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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Juan José Santamaría Flecha <juanjo.santamaria@gmail.com>
Cc: egashira.yusuke@fujitsu.com, PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Subject: Re: BUG #17254: Crash with 0xC0000409 in pg_stat_statements when pg_stat_tmp\pgss_query_texts.stat exceeded 2GB.
Date: Sat, 30 Oct 2021 16:50:48 -0400
Message-ID: <856857.1635627048@sss.pgh.pa.us> (raw)
In-Reply-To: <CAC+AXB2vCUOj6x8drBVUVCgjyy4ZFUu-TFBuNVW=7Emh44EC=w@mail.gmail.com>
References: <17254-a926c89dc03375c2@postgresql.org>
	<CAC+AXB21yF41p4fWgUOkG1PBA-Ezw-8U0Q=Bint9OQ56qyMPYw@mail.gmail.com>
	<CAC+AXB0fozNPMgRTP+PgFMrGcSn2zER0zgcrEbRV0NvpZqmE=A@mail.gmail.com>
	<CAC+AXB2tWxoZgj6BnoQaxiWw=vKBxUPtyBn7d8jhHRqxv7xRRw@mail.gmail.com>
	<840436.1635611203@sss.pgh.pa.us>
	<CAC+AXB2vCUOj6x8drBVUVCgjyy4ZFUu-TFBuNVW=7Emh44EC=w@mail.gmail.com>

=?UTF-8?Q?Juan_Jos=C3=A9_Santamar=C3=ADa_Flecha?= <juanjo.santamaria@gmail.com> writes:
> On Sat, Oct 30, 2021 at 6:26 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I think instead, we need to turn the subsequent one-off read() call into a
>> loop that reads no more than INT_MAX bytes at a time.  It'd be possible
>> to restrict that to Windows, but probably no harm in doing it the same
>> way everywhere.

> Seems reasonable to me, can such a change be back-patched?

Don't see why not.

>> A different line of thought is that maybe we shouldn't be letting the
>> file get so big in the first place.  Letting every backend have its
>> own copy of a multi-gigabyte stats file is going to be problematic,
>> and not only on Windows.  It looks like the existing logic just considers
>> the number of hash table entries, not their size ... should we rearrange
>> things to keep a running count of the space used?

> +1. There should be a mechanism to limit the effective memory size.

This, on the other hand, would likely be something for HEAD only.
But now that we've seen a field complaint, it seems like a good
thing to pursue.

			regards, tom lane





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  Subject: Re: BUG #17254: Crash with 0xC0000409 in pg_stat_statements when pg_stat_tmp\pgss_query_texts.stat exceeded 2GB.
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