2010/9/28 Tom Lane <tgl@sss.pgh.pa.us>:
> Pavel Stehule <pavel.stehule@gmail.com> writes:
>> 2010/9/28 Tom Lane <tgl@sss.pgh.pa.us>:
>>> As an example, is this a for-in-query or a
>>> for-in-array?
>>>
>>> FOR v IN (SELECT arraycol FROM tab) LOOP ...
>
>> This is a subquery - so it is a for-in-array - should return one row
>> with one column.
>
> That's not obvious at all. It's legal right now to write that, and it
> will be interpreted as for-in-query.
but it has not a sense. It's based on implementation and I am sure, so
this isn't documented. Yes, we are able to write
a := 10 FROM tab WHERE y = 10
but it is just more bug then required feature.
FOR v IN (SELECT FROM) when select returns more than one row is big
inconsistency - and this is bug, when this is allowed
Regards
Pavel
Furthermore, there are cases where
> it's essential to be able to write a left paren before SELECT, so that
> you can control the precedence of UNION/INTERSECT/EXCEPT constructs.
> So you're proposing to remove functionality and break existing code in
> order to have a "simple" syntax for for-in-array.
>
> regards, tom lane
>