diff options
Diffstat (limited to 'src/backend/access/hash/hash.c')
| -rw-r--r-- | src/backend/access/hash/hash.c | 45 |
1 files changed, 38 insertions, 7 deletions
diff --git a/src/backend/access/hash/hash.c b/src/backend/access/hash/hash.c index b008c0aa4a..01da35ec9f 100644 --- a/src/backend/access/hash/hash.c +++ b/src/backend/access/hash/hash.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.99 2008/03/15 20:46:31 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/access/hash/hash.c,v 1.100 2008/03/16 23:15:08 tgl Exp $ * * NOTES * This file contains only the public interface routines. @@ -22,13 +22,15 @@ #include "access/hash.h" #include "catalog/index.h" #include "commands/vacuum.h" +#include "optimizer/cost.h" #include "optimizer/plancat.h" /* Working state for hashbuild and its callback */ typedef struct { - double indtuples; + HSpool *spool; /* NULL if not using spooling */ + double indtuples; /* # tuples accepted into index */ } HashBuildState; static void hashbuildCallback(Relation index, @@ -51,6 +53,7 @@ hashbuild(PG_FUNCTION_ARGS) IndexBuildResult *result; BlockNumber relpages; double reltuples; + uint32 num_buckets; HashBuildState buildstate; /* @@ -61,19 +64,43 @@ hashbuild(PG_FUNCTION_ARGS) elog(ERROR, "index \"%s\" already contains data", RelationGetRelationName(index)); - /* estimate the number of rows currently present in the table */ + /* Estimate the number of rows currently present in the table */ estimate_rel_size(heap, NULL, &relpages, &reltuples); - /* initialize the hash index metadata page and initial buckets */ - _hash_metapinit(index, reltuples); + /* Initialize the hash index metadata page and initial buckets */ + num_buckets = _hash_metapinit(index, reltuples); - /* build the index */ + /* + * If we just insert the tuples into the index in scan order, then + * (assuming their hash codes are pretty random) there will be no locality + * of access to the index, and if the index is bigger than available RAM + * then we'll thrash horribly. To prevent that scenario, we can sort the + * tuples by (expected) bucket number. However, such a sort is useless + * overhead when the index does fit in RAM. We choose to sort if the + * initial index size exceeds effective_cache_size. + * + * NOTE: this test will need adjustment if a bucket is ever different + * from one page. + */ + if (num_buckets >= (uint32) effective_cache_size) + buildstate.spool = _h_spoolinit(index, num_buckets); + else + buildstate.spool = NULL; + + /* prepare to build the index */ buildstate.indtuples = 0; /* do the heap scan */ reltuples = IndexBuildHeapScan(heap, index, indexInfo, hashbuildCallback, (void *) &buildstate); + if (buildstate.spool) + { + /* sort the tuples and insert them into the index */ + _h_indexbuild(buildstate.spool); + _h_spooldestroy(buildstate.spool); + } + /* * Return statistics */ @@ -110,7 +137,11 @@ hashbuildCallback(Relation index, return; } - _hash_doinsert(index, itup); + /* Either spool the tuple for sorting, or just put it into the index */ + if (buildstate->spool) + _h_spool(itup, buildstate->spool); + else + _hash_doinsert(index, itup); buildstate->indtuples += 1; |