Re: Recognizing range constraints (was Re: Plan for relatively simple query seems to be very inefficient)

Mischa <mischa.Sandberg@telus.net> writes:
> Quoting Tom Lane <tgl@sss.pgh.pa.us>:
>> WHERE a.x > b.y AND a.x < 42

> Out of curiosity, will the planner induce "b.y < 42" out of this?

No.  There's some smarts about transitive equality, but none about
transitive inequalities.  Offhand I'm not sure if it'd be useful to add
such.  The transitive-equality code pulls its weight because you so
often have situations like

    create view v as select a.x, ... from a join b on (a.x = b.y);

    select * from v where x = 42;

but I'm less able to think of common use-cases for transitive
inequality ...

            regards, tom lane