| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, pgsql-patches(at)postgresql(dot)org |
| Subject: | Re: Aggressive freezing in lazy-vacuum |
| Date: | 2007-03-05 16:02:31 |
| Message-ID: | 18982.1173110551@sss.pgh.pa.us |
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| Lists: | pgsql-hackers pgsql-patches pgsql-performance |
ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> writes:
> This is a stand-alone patch for aggressive freezing. I'll propose
> to use OldestXmin instead of FreezeLimit as the freeze threshold
> in the circumstances below:
I think it's a really bad idea to freeze that aggressively under any
circumstances except being told to (ie, VACUUM FREEZE). When you
freeze, you lose history information that might be needed later --- for
forensic purposes if nothing else. You need to show a fairly amazing
performance gain to justify that, and I don't think you can.
regards, tom lane
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