Quoting Tom Lane <[EMAIL PROTECTED]>:

> Mischa <[EMAIL PROTECTED]> writes:
> > Quoting Tom Lane <[EMAIL PROTECTED]>:
> >> 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 [...]
> but I'm less able to think of common use-cases for transitive
> inequality ...

Thanks. My apologies for not just going and looking at the code first.

Equality-transitives: yes, worth their weight in gold.
Inequality-transitivies: I see in OLAP queries (usually ranges), or in queries
against big UNION ALL views, where const false inequalities are the norm.
"a.x > b.y and a.x < c.z" comes up in OLAP, too, usually inside an EXISTS(...),
where you are doing something analogous to finding a path.




---------------------------(end of broadcast)---------------------------
TIP 9: the planner will ignore your desire to choose an index scan if your
      joining column's datatypes do not match

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