Re: [HACKERS] PostgreSQL 10 changes in exclusion constraints - didsomething change? CASE WHEN behavior oddity

On 2017-06-04 14:16:14 -0700, Mark Dilger wrote:
> Sorry, I was not clear.  What I meant to get at was that if you remove from the
> executor all support for SRFs inside case statements, you might foreclose the option
> of extending the syntax at some later date to allow aggregates over
> SRFs.

Seems very unlikely that we'd ever want to do that.  The right way to do
this is to simply move the SRF into the from list.  Having the executor
support arbitrary sources of tuples would just complicate and slow down
already complicated and slow code...


> I'm
> not saying that this works currently, but in principle if you allowed that SUM() that
> I put up there, you'd get back exactly one row from it, same as you get from the
> ELSE clause.  That would seem to solve the problem without going so far as
> completely disallowing the SRF altogether.

But what would the benefit be?


Greetings,

Andres Freund