS)
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elog(ERROR, "index \"%s\" already contains data",
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RelationGetRelationName(index));
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/* estimate the number of rows currently present in the table */
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/* Estimate the number of rows currently present in the table */
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estimate_rel_size(heap, NULL, &relpages, &reltuples);
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/* initialize the hash index metadata page and initial buckets */
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_hash_metapinit(index, reltuples);
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/* Initialize the hash index metadata page and initial buckets */
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num_buckets = _hash_metapinit(index, reltuples);
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/* build the index */
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/*
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* If we just insert the tuples into the index in scan order, then
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* (assuming their hash codes are pretty random) there will be no locality
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* of access to the index, and if the index is bigger than available RAM
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* then we'll thrash horribly. To prevent that scenario, we can sort the
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* tuples by (expected) bucket number. However, such a sort is useless
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* overhead when the index does fit in RAM. We choose to sort if the
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* initial index size exceeds effective_cache_size.
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*
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* NOTE: this test will need adjustment if a bucket is ever different
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* from one page.
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*/
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if (num_buckets >= (uint32) effective_cache_size)
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buildstate.spool = _h_spoolinit(index, num_buckets);
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else
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buildstate.spool = NULL;
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/* prepare to build the index */
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buildstate.indtuples = 0;
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/* do the heap scan */
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reltuples = IndexBuildHeapScan(heap, index, indexInfo,
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hashbuildCallback, (void *) &buildstate);
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if (buildstate.spool)
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{
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/* sort the tuples and insert them into the index */
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_h_indexbuild(buildstate.spool);
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_h_spooldestroy(buildstate.spool);
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}
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/*
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* Return statistics
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*/
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@ -110,7 +137,11 @@ hashbuildCallback(Relation index,
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return;
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}
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_hash_doinsert(index, itup);
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/* Either spool the tuple for sorting, or just put it into the index */
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if (buildstate->spool)
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_h_spool(itup, buildstate->spool);
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else
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_hash_doinsert(index, itup);
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buildstate->indtuples += 1;
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@ -8,7 +8,7 @@
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*
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/access/hash/hashpage.c,v 1.73 2008/03/15 20:46:31 tgl Exp $
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* $PostgreSQL: pgsql/src/backend/access/hash/hashpage.c,v 1.74 2008/03/16 23:15:08 tgl Exp $
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*
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* NOTES
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* Postgres hash pages look like ordinary relation pages. The opaque
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@ -315,13 +315,14 @@ _hash_chgbufaccess(Relation rel,
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* the initial buckets, and the initial bitmap page.
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*
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* The initial number of buckets is dependent on num_tuples, an estimate
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* of the number of tuples to be loaded into the index initially.
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* of the number of tuples to be loaded into the index initially. The
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* chosen number of buckets is returned.
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*
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* We are fairly cavalier about locking here, since we know that no one else
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* could be accessing this index. In particular the rule about not holding
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* multiple buffer locks is ignored.
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*/
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void
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uint32
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_hash_metapinit(Relation rel, double num_tuples)
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{
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HashMetaPage metap;
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@ -437,11 +438,22 @@ _hash_metapinit(Relation rel, double num_tuples)
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metap->hashm_ovflpoint = log2_num_buckets;
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metap->hashm_firstfree = 0;
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/*
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* Release buffer lock on the metapage while we initialize buckets.
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* Otherwise, we'll be in interrupt holdoff and the CHECK_FOR_INTERRUPTS
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* won't accomplish anything. It's a bad idea to hold buffer locks
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* for long intervals in any case, since that can block the bgwriter.
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*/
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_hash_chgbufaccess(rel, metabuf, HASH_WRITE, HASH_NOLOCK);
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/*
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* Initialize the first N buckets
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*/
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for (i = 0; i < num_buckets; i++)
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{
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/* Allow interrupts, in case N is huge */
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CHECK_FOR_INTERRUPTS();
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buf = _hash_getnewbuf(rel, BUCKET_TO_BLKNO(metap, i));
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pg = BufferGetPage(buf);
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pageopaque = (HashPageOpaque) PageGetSpecialPointer(pg);
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@ -453,6 +465,9 @@ _hash_metapinit(Relation rel, double num_tuples)
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_hash_wrtbuf(rel, buf);
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}
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/* Now reacquire buffer lock on metapage */
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_hash_chgbufaccess(rel, metabuf, HASH_NOLOCK, HASH_WRITE);
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/*
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* Initialize first bitmap page
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*/
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@ -460,6 +475,8 @@ _hash_metapinit(Relation rel, double num_tuples)
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/* all done */
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_hash_wrtbuf(rel, metabuf);
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return num_buckets;
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}
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/*
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@ -0,0 +1,116 @@
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/*-------------------------------------------------------------------------
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*
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* hashsort.c
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* Sort tuples for insertion into a new hash index.
