Re: A Guide to Constraint Exclusion (Partitioning)

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> And this decision is made separately for each child table, so the fact that
> a seqscan might be the best bet for the target partition doesn't stop the
> planner from using the indexscan in other partitions.

That was the detail I was missing. I'm surprised because I actually tested
this before I sent the message and saw a plan like this with a single
sequential scan node despite the three child tables:

staging=> explain select * from _test where a=1;
QUERY PLAN
------------------------------------------------------
Seq Scan on _test (cost=0.00..22.50 rows=5 width=4)
Filter: (a = 1)
(2 rows)

[This is on 7.4, maybe the 8.0 plans are more explicit though I don't recall
any mention of changes in that area]

--
greg