Cool! Thanks for the speedy reply, link, and summary! I'm not sure how I missed this, but apologies for the noise.
-Paul-
On Thu, Jul 11, 2024 at 4:49 PM Andrei Lepikhov <lepihov@gmail.com> wrote:
On 12/7/2024 06:31, Paul George wrote: > In the example below, I noticed that the JOIN predicate "t1.a<1" is not > pushed down to the scan over "t2", though it superficially seems like it > should be. It has already discussed at least couple of years ago, see [1]. Summarising, it is more complicated when equivalences and wastes CPU cycles more probably than helps.
> > create table t as (select 1 a); > analyze t; > explain (costs off) select * from t t1 join t t2 on t1.a=t2.a and t1.a<1; > QUERY PLAN > ------------------------------- > Hash Join > Hash Cond: (t2.a = t1.a) > -> Seq Scan on t t2 > -> Hash > -> Seq Scan on t t1 > Filter: (a < 1) > (6 rows) > > The same is true for the predicate "t1.a in (0, 1)". For comparison, the > predicate "t1.a=1" does get pushed down to both scans. > > explain (costs off) select * from t t1 join t t2 on t1.a=t2.a and t1.a=1; > QUERY PLAN > ------------------------- > Nested Loop > -> Seq Scan on t t1 > Filter: (a = 1) > -> Seq Scan on t t2 > Filter: (a = 1) > (5 rows)