"David West" <david.west@cusppoint.com> writes:
> I'm wondering why the postgres planner is not capable of determining the
> correct partition for a simple select for the following partitioning scheme,
The planner doesn't know anything about the behavior of %.
Heed the fine manual's advice:
Keep the partitioning constraints simple, else the planner may not be
able to prove that partitions don't need to be visited. Use simple
equality conditions for list partitioning, or simple range tests for
range partitioning, as illustrated in the preceding examples. A good
rule of thumb is that partitioning constraints should contain only
comparisons of the partitioning column(s) to constants using
B-tree-indexable operators.
regards, tom lane