Re: Some queries starting to hang - Mailing list pgsql-performance

From Tom Lane
Subject Re: Some queries starting to hang
Date
Msg-id 17426.1149606369@sss.pgh.pa.us
Whole thread Raw
In response to Re: Some queries starting to hang  (Simon Riggs <simon@2ndquadrant.com>)
Responses Re: Some queries starting to hang  ("Jim C. Nasby" <jnasby@pervasive.com>)
Re: Some queries starting to hang  (Andrew Sullivan <ajs@crankycanuck.ca>)
Re: Some queries starting to hang  ("Craig A. James" <cjames@modgraph-usa.com>)
List pgsql-performance
Simon Riggs <simon@2ndquadrant.com> writes:
> You mentioned it would be good if the OP had delivered an EXPLAIN
> ANALYZE; I agree(d). The lack of EXPLAIN ANALYZE is frequently because
> you can't get them to run to completion - more so when the query you
> wish to analyze doesn't appear to complete either.

Well, he could have shown EXPLAIN ANALYZE for the server that was
managing to run the query in a reasonable amount of time.

> The idea I just had was: why do we need EXPLAIN ANALYZE to run to
> completion? In severe cases like this thread, we might be able to
> discover the root cause by a *partial* execution of the plan, as long as
> it was properly instrumented. That way, the OP might have been able to
> discover the root cause himself...

I don't think that helps, as it just replaces one uncertainty by
another: how far did the EXPLAIN really get towards completion of the
plan?  You still don't have any hard data.

            regards, tom lane

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