On 30/11/17 00:47, Andres Freund wrote:
> On 2017-11-30 00:45:44 +0100, Petr Jelinek wrote:
>> I don't understand. I mean sure the SnapBuildWaitSnapshot() can live
>> with it, but the problematic logic happens inside the
>> XactLockTableInsert() and SnapBuildWaitSnapshot() has no way of
>> detecting the situation short of reimplementing the
>> XactLockTableInsert() instead of calling it.
>
> Right. But we fairly trivially can change that. I'm remarking on it
> because other people's, not yours, suggestions aimed at making this
> bulletproof. I just wanted to make clear that I don't think that's
> necessary at all.
>
Okay, then I guess we are in agreement. I can confirm that the attached
fixes the issue in my tests. Using SubTransGetTopmostTransaction()
instead of SubTransGetParent() means 3 more ifs in terms of extra CPU
cost for other callers. I don't think it's worth worrying about given we
are waiting for heavyweight lock, but if we did we can just inline the
code directly into SnapBuildWaitSnapshot().
--
Petr Jelinek http://www.2ndQuadrant.com/
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