Date: Fri, 12 May 2017 13:15:00 -0400
From: Bruce Momjian <bruce@momjian.us>
To: john.christofolakos@gmail.com
Cc: pgsql-docs@postgresql.org
Subject: Re: clarify constraint exclusion vs prepared statements
Message-ID: <20170512171500.GC6721@momjian.us>
References: <20170427202303.24360.26831@wrigleys.postgresql.org>
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On Thu, Apr 27, 2017 at 08:23:03PM +0000, john.christofolakos@gmail.com wrote:
> The following documentation comment has been logged on the website:
> 
> Page: https://www.postgresql.org/docs/9.2/static/ddl-partitioning.html
> Description:
> 
> Section 5.9.6 of the documentation discusses caveats re use of constraint
> exclusion on partitioned tables. It seems the restriction that the query
> constraints must be expressed in terms of constants has been lifted, and now
> constraints may be expressed in terms of parameterised values.
> 
> I&#39;m wondering if the restriction would still apply, though, in the case that
> the query is being prepared in advance, then the constraint value passed in
> as a parameter at execution time. It seems to me that constraint exclusion
> would not be applied in this case, but would like clarification on this
> point.

I think you are right that we don't support any constraint exclusion at
execution time, but using EXPLAIN should show you what it is doing.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +


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