FW: Constraint exclusion in partitions

Sent that on pgsql-novice list but did not get any answers yet.

Maybe someone could help me understand here J

Hi all,

I have split a large table (billions of records) into multiple partitions,
hoping the access would be faster. I used an ID to make partitions check
(check (id >= 100 AND id < 200).) and created over 80 tables (children) that
are now filled with data.

However, after I did it, I read a second time the following sentence in the
documentation and started wondering what it actually means . "Constraint
exclusion only works when the query's WHERE clause contains constants (or
externally supplied parameters)"

I understand that the following query will use constraint exclusion and will
run faster.

a- Select * from parent_table where id >=9999; -- using a constant

But how constraint exclusion would react with the following queries .

b- Select * from parent_table where id between 2345 and 6789; -- using
a range of ids

c- Select * from parent_table where id in(select ids from
anothertable); -- using a list of ids from a select

Since I mostly use queries of type b and c, I am wondering if partitioning
the large table was appropriate and if the queries are going to be longer to
run.

Thank in advance

Daniel

Doc: http://www.postgresql.org/docs/9.3/static/ddl-partitioning.html