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Subject: Re: Abnormally high memory usage/OOM triggered
From: scott ribe <scott_ribe@elevated-dev.com>
In-Reply-To: <15a90b55-5151-ce22-16ee-7ff883e5eb97@gmail.com>
Date: Thu, 18 Jan 2018 10:34:59 -0700
Cc: pgsql-admin@lists.postgresql.org
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Message-Id: <460E4952-3C5F-4A17-A426-09FD0249FF82@elevated-dev.com>
References: <4d52fee7-73ba-16a9-9c27-8ae5107ee6ae@gmail.com>
 <5E0AB8DB-F13B-41BF-843A-FE64FBE9C097@elevated-dev.com>
 <15a90b55-5151-ce22-16ee-7ff883e5eb97@gmail.com>
To: Davlet Panech <dpanech@gmail.com>
Precedence: bulk

On Jan 18, 2018, at 10:13 AM, Davlet Panech <dpanech@gmail.com> wrote:
>=20
> On 1/17/2018 5:57 PM, scott ribe wrote:
>> On Jan 17, 2018, at 2:57 PM, Davlet Panech <dpanech@gmail.com> wrote:
>>>=20
>>> Does my configuration look reasonable? I just don't understand how =
it could possibly use up 19 GB of memory based on the configuration =
below. Is there a memory leak in there somewhere?
>> It does seem awfully high, but... An update can involve a join across =
multiple tables. Or an update can run a trigger which can cascade. =
Either of those could result in an "accidental cross product" join, =
which can always blow up memory.
> There must be a way to put an upper limit on memory even for such =
cases. I was under the impression that parameters such as "work_mem" =
serve that purpose, is that not the case? So an "accidental cross =
product" join's memory usage is unbounded? It can't be... could somebody =
confirm this please?

You are correct as far as I know, so yeah, that case should result in =
filling disk, not RAM

--
Scott Ribe
https://www.linkedin.com/in/scottribe/
(303) 722-0567