Re: Need help identifying a periodic performance issue.

[Robert Creager]

> On Nov 17, 2021, at 10:42 PM, Justin Pryzby <pry...@telsasoft.com> wrote:
> 
> This message originated outside your organization.
> 
> On Thu, Nov 18, 2021 at 04:39:42PM +1300, Thomas Munro wrote:
>> On Thu, Nov 18, 2021 at 1:18 PM Robert Creager <robe...@spectralogic.com> 
>> wrote:
>>> So, how do I go about capturing more information for the big brains (you 
>>> guys) to help figure this out?  I have all our resources at mine (and hence 
>>> your) disposal.
>> 
>> As a workaround, does it help if you issue DISCARD PLANS before your
>> COPY jobs, or alternatively start with a fresh connection?  I'm

I can certainly give that a try.

> It also seems to work if one does SET plan_cache_mode=force_custom_plan;
> 
> Robert might try that, either in postresql.conf, or SET in the client that's
> doing COPY.

Which would be better?  Discard plans or forcing custom plans?  Seems like 
wrapping a copy might be better than the Postgres.conf change as that would 
affect all statements.  What kind of performance hit would we be taking with 
that do you estimate?  Microseconds per statement?  Yeah, hard to say, depends 
on hardware and such.  Would there be any benefit overall to doing that?  
Forcing the replan?

Best,
Robert