Martin Lesser <ml-pgsql@bettercom.de> writes:
> I try to partition a large table (~ 120 mio. rows) into 50 smaller
> tables but using the IMO immutable %-function constraint exclusion
> does not work as expected:
The constraint exclusion mechanism is not as bright as you think.
There are some very limited cases where it can make a deduction that
a WHERE clause implies a CHECK constraint that's not an exact textual
equivalent ... but all those cases have to do with related b-tree
operators, and % is not one.
It's usually better to use partitioning rules that have something to
do with the WHERE-clauses you'd be using anyway. For instance, try
to partition on ranges of id1 instead of id1 % 50. That works because
the CHECK clauses will be like "id1 >= x and id1 < y" and those
operators are btree-related to the "id1 = z" clauses you'll have in
the query.
regards, tom lane
