Re: Avoid computing ORDER BY junk columns unnecessarily - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Avoid computing ORDER BY junk columns unnecessarily
Date
Msg-id 1067708.1703266312@sss.pgh.pa.us
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In response to Re: Avoid computing ORDER BY junk columns unnecessarily  (Heikki Linnakangas <hlinnaka@iki.fi>)
Responses Re: Avoid computing ORDER BY junk columns unnecessarily
Re: Avoid computing ORDER BY junk columns unnecessarily
List pgsql-hackers
Heikki Linnakangas <hlinnaka@iki.fi> writes:
> On 22/12/2023 17:24, Tom Lane wrote:
>> How much of your patchset still makes sense if we assume that we
>> can always extract the ORDER BY column values from the index?

> That would make it much less interesting. But I don't think that's a 
> good assumption. Especially in the kNN case, the ORDER BY value would 
> not be stored in the index. Most likely the index needs to calculate it 
> in some form, but it might take shortcuts like avoiding the sqrt().

Yeah, fair point.  I'll try to take a look at your patchset after
the holidays.

            regards, tom lane



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