OK... I think we may have cracked this.
First, do you think that 128MB work_mem is ok? We have a 64GB machine and
expecting fewer than 100 connections. This is really an ETL workload
environment at this time.
Second, here is what i found and what messed us up.
select current_setting('random_page_cost'); --> 4
alter database "CMS_TMP" set random_page_cost=0.00000001;
select current_setting('random_page_cost'); --> 4 ????
I also tried:
select current_setting('random_page_cost'); --> 4
select set_config('random_page_cost', '0.000001', true);
select current_setting('random_page_cost'); --> 4 ????
Is there something that is happening that is causing those settings to not
stick? I then tried:
select current_setting('random_page_cost'); --> 4
select set_config('random_page_cost', '0.000001', false); -- false now,
i.e., global
select current_setting('random_page_cost'); --> 0.000001 !!!!
So i think we just spent 4 days on that issue. I then did
select set_config('enable_seqscan', 'off', false);
And the plan is now using an index scan, and we are getting 12K rows/s in
throughput immediately!!! 😊
So i guess my final question is that i really want to only affect that one
query executing, and i seem to not be able to change the settings used by the
planner just for that one transaction. I have to change it globally which i
would prefer not to do. Any help here?
Thanks,
Laurent.
________________________________
From: [email protected] <[email protected]>
Sent: Friday, January 25, 2019 1:36:21 PM
To: Tom Lane
Cc: [email protected]
Subject: Re: Zero throughput on a query on a very large table.
Sorry :) When i look at the "SQL" tab in PGAdmin when i select the index in the
schema browser. But you are right that /d doesn't show that.
________________________________
From: Tom Lane <[email protected]>
Sent: Friday, January 25, 2019 1:34:01 PM
To: [email protected]
Cc: [email protected]
Subject: Re: Zero throughput on a query on a very large table.
"[email protected]" <[email protected]> writes:
> Also, the original statement i implemented did not have all of that. This is
> the normalized SQL that Postgres now gives when looking at the indices.
[ squint... ] What do you mean exactly by "Postgres gives that"?
I don't see any redundant COLLATE clauses in e.g. psql \d.
regards, tom lane
