| From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
|---|---|
| To: | Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> |
| Cc: | "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)fujitsu(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, k(dot)jamison(at)fujitsu(dot)com, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [Patch] Optimize dropping of relation buffers using dlist |
| Date: | 2020-12-22 02:57:13 |
| Message-ID: | CAA4eK1L5+f_K2Fg+4K8v0GEbS=XJ9BYBYUx02mfk--fpOEzEwA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Dec 22, 2020 at 8:12 AM Kyotaro Horiguchi
<horikyota(dot)ntt(at)gmail(dot)com> wrote:
>
> At Tue, 22 Dec 2020 08:08:10 +0530, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote in
>
> > Why would all client backends wait for AccessExclusive lock on this
> > relation? Say, a client needs a buffer for some other relation and
> > that might evict this buffer after we release the lock on the
> > partition. In StrategyGetBuffer, it is important to either have a pin
> > on the buffer or the buffer header itself must be locked to avoid
> > getting picked as victim buffer. Am I missing something?
>
> I think exactly like that. If we acquire the bufHdr lock before
> releasing the partition lock, that steal doesn't happen but it doesn't
> seem good as a locking protocol.
>
Right, so let's keep the code as it is but I feel it is better to add
some comments explaining the rationale behind this code.
--
With Regards,
Amit Kapila.
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