RE: Question on what Duration in the log

Thanks Tom

Perfect.

Anthony Vitale
 
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-----Original Message-----
From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Sent: Wednesday, April 9, 2025 11:02 AM
To: Vitale, Anthony, Sony Music <anthony(dot)vitale(at)sonymusic(dot)com>
Cc: pgsql-performance(at)lists(dot)postgresql(dot)org
Subject: Re: Question on what Duration in the log

EXTERNAL SENDER

"Vitale, Anthony, Sony Music" <anthony(dot)vitale(at)sonymusic(dot)com> writes:
> In my PG Version 14 log I have set to log the duration of sql (Example of one log row below).
> 2025-04-08 07:31:57 UTC:XXX(55994):XXX:[8949]:LOG: duration: 6555.756
> ms execute S_381: {Actual Parameterized Sql executed} This Shows the Execution of a JDBC Server Side Prepared statement (i.e S_381) which took 6.5 seconds.

> When I run the Sql using explain analyze it runs shows an execution
> time of 73 ms Planning Time: 0.773 ms Execution Time: 73.578 ms

They're not measuring the same thing really, because EXPLAIN isn't counting the time needed to transmit data to the client.

This is not just a matter of network overhead (though that can be
substantial) but also the time required to format the values into text. If you are talking about large values, which I bet you are, there is also the time needed to fetch them from out-of-line TOAST storage, which is another thing that doesn't happen in EXPLAIN.

Since v17, EXPLAIN has grown a SERIALIZE option that causes it to do everything except the network transmission, which might be of interest in analyzing this further.

regards, tom lane

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