Re: Turning off HOT/Cleanup sometimes

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