Hello, could it be possible then to define a custom CTE as the result of a function? somthing like :
with first_cte AS ( select blabla) , second_cte AS ( a_function_returning_a_set(parameters) ) SELECT blabla A CTE is much like what you would like bborie : you can reference previously defined CTE, and you output a set of row. Cheers, Rémi-C 2013/12/8 Pavel Stehule <pavel.steh...@gmail.com> > Hello > > > 2013/12/8 Bborie Park <dustym...@gmail.com> > >> I'm wondering if an aggregate function can return a set of records? >> > > No, final function cannot returns set. It is disallowed. > > Theoretically, it should be possible - it is explicitly prohibited. But if > it will be allowed, you can get same problems like using SRF function in > target list. > > postgres=# select generate_series(1,2),generate_series(1,2); > generate_series │ generate_series > ─────────────────┼───────────────── > 1 │ 1 > 2 │ 2 > (2 rows) > > Time: 49.332 ms > postgres=# select generate_series(1,2),generate_series(1,3); > generate_series │ generate_series > ─────────────────┼───────────────── > 1 │ 1 > 2 │ 2 > 1 │ 3 > 2 │ 1 > 1 │ 2 > 2 │ 3 > (6 rows) > > Time: 0.445 ms > > It will be hard defined a expected behaviour when somebody use more these > aggregates in same query and returns different number of rows. > > > Regards > > Pavel > > > >> >> Say I have a table with a column of type raster (PostGIS). I want to get >> the number of times the pixel values 1, 3 and 4 occur in that raster >> column. I am hoping to build an aggregrate function that returns the >> following... >> >> value | count >> --------+-------- >> 1 | 12 >> --------+-------- >> 2 | 12 >> --------+-------- >> 3 | 12 >> >> Is it possible for an aggregate function to return a set? I've written >> some test cases and it looks like the answer is No but I'd like >> confirmation. >> >> Thanks, >> Bborie Park >> >> PostGIS Steering Committee >> > >
