1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131

use crate::backend::{Backend, DieselReserveSpecialization};
use crate::expression::helper_types::{Asc, Desc};
use crate::query_builder::combination_clause::CombinationClause;
use crate::query_builder::{AstPass, Query, QueryFragment, QueryId};
use crate::{QueryResult, RunQueryDsl};

/// This trait is not yet part of Diesel's public API. It may change in the
/// future without a major version bump.
///
/// This trait exists as a stop-gap for users who need to order by column position
/// in their queries, so that they are not forced to drop entirely to raw SQL. The
/// arguments to `positional_order_by` are not checked, nor is the select statement
/// forced to be valid.
pub trait PositionalOrderDsl<Expr: Order>: Sized {
    fn positional_order_by(self, expr: Expr) -> PositionalOrderClause<Self, Expr::Fragment> {
        PositionalOrderClause {
            source: self,
            expr: expr.into_fragment(),
        }
    }
}

#[derive(Debug, Clone, Copy, QueryId)]
pub struct PositionalOrderClause<Source, Expr> {
    source: Source,
    expr: Expr,
}

impl<Combinator, Rule, Source, Rhs, Expr: Order> PositionalOrderDsl<Expr>
    for CombinationClause<Combinator, Rule, Source, Rhs>
{
}

impl<Source, Expr> Query for PositionalOrderClause<Source, Expr>
where
    Source: Query,
{
    type SqlType = Source::SqlType;
}

impl<Source, Expr, Conn> RunQueryDsl<Conn> for PositionalOrderClause<Source, Expr> {}

impl<Source, Expr, DB> QueryFragment<DB> for PositionalOrderClause<Source, Expr>
where
    DB: Backend + DieselReserveSpecialization,
    Source: QueryFragment<DB>,
    Expr: QueryFragment<DB>,
{
    fn walk_ast<'b>(&'b self, mut pass: AstPass<'_, 'b, DB>) -> QueryResult<()> {
        self.source.walk_ast(pass.reborrow())?;
        pass.push_sql(" ORDER BY ");
        self.expr.walk_ast(pass)
    }
}

#[derive(Debug, Clone, Copy, QueryId)]
pub struct OrderColumn(u32);

impl<DB: Backend> QueryFragment<DB> for OrderColumn {
    fn walk_ast<'b>(&'b self, mut pass: AstPass<'_, 'b, DB>) -> QueryResult<()> {
        pass.push_sql(&self.0.to_string());
        Ok(())
    }
}

impl From<u32> for OrderColumn {
    fn from(order: u32) -> Self {
        OrderColumn(order)
    }
}

pub trait IntoOrderColumn: Into<OrderColumn> {
    fn asc(self) -> Asc<OrderColumn> {
        Asc { expr: self.into() }
    }
    fn desc(self) -> Desc<OrderColumn> {
        Desc { expr: self.into() }
    }
}

impl<T> IntoOrderColumn for T where T: Into<OrderColumn> {}

pub trait Order: Copy {
    type Fragment;

    fn into_fragment(self) -> Self::Fragment;
}

impl<T: Into<OrderColumn> + Copy> Order for T {
    type Fragment = OrderColumn;

    fn into_fragment(self) -> Self::Fragment {
        self.into()
    }
}

impl Order for Asc<OrderColumn> {
    type Fragment = Asc<OrderColumn>;

    fn into_fragment(self) -> Self::Fragment {
        self
    }
}

impl Order for Desc<OrderColumn> {
    type Fragment = Desc<OrderColumn>;

    fn into_fragment(self) -> Self::Fragment {
        self
    }
}

macro_rules! impl_order_for_all_tuples {
    ($(
        $unused1:tt {
            $(($idx:tt) -> $T:ident, $unused2:ident, $unused3:tt,)+
        }
    )+) => {
        $(
            impl<$($T: Order),+> Order for ($($T,)+) {
                type Fragment = ($(<$T as Order>::Fragment,)+);

                fn into_fragment(self) -> Self::Fragment {
                    ($(self.$idx.into_fragment(),)+)
                }
            }
        )+
    };
}

diesel_derives::__diesel_for_each_tuple!(impl_order_for_all_tuples);