Aggregate elimination with UNIQUE and NOT NULL column

If columns are part of a GROUP BY expression and they are UNIQUE and do not accept NULL values, i.e. PK or UK+NOTNULL, the Aggregate operator can be transformed into a Project operator, as each row will end up in a different group.

For instance, given that pk is the PRIMARY KEY for the table, the GROUP BY could be removed from grouping columns for following query:

SELECT pk, value1
FROM table_1
GROUP BY value1, pk, value2;