entc/gen: reduce the usage of DISTINCT in queries (#3305)

Most queries are not graph traversals but rather regular table scans,
in which case the DISTINCT clause is not needed as duplicates cannot be
returned (unless query was modified by the user).

examples/privacyadmin/ent/user_query.go

@@ -375,20 +375,12 @@ func (uq *UserQuery) sqlCount(ctx context.Context) (int, error) {
 }
 
 func (uq *UserQuery) querySpec() *sqlgraph.QuerySpec {
-	_spec := &sqlgraph.QuerySpec{
-		Node: &sqlgraph.NodeSpec{
-			Table:   user.Table,
-			Columns: user.Columns,
-			ID: &sqlgraph.FieldSpec{
-				Type:   field.TypeInt,
-				Column: user.FieldID,
-			},
-		},
-		From:   uq.sql,
-		Unique: true,
-	}
+	_spec := sqlgraph.NewQuerySpec(user.Table, user.Columns, sqlgraph.NewFieldSpec(user.FieldID, field.TypeInt))
+	_spec.From = uq.sql
 	if unique := uq.ctx.Unique; unique != nil {
 		_spec.Unique = *unique
+	} else if uq.path != nil {
+		_spec.Unique = true
 	}
 	if fields := uq.ctx.Fields; len(fields) > 0 {
 		_spec.Node.Columns = make([]string, 0, len(fields))