| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> |
| Cc: | fabricio(dot)silva(at)linkcom(dot)com(dot)br, "Craig Ringer" <craig(at)postnewspapers(dot)com(dot)au>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: How does PG know if data is in memory? |
| Date: | 2010-10-01 14:40:11 |
| Message-ID: | 12383.1285944011@sss.pgh.pa.us |
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| Lists: | pgsql-performance |
"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> writes:
> I agree with that, but I think there's an even more insidious issue
> here. Biasing plans heavily toward using what is already in cache
> could have a destabilizing effect on performance.
Not to mention the destabilizing effect on the plans themselves.
Behavior like that would make EXPLAIN nearly useless, because the plan
you get would vary from moment to moment even when "nothing is
changing". It's fairly clear that people don't actually want that.
regards, tom lane
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