| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Sam Liddicott" <sam(dot)liddicott(at)ananova(dot)com> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: 7.2.1 optimises very badly against 7.2 |
| Date: | 2002-07-08 20:44:16 |
| Message-ID: | 26758.1026161056@sss.pgh.pa.us |
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| Lists: | pgsql-general |
"Sam Liddicott" <sam(dot)liddicott(at)ananova(dot)com> writes:
>> Indeed. What do 7.2 and 7.2.1 have in the pg_stats row for
>> broadcast.channelregionid? What is the real distribution of that
>> column?
> 7.2 says:
> [snip]
Well, that's annoying: the new ANALYZE code is in fact more accurate
than the old (it's estimating 429 distinct values, vs. formerly 4532,
when the true figure is 636) but it's nonetheless making a worse final
choice of plan.
If you turn off enable_seqscan, what EXPLAIN results do you get from
7.2.1? How about if you leave enable_seqscan on, but reduce
random_page_cost from the default 4.0 to perhaps 3.0?
regards, tom lane
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