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

Mischa <mischa(dot)Sandberg(at)telus(dot)net> writes:
> Quoting Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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