On Fri, Sep 27, 2019 at 02:33:32PM +0530, Amit Kapila wrote:
On Tue, Jan 9, 2018 at 7:55 AM Peter Eisentraut
<peter.eisentr...@2ndquadrant.com> wrote:
On 1/3/18 14:53, Tomas Vondra wrote:
>> I don't see the need to tie this setting to maintenance_work_mem.
>> maintenance_work_mem is often set to very large values, which could
>> then have undesirable side effects on this use.
>
> Well, we need to pick some default value, and we can either use a fixed
> value (not sure what would be a good default) or tie it to an existing
> GUC. We only really have work_mem and maintenance_work_mem, and the
> walsender process will never use more than one such buffer. Which seems
> to be closer to maintenance_work_mem.
>
> Pretty much any default value can have undesirable side effects.
Let's just make it an independent setting unless we know any better. We
don't have a lot of settings that depend on other settings, and the ones
we do have a very specific relationship.
>> Moreover, the name logical_work_mem makes it sound like it's a logical
>> version of work_mem. Maybe we could think of another name.
>
> I won't object to a better name, of course. Any proposals?
logical_decoding_[work_]mem?
Having a separate variable for this can give more flexibility, but
OTOH it will add one more knob which user might not have a good idea
to set. What are the problems we see if directly use work_mem for
this case?
IMHO it's similar to autovacuum_work_mem - we have an independent
setting, but most people use it as -1 so we use maintenance_work_mem as
a default value. I think it makes sense to do the same thing here.
It does ad an extra knob anyway (I don't think we should just use
maintenance_work_mem directly, the user should have an option to
override it when needed). But most users will not notice.
FWIW I don't think we should use work_mem, maintenace_work_mem seems
somewhat more appropriate here (not related to queries, etc.).
If we can't use work_mem, then I think the name proposed by you
(logical_decoding_work_mem) sounds good to me.
Yes, that name seems better.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
