Re: description of Aggregate Expressions

John Lumby wrote:
<  
< Tom Lane wrote
< 
< > > How about replacing "expression [ , ... ]"  by "parameter_list" in the description, 
< > > and then stating that parameter_list can be either a single expression or , 
< > >  if the particular aggregate function accepts it (for which,   consult that function's reference),
< > >   a comma-separated list of expressions.
< > 
< > That's just as wrong.  As we tried to explain before, the
< > parenthesized-list syntax is a row constructor, so it only works
< > in cases where the aggregate function can accept a composite
< > argument type.  Most don't.
< >
< 
< But surely not *all* cases of a multi-expression parameter list of an aggregate function are row constructors are they?    What about
< 
< select parent_id, name, GROUPING(parent_id , name), count(*) FROM mytable GROUP BY ROLLUP(parent_id , name);
< 
< In the piece "GROUPING(parent_id , name)" ,
<   is "(parent_id , name)"  a row constructor or a list of two expressions?
< 
< Or are you saying those are one and the same thing?
< 

I think I can answer my own question   -  No they are not the same  -   because :

select parent_id, name, GROUPING(ROW(parent_id , name)), count(*) FROM mytable GROUP BY ROLLUP(parent_id , name);
ERROR:  arguments to GROUPING must be grouping expressions of the associated query level
LINE 1: select parent_id, name, GROUPING(ROW(parent_id , name)), cou...
                                         ^