| From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Turning off HOT/Cleanup sometimes |
| Date: | 2014-09-15 21:13:44 |
| Message-ID: | CA+U5nMKAXhMiSD71uMsatyVVz-KuWnLrBTxb0pGFA09ecr4tsQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 15 September 2014 17:09, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> Do we really want to disable HOT for all catalog scans?
The intention of the patch is that catalog scans are treated
identically to non-catalog scans. The idea here is that HOT cleanup
only occurs on scans on target relations, so only INSERT, UPDATE and
DELETE do HOT cleanup.
It's possible that many catalog scans don't follow the normal target
relation logic, so we might argue we should use HOT every time. OTOH,
since we now have separate catalog xmins we may find that using HOT on
catalogs is no longer effective. So I could go either way on how to
proceed; its an easy change either way.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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