Re: Protect syscache from bloating with negative cache entries

From: David Steele <david(at)pgmasters(dot)net>
To: David Steele <david(at)pgmasters(dot)net>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
Cc: michael(dot)paquier(at)gmail(dot)com, Jim(dot)Nasby(at)bluetreble(dot)com, tgl(at)sss(dot)pgh(dot)pa(dot)us, 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: 2017-03-08 03:23:14
Message-ID: 3b7b7f90-db46-8c37-c4f7-443330c3ae33@pgmasters.net
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On 3/3/17 4:54 PM, David Steele wrote:

> On 2/1/17 1:25 AM, Kyotaro HORIGUCHI wrote:
>> Hello, thank you for moving this to the next CF.
>>
>> At Wed, 1 Feb 2017 13:09:51 +0900, Michael Paquier <michael(dot)paquier(at)gmail(dot)com> wrote in <CAB7nPqRFhUv+GX=eH1bo7xYHS79-gRj1ecu2QoQtHvX9RS=JYA(at)mail(dot)gmail(dot)com>
>>> On Tue, Jan 24, 2017 at 4:58 PM, Kyotaro HORIGUCHI
>>> <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
>>>> Six new syscaches in 665d1fa was conflicted and 3-way merge
>>>> worked correctly. The new syscaches don't seem to be targets of
>>>> this patch.
>>> To be honest, I am not completely sure what to think about this patch.
>>> Moved to next CF as there is a new version, and no new reviews to make
>>> the discussion perhaps move on.
>> I'm thinking the following is the status of this topic.
>>
>> - The patch stll is not getting conflicted.
>>
>> - This is not a hollistic measure for memory leak but surely
>> saves some existing cases.
>>
>> - Shared catcache is another discussion (and won't really
>> proposed in a short time due to the issue on locking.)
>>
>> - As I mentioned, a patch that caps the number of negative
>> entries is avaiable (in first-created - first-delete manner)
>> but it is having a loose end of how to determine the
>> limitation.
> While preventing bloat in the syscache is a worthwhile goal, it appears
> there are a number of loose ends here and a new patch has not been provided.
>
> It's a pretty major change so I recommend moving this patch to the
> 2017-07 CF.

Not hearing any opinions pro or con, I'm moving this patch to the
2017-07 CF.

--
-David
david(at)pgmasters(dot)net

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