use crate::backend::{Backend, DieselReserveSpecialization};
use crate::dsl::SqlTypeOf;
use crate::expression::{
AppearsOnTable, Expression, QueryMetadata, Selectable, SelectableExpression,
TypedExpressionType, ValidGrouping,
};
use crate::query_builder::*;
use crate::result::QueryResult;
#[derive(Debug)]
pub struct SelectBy<T: Selectable<DB>, DB: Backend> {
selection: T::SelectExpression,
p: std::marker::PhantomData<(T, DB)>,
}
impl<T, DB> Clone for SelectBy<T, DB>
where
DB: Backend,
T: Selectable<DB>,
{
fn clone(&self) -> Self {
Self {
selection: T::construct_selection(),
p: std::marker::PhantomData,
}
}
}
impl<T, DB> Copy for SelectBy<T, DB>
where
T: Selectable<DB>,
DB: Backend,
T::SelectExpression: Copy,
{
}
impl<T, E, DB> QueryId for SelectBy<T, DB>
where
DB: Backend,
T: Selectable<DB, SelectExpression = E>,
E: QueryId + Expression,
{
type QueryId = E::QueryId;
const HAS_STATIC_QUERY_ID: bool = E::HAS_STATIC_QUERY_ID;
}
impl<T, DB> SelectBy<T, DB>
where
T: Selectable<DB>,
DB: Backend,
{
pub(crate) fn new() -> Self {
Self {
selection: T::construct_selection(),
p: std::marker::PhantomData,
}
}
}
impl<T, E, DB> Expression for SelectBy<T, DB>
where
DB: Backend,
T: Selectable<DB, SelectExpression = E>,
E: QueryId + Expression,
{
type SqlType = SelectBy<T, DB>;
}
impl<T, DB> TypedExpressionType for SelectBy<T, DB>
where
T: Selectable<DB>,
DB: Backend,
{
}
impl<T, GB, E, DB> ValidGrouping<GB> for SelectBy<T, DB>
where
DB: Backend,
T: Selectable<DB, SelectExpression = E>,
E: Expression + ValidGrouping<GB>,
{
type IsAggregate = E::IsAggregate;
}
impl<T, DB> QueryMetadata<SelectBy<T, DB>> for DB
where
DB: Backend,
T: Selectable<DB>,
DB: QueryMetadata<SqlTypeOf<T::SelectExpression>>,
{
fn row_metadata(lookup: &mut Self::MetadataLookup, out: &mut Vec<Option<Self::TypeMetadata>>) {
<DB as QueryMetadata<SqlTypeOf<<T as Selectable<DB>>::SelectExpression>>>::row_metadata(
lookup, out,
)
}
}
impl<T, DB> QueryFragment<DB> for SelectBy<T, DB>
where
T: Selectable<DB>,
T::SelectExpression: QueryFragment<DB>,
DB: Backend + DieselReserveSpecialization,
{
fn walk_ast<'b>(&'b self, out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
self.selection.walk_ast(out)
}
}
impl<T, QS, DB> SelectableExpression<QS> for SelectBy<T, DB>
where
DB: Backend,
T: Selectable<DB>,
T::SelectExpression: SelectableExpression<QS>,
Self: AppearsOnTable<QS>,
{
}
impl<T, QS, DB> AppearsOnTable<QS> for SelectBy<T, DB>
where
DB: Backend,
T: Selectable<DB>,
T::SelectExpression: AppearsOnTable<QS>,
Self: Expression,
{
}