Re: Typmod associated with multi-row VALUES constructs

2016-12-08 14:03 GMT+01:00 Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>:

> Tom Lane wrote:
> > Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> > > Tom Lane wrote:
> > >> In HEAD, we could change the RTE data structure so that
> > >> transformValuesClause could save the typmod information in the RTE,
> > >> keeping the lookups cheap.
> >
> > > Hmm, I think this would be useful for the XMLTABLE patch too. I talked
> > > a bit about it at
> > > https://www.postgresql.org/message-id/20161122204730.
> dgipy6gxi25j4e6a(at)alvherre(dot)pgsql
> >
> > I dunno. If your example there is correct that XMLTABLE can be called as
> > a plain function in a SELECT list, then I doubt that we want to tie
> > anything about it to the RTE data structure. If anything, the case where
> > it appears in FROM seems to need to be treated as a generic RTE_FUNCTION
> > case.
>
> Well, XMLTABLE is specified by the standard to be part of <table primary>,
> which it turn is part of <table reference>. I can't immediately tell
> whether it allows XMLTABLE to be called like a regular function. The
> current patch allows it, but maybe that's not right, and it's probably
> not that useful anyway.
>

It looks like function, and we support on both sides, so I implemented
both.

Probably, there is only 10 rows more related to this feature. Using this
function in target list is not critical feature - now with LATERAL JOIN we
can live without it. It is just some few steps forward to our user.

Again - implementation of this feature is probably few lines only.

>
> > I've been trying to avoid getting involved in the XMLTABLE patch, mainly
> > because I know zip about XML, but maybe I need to take a look.
>
> I think it'd be productive that you did so. The XML part of it is
> reasonably well isolated, so you could give your opinion on the core
> parser / executor parts without looking at the XML part.
>

The critical part has zero relation to XML. All is some game with tupledesc.

Regards

Pavel

>
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