Why we don't introduce a temporary functions instead?
You can already do that:
create function pg_temp.tempfunc(i int4) returns int4 as $$ begin end; $$ language plpgsql;
it looks much more like workaround than supported feature.
What do you mean? How would the temporary functions you suggest look like?
CREATE TEMPORARY FUNCTION ...
Compared to DO, you have to do extra steps to create the function, and drop it when you're done. And you can't use them in a hot standby, because it changes the catalogs. (although a better solution to that would be to make it work, as well as temporary tables, but that's a much bigger project).
Maybe we don't need any of this, you can just use temporary function. But clearly someone though that DO statements are useful in general, because we've had temporary functions for ages and we nevertheless added the DO statement.
I afraid so we create little bit obscure syntaxes, without real effect and real cost
Any new useful syntax should be clean, simple, natural and shorter than create function ...
Sure. I think adding a RETURNS clause to the existing DO syntax would be all of those.
and without risks a conflicts with ANSI SQL
DO is not in the standard, so no risk of conflicts there.
I had a "WIDTH ... " proposal on my mind
I prefer a typed session variables, where is not risk of SQL injection or some performance lost. The benefit of typed server side variables can be for wide group of users.
I don't see how session variables would help here. Sure, you could "return" a value from the DO-block by stashing it to a session variable and reading it out afterwards, but that's awkward.
you can use a global variables for injection values into block.
I am not against to do some simple parametrization, but some more complex work with DO statement I don't would. It is messy now, and I don't see any benefit from this area
