From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Dilip Kumar <dilipbalaut(at)gmail(dot)com> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Proposal: scan key push down to heap [WIP] |
Date: | 2016-12-01 21:41:51 |
Message-ID: | 20161201214151.6ctdntqkwavm2jax@alap3.anarazel.de |
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Lists: | pgsql-hackers |
On 2016-11-30 16:11:23 +0530, Dilip Kumar wrote:
> On Tue, Nov 29, 2016 at 11:21 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> > On Mon, Nov 28, 2016 at 11:17 PM, Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> >> Actually we want to call slot_getattr instead heap_getattr, because of
> >> problem mentioned by Andres upthread and we also saw in test results.
> >
> > Ah, right.
> >
> >> Should we make a copy of HeapKeyTest lets say ExecKeyTest and keep it
> >> under executor ?
> >
> > Sure.
>
> I have worked on the idea you suggested upthread. POC patch is
> attached.
Hm. I'm more than a bit doubful about this approach. Shouldn't we just
*always* do this as part of expression evaluation, instead of
special-casing for seqscans?
I.e. during planning recognize that an OpExpr can be evaluated as a
scankey and then emit different qual evaluation instructions? Because
then the benefit can be everywhere, instead of just seqscans.
I'll post my new expression evaluation stuff - which doesn't do this
atm, but makes ExecQual faster in other ways - later this week. If we
could get the planner (or parse-analysis?) to set an OpExpr flag that
signals that the expression can be evaluated as a scankey, that'd be
easy.
Greetings,
Andres Freund
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