Re: Changed SRF in targetlist handling

Andres Freund <andres@anarazel.de> writes:
> On 2016-05-23 13:10:29 -0400, Tom Lane wrote:
>> Would that not lead to, in effect, duplicating all of execQual.c?  The new
>> executor node would still have to be prepared to process all expression
>> node types.

> I don't think it necessarily has to. ISTM that if we add a version of
> ExecProject()/ExecTargetList() that continues returning multiple rows,
> we can make the knowledge about the one type of expression we allow to
> return multiple rows.  That'd require a bit of uglyness to implement
> stuff like
> SELECT generate_series(1, 2)::text, generate_series(1, 2) * 5;
> etc. It seems we'd basically have to do one projection step for the
> SRFs, and then another for the rest.  I'm inclined to think that's
> acceptable to get rid of a lot of the related uglyness.

[ shrug... ]  That seems like it's morally equivalent to (but uglier than)
what I wanted to do, which is to teach the planner to rewrite the query to
put the SRFs into a lateral FROM item.  Splitting the tlist into two
levels will work out to be exactly the same rewriting problem.
        regards, tom lane