Re: increased max_parallel_workers_per_gather results in fewer workers?

From: Luis Carril <luis(dot)carril(at)swarm64(dot)com>
To: Philip Semanchuk <philip(at)americanefficient(dot)com>
Cc: "pgsql-performance(at)lists(dot)postgresql(dot)org" <pgsql-performance(at)lists(dot)postgresql(dot)org>, Sebastian Dressler <sebastian(at)swarm64(dot)com>
Subject: Re: increased max_parallel_workers_per_gather results in fewer workers?
Date: 2020-06-04 06:41:27
Message-ID: LEXPR01MB1182C770FBB48C33231CD2CAE7890@LEXPR01MB1182.DEUPRD01.PROD.OUTLOOK.DE
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Hi,
on top of the settings that Sebastian suggested, you can also try disabling the participation of the leader (i.e. the main backend process for your connection) in the distribution of the parallel workload:

SET parallel_leader_participation TO false

Depending on your workload the leader could be saturated if it has to do a share of the workload and aggregate the results of all the workers.

Cheers
Luis

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