Re: [HACKERS] Optimizer fed bad data about some system-table indexes

> Bruce Momjian <maillist@candle.pha.pa.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?

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