Re: a patch for row-at-a-time execution for table functions

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On 04/23/2013 06:09 PM, David Gudeman wrote:
> The primary change we made to Postgres in order to support our own 
> version of foreign data wrappers was a row-at-a-time execution for 
> table functions. In standard Postgres, when you execute a table 
> function, it gathers all of the rows at once and stuffs them into
> a buffer in order to support cursors, even if it is just a vanilla 
> forward scan. We modified the code so that when you do vanilla
> forward scans it executes the function one row at a time. This
> wasn't a big change since the support for executing functions that
> way was always in there but it was bypassed in the plan execution
> code. Probably someone always intended to do this, but never got
> around to it.

Guilty as charged :-(

> We also encountered what I think is a bug in the way that the
> cleanup callback functions are called at the end of a table
> function. I'm not sure I remember the details correctly, but I
> believe it was freeing the memory region used for the private state
> before calling the cleanup function. If that was the bug though,
> why didn't I just use malloc for the private state? I'll have to
> review my notes on that one...
> 
> Anyway, my company has agreed to let me post a patch for these 
> changes. Before I go to the work of getting the patches ready, I'd 
> like to take the temperature of the commiters and find out if there
> is any likelihood of getting these patches accepted.
> 
> Anyone?

+1

I have always been in favor of having this option -- in fact that was
the way it was originally coded IIRC. Something caused us to switch to
materialized mode and we decided we would wait a while to see how that
went before worrying again about value-per-call mode.

At this point you're looking at 9.4 for this, but I'll try to help see
it through since it has long been on my TODO list.

Joe



- -- 
Joe Conway
credativ LLC: http://www.credativ.us
Linux, PostgreSQL, and general Open Source
Training, Service, Consulting, & 24x7 Support
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