Usage of tuples/composite types in functions like count

[oeed]

An issue/discussion might already exist about this, although I wasn't able to find one so sorry if it does (I seem to recall discussing this at some point, but maybe it was on Gitter).

I have a situation where I need to count distinct values in a column that is a composite type/tuple (Postgres). For a highly contrived example:

CREATE TYPE person_info AS (
    name TEXT,
    age INT
);

CREATE TABLE employees (
    id SERIAL PRIMARY KEY,
    info person_info
);

SELECT COUNT(DISTINCT info) FROM employees;

The current count functions (along with other similar functions) restrict the expression to SingleValue, however, which isn't implemented on tuples. Is there perhaps another more suitable that these bounds could be changed to, or perhaps a new trait for such values on the Postgres backend? Thoughts?

[weiznich]

Given your example I'm not sure I can follow. There is already support for COUNT(DISTINCT …), so your example query should be just employees::table.select(dsl::count_distinct(employees::info))

Or do you look for passing more than one value to distinct? In that case: Yes that's not supported yet. The situation there is as with all the other issues/request to allow tuples there: It needs someone that work on a design first. We are open to suggestions there.

[oeed]

Ah apologies, I see. The issue I was making was trying to use a pure tuple was my column SQL type. I instead needed to use the Record type to wrap my tuple, which does implement SingleValue. Thanks