Re: "stored procedures" - use cases?

2011/5/10 Bruce Momjian <bruce(at)momjian(dot)us>:
> Christopher Browne wrote:
>> > Multiple resultsets in one call would be a good thing, though, no?
>> >
>> > cheers
>>
>> I *thought* the purpose of having stored procedures was to allow a
>> substrate supporting running multiple transactions, so it could do
>> things like:
>> - Managing vacuums
>> - Managing transactions
>> - Replacing some of the need for dblink.
>> - Being an in-DB piece that could manage LISTENs
>>
>> It seems to be getting "bikeshedded" into something with more
>> "functional argument functionality" than stored functions.
>>
>> I think we could have a perfectly successful implementation of "stored
>> procedures" that supports ZERO ability to pass arguments in or out.
>> That's quite likely to represent a good start.
>
> I am kind of confused too, particularly with the CALL syntax.  I thought
> our function call usage was superior in every way to CALL, so why
> implement CALL?  I assume for SQL-standards compliance, right?  Does
> multiple result sets require CALL?  I assume autonomous transactions
> don't require CALL.
>

no - you are little bit confused :). CALL and function execution
shares nothing. There is significant differences between function and
procedure. Function is called only from executor - from some plan, and
you have to know a structure of result before run. The execution of
CALL is much simple - you just execute code - without plan and waiting
for any result - if there is.

> Are we assuming no one is going to want a function that allows multiple
> result sets or autonomous transactions?  That seems unlikely.  I would
> think CALL is independent of those features.  Maybe we need those
> features to support SQL-standard CALL, and we will just add those
> features to functions too.
>

We can use a SETOF cursors for returning a multiple result sets now.
But there are a few complications:

a) The client should to wait for finish of all sets from multiple
result sets - minimally in PL/pgSQL
b) client 'psql' doesn't support a unpacking result when result is
multiple result set
c) The using cursors isn't too comfortable - in comparation to MS SQL or MySQL

Regards

Pavel

> --
>  Bruce Momjian  <bruce(at)momjian(dot)us>        http://momjian.us
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>  + It's impossible for everything to be true. +
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