| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> |
| Cc: | Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, robertmhaas(at)gmail(dot)com, craig(at)2ndquadrant(dot)com, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Protect syscache from bloating with negative cache entries |
| Date: | 2017-01-22 23:03:41 |
| Message-ID: | 26168.1485126221@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> writes:
>> Ahh, I hadn't considered that. So one idea would be to only track
>> negative entries on caches where we know they're actually useful. That
>> might make the performance hit of some of the other ideas more
>> tolerable. Presumably you're much less likely to pollute the namespace
>> cache than some of the others.
> Ok, after reading the code I see I only partly understood what you were
> saying. In any case, it might still be useful to do some testing with
> CATCACHE_STATS defined to see if there's caches that don't accumulate a
> lot of negative entries.
There definitely are, according to my testing, but by the same token
it's not clear that a shutoff check would save anything.
regards, tom lane
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