Re: Abnormally high memory usage/OOM triggered

Davlet Panech <dpanech(at)gmail(dot)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 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?

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