Re: clarify constraint exclusion vs prepared statements

On Thu, Apr 27, 2017 at 08:23:03PM +0000, john(dot)christofolakos(at)gmail(dot)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'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.

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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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