diesel/expression/
select_by.rs

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1use crate::backend::{Backend, DieselReserveSpecialization};
2use crate::dsl::SqlTypeOf;
3use crate::expression::{
4    AppearsOnTable, Expression, QueryMetadata, Selectable, SelectableExpression,
5    TypedExpressionType, ValidGrouping,
6};
7use crate::query_builder::*;
8use crate::result::QueryResult;
9
10#[derive(Debug)]
11pub struct SelectBy<T: Selectable<DB>, DB: Backend> {
12    selection: T::SelectExpression,
13    p: std::marker::PhantomData<(T, DB)>,
14}
15
16impl<T, DB> Clone for SelectBy<T, DB>
17where
18    DB: Backend,
19    T: Selectable<DB>,
20{
21    fn clone(&self) -> Self {
22        Self {
23            selection: T::construct_selection(),
24            p: std::marker::PhantomData,
25        }
26    }
27}
28
29impl<T, DB> Copy for SelectBy<T, DB>
30where
31    T: Selectable<DB>,
32    DB: Backend,
33    T::SelectExpression: Copy,
34{
35}
36
37impl<T, E, DB> QueryId for SelectBy<T, DB>
38where
39    DB: Backend,
40    T: Selectable<DB, SelectExpression = E>,
41    E: QueryId + Expression,
42{
43    type QueryId = E::QueryId;
44
45    const HAS_STATIC_QUERY_ID: bool = E::HAS_STATIC_QUERY_ID;
46}
47
48impl<T, DB> SelectBy<T, DB>
49where
50    T: Selectable<DB>,
51    DB: Backend,
52{
53    pub(crate) fn new() -> Self {
54        Self {
55            selection: T::construct_selection(),
56            p: std::marker::PhantomData,
57        }
58    }
59}
60
61impl<T, E, DB> Expression for SelectBy<T, DB>
62where
63    DB: Backend,
64    T: Selectable<DB, SelectExpression = E>,
65    E: QueryId + Expression,
66{
67    type SqlType = SelectBy<T, DB>;
68}
69
70impl<T, DB> TypedExpressionType for SelectBy<T, DB>
71where
72    T: Selectable<DB>,
73    DB: Backend,
74{
75}
76
77impl<T, GB, E, DB> ValidGrouping<GB> for SelectBy<T, DB>
78where
79    DB: Backend,
80    T: Selectable<DB, SelectExpression = E>,
81    E: Expression + ValidGrouping<GB>,
82{
83    type IsAggregate = E::IsAggregate;
84}
85
86impl<T, DB> QueryMetadata<SelectBy<T, DB>> for DB
87where
88    DB: Backend,
89    T: Selectable<DB>,
90    DB: QueryMetadata<SqlTypeOf<T::SelectExpression>>,
91{
92    fn row_metadata(lookup: &mut Self::MetadataLookup, out: &mut Vec<Option<Self::TypeMetadata>>) {
93        <DB as QueryMetadata<SqlTypeOf<<T as Selectable<DB>>::SelectExpression>>>::row_metadata(
94            lookup, out,
95        )
96    }
97}
98
99impl<T, DB> QueryFragment<DB> for SelectBy<T, DB>
100where
101    T: Selectable<DB>,
102    T::SelectExpression: QueryFragment<DB>,
103    DB: Backend + DieselReserveSpecialization,
104{
105    fn walk_ast<'b>(&'b self, out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
106        self.selection.walk_ast(out)
107    }
108}
109
110impl<T, QS, DB> SelectableExpression<QS> for SelectBy<T, DB>
111where
112    DB: Backend,
113    T: Selectable<DB>,
114    T::SelectExpression: SelectableExpression<QS>,
115    Self: AppearsOnTable<QS>,
116{
117}
118
119impl<T, QS, DB> AppearsOnTable<QS> for SelectBy<T, DB>
120where
121    DB: Backend,
122    T: Selectable<DB>,
123    T::SelectExpression: AppearsOnTable<QS>,
124    Self: Expression,
125{
126}
diesel/expression/select_by.rs

diesel/expression/
select_by.rs
