Re: Proposal: scan key push down to heap [WIP]

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: Dilip Kumar <dilipbalaut(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: 2016-11-29 17:50:31
Message-ID: CA+Tgmoad=HUW=RbbTziZGDt74zJxW_S18AixJsObfv3if05waA@mail.gmail.com
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On Mon, Nov 28, 2016 at 11:25 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
> On 2016-11-28 09:55:00 -0500, Robert Haas wrote:
>> I think we should go with this approach. I don't think it's a good
>> idea to have the heapam layer know about executor slots.
>
> I agree that that's not pretty.
>
>> Even though
>> it's a little sad to pass up an opportunity for a larger performance
>> improvement, this improvement is still quite good.
>
> It's imo not primarily about a larger performance improvement, but about
> avoid possible regressions. Doubling deforming of wide tuples will have
> noticeable impact on some workloads. I don't think we can disregard
> that.

I wasn't proposing to disregard that. I'm saying hoist the tests up
into nodeSeqScan.c where they can use the slot without breaking the
abstraction. It's not quite as fast but it's a lot cleaner.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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