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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Jakub Glapa <jakub.glapa@gmail.com>
Cc: Forums postgresql <pgsql-general@postgresql.org>
Subject: Re: ERROR: too many dynamic shared memory segments
Date: Mon, 27 Nov 2017 14:16:25 -0500
Message-ID: <14346.1511810185@sss.pgh.pa.us> (raw)
In-Reply-To: <CAEepm=1TVDQYEgCJLj-P-zFT0gKDEubz+qbxqD8i4hxiAjZRkw@mail.gmail.com>
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	<CAJk1zg2XqYa1Dx14z9X3qkUgWH6kpoNbvSGT_=NtzDPnMhfFHg@mail.gmail.com>
	<CAEepm=1TVDQYEgCJLj-P-zFT0gKDEubz+qbxqD8i4hxiAjZRkw@mail.gmail.com>

Thomas Munro <thomas.munro@enterprisedb.com> writes:
> Ah, so you have many Gather nodes under Append?  That's one way to eat
> arbitrarily many DSM slots.  We allow for 64 + 2 * max_backends.  Does
> it help if you increase max_connections?  I am concerned about the
> crash failure mode you mentioned in the first email though: we should
> always be able to handle that condition gracefully.

I suspect this is an instance of the issue I complained about before [1]
that parallel query is unable to cope with worker start failure.

			regards, tom lane

[1] https://www.postgresql.org/message-id/4905.1492813727@sss.pgh.pa.us

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