Re: Possible memory leak in PostgreSQL 12.2 on truncate, insert or delete when type interval is involved

From: Hazuki Amamiya <hatsuki_a-ie(at)yahoo(dot)com(dot)hk>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "pgsql-bugs(at)lists(dot)postgresql(dot)org" <pgsql-bugs(at)lists(dot)postgresql(dot)org>
Subject: Re: Possible memory leak in PostgreSQL 12.2 on truncate, insert or delete when type interval is involved
Date: 2020-02-18 03:48:49
Message-ID: 101845571.3678442.1581997729928@mail.yahoo.com
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Hi Tom,
Indeed my scripts seems not able to replicate what happened in my production server. With my production script in my production server, both RES and VIRT do increase. Just I am unable to replicate it with a simple script and simple database schema.

Since the workaround is rather easy by establishing a new connection session every certain time, I would like to close this bug report.
Thanks for your help.
hazuki
On Tuesday, 18 February 2020, 06:22:41 GMT+8, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

Hazuki Amamiya <hatsuki_a-ie(at)yahoo(dot)com(dot)hk> writes:
> Recently, there is a memory leak in the game server I hosted. After checking the log, the leak seems appeared after I upgrade PostgreSQL from 11 to 12.1, and I have no luck even I upgraded the PostgreSQL to 12.2 [PostgreSQL 12.2 (Debian 12.2-1.pgdg100+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 8.3.0-6) 8.3.0, 64-bit] in Debian 10.

FWIW, I see no sign of a memory leak with this example.

> While the script continuing to run, the RES (shown in command “top”) will keep increasing forever.

Does it really increase "forever"?  A fairly common cause of confusion
is that top will report the process' space consumption as gradually
increasing until all of Postgres' shared buffers have been touched
(after which the number stops growing).  That's not a leak, it's just
an artifact of how top chooses to count usage of shared memory.
Usually, if you don't see the total "VIRT" column increasing, there's
no real leak happening.

            regards, tom lane

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