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*
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* When building a very large hash index, we pre-sort the tuples by bucket
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* number to improve locality of access to the index, and thereby avoid
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* thrashing. We use tuplesort.c to sort the given index tuples into order.
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*
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* Note: if the number of rows in the table has been underestimated,
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* bucket splits may occur during the index build. In that case we'd
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* be inserting into two or more buckets for each possible masked-off
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* hash code value. That's no big problem though, since we'll still have
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* plenty of locality of access.
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*
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*
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* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* $PostgreSQL: pgsql/src/backend/access/hash/hashsort.c,v 1.1 2008/03/16 23:15:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/hash.h"
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#include "miscadmin.h"
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#include "utils/tuplesort.h"
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/*
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* Status record for spooling/sorting phase.
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*/
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struct HSpool
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{
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Tuplesortstate *sortstate; /* state data for tuplesort.c */
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Relation index;
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};
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/*
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* create and initialize a spool structure
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*/
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HSpool *
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_h_spoolinit(Relation index, uint32 num_buckets)
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{
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HSpool *hspool = (HSpool *) palloc0(sizeof(HSpool));
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uint32 hash_mask;
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hspool->index = index;
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/*
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* Determine the bitmask for hash code values. Since there are currently
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* num_buckets buckets in the index, the appropriate mask can be computed
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* as follows.
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*
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* Note: at present, the passed-in num_buckets is always a power of 2,
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* so we could just compute num_buckets - 1. We prefer not to assume
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* that here, though.
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*/
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hash_mask = (((uint32) 1) << _hash_log2(num_buckets)) - 1;
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/*
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* We size the sort area as maintenance_work_mem rather than work_mem to
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* speed index creation. This should be OK since a single backend can't
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* run multiple index creations in parallel.
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*/
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hspool->sortstate = tuplesort_begin_index_hash(index,
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hash_mask,
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maintenance_work_mem,
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false);
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return hspool;
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}
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/*
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* clean up a spool structure and its substructures.
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*/
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void
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_h_spooldestroy(HSpool *hspool)
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{
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tuplesort_end(hspool->sortstate);
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pfree(hspool);
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}
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/*
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* spool an index entry into the sort file.
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*/
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void
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_h_spool(IndexTuple itup, HSpool *hspool)
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{
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tuplesort_putindextuple(hspool->sortstate, itup);
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}
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/*
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* given a spool loaded by successive calls to _h_spool,
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* create an entire index.
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*/
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void
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_h_indexbuild(HSpool *hspool)
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{
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IndexTuple itup;
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bool should_free;
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tuplesort_performsort(hspool->sortstate);
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while ((itup = tuplesort_getindextuple(hspool->sortstate,
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true, &should_free)) != NULL)
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{
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_hash_doinsert(hspool->index, itup);
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if (should_free)
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pfree(itup);
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}
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}
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|
@ -57,7 +57,7 @@
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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||||
* IDENTIFICATION
|
||||
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtsort.c,v 1.114 2008/01/01 19:45:46 momjian Exp $
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* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtsort.c,v 1.115 2008/03/16 23:15:08 tgl Exp $
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*
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*-------------------------------------------------------------------------
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||||
*/
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|
@ -158,8 +158,8 @@ _bt_spoolinit(Relation index, bool isunique, bool isdead)
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* work_mem.
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*/
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btKbytes = isdead ? work_mem : maintenance_work_mem;
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btspool->sortstate = tuplesort_begin_index(index, isunique,
|
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btKbytes, false);
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btspool->sortstate = tuplesort_begin_index_btree(index, isunique,
|
||||
btKbytes, false);
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||||
|
||||
return btspool;
|
||||
}
|
||||
|
|
|
|||
|
|
@ -91,7 +91,7 @@
|
|||
* Portions Copyright (c) 1994, Regents of the University of California
|
||||
*
|
||||
* IDENTIFICATION
|
||||
* $PostgreSQL: pgsql/src/backend/utils/sort/tuplesort.c,v 1.81 2008/01/01 19:45:55 momjian Exp $
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||||
* $PostgreSQL: pgsql/src/backend/utils/sort/tuplesort.c,v 1.82 2008/03/16 23:15:08 tgl Exp $
|
||||
*
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||||
*-------------------------------------------------------------------------
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||||
*/
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|
@ -100,6 +100,7 @@
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|||
|
||||
#include <limits.h>
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#include "access/hash.h"
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#include "access/heapam.h"
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#include "access/nbtree.h"
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#include "catalog/pg_amop.h"
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|
|
@ -336,12 +337,17 @@ struct Tuplesortstate
|
|||
|
||||
/*
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* These variables are specific to the IndexTuple case; they are set by
|
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* tuplesort_begin_index and used only by the IndexTuple routines.
