Re: Problem with constraint exclusion on partitions

On Saturday, December 20, 2014, Mike Pultz [via PostgreSQL] <
ml-node+s1045698n5831551h5(at)n5(dot)nabble(dot)com> 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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