Re: Proposal: plpgsql - "for in array" statement

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 ...

Either answer is plausible depending on whether you assume the
parentheses make it a subquery.

Pick something less easily confusable with the existing constructs.
        regards, tom lane