Re: Increasing catcache size

Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Tom Lane wrote:
> >> I just thought of a more radical idea: do we need a limit on catcache
> >> size at all? On "normal size" databases I believe that we never hit
> >> 5000 entries at all (at least, last time I ran the CATCACHE_STATS code
> >> on the regression tests, we didn't get close to that). We don't have
> >> any comparable limit in the relcache and it doesn't seem to hurt us,
> >> even though a relcache entry is a pretty heavyweight object.
>
> > Well, assuming you never access all those tables, you don't use lots of
> > memory, but if you are accessing a lot, it seems memory for all your
> > tables is a minimal overhead.
>
> I re-did the test of running the regression tests with CATCACHE_STATS
> enabled. The largest catcache population in any test was 1238 tuples,
> and most backends had 500 or less. I'm not sure whether you'd really
> want to consider the regression database as representative of small
> production databases, but granted that assumption, the current limit of
> 5000 tuples isn't limiting anything on small-to-middling databases.
> (Note we are counting tables and other cataloged objects, *not* volume
> of data stored --- so the regression database could easily be much
> bigger than many production DBs by this measure.)
>
> So I'm pretty strongly inclined to just dike out the limit. If you're
> running a database big enough to hit the existing limit, you can well
> afford to put more memory into the catcache.

And if we get problem reports, we can fix it.

--
Bruce Momjian http://candle.pha.pa.us
EnterpriseDB http://www.enterprisedb.com

+ If your life is a hard drive, Christ can be your backup. +