Daniel Gustafsson <daniel@yesql.se> writes:
> On 14 Dec 2022, at 13:54, David G. Johnston <david.g.johnston@gmail.com> wrote:
>> There is a decent chance that the fix here is to prohibit doing what you did here - a PK cannot contain nulls in any
ofits columns so indeed choosing an index that specifies how nulls behave is non-sensical. That said, it also doesn’t
hurtso long as the column itself is indeed not null. But extending the syntax doesn’t seem that appealing.
> Even if we prohibit this, there is still the case of all existing systems which
> can't be dumped. I wonder if the solution is to teach pg_dump to not create
> NULLS NOT DISTINCT primary key constraints? The simple attached fix creates a
> valid PK constraint on the above schema.
It doesn't make sense for pg_dump to editorialize on a schema that
we otherwise consider valid; people would rightfully complain that
dump/restore changed things. So we need to do both things: prohibit
adopting such an index as a PK constraint (but I guess it's okay
for plain unique constraints?), and adjust pg_dump to compensate
for the legacy case where it was already done.
regards, tom lane