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||||
* tuplesort_begin_index_xxx and used only by the IndexTuple routines.
|
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*/
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||||
Relation indexRel;
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||||
Relation indexRel; /* index being built */
|
||||
|
||||
/* These are specific to the index_btree subcase: */
|
||||
ScanKey indexScanKey;
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bool enforceUnique; /* complain if we find duplicate tuples */
|
||||
|
||||
/* These are specific to the index_hash subcase: */
|
||||
uint32 hash_mask; /* mask for sortable part of hash code */
|
||||
|
||||
/*
|
||||
* These variables are specific to the Datum case; they are set by
|
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* tuplesort_begin_datum and used only by the DatumTuple routines.
|
||||
|
|
@ -437,14 +443,17 @@ static void writetup_heap(Tuplesortstate *state, int tapenum,
|
|||
static void readtup_heap(Tuplesortstate *state, SortTuple *stup,
|
||||
int tapenum, unsigned int len);
|
||||
static void reversedirection_heap(Tuplesortstate *state);
|
||||
static int comparetup_index(const SortTuple *a, const SortTuple *b,
|
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static int comparetup_index_btree(const SortTuple *a, const SortTuple *b,
|
||||
Tuplesortstate *state);
|
||||
static int comparetup_index_hash(const SortTuple *a, const SortTuple *b,
|
||||
Tuplesortstate *state);
|
||||
static void copytup_index(Tuplesortstate *state, SortTuple *stup, void *tup);
|
||||
static void writetup_index(Tuplesortstate *state, int tapenum,
|
||||
SortTuple *stup);
|
||||
static void readtup_index(Tuplesortstate *state, SortTuple *stup,
|
||||
int tapenum, unsigned int len);
|
||||
static void reversedirection_index(Tuplesortstate *state);
|
||||
static void reversedirection_index_btree(Tuplesortstate *state);
|
||||
static void reversedirection_index_hash(Tuplesortstate *state);
|
||||
static int comparetup_datum(const SortTuple *a, const SortTuple *b,
|
||||
Tuplesortstate *state);
|
||||
static void copytup_datum(Tuplesortstate *state, SortTuple *stup, void *tup);
|
||||
|
|
@ -606,9 +615,9 @@ tuplesort_begin_heap(TupleDesc tupDesc,
|
|||
}
|
||||
|
||||
Tuplesortstate *
|
||||
tuplesort_begin_index(Relation indexRel,
|
||||
bool enforceUnique,
|
||||
int workMem, bool randomAccess)
|
||||
tuplesort_begin_index_btree(Relation indexRel,
|
||||
bool enforceUnique,
|
||||
int workMem, bool randomAccess)
|
||||
{
|
||||
Tuplesortstate *state = tuplesort_begin_common(workMem, randomAccess);
|
||||
MemoryContext oldcontext;
|
||||
|
|
@ -625,14 +634,13 @@ tuplesort_begin_index(Relation indexRel,
|
|||
|
||||
state->nKeys = RelationGetNumberOfAttributes(indexRel);
|
||||
|
||||
state->comparetup = comparetup_index;
|
||||
state->comparetup = comparetup_index_btree;
|
||||
state->copytup = copytup_index;
|
||||
state->writetup = writetup_index;
|
||||
state->readtup = readtup_index;
|
||||
state->reversedirection = reversedirection_index;
|
||||
state->reversedirection = reversedirection_index_btree;
|
||||
|
||||
state->indexRel = indexRel;
|
||||
/* see comments below about btree dependence of this code... */
|
||||
state->indexScanKey = _bt_mkscankey_nodata(indexRel);
|
||||
state->enforceUnique = enforceUnique;
|
||||
|
||||
|
|
@ -641,6 +649,40 @@ tuplesort_begin_index(Relation indexRel,
|
|||
return state;
|
||||
}
|
||||
|
||||
Tuplesortstate *
|
||||
tuplesort_begin_index_hash(Relation indexRel,
|
||||
uint32 hash_mask,
|
||||
int workMem, bool randomAccess)
|
||||
{
|
||||
Tuplesortstate *state = tuplesort_begin_common(workMem, randomAccess);
|
||||
MemoryContext oldcontext;
|
||||
|
||||
oldcontext = MemoryContextSwitchTo(state->sortcontext);
|
||||
|
||||
#ifdef TRACE_SORT
|
||||
if (trace_sort)
|
||||
elog(LOG,
|
||||
"begin index sort: hash_mask = 0x%x, workMem = %d, randomAccess = %c",
|
||||
hash_mask,
|
||||
