Re: [sqlsmith] Crash in apply_projection_to_path

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andreas Seltenreich <seltenreich(at)gmx(dot)de>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [sqlsmith] Crash in apply_projection_to_path
Date: 2016-04-29 02:06:27
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Andreas Seltenreich <seltenreich(at)gmx(dot)de> writes:
> the following query against the regression database crashes master as of
> 23b09e15.

> select 1 from depth0 inner join depth1 on (depth0.c = depth1.c)
> where depth0.c @@ depth1.c limit 1;

What's going on here is that add_partial_path is recycling a now-dominated
partial path without regard for the fact that there's already a GatherPath
pointing at that old partial path. Later use of the GatherPath tries to
make use of its now-dangling subpath pointer.

I'd be inclined to think that it's silly to build GatherPaths in advance
of having finalized the list of partial paths for a rel.

regards, tom lane

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