Re: Same expression more than once in partition key

On Fri, Jun 23, 2017 at 4:04 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> writes:
>> We also allow the same column more than once in an index. We probably
>> don't have to be more strict here.
>
> There actually are valid uses for the same column more than once in
> an index, eg if you use a different operator class for each instance.
> I find it hard to envision a similar use-case in partitioning though.

Maybe you already realize this, but partitioning, like index creation,
allows an opclass to be specified:

rhaas=# create table foo (a text, b text) partition by range (a
text_ops, b text_pattern_ops);
CREATE TABLE

I don't really see anybody wanting to do that, but I don't really see
anyone wanting to do with an index either.

My inclination is to reject this patch as not solving any actual problem.

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