Re: Zero throughput on a query on a very large table.

Correct, but in the Java code, it's multiple statements in a single transaction, so it should stick. Not sure if something else stupid is going on.

Good to know about the ALTER DATABASE effect. I didn't realize that.

Thanks a billion.

Laurent.

________________________________
From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Sent: Friday, January 25, 2019 3:04:37 PM
To: ldh(at)laurent-hasson(dot)com
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Zero throughput on a query on a very large table.

"ldh(at)laurent-hasson(dot)com" <ldh(at)laurent-hasson(dot)com> writes:
> 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 ????

ALTER DATABASE only affects subsequently-started sessions.

> 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 ????

That "true" means "local to the current transaction", which is
just the one statement if you don't have a BEGIN.

regards, tom lane