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Re: Dynamic Partitioning using Segment Visibility Maps

From: Simon Riggs <simon(at)2ndquadrant(dot)com>
To: Gavin Sherry <swm(at)alcove(dot)com(dot)au>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Dynamic Partitioning using Segment Visibility Maps
Date: 2008-01-11 08:07:18
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Lists: pgsql-hackers
On Fri, 2008-01-11 at 02:28 +0100, Gavin Sherry wrote:
> On Thu, Jan 10, 2008 at 09:30:10PM +0000, Simon Riggs wrote:
> > > > We cannot perform partition exclusion using this type of WHERE clause at
> > > > planning time because the CURRENT DATE function is STABLE. 
> > > 
> > > We can do the exact same thing -- if it's a direction people want to
> > > take. In fact, we can do it better/faster because once we've evaluated one 
> > > partition we know that there are no others to evaluate.
> > 
> > Lost you completely here. I'm explaining to you that *nobody* can solve
> > those problems solely at planning time, by definition, so it has to be
> > done at execution time. I'm not saying anything about your way, my way.
> Sorry, I wasn't clear enough. I was trying to say, if we're going to do
> something in the executor (for right or wrong) the declarative approach
> can do it too. Since there will be partition bounding information
> available, we can do partition selection in the executor (maybe the
> planner should tell us to do it).

Of course. It's an identical situation for both. Regrettably, none of
your comments about dynamic partitioning and planning were accurate as a

> Okay. As I said above, nothing in declarative partitioning rules out
> partition selection with stable functions. So, we lets do it, assuming
> everyone else thinks it is a good idea.

If you check the archives this was long ago been identified as a
requirement. And I said exactly the things you said, BTW, when trying to
say it didn't matter.

I've kept a list of requests for improvement that I can share with you;
I've always been loathe to publish a list of bad points.

  Simon Riggs

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