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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thom Brown <thom@linux.com>
cc: 2320415112@qq.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #19567: Redundant outer DISTINCT causes a second full
 aggregation above UNION
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Comments: In-reply-to Thom Brown <thom@linux.com>
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Thom Brown <thom@linux.com> writes:
> This doesn't look like a bug, but rather an enhancement request.

Yeah, not one of these are bugs.  Some of them might be missed
optimization opportunities.  But you'd need to show that the extra
planning cost of detecting such cases is worthwhile, ie there's
a reasonably large fraction of real-world queries that would
benefit materially.

			regards, tom lane