Re: fixing CREATEROLE

Wolfgang Walther:
> Tom Lane:
>> No, we don't support partial indexes on catalogs, and I don't think
>> we want to change that.  Partial indexes would require expression
>> evaluations occurring at very inopportune times.
>
> I see. Is that the same for indexes *on* an expression? Or would those
> be ok?
>
> With a custom operator, an EXCLUDE constraint on the ROW(reldatabase,
> relname) expression could work. The operator would compare:
> - (0, name1) and (0, name2) as name1 == name2
> - (db1, name1) and (0, name2) as name1 == name2
> - (0, name1) and (db2, name2) as name1 == name2
> - (db1, name1) and (db2, name2) as db1 == db2 && name1 == name2
>
> or just (db1 == 0 || db2 == 0 || db1 == db2) && name1 == name2.

Does it even need to be on the expression? I don't think so. It would be
enough to just make it compare relname WITH = and reldatabase WITH the
custom operator (db1 == 0 || db2 == 0 || db1 == db2), right?

Best,

Wolfgang