Re: Implement targetlist SRFs using ROWS FROM() (was Changed SRF in targetlist handling)

From: Andres Freund <andres(at)anarazel(dot)de>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Implement targetlist SRFs using ROWS FROM() (was Changed SRF in targetlist handling)
Date: 2017-01-17 18:53:46
Message-ID: 20170117185346.z55d3jnsaf24yr4m@alap3.anarazel.de
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On 2017-01-17 13:43:38 -0500, Tom Lane wrote:
> Although ... looking closer at Andres' patch, the new node type *is*
> channeling Result, in the sense that it might or might not have any input
> plan. This probably traces to what I wrote in September:
>
> + * XXX Possibly-temporary hack: if the subpath is a dummy ResultPath,
> + * don't bother with it, just make a Result with no input. This avoids an
> + * extra Result plan node when doing "SELECT srf()". Depending on what we
> + * decide about the desired plan structure for SRF-expanding nodes, this
> + * optimization might have to go away, and in any case it'll probably look
> + * a good bit different.
>
> I'm not convinced that that optimization is worth preserving, but if we
> keep it then ProjectSet isn't le mot juste here, any more than you'd want
> to rename Result to Project without changing its existing
> functionality.

Right. I'd removed that, and re-added it; primarily because the plans
looked more complex without it. After all, you'd thought it worth adding
that hack ;) I'm happy with removing it again too.

Andres

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