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Re: TABLE-function patch vs plpgsql

From: "Pavel Stehule" <pavel(dot)stehule(at)gmail(dot)com>
To: "Hannu Krosing" <hannu(at)krosing(dot)net>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: TABLE-function patch vs plpgsql
Date: 2008-07-30 06:40:50
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers

2008/7/30 Hannu Krosing <hannu(at)krosing(dot)net>:
> On Wed, 2008-07-30 at 07:29 +0200, Pavel Stehule wrote:
>> 2008/7/29 Hannu Krosing <hannu(at)krosing(dot)net>:
>> > On Thu, 2008-07-17 at 19:13 -0400, Tom Lane wrote:
>> >> I've been working on the TABLE-function patch, and I am coming to the
>> >> conclusion that it's really a bad idea for plpgsql to not associate
>> >> variables with output columns --- that is, I think we should make
>> >> RETURNS TABLE columns semantically just the same as OUT parameters.
>> >
>> > I just looked at recent cahnges in pl/python, and found out that RETURNS
>> > TABLE is _NOT_ semantically just the same as OUT parameters, at least at
>> > API level.
>> >
>> > Why can't it be ?
>> >
>> > Why is PROARGMODE_TABLE needed at all ?
>> because I need to separate classic OUT args from table args.
> I read your explanation, and I still don't understand, why can't TABLE
> and SETOF RECORD + OUT args be just different spellings of the same
> thing.
> Is there a scenario, where both are needed in the same function ?
>>  TABLE function has more clean syntax, then our SRF functions,
> True. But why is separation on C API level needed ?

do you know any better way? I need to carry result description, and
using proargmodes is natural. In other case I needed add column to
pg_proc with result descriptor.

>> and it isn't
>> related only to SQL/PSM. It works nice together with SQL language.
>> Actually TABLE   variables are exactly same as OUT variables (in
>> plpgsq), that is possible, but I am not sure, if it's best too.
> Still I have the same question - What is the difference ?

* remove varname and colname colisions
* solve unclean result type rules (one column .. specific type, two
and more .. record)

>> I have prototype where is possible declare variables derivated from
>> function return type
>> create function foo(..) returns table(x int, y int) as $$
>> declare result foo%rowtype; resx foo.x%type; ....
> I still don't see, why the same thing can't work on
> create function foo(OUT x int, OUT y int) returns setof record as $$
> declare result foo%rowtype; resx foo.x%type; ...

no it isn't. In this case you has local variables x, y - it's one from
typical postgresql bug

create function foo(out x int, out y iny)
returns setof record as $$
  for x,y in select x,y from tab loop -- it's wrong!!
    return next;
  end loop;

create function foo(out x int, out y int)
returns setof record as $$
  return query select x, y from tab; -- it's wrong too !

>> all this has to minimalist risk of variables and sql object name collisions.
> Are there any cases, where TABLE functions and OUT + returns SETOF
> RECORD functions are _called_ differently ?


Pavel Stehule

> ------------------
> Hannu

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Subject: Re: Type Categories for User-Defined Types
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