| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Richard Huxton <dev(at)archonet(dot)com> |
| Cc: | Richard Broersma Jr <rabroersma(at)yahoo(dot)com>, Phoenix Kiula <phoenix(dot)kiula(at)gmail(dot)com>, Postgres General <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Partial index with regexp not working |
| Date: | 2007-09-11 14:16:37 |
| Message-ID: | 27812.1189520197@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Richard Huxton <dev(at)archonet(dot)com> writes:
> The planner isn't smart enough to figure out which queries can use this
> index by examining them, it just looks for (NOT paid) in the WHERE
> clause and if it doesn't find it, ignores the index.
Well, it's a little bit brighter than that: it has some smarts about
btree-indexable comparisons and about null-testing. For instance, it
can figure out that "x > 3" implies "x > 0", and so a query WHERE x > 3
could use a partial index WHERE x > 0. Also, assuming that the >
operator is strict, it would recognize that WHERE x IS NOT NULL is
implied.
But there's certainly not anything in there that can make inferences
about regex matches.
regards, tom lane
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