Re: BUG #17158: Distinct ROW fails with Postgres 14

On Tue, 24 Aug 2021 at 21:02, PG Bug reporting form
<noreply@postgresql.org> wrote:
> -- This works fine before pg14.
> SELECT DISTINCT ROW(col1, col2, col3, col4, col5, col6, col70, col7, col8,
> col9, col10,
> col11, col12, col13, col14, col15, col16, col17, col18, col19, col20, col21,
> col22, col23, col24, col25,
> col26, col27, col28, col29, col32, col33, col34, col35, col36, col37, col38)
> AS "row" FROM local WHERE true;
> ERROR:  could not identify a hash function for type bit

It looks like 01e658fa74 is to blame for this.

The test case can be simplified down to just:

create table local (b bit);
insert into local values('1'),('0');
SELECT DISTINCT ROW(b) FROM local;

Tom did have a look at this and raise the question about the
possibility of not being able to hash in [1].

If it's going to be a problem detecting the lack of hashability during
planning then maybe we can just add a hash opclass for BIT to fix this
particular case.

I've copied in Peter as 01e658fa74 is one of his.

David

[1] https://www.postgresql.org/message-id/20201019233234.r6lyxbvdg5s77rvd%40alap3.anarazel.de