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Re: scrollable cursor sup. for SPI

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Pavel Stehule <pavel(dot)stehule(at)hotmail(dot)com>
Cc: tgl(at)sss(dot)pgh(dot)pa(dot)us, neilc(at)samurai(dot)com, pgsql-patches(at)postgresql(dot)org, jonah(dot)harris(at)gmail(dot)com
Subject: Re: scrollable cursor sup. for SPI
Date: 2007-01-20 01:47:27
Message-ID: 200701200147.l0K1lRC20154@momjian.us (view raw or flat)
Thread:
Lists: pgsql-patches
Where are we on this patch?

---------------------------------------------------------------------------

Pavel Stehule wrote:
> 
> >"Pavel Stehule" <pavel(dot)stehule(at)hotmail(dot)com> writes:
> > > if I comprehended it well CURSOR_OPT_SCROLL is set only when SCROLL is 
> >cheap
> > > (not when is possible). It's true?
> >
> >Nope.  If you want a scrollable plan you need to make sure you tell the
> >planner about it.  SPI_cursor_open is not in charge, it's merely looking
> >at what the planner did.
> >
> >As for that other stuff, when and if we support it, it would be time to
> >add a SPI entry point that supports it.  I'm disinclined to add an API
> >on speculation though --- by the time the feature actually exists, we
> >might not like the API anymore anyway.
> >
> 
> I did step back and did some test. game with CURSOR_OPT_SCROLL has not sense 
> in SPI_cursor_open. I didn't tests with table's joins where this problem is 
> visible before.
> 
> I propose add new function SPI_prepare_with_option(..) which allow set 
> option for planner. Isn't problem add to SPI_open_cursor assert for holdable 
> cursors. This needs propably rewriting functions pg_plan_query and 
> pg_plan_queries.
> 
> Or new function SPI_prepare_cursor(...) which can be similar 
> PerformCursorOpen. This doesn't change others functions.
> 
> All comments are welcome
> Pavel Stehule
> 
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-- 
  Bruce Momjian   bruce(at)momjian(dot)us
  EnterpriseDB    http://www.enterprisedb.com

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