From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
---|---|
To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
Cc: | 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: | 2014-09-12 14:20:27 |
Message-ID: | 20140912142026.GL4701@eldon.alvh.no-ip.org |
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Thread: | |
Lists: | pgsql-hackers |
Simon Riggs wrote:
> On 12 September 2014 14:54, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> wrote:
>
> > My idea is that we would have a new executor flag, say
> > EXEC_FLAG_READ_ONLY; we would set it on nodes that are known to be
> > read-only, and reset it on those that aren't, such as LockRows and
> > ModifyTable (obviously we need to pass it down correctly from parent to
> > children). Then in ExecInitSeqScan and ExecInitIndexScan, if we see the
> > flag set, we call heap/index_set_allow_prune(false) for the heap scan;
> > same thing in index scans. (I envisioned it as a boolean rather than
> > enabling a certain number of cleanups per scan.)
> >
> > I tried to code this but I think it doesn't work correctly, and no time
> > for debug currently. Anyway let me know what you think of this general
> > idea.
>
> Thanks for looking at this.
>
> My concern was to ensure that UPDATEs and DELETEs continue to call
> heap_page_prune_opt while larger SELECTs do not.
>
> This is achieved without a counter, so after some thought like it
> better; simple is good. Happy to progress from here, or you can?
Please feel free to take over.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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