From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com>, Rafia Sabih <rafia(dot)sabih(at)enterprisedb(dot)com>, tushar <tushar(dot)ahuja(at)enterprisedb(dot)com>, Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Parallel bitmap heap scan |
Date: | 2017-02-20 19:04:50 |
Message-ID: | 3114.1487617490@sss.pgh.pa.us |
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Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Mon, Feb 20, 2017 at 6:19 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> The thing that you really have to worry about for this kind of proposal
>> is "what if the query errors out and we never get to ExecEndNode"?
>> It's particularly nasty if you're talking about parallel queries where
>> maybe only one or some of the processes involved detect an error.
> I think that's not actually a problem, because we've already got code
> to make sure that all DSM resources associated with the query get
> blown away in that case. Of course, that code might have bugs, but if
> it does, I think it's better to try to fix those bugs than to insert
> some belt-and-suspenders mechanism for reclaiming every possible chunk
> of memory in retail fashion, just like we blow up es_query_cxt rather
> than trying to pfree allocations individually.
Actually, I think we're saying the same thing: rely on the general DSM
cleanup mechanism, don't insert extra stuff that you expect will get
done by executor shutdown.
regards, tom lane
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