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From: David Rowley <[email protected]>
To: Tom Lane <[email protected]>
Cc: ma lz <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: Why not do distinct before SetOp
Date: Wed, 6 Nov 2024 12:38:00 +1300
Message-ID: <CAApHDvrXUuhGJ_rzsuLY3f1mou1w5RT4zxEb45gbBR3ap6vy4g@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
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	<[email protected]>
	<CAApHDvod=mg8xKbBTFTu7HPWzLk+UhHVdXXwQEj9eNh5buVaiQ@mail.gmail.com>
	<[email protected]>

On Wed, 6 Nov 2024 at 12:09, Tom Lane <[email protected]> wrote:
> Of course, I might be overestimating the performance benefit we'd get.
> But I'm tempted to give it a try.

I'm glad. I'm curious to see if you're right about the projection
overhead of the flags. If you're right, it seems like a not too
difficult optimisation to get in.

I like the idea as it also gets rid of the flag cruft from
prepunion.c, which saves having to add flags conditionally if
INTERCEPT/EXCEPT were ever made to use joins.

David






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