| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | bombadil(at)wanadoo(dot)es |
| Cc: | Lista PostgreSql <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Problem (bug?) with like |
| Date: | 2001-12-03 15:40:45 |
| Message-ID: | 13305.1007394045@sss.pgh.pa.us |
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| Lists: | pgsql-general pgsql-hackers |
bombadil(at)wanadoo(dot)es writes:
> Here are my queries:
You sure you didn't paste in the same result for #2 and #3? They're
the same plan with the same rows estimates --- but I'd expect the rows
estimates, at least, to change given the more-selective LIKE pattern.
Also, how many rows are there really that match '%DA%' and '%DAVID%'?
I suspect the planner is being overoptimistic about the selectivity of
'%DAVID%', and is choosing a plan that doesn't work well when there are
lots of DAVIDs :-(
regards, tom lane
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