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Re: WIP patch: convert SQL-language functions to return tuplestores

From: "Pavel Stehule" <pavel(dot)stehule(at)gmail(dot)com>
To: "Robert Haas" <robertmhaas(at)gmail(dot)com>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Dimitri Fontaine" <dfontaine(at)hi-media(dot)com>, pgsql-hackers(at)postgresql(dot)org, "Gregory Stark" <stark(at)enterprisedb(dot)com>, "Martijn van Oosterhout" <kleptog(at)svana(dot)org>
Subject: Re: WIP patch: convert SQL-language functions to return tuplestores
Date: 2008-10-31 08:12:29
Message-ID: 162867790810310112u27c7469bs47006b4904c928d5@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
2008/10/30 Robert Haas <robertmhaas(at)gmail(dot)com>:
>> With session variables we could implement srf function in plpgsql like
>> current C srf function. Like
>>
>> create or replace function foo(....)
>> returns record as $$
>> #option with_srf_context(datatype of srf context)
>> begin
>>   return row(...);
>> end;
>> $$ language plpgsql;
>
> Oh, sure - but what you can do with this will be somewhat limited
> compared to a Perl hash reference off which you can chain any
> arbitrary data structure with ease.  I'd want to see an actual use
> case for this before anyone bothered implementing it.  I was actually
> thinking one way to do it would be to extend the variable declaration
> syntax so that you could declare n>=0 variables as SRF context
> variables, which I think is nicer, but even that I think is of limited
> usefulness.  I think the biggest value of PL/plgsql is the ability to
> RETURN QUERY, and I think the ability to push a lazy execution model
> down into that subordinate query is where the win is.  That case won't
> be helped at all by this sort of alternate calling convention - in
> fact it'll be nearly impossible to even do that at all with this type
> of execution model.
>

RETURN QUERY should be implemented for lazy execution model. And it
should be fast and not to much dificult.

Pavel


> ...Robert
>

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