Re: Problem with constraint exclusion on partitions

[David G Johnston <david.g.johnston@xxxxxxxxx>]

On Saturday, December 20, 2014, Mike Pultz [via PostgreSQL] <[hidden email]> wrote:
> 	Hey David,
>
> > What version are you using?
>
> Sorry, I'm on 9.3.4.
>
> >Now() is a volatile function so the planner cannot omit partitions.
> >
> >Replace that with a constant and now it can.
>
> I'm not sure what you mean- now() is a stable function:

My mistake but unless it is immutable the planner cannot evaluate it, it has to defer to the executor.  The executor can evaluate it a single time for the query but it is still left with the original execution plan given to it by the planner.

it's the timestamp at the start of the transaction- so the planner should
have a set value for all rows. 

Am I missing something else?

Precise responsibility and timing mechanics between the planner and executor which I cannot give adequate exposition on off the top of my head...

David J.

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