Re: Same expression more than once in partition key

Yugo Nagata <nagata(at)sraoss(dot)co(dot)jp> writes:
> When we create a range partitioned table, we cannot use
> a column more than once in the partition key.

> postgres=# create table t (i int) partition by range(i,i);
> ERROR: column "i" appears more than once in partition key

AFAIK, that's just a simple test for obvious mistakes; it's not a
property that's essential for correctness.

> However, I can use same expression more than once in partition key.

... and so, I can't get excited about extending it to expressions.
Where would you stop --- for example, are i and (i) equal? What
about (i) and (case when true then i else j end)? In principle,
the system could recognize both those identities, but it seems
silly to expend code on it just for nagware purposes.

regards, tom lane