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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2003-12-29 21:44:49 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2003-12-29 21:44:49 +0000 |
| commit | b53ca9bbcb2892c6c24f7ab4aa087b35ef1222e6 (patch) | |
| tree | db16cc9d08e46c41d75e6b60fc9df437fe1d2738 /src | |
| parent | 07f9f4d41352ff8cd45ba04ebb8b36764fed65df (diff) | |
| download | postgresql-b53ca9bbcb2892c6c24f7ab4aa087b35ef1222e6.tar.gz postgresql-b53ca9bbcb2892c6c24f7ab4aa087b35ef1222e6.zip | |
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Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/optimizer/path/clausesel.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/src/backend/optimizer/path/clausesel.c b/src/backend/optimizer/path/clausesel.c index 17cde28aec6..7e5456d85b5 100644 --- a/src/backend/optimizer/path/clausesel.c +++ b/src/backend/optimizer/path/clausesel.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/optimizer/path/clausesel.c,v 1.61 2003/11/29 19:51:50 pgsql Exp $ + * $PostgreSQL: pgsql/src/backend/optimizer/path/clausesel.c,v 1.62 2003/12/29 21:44:49 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -108,6 +108,10 @@ restrictlist_selectivity(Query *root, * If the calculation yields zero or negative, however, we chicken out and * use a default estimate; that probably means that one or both * selectivities is a default estimate rather than an actual range value. + * + * A free side-effect is that we can recognize redundant inequalities such + * as "x < 4 AND x < 5"; only the tighter constraint will be counted. + * * Of course this is all very dependent on the behavior of * scalarltsel/scalargtsel; perhaps some day we can generalize the approach. */ |