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Re: planner fails on HEAD

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: planner fails on HEAD
Date: 2011-12-04 22:11:07
Message-ID: 18665.1323036667@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
> 2011/12/4 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
>> [ scratches head ... ]  Given that it got past the previous assertions,
>> surely that ought to be impossible.  Could we see the values of
>> cost_mergejoin's local variables, please?

> It is strange

> when I put a fprintf(stderr, "const literal") to exactly before or
> somewhere after assertion, then assertion is ok. Without fprintf
> assertion fails again

> it looks like gcc bug - gcc 4.5.1 20100924 (Red Hat 4.5.1) It was
> configured just with --enable-debug and --enable-cassert

Hmm.  I'm betting that gcc has flushed one value to memory but the other
one is still in a register that's wider than memory, creating a roundoff
hazard.  Can you look at the generated assembly code?

			regards, tom lane

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