From: Arthur Zakirov <a.zakirov@postgrespro.ru>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Pavel Stehule <pavel.stehule@gmail.com>
Cc: Andres Freund <andres@anarazel.de>
Cc: Ildus Kurbangaliev <i.kurbangaliev@postgrespro.ru>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: [PROPOSAL] Shared Ispell dictionaries
Date: Sun, 25 Mar 2018 23:54:10 +0300
Message-ID: <20180325205408.GA19457@arthur.localdomain> (raw)
In-Reply-To: <25186.1521951490@sss.pgh.pa.us>
References: <d4d52484-e269-9d7b-cef5-c1e95a03d9c6@2ndquadrant.com>
<20180319110648.GA32319@zakirov.localdomain>
<2ae9588a-f3cb-777d-1958-c76c22225823@2ndquadrant.com>
<20180320131149.GA12884@zakirov.localdomain>
<ebcb7f9d-eec2-3138-efde-af83b6a0f04f@2ndquadrant.com>
<20180321090050.GA21751@zakirov.localdomain>
<20180322105603.GA23544@zakirov.localdomain>
<28250.1521924996@sss.pgh.pa.us>
<ada73d07-6c88-acab-7e31-75b2eb724d24@2ndquadrant.com>
<25186.1521951490@sss.pgh.pa.us>
On Sun, Mar 25, 2018 at 12:18:10AM -0400, Tom Lane wrote:
> My thought was (a) the ROLLBACK case is ok, because the next use of
> the dictionary will reload it, and (b) the reload-concurrently-with-
> DROP case is annoying, because indeed it leaks, but the window is small
> and it probably won't be an issue in practice. We would need to be
> sure that the DSM segment goes away at postmaster restart, but given
> that I think it'd be tolerable. Of course it'd be better not to have
> the race, but I see no easy way to prevent it -- do you?
I'm not sure that I understood the second case correclty. Can cache
invalidation help in this case? I don't have confident knowledge of cache
invalidation. It seems to me that InvalidateTSCacheCallBack() should
release segment after commit.
But cache isn't invalidated if a backend was terminated after a
dictionary reloading. on_shmem_exit() could help, but we need a leaked
dictionaries list for that.
P.S. I think it isn't right to release all dictionaries segment in
InvalidateTSCacheCallBack(). Otherwise any DROP can release all
segments. It would be worth to release a specific dictionary.
--
Arthur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company
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To: pgsql-hackers@postgresql.org
Cc: a.zakirov@postgrespro.ru, tgl@sss.pgh.pa.us, tomas.vondra@2ndquadrant.com, pavel.stehule@gmail.com, andres@anarazel.de, i.kurbangaliev@postgrespro.ru
Subject: Re: [PROPOSAL] Shared Ispell dictionaries
In-Reply-To: <20180325205408.GA19457@arthur.localdomain>
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