Re: We're leaking predicate locks in HEAD

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: We're leaking predicate locks in HEAD
Date: 2019-05-08 03:53:06
Message-ID: 6018.1557287586@sss.pgh.pa.us
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Thomas Munro <thomas(dot)munro(at)gmail(dot)com> writes:
> Reproduced here. Once the system reaches a state where it's leaking
> (which happens only occasionally for me during installcheck-parallel),
> it keeps leaking for future SSI transactions. The cause is
> SxactGlobalXmin getting stuck. The attached fixes it for me. I can't
> remember why on earth I made that change, but it is quite clearly
> wrong: you have to check every transaction, or you might never advance
> SxactGlobalXmin.

Hm. So I don't have any opinion about whether this is a correct fix for
the leak, but I am quite distressed that the system failed to notice that
it was leaking predicate locks. Shouldn't there be the same sort of
leak-detection infrastructure that we have for most types of resources?

regards, tom lane

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