Re: Abnormally high memory usage/OOM triggered - Mailing list pgsql-admin

From Tom Lane
Subject Re: Abnormally high memory usage/OOM triggered
Date
Msg-id 7976.1516297077@sss.pgh.pa.us
Whole thread Raw
In response to Re: Abnormally high memory usage/OOM triggered  (Davlet Panech <dpanech@gmail.com>)
List pgsql-admin
Davlet Panech <dpanech@gmail.com> writes:
> On 1/17/2018 5:57 PM, scott ribe wrote:
>> It does seem awfully high, but... An update can involve a join across multiple tables. Or an update can run a
triggerwhich 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?

A large join result could blow out memory on the client side, unless the
client is careful to read it in segments, which most clients aren't.
I expect the server to be smarter though.

            regards, tom lane


pgsql-admin by date:

Previous
From: scott ribe
Date:
Subject: Re: Abnormally high memory usage/OOM triggered
Next
From: Keith
Date:
Subject: Re: Abnormally high memory usage/OOM triggered