auto_explain sample rate

From: Craig Ringer <craig(at)2ndquadrant(dot)com>
To: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: auto_explain sample rate
Date: 2015-05-29 01:39:00
Message-ID: CAMsr+YHMZC6COFE4q+246Q_X_6HEdswh=Pu9RROhuNW-=LmgPA@mail.gmail.com
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Hi all

It's sometimes desirable to collect auto_explain data with ANALYZE in order
to track down hard-to-reproduce issues, but the performance impacts can be
pretty hefty on the DB.

I'm inclined to add a sample rate to auto_explain so that it can trigger
only on x percent of queries, and also add a sample test hook that can be
used to target statements of interest more narrowly (using a C hook
function).

Sound like a reasonable approach?

--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

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