1 use expression::Expression;
2 use query_builder::{AsQuery, Query};
3 use query_source::Table;
4 
5 /// This trait is not yet part of Diesel's public API. It may change in the
6 /// future without a major version bump.
7 ///
8 /// This trait exists as a stop-gap for users who need to use `GROUP BY` in
9 /// their queries, so that they are not forced to drop entirely to raw SQL. The
10 /// arguments to `group_by` are not checked, nor is the select statement
11 /// forced to be valid.
12 ///
13 /// Since Diesel otherwise assumes that you have no `GROUP BY` clause (which
14 /// would mean that mixing an aggregate and non aggregate expression in the same
15 /// query is an error), you may need to use `sql` for your select clause.
16 pub trait GroupByDsl<Expr: Expression> {
17     /// The type returned by `.group_by`
18     type Output: Query;
19 
20     /// See the trait documentation.
group_by(self, expr: Expr) -> Self::Output21     fn group_by(self, expr: Expr) -> Self::Output;
22 }
23 
24 impl<T, Expr> GroupByDsl<Expr> for T
25 where
26     Expr: Expression,
27     T: Table + AsQuery,
28     T::Query: GroupByDsl<Expr>,
29 {
30     type Output = <T::Query as GroupByDsl<Expr>>::Output;
31 
group_by(self, expr: Expr) -> Self::Output32     fn group_by(self, expr: Expr) -> Self::Output {
33         self.as_query().group_by(expr)
34     }
35 }
36