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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2000-03-30 00:53:30 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2000-03-30 00:53:30 +0000 |
| commit | e55985d3be4aed47c703674c735c124ff0b3c03c (patch) | |
| tree | 4be5accd90a1c1561737d9297ab0df7eec74118c /src | |
| parent | 341dc91820b3f80ae69a51f2780fd0d8afcb2c47 (diff) | |
| download | postgresql-e55985d3be4aed47c703674c735c124ff0b3c03c.tar.gz postgresql-e55985d3be4aed47c703674c735c124ff0b3c03c.zip | |
Tweak indexscan cost estimation: round estimated # of tuples visited up
to next integer. Previously, if selectivity was small, we could compute
very tiny scan cost on the basis of estimating that only 0.001 tuple
would be fetched, which is silly. This naturally led to some rather
silly plans...
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 10 | ||||
| -rw-r--r-- | src/backend/utils/adt/selfuncs.c | 8 |
2 files changed, 10 insertions, 8 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index 4270032d278..37b4dfc42e7 100644 --- a/src/backend/optimizer/path/costsize.c +++ b/src/backend/optimizer/path/costsize.c @@ -42,7 +42,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.54 2000/03/22 22:08:33 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.55 2000/03/30 00:53:29 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -262,11 +262,11 @@ cost_index(Path *path, Query *root, * effect. Would be nice to do better someday. */ - tuples_fetched = indexSelectivity * baserel->tuples; + tuples_fetched = ceil(indexSelectivity * baserel->tuples); if (tuples_fetched > 0 && baserel->pages > 0) - pages_fetched = baserel->pages * - log(tuples_fetched / baserel->pages + 1.0); + pages_fetched = ceil(baserel->pages * + log(tuples_fetched / baserel->pages + 1.0)); else pages_fetched = tuples_fetched; @@ -594,7 +594,7 @@ cost_hashjoin(Path *path, * conservatively as the inner disbursion times the inner tuple count. */ run_cost += cpu_operator_cost * outer_path->parent->rows * - (inner_path->parent->rows * innerdisbursion); + ceil(inner_path->parent->rows * innerdisbursion); /* * Estimate the number of tuples that get through the hashing filter diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index af7a449f697..0cd408ed78f 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -15,13 +15,15 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.61 2000/03/23 00:55:42 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.62 2000/03/30 00:53:30 tgl Exp $ * *------------------------------------------------------------------------- */ #include "postgres.h" +#include <math.h> + #include "access/heapam.h" #include "catalog/catname.h" #include "catalog/pg_operator.h" @@ -900,10 +902,10 @@ genericcostestimate(Query *root, RelOptInfo *rel, lfirsti(rel->relids)); /* Estimate the number of index tuples that will be visited */ - numIndexTuples = *indexSelectivity * index->tuples; + numIndexTuples = ceil(*indexSelectivity * index->tuples); /* Estimate the number of index pages that will be retrieved */ - numIndexPages = *indexSelectivity * index->pages; + numIndexPages = ceil(*indexSelectivity * index->pages); /* * Compute the index access cost. |