From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: pgsql-hackers@postgresql.org
Subject: Re: Implement targetlist SRFs using ROWS FROM() (was Changed SRF in
 targetlist handling)
In-reply-to: <20160915210843.rhvyqwxjopkp26zc@alap3.anarazel.de>
References: <20160912173815.dlew2xsblcso33sw@alap3.anarazel.de>
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 <23413.1473723322@sss.pgh.pa.us>
 <20160912234630.caueobrrbg5vse5y@alap3.anarazel.de>
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Thu, 15 Sep 2016 14:08:43 -0700"
Date: Thu, 15 Sep 2016 17:12:55 -0400
Message-ID: <15003.1473973975@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

Andres Freund <andres@anarazel.de> writes:
> On 2016-09-15 16:48:59 -0400, Tom Lane wrote:
>> The patch that I posted would run both the generate_series(1, 2) and
>> generate_series(2,4) calls in the same SRF node, forcing them to run in
>> lockstep, after which their results would be fed to the SRF node doing
>> the top-level SRFs.  We could probably change it to run them in separate
>> nodes, but I don't see any principled way to decide which one goes first
>> (and in some variants of this example, it would matter).

> I think that's fine. I personally still think we're *much* better off
> getting rid of the non-lockstep variants. You're still on the fence
> about retaining the LCM behaviour (for the same nesting level at least)?

I'm happy to get rid of the LCM behavior, I just want to have some wiggle
room to be able to get it back if somebody really needs it.

			regards, tom lane


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