diff options
| -rw-r--r-- | src/backend/optimizer/path/costsize.c | 9 | ||||
| -rw-r--r-- | src/backend/utils/adt/selfuncs.c | 15 |
2 files changed, 18 insertions, 6 deletions
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c index 37b4dfc42e7..f6bdcb828b9 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 1.55 2000/03/30 00:53:29 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/optimizer/path/costsize.c,v 1.56 2000/04/09 04:31:36 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -262,9 +262,12 @@ cost_index(Path *path, Query *root, * effect. Would be nice to do better someday. */ - tuples_fetched = ceil(indexSelectivity * baserel->tuples); + tuples_fetched = indexSelectivity * baserel->tuples; + /* Don't believe estimates less than 1... */ + if (tuples_fetched < 1.0) + tuples_fetched = 1.0; - if (tuples_fetched > 0 && baserel->pages > 0) + if (baserel->pages > 0) pages_fetched = ceil(baserel->pages * log(tuples_fetched / baserel->pages + 1.0)); else diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index 0cd408ed78f..7e03b10d431 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -15,7 +15,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.62 2000/03/30 00:53:30 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/utils/adt/selfuncs.c,v 1.63 2000/04/09 04:31:37 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -902,10 +902,19 @@ genericcostestimate(Query *root, RelOptInfo *rel, lfirsti(rel->relids)); /* Estimate the number of index tuples that will be visited */ - numIndexTuples = ceil(*indexSelectivity * index->tuples); + numIndexTuples = *indexSelectivity * index->tuples; /* Estimate the number of index pages that will be retrieved */ - numIndexPages = ceil(*indexSelectivity * index->pages); + numIndexPages = *indexSelectivity * index->pages; + + /* + * Always estimate at least one tuple and page are touched, + * even when indexSelectivity estimate is tiny. + */ + if (numIndexTuples < 1.0) + numIndexTuples = 1.0; + if (numIndexPages < 1.0) + numIndexPages = 1.0; /* * Compute the index access cost. |