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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2001-05-09 00:35:09 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2001-05-09 00:35:09 +0000 |
| commit | 6cda3ad8feb9b534fe9fb5866bbe5930596d0027 (patch) | |
| tree | af13dbf295f98b9f4addf5f18ddaf3dd8d2f9341 /doc/src | |
| parent | b66a0cca57e21e2fdf00f81e1976bd76fabf0fc1 (diff) | |
| download | postgresql-6cda3ad8feb9b534fe9fb5866bbe5930596d0027.tar.gz postgresql-6cda3ad8feb9b534fe9fb5866bbe5930596d0027.zip | |
Cause planner to make use of average-column-width statistic that is now
collected by ANALYZE. Also, add some modest amount of intelligence to
guesses that are used for varlena columns in the absence of any ANALYZE
statistics. The 'width' reported by EXPLAIN is finally something less
than totally bogus for varlena columns ... and, in consequence, hashjoin
estimating should be a little better ...
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/perform.sgml | 9 |
1 files changed, 1 insertions, 8 deletions
diff --git a/doc/src/sgml/perform.sgml b/doc/src/sgml/perform.sgml index 77e1c77d8f6..bfe66eb5dc5 100644 --- a/doc/src/sgml/perform.sgml +++ b/doc/src/sgml/perform.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.3 2001/03/24 23:03:26 petere Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.4 2001/05/09 00:35:09 tgl Exp $ --> <chapter id="performance-tips"> @@ -98,13 +98,6 @@ $Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.3 2001/03/24 23:03:26 pete </para> <para> - Average width is pretty bogus because the thing really doesn't have - any idea of the average length of variable-length columns. I'm thinking - about improving that in the future, but it may not be worth the trouble, - because the width isn't used for very much. - </para> - - <para> Here are some examples (using the regress test database after a vacuum analyze, and almost-7.0 sources): |