Re: Problem with constraint exclusion on partitions - Mailing list pgsql-general

From David G Johnston
Subject Re: Problem with constraint exclusion on partitions
Date
Msg-id CAKFQuwbzz5-nFoZpc_iJAn6kCT6qtHU-=0MfMHhm7hZEfjpkSw@mail.gmail.com
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In response to Re: Problem with constraint exclusion on partitions  ("Mike Pultz" <mike@mikepultz.com>)
Responses Re: Problem with constraint exclusion on partitions  (David G Johnston <david.g.johnston@gmail.com>)
List pgsql-general
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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