| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | David Gould <daveg(at)sonic(dot)net> |
| Cc: | Alexander Kuzmenkov <a(dot)kuzmenkov(at)postgrespro(dot)ru>, pgsql-hackers(at)lists(dot)postgresql(dot)org, Alina Alexeeva <alexeeva(at)adobe(dot)com>, Ullas Lakkur Raghavendra <lakkurra(at)adobe(dot)com> |
| Subject: | Re: [patch] BUG #15005: ANALYZE can make pg_class.reltuples inaccurate. |
| Date: | 2018-03-13 15:20:39 |
| Message-ID: | 997.1520954439@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
David Gould <daveg(at)sonic(dot)net> writes:
> I also thought about the theory and am confident that there really is no way
> to trick it. Basically if there are enough pages that are different to affect
> the overall density, say 10% empty or so, there is no way a random sample
> larger than a few hundred probes can miss them no matter how big the table is.
> If there are few enough pages to "hide" from the sample, then they are so few
> they don't matter anyway.
> After all this my vote is for back patching too. I don't see any case where
> the patched analyze is or could be worse than what we are doing. I'm happy to
> provide my test cases if anyone is interested.
Yeah, you have a point. I'm still worried about unexpected side-effects,
but it seems like overall this is very unlikely to hurt anyone. I'll
back-patch (minus the removal of the unneeded vac_estimate_reltuples
argument).
regards, tom lane
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