Re: "Constraint exclusion" is not general enough

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org, Martin Lesser <ml-pgsql(at)bettercom(dot)de>
Subject: Re: "Constraint exclusion" is not general enough
Date: 2006-08-07 18:38:21
Message-ID: 3836.1154975901@sss.pgh.pa.us
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Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> To achieve the "indexed" partition pruning, we'd need
> - a way to specify that all constraints are mutually exclusive
> - a declarative approach for saying something like "arranged in date
> sequence"
> - preferably a way to have this happen at run-time so we can hard-plan a
> query with CURRENT_TIMESTAMP in the WHERE clause

Definitely a direction worth pursuing, but it seems like it would be a
completely separate code path from the existing constraint-checking
code. I'd imagine that instead of having to prove theorems about which
tables to scan, a declarative approach would let us "just know" what
to do.

regards, tom lane

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