Unused columns in WHERE clause

Question

I found this query in our codebase:

DELETE FROM "Foo"
WHERE ("Foo"."Id", "Foo"."CreatedAt")
IN (SELECT "f"."Id", "f"."CreatedAt"
    FROM "Foo" AS "f"
    WHERE "f"."CreatedAt" <= CURRENT_TIMESTAMP);

It deletes records created before the current time.

This gives the same result:

DELETE FROM "Foo"
WHERE "Foo"."CreatedAt"
IN (SELECT "f"."CreatedAt"
    FROM "Foo" AS "f"
    WHERE "f"."CreatedAt" <= CURRENT_TIMESTAMP);

I don't know why the Foo.Id is included in the WHERE clause - maybe leftover junk from various refactorings (e.g. it could have been used for batch delete with ORDER BY "f"."Id" LIMIT 1000). But because it's a PK, I'm reluctant to remove it, as maybe it's there for a reason.

Is there a theoretical / perf reason for having it in there, or are the two queries equivalent?

(This targets both postgres and sqlite.)

Answer 1

Both queries are ridiculously complicated. Use

DELETE FROM "Foo"
WHERE "CreatedAt" < current_timestamp;