Tom Lane wrote: > Michael Fuhr <[EMAIL PROTECTED]> writes: > > I've noticed that row count estimates for expression indexes appear > > to rely on default_statistics_target rather than on a column's > > actual statistics target. That is, if I use ALTER TABLE SET > > STATISTICS to increase a column's statistics target and then run > > ANALYZE, then estimates for non-expression-index queries improve > > as expected. However, queries that use an expression index remain > > accurate for only around the N most common values, where N is the > > default_statistics_target that was in effect when ANALYZE ran. > > The code does in fact honor per-column statistics targets attached to > expression indexes, viz > > alter table myfuncindex alter column pg_expression_1 set statistics 100; > > This isn't documented, mainly because pg_dump doesn't promise to dump > such things, which it doesn't do because I didn't want to see the > "pg_expression_N" naming for expression index columns become graven on > stone tablets. I seem to recall bringing up the question of whether > we could find a less implementation-specific way of commanding this > behavior, but I can't find it in the archives right now.
Is this a TODO? -- Bruce Momjian | http://candle.pha.pa.us pgman@candle.pha.pa.us | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
