Support for Postgres's MIN(..) and MAX(..) functions

Author: Photonios

psqlextra/expressions.py

@@ -86,3 +86,28 @@ def resolve_expression(self, *args, **kwargs) -> HStoreColumn:
             self.key
         )
         return expression
+
+class NonGroupableFunc(expressions.Func):
+    """A version of Django's :see:Func expression that
+    is _never_ included in the GROUP BY clause."""
+
+    def get_group_by_cols(self):
+        """Gets the columns to be included in the GROUP BY clause.
+
+        We have to override this because Django's default behavior
+        is to include function calls in GROUP by clauses."""
+        return []
+
+
+class Min(NonGroupableFunc):
+    """Exposes PostgreSQL's MIN(..) func."""
+
+    def __init__(self, expression):
+        super().__init__(expression, function='MIN')
+
+
+class Max(NonGroupableFunc):
+    """Exposes PostgreSQL's Max(..) func."""
+
+    def __init__(self, expression):
+        super().__init__(expression, function='Max')