From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
cc: pgsql-performance@postgresql.org,
 Gunnlaugur Thor Briem <gunnlaugur@gmail.com>
Subject: Re: EXPLAIN (no ANALYZE) taking an hour for INSERT FROM SELECT
In-reply-to: <54F9E179.4000804@2ndquadrant.com>
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Comments: In-reply-to Tomas Vondra <tomas.vondra@2ndquadrant.com>
 message dated "Fri, 06 Mar 2015 18:18:49 +0100"
Date: Fri, 06 Mar 2015 13:36:01 -0500
Message-ID: <995.1425666961@sss.pgh.pa.us>
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Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
> On 6.3.2015 01:44, Tom Lane wrote:
>> I'm wondering about the issue addressed by commit fccebe421 ("Use 
>> SnapshotDirty rather than an active snapshot to probe index
>> endpoints").

> How would fccebe421 explain the large amount of random writes (~4MB/s
> for more than an hour), reported in the initial post? And why would that
> only affect the EXPLAIN and not the bare query?

Hard to say.  There's probably additional factors involved, and this
may ultimately turn out to be unrelated.  But it seemed like it might
be an issue, particularly since the plan had a mergejoin with lots of
clauses ...

			regards, tom lane


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