2010/9/28 Tom Lane <tgl@sss.pgh.pa.us>:
> Pavel Stehule <pavel.stehule@gmail.com> writes:
>> I looked on some constructs that helps with iteration over array in
>> plpgsql. I propose a following syntax:
>
>> FOR var IN [array variable | array expression]
>> LOOP
>
> I don't have any opinion about whether the functionality proposed here
> is worth the trouble, but I do have an opinion about that syntax: it's
> an awful choice. plpgsql has enough trouble already distinguishing
> between integer for-loops and query for-loops, not to mention trouble
> in producing a helpful error message when somebody gets either of those
> constructs slightly wrong. Providing a variant where a single
> expression can follow IN will make both of those problems an order of
> magnitude worse. 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. Similar construct is in SQL/PSM
where you can to write SET var = (SELECT ...)
You cannot to write just (SELECT ...) anywhere
> Either answer is plausible depending on whether you assume the
> parentheses make it a subquery.
>
> Pick something less easily confusable with the existing constructs.
It's not simple - FOR i IN array is natural - Original ADA use a very
similar construct.
FOR i IN ARRAY has problem with constant array - FOR i IN ARRAY ARRAY[1,2,3,]
and FOREACH is used in Oracle for absolutely different task.
>
we have now a for-in-cursor, so there is a precedent.
regards
Pavel
> regards, tom lane
>