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Re: Plan for update ... where a is not distinct from b - Mailing list pgsql-general

From Tom Lane
Subject Re: Plan for update ... where a is not distinct from b
Date
Msg-id 13950.1511879733@sss.pgh.pa.us
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In response to Plan for update ... where a is not distinct from b  ("Peter J. Holzer" <hjp-pgsql@hjp.at>)
Responses Re: Plan for update ... where a is not distinct from b
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"Peter J. Holzer" <hjp-pgsql@hjp.at> writes:
> I noticed that an update was taking a long time and found this:
> [ crappy plan for join on IS NOT DISTINCT ]

Yeah, there's no optimization smarts at all for IS [NOT] DISTINCT.
It can't be converted into a merge qual, nor a hash qual, nor an
indexscan qual.

In principle this could be improved, but given how much work it'd be
and how seldom anyone complains, it's not likely to happen anytime soon.
        regards, tom lane

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