Re: Removing useless DISTINCT clauses

On 24 August 2018 at 03:29, Finnerty, Jim <jfinnert@amazon.com> wrote:
> Thank you Álvaro.  Here's the distinct_opt_v7 patch.

Determining if there's just 1 base relation by checking the length the
rtable is not a good way. If you want to see why, try creating a
primary key on a partitioned table.

My personal opinion of only being able to completely remove the
DISTINCT when there's a single item in the rtable (or a single base
table) is that it's just too poor to bother with.  I think such a
solution is best left to another patch and it should be much more
complete and be able to track the unique properties through joins.

--
 David Rowley                   http://www.2ndQuadrant.com/
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