workMem, randomAccess ? 't' : 'f');
|
||||
#endif
|
||||
|
||||
state->nKeys = 1; /* Only one sort column, the hash code */
|
||||
|
||||
state->comparetup = comparetup_index_hash;
|
||||
state->copytup = copytup_index;
|
||||
state->writetup = writetup_index;
|
||||
state->readtup = readtup_index;
|
||||
state->reversedirection = reversedirection_index_hash;
|
||||
|
||||
state->indexRel = indexRel;
|
||||
state->hash_mask = hash_mask;
|
||||
|
||||
MemoryContextSwitchTo(oldcontext);
|
||||
|
||||
return state;
|
||||
}
|
||||
|
||||
Tuplesortstate *
|
||||
tuplesort_begin_datum(Oid datumType,
|
||||
Oid sortOperator, bool nullsFirstFlag,
|
||||
|
|
@ -2637,14 +2679,14 @@ reversedirection_heap(Tuplesortstate *state)
|
|||
/*
|
||||
* Routines specialized for IndexTuple case
|
||||
*
|
||||
* NOTE: actually, these are specialized for the btree case; it's not
|
||||
* clear whether you could use them for a non-btree index. Possibly
|
||||
* you'd need to make another set of routines if you needed to sort
|
||||
* according to another kind of index.
|
||||
* 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 int
|
||||
comparetup_index(const SortTuple *a, const SortTuple *b, Tuplesortstate *state)
|
||||
comparetup_index_btree(const SortTuple *a, const SortTuple *b,
|
||||
Tuplesortstate *state)
|
||||
{
|
||||
/*
|
||||
* This is similar to _bt_tuplecompare(), but we have already done the
|
||||
|
|
@ -2748,6 +2790,62 @@ comparetup_index(const SortTuple *a, const SortTuple *b, Tuplesortstate *state)
|
|||
return 0;
|
||||
}
|
||||
|
||||
static int
|
||||
comparetup_index_hash(const SortTuple *a, const SortTuple *b,
|
||||
Tuplesortstate *state)
|
||||
{
|
||||
/*
|
||||
* It's slightly annoying to redo the hash function each time, although
|
||||
* most hash functions ought to be cheap. Is it worth having a variant
|
||||
* tuple storage format so we can store the hash code?
|
||||
*/
|
||||
uint32 hash1;
|
||||
uint32 hash2;
|
||||
IndexTuple tuple1;
|
||||
IndexTuple tuple2;
|
||||
|
||||
/* Allow interrupting long sorts */
|
||||
CHECK_FOR_INTERRUPTS();
|
||||
|
||||
/* Compute hash codes and mask off bits we don't want to sort by */
|
||||
Assert(!a->isnull1);
|
||||
Assert(!b->isnull1);
|
||||
|
||||
hash1 = _hash_datum2hashkey(state->indexRel, a->datum1) & state->hash_mask;
|
||||
hash2 = _hash_datum2hashkey(state->indexRel, b->datum1) & state->hash_mask;
|
||||
|
||||
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 offers cheap insurance against
|
||||
* performance problems with bad qsort implementations that have trouble
|
||||
* with large numbers of equal keys.
|
||||
*/
|
||||
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;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
static void
|
||||
copytup_index(Tuplesortstate *state, SortTuple *stup, void *tup)
|
||||
{
|
||||
|
|
@ -2810,7 +2908,7 @@ readtup_index(Tuplesortstate *state, SortTuple *stup,
|
|||
}
|
||||
|
||||
static void
|
||||
reversedirection_index(Tuplesortstate *state)
|
||||
reversedirection_index_btree(Tuplesortstate *state)
|
||||
{
|
||||
ScanKey scanKey = state->indexScanKey;
|
||||
int nkey;
|
||||
|
|
@ -2821,6 +2919,13 @@ reversedirection_index(Tuplesortstate *state)
|
|||
}
|
||||
}
|
||||
|
||||
static void
|
||||
reversedirection_index_hash(Tuplesortstate *state)
|
||||
{
|
||||
/* We don't support reversing direction in a hash index sort */
|
||||
elog(ERROR, "reversedirection_index_hash is not implemented");
|
||||
}
|
||||
|
||||
|
||||
/*
|
||||
* Routines specialized for DatumTuple case
|
||||
|
|
|
|||
|
|
@ -7,7 +7,7 @@
|
|||
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
|
||||
* Portions Copyright (c) 1994, Regents of the University of California
|
||||
*
|
||||
* $PostgreSQL: pgsql/src/include/access/hash.h,v 1.85 2008/03/15 20:46:31 tgl Exp $
|
||||
* $PostgreSQL: pgsql/src/include/access/hash.h,v 1.86 2008/03/16 23:15:08 tgl Exp $
|
||||
*
|
||||
* NOTES
|
||||
* modeled after Margo Seltzer's hash implementation for unix.
