| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>, "Imai, Yoshikazu" <imai(dot)yoshikazu(at)jp(dot)fujitsu(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Simon Riggs <simon(at)2ndquadrant(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: Speed up transaction completion faster after many relations are accessed in a transaction |
| Date: | 2019-04-07 14:41:12 |
| Message-ID: | CAKJS1f_OouptEoX1jDMD-xNx37awqZbLBVxDADSjdk-_gm9bQA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, 8 Apr 2019 at 02:36, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> wrote:
> > LockMethodLocalHash is special in that it predictably goes to empty
> > at the end of every transaction, so that de-bloating at that point
> > is a workable strategy. I think we'd probably need something more
> > robust if we were trying to fix this generally for all hash tables.
> > But if we're going to go with the one-off hack approach, we should
> > certainly try to keep that hack as simple as possible.
>
> As cheap as possible sounds good, but I'm confused at why you think
> the table will always be empty at the end of transaction. It's my
> understanding and I see from debugging that session level locks remain
> in there. If I don't copy those into the new table they'll be lost.
Or we could just skip the table recreation if there are no
session-levels. That would require calling hash_get_num_entries() on
the table again and just recreating the table if there are 0 locks.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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