Re: COALESCE with single argument looks like identity function - Mailing list pgsql-hackers

From Tom Lane
Subject Re: COALESCE with single argument looks like identity function
Date
Msg-id 834617.1744380059@sss.pgh.pa.us
Whole thread Raw
In response to COALESCE with single argument looks like identity function  (Maksim Milyutin <maksim.milyutin@tantorlabs.ru>)
Responses Re: COALESCE with single argument looks like identity function
List pgsql-hackers
Maksim Milyutin <maksim.milyutin@tantorlabs.ru> writes:
> I've noticed that COALESCE function doesn't converge to argument 
> expression if it is alone in argument list of COALESCE as part 
> simplification routine for expressions in planner. This might suppress 
> further useful transformations when non-strict ops are required from 
> some expression like converging OUTER JOIN to INNER one with WHERE qual 
> containing COALESCE over single column from inner side.

Seems like a reasonable idea --- it's probably a rare case, but the
check is cheap enough.  I'd add some comments though.

Please add this to the open commitfest so we don't lose track of it.

            regards, tom lane



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