diesel/query_builder/
distinct_clause.rs

1use crate::backend::DieselReserveSpecialization;
2use crate::query_builder::*;
3use crate::query_dsl::order_dsl::ValidOrderingForDistinct;
4
5#[derive(Debug, Clone, Copy, QueryId)]
6pub struct NoDistinctClause;
7#[derive(Debug, Clone, Copy, QueryId)]
8pub struct DistinctClause;
9
10impl<DB> QueryFragment<DB> for NoDistinctClause
11where
12    DB: Backend + DieselReserveSpecialization,
13{
14    fn walk_ast<'b>(&'b self, _: AstPass<'_, 'b, DB>) -> QueryResult<()> {
15        Ok(())
16    }
17}
18
19impl<DB> QueryFragment<DB> for DistinctClause
20where
21    DB: Backend + DieselReserveSpecialization,
22{
23    fn walk_ast<'b>(&'b self, mut out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
24        out.push_sql("DISTINCT ");
25        Ok(())
26    }
27}
28
29impl<O> ValidOrderingForDistinct<NoDistinctClause> for O {}
30impl<O> ValidOrderingForDistinct<DistinctClause> for O {}
31
32// This is rexported from another location
33#[allow(unreachable_pub, unused_imports)]
34#[cfg(feature = "postgres_backend")]
35pub use crate::pg::DistinctOnClause;