From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | "Gurjeet Singh" <singh(dot)gurjeet(at)gmail(dot)com> |
Cc: | "PGSQL Hackers" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: A question about ExplainOnePlan() |
Date: | 2006-12-13 16:00:49 |
Message-ID: | 6807.1166025649@sss.pgh.pa.us |
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"Gurjeet Singh" <singh(dot)gurjeet(at)gmail(dot)com> writes:
> In ExplainOnePlan(), we are calling ExecutorStart() and ExecutorEnd()
> even if we are not doing EXPLAIN ANALYZE. Whereas, ExecutorRun() is called
> only if we are ANALYZEing.
> Can we avoid calls to Executor{Start|End}() here, or is it necessary to
> call them even for non-ANALYZE case?
No; at least not unless you want to duplicate the permission-checking
machinery inside ExecutorStart. Otherwise EXPLAIN could be used to
obtain information about tables you're not supposed to be able to read
(for instance, the estimated number of rows matching a WHERE condition
could be sensitive information).
Also, you'd have to uglify explain.c quite a lot to be able to handle
the case of traversing a plan tree without a matching planstate tree.
regards, tom lane
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