|
||||
|
|
@ -298,7 +298,7 @@ extern void _hash_dropbuf(Relation rel, Buffer buf);
|
|||
extern void _hash_wrtbuf(Relation rel, Buffer buf);
|
||||
extern void _hash_chgbufaccess(Relation rel, Buffer buf, int from_access,
|
||||
int to_access);
|
||||
extern void _hash_metapinit(Relation rel, double num_tuples);
|
||||
extern uint32 _hash_metapinit(Relation rel, double num_tuples);
|
||||
extern void _hash_pageinit(Page page, Size size);
|
||||
extern void _hash_expandtable(Relation rel, Buffer metabuf);
|
||||
|
||||
|
|
@ -313,6 +313,14 @@ extern bool _hash_next(IndexScanDesc scan, ScanDirection dir);
|
|||
extern bool _hash_first(IndexScanDesc scan, ScanDirection dir);
|
||||
extern bool _hash_step(IndexScanDesc scan, Buffer *bufP, ScanDirection dir);
|
||||
|
||||
/* hashsort.c */
|
||||
typedef struct HSpool HSpool; /* opaque struct in hashsort.c */
|
||||
|
||||
extern HSpool *_h_spoolinit(Relation index, uint32 num_buckets);
|
||||
extern void _h_spooldestroy(HSpool *hspool);
|
||||
extern void _h_spool(IndexTuple itup, HSpool *hspool);
|
||||
extern void _h_indexbuild(HSpool *hspool);
|
||||
|
||||
/* hashutil.c */
|
||||
extern bool _hash_checkqual(IndexScanDesc scan, IndexTuple itup);
|
||||
extern uint32 _hash_datum2hashkey(Relation rel, Datum key);
|
||||
|
|
|
|||
|
|
@ -13,7 +13,7 @@
|
|||
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
|
||||
* Portions Copyright (c) 1994, Regents of the University of California
|
||||
*
|
||||
* $PostgreSQL: pgsql/src/include/utils/tuplesort.h,v 1.28 2008/01/01 19:45:59 momjian Exp $
|
||||
* $PostgreSQL: pgsql/src/include/utils/tuplesort.h,v 1.29 2008/03/16 23:15:08 tgl Exp $
|
||||
*
|
||||
*-------------------------------------------------------------------------
|
||||
*/
|
||||
|
|
@ -41,16 +41,24 @@ typedef struct Tuplesortstate Tuplesortstate;
|
|||
* rather than forming actual HeapTuples (which'd have to be converted to
|
||||
* MinimalTuples).
|
||||
*
|
||||
* Yet a third slightly different interface supports sorting bare Datums.
|
||||
* The IndexTuple case is itself broken into two subcases, one for btree
|
||||
* indexes and one for hash indexes; the latter variant actually sorts
|
||||
* the tuples by hash code. The API is the same except for the "begin"
|
||||
* routine.
|
||||
*
|
||||
* Yet another slightly different interface supports sorting bare Datums.
|
||||
*/
|
||||
|
||||
extern Tuplesortstate *tuplesort_begin_heap(TupleDesc tupDesc,
|
||||
int nkeys, AttrNumber *attNums,
|
||||
Oid *sortOperators, bool *nullsFirstFlags,
|
||||
int workMem, bool randomAccess);
|
||||
extern Tuplesortstate *tuplesort_begin_index(Relation indexRel,
|
||||
bool enforceUnique,
|
||||
int workMem, bool randomAccess);
|
||||
extern Tuplesortstate *tuplesort_begin_index_btree(Relation indexRel,
|
||||
bool enforceUnique,
|
||||
int workMem, bool randomAccess);
|
||||
extern Tuplesortstate *tuplesort_begin_index_hash(Relation indexRel,
|
||||
uint32 hash_mask,
|
||||
int workMem, bool randomAccess);
|
||||
extern Tuplesortstate *tuplesort_begin_datum(Oid datumType,
|
||||
Oid sortOperator, bool nullsFirstFlag,
|
||||
int workMem, bool randomAccess);
|
||||
|
|
|
|||
Loading…
Reference in New Issue