Re: should check collations when creating partitioned index

On Mon, 2023-11-13 at 10:24 +0100, Peter Eisentraut wrote:
> create table t1 (a int, b text) partition by hash (b);
> create table t1a partition of t1 for values with (modulus 2,
> remainder 0);
> create table t1b partition of t1 for values with (modulus 2,
> remainder 1);
> create unique index i1 on t1 (b collate case_insensitive);
> insert into t1 values (1, 'a'), (2, 'A');  -- this succeeds
>
> The attached patch adds the required collation check.  In the
> example,
> it would not allow the index i1 to be created.

In the patch, you check for an exact collation match. Considering this
case only depends on equality, I think it would be correct if the
requirement was that (a) both collations are deterministic; or (b) the
collations match exactly.

This is related to the discussion here:

https://postgr.es/m/b7a9f32eee8d24518f791168bc6fb653d1f95f4d.camel@j-davis.com

Regards,
    Jeff Davis