Macro diesel::allow_columns_to_appear_in_same_group_by_clause

macro_rules! allow_columns_to_appear_in_same_group_by_clause {
    ($($left_path : tt) :: +, $($right_path : tt) :: + $(,) ?) => { ... };
    ($($left_path : tt) :: +, $($right_path : tt) :: +, $($other : tt) *) => { ... };
    ($last_col : ty,) => { ... };
    () => { ... };
}

Allow two or more columns which are otherwise unrelated to be used together in a group by clause.

This macro must be invoked any time two columns need to appear in the same group by clause. When this macro is invoked with more than 2 columns, every combination of those columns will be allowed to appear together.

Example

// This would be required to do
// `users::table.inner_join(posts::table).group_by((users::name, users::hair_color, posts::id))`
allow_columns_to_appear_in_same_group_by_clause!(users::name, users::hair_color, posts::id);

When more than two columns are passed, the relevant code is generated for every combination of those columns. This code would be equivalent to the previous example.

allow_columns_to_appear_in_same_group_by_clause!(users::name, users::hair_color);
allow_columns_to_appear_in_same_group_by_clause!(users::name, posts::id);
allow_columns_to_appear_in_same_group_by_clause!(users::hair_color, posts::id);