Re: [HACKERS] Query fails when SRFs are part of FROM clause (Commitid: 69f4b9c85f)

Hi,

On 2017-01-27 17:58:04 +0530, Rushabh Lathia wrote:
> Consider the below test;
> 
> CREATE TABLE tab ( a int primary key);
> 
> SELECT  *
> FROM pg_constraint pc,
> CAST(CASE WHEN pc.contype IN ('f','u','p') THEN generate_series(1,
> array_upper(pc.conkey, 1)) ELSE NULL END AS int) AS position;
> 
> Above query is failing with "set-valued function called in context that
> cannot
> accept a set".

I think that's correct. Functions in FROM are essentially a shorthand
for ROWS FROM(). And ROWS FROM doesn't allow arbitrary expressions.  It
works if you remove the CASE because then it's a valid ROWS FROM
content.


If, I didn't check, that worked previously, I think that was more
accident than intent.

> But if I remove the CASE from the query then it working just
> good.
> 
> Like:
> 
> SELECT  *
> FROM pg_constraint pc,
> CAST(generate_series(1, array_upper(pc.conkey, 1)) AS int) AS position;

This IMO shouldn't work either due to the CAST. But indeed it does.


> This started failing with 69f4b9c85f168ae006929eec44fc44d569e846b9. It seems
> check_srf_call_placement() sets the hasTargetSRFs flag and but when the SRFs
> at the rtable ofcourse this flag doesn't get set. It seems like missing
> something
> their, but I might be completely wrong as not quire aware of this area.

That's right, because it's not in the targetlist.

Regards,

Andres