Re: Partition-wise join for join between (declaratively) partitioned tables

On Wed, Apr 26, 2017 at 12:19 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> What I'm going to ask one more time, though, is why we are even discussing
> this. Surely the partition bounds of a partitioned table must all be of
> the same type already. If there is a case where they are not, that is
> a bug we had better close off before v10 ships, not a feature that we
> need to write a lot of code to accommodate.

This question was answered before, by Ashutosh.

http://postgr.es/m/CAFjFpRfaKSO4YZjVv7jkcMEMVgDcnqc4yhqVWhO5gczB5mW8eQ@mail.gmail.com

Since you either didn't read his answer, or else didn't understand it
and didn't bother asking for clarification, I'll try to be more blunt:
of course all of the partition bounds of a single partitioned table
have to be of the same type. We're not talking about that, because no
kidding. This thread is about the possibility -- in a future release
-- of implementing a join between two different partitioned tables by
joining each pair of matching partitions. To do that, you need the
tables to be compatibly partitioned, which requires that the
partitioning columns use the same opfamily for each partitioning
column but not necessarily that the types be the same. Making
partition-wise join work in the case where the partitioning columns
are of different types within an opfamily (like int4 vs. int8) is
giving Ashutosh a bit of trouble. So this is about a cross-type join,
not multiple types within a single partitioning hierarchy, as you
might also gather from the subject line of this thread.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company