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use expression::SelectableExpression;
use pg::Pg;
use query_builder::{AstPass, QueryFragment, SelectQuery, SelectStatement};
use query_dsl::methods::DistinctOnDsl;
use result::QueryResult;
#[derive(Debug, Clone, Copy, QueryId)]
pub struct DistinctOnClause<T>(pub(crate) T);
impl<T> QueryFragment<Pg> for DistinctOnClause<T>
where
T: QueryFragment<Pg>,
{
fn walk_ast(&self, mut out: AstPass<Pg>) -> QueryResult<()> {
out.push_sql("DISTINCT ON (");
self.0.walk_ast(out.reborrow())?;
out.push_sql(")");
Ok(())
}
}
impl<ST, F, S, D, W, O, L, Of, G, Selection> DistinctOnDsl<Selection>
for SelectStatement<F, S, D, W, O, L, Of, G>
where
Selection: SelectableExpression<F>,
Self: SelectQuery<SqlType = ST>,
SelectStatement<F, S, DistinctOnClause<Selection>, W, O, L, Of, G>: SelectQuery<SqlType = ST>,
{
type Output = SelectStatement<F, S, DistinctOnClause<Selection>, W, O, L, Of, G>;
fn distinct_on(self, selection: Selection) -> Self::Output {
SelectStatement::new(
self.select,
self.from,
DistinctOnClause(selection),
self.where_clause,
self.order,
self.limit,
self.offset,
self.group_by,
self.locking,
)
}
}