From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
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To: | tgl(at)sss(dot)pgh(dot)pa(dot)us (Tom Lane) |
Cc: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: [HACKERS] Optimizer fed bad data about some system-table indexes |
Date: | 1999-05-01 19:17:34 |
Message-ID: | 199905011917.PAA06808@candle.pha.pa.us |
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Lists: | pgsql-hackers |
> Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Hmm. If you can get it to work without the file, great, or you could
> > just delete the file when vacuum is performed, so the next backend
> > recreates the file. That would work too.
>
> That's a good idea. I made a test database with a couple thousand
> tables in it, and found that when pg_class gets that big it does take
> a measurable amount of time to rebuild the index info if the relcache
> init file is not there. (Looked like about a third of a second on my
> machine.) Since backend startup time is a hotbutton item for some
> folks, I'm not going to take out the init file code. I'll just make
> VACUUM remove the file, and then the first backend start after a VACUUM
> will rebuild the file with up-to-date statistics for the system indexes.
That sounds like a big win. 1/3 second is large. If they vacuum a
single table, and it is not a system table, can the removal be skipped?
--
Bruce Momjian | http://www.op.net/~candle
maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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