From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: POC: converting Lists into arrays |
Date: | 2019-03-03 04:34:24 |
Message-ID: | 20190303043424.itzy3ge52xrkpmpr@alap3.anarazel.de |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Hi,
On 2019-03-02 18:11:43 -0500, Tom Lane wrote:
> I wonder what test cases Andres has been looking at that convince
> him that we need a reimplementation of Lists.
My main observation was from when the expression evaluation was using
lists all over. List iteration overhead was very substantial there. But
that's not a problem anymore, because all of those are gone now due to
the expression rewrite. I personally wasn't actually advocating for a
new list implementation, I was/am advocating that we should move some
tasks over to a more optimized representation.
I still regularly see list overhead matter in production workloads. A
lot of it being memory allocator overhead, which is why I'm concerned
with a rewrite that doesn't reduce the number of memory allocations. And
a lot of it is stuff that you won't see in pgbench - e.g. there's a lot
of production queries that join a bunch of tables with a few dozen
columns, where e.g. all the targetlists are much longer than what you'd
see in pgbench -S.
Greetings,
Andres Freund
From | Date | Subject | |
---|---|---|---|
Next Message | Alexander Korotkov | 2019-03-03 04:35:52 | Re: WIP: BRIN multi-range indexes |
Previous Message | Alexander Korotkov | 2019-03-03 04:29:26 | Re: WIP: BRIN multi-range indexes |