diesel/expression/
count.rs

1#[cfg(doc)]
2use super::functions::aggregate_expressions::{
3    AggregateExpressionMethods, WindowExpressionMethods,
4};
5use super::functions::declare_sql_function;
6use super::{Expression, ValidGrouping};
7use crate::backend::Backend;
8use crate::internal::sql_functions::{
9    FunctionFragment, IsWindowFunction, OverClause, WindowFunctionFragment,
10};
11use crate::query_builder::*;
12use crate::result::QueryResult;
13use crate::sql_types::{BigInt, DieselNumericOps, SingleValue, SqlType};
14
15#[declare_sql_function]
16extern "SQL" {
17    /// Creates a SQL `COUNT` expression
18    ///
19    /// As with most bare functions, this is not exported by default. You can import
20    /// it specifically as `diesel::dsl::count`, or glob import
21    /// `diesel::dsl::*`
22    ///
23    /// ## Window Function Usage
24    ///
25    /// This function can be used as window function. See [`WindowExpressionMethods`] for details
26    ///
27    /// ## Aggregate Function Expression
28    ///
29    /// This function can be used as aggregate expression. See [`AggregateExpressionMethods`] for details.
30    ///
31    /// # Examples
32    ///
33    /// ## Normal function usage
34    ///
35    /// ```rust
36    /// # include!("../doctest_setup.rs");
37    /// # use diesel::dsl::*;
38    /// #
39    /// # fn main() {
40    /// #     use schema::animals::dsl::*;
41    /// #     let connection = &mut establish_connection();
42    /// assert_eq!(Ok(1), animals.select(count(name)).first(connection));
43    /// # }
44    /// ```
45    ///
46    /// ## Window function
47    ///
48    /// ```rust
49    /// # include!("../doctest_setup.rs");
50    /// # use diesel::dsl::*;
51    /// #
52    /// # fn main() {
53    /// #     use schema::animals::dsl::*;
54    /// #     let connection = &mut establish_connection();
55    /// assert_eq!(
56    ///     Ok(1),
57    ///     animals
58    ///         .select(count(name).partition_by(id))
59    ///         .first(connection)
60    /// );
61    /// # }
62    /// ```
63    ///
64    /// ## Aggregate function expression
65    ///
66    /// ```rust
67    /// # include!("../doctest_setup.rs");
68    /// # use diesel::dsl::*;
69    /// #
70    /// # fn main() {
71    /// #     use schema::animals::dsl::*;
72    /// #     let connection = &mut establish_connection();
73    /// assert_eq!(
74    ///     Ok(1),
75    ///     animals
76    ///         .select(count(name).aggregate_distinct())
77    ///         .first(connection)
78    /// );
79    /// # }
80    /// ```
81    #[aggregate]
82    #[window]
83    fn count<T: SqlType + SingleValue>(expr: T) -> BigInt;
84}
85
86/// Creates a SQL `COUNT(*)` expression
87///
88/// For selecting the count of a query, and nothing else, you can just call
89/// [`count`](crate::query_dsl::QueryDsl::count())
90/// on the query instead.
91///
92/// As with most bare functions, this is not exported by default. You can import
93/// it specifically as `diesel::dsl::count_star`, or glob import
94/// `diesel::dsl::*`
95///
96/// # Examples
97///
98/// ```rust
99/// # include!("../doctest_setup.rs");
100/// # use diesel::dsl::*;
101/// #
102/// # fn main() {
103/// #     use schema::users::dsl::*;
104/// #     let connection = &mut establish_connection();
105/// assert_eq!(Ok(2), users.select(count_star()).first(connection));
106/// # }
107/// ```
108pub fn count_star() -> CountStar {
109    CountStar
110}
111
112#[derive(Debug, Clone, Copy, QueryId, DieselNumericOps, ValidGrouping)]
113#[diesel(aggregate)]
114#[doc(hidden)]
115pub struct CountStar;
116
117impl Expression for CountStar {
118    type SqlType = BigInt;
119}
120
121impl<DB: Backend> FunctionFragment<DB> for CountStar {
122    const FUNCTION_NAME: &'static str = "COUNT";
123
124    fn walk_arguments<'b>(&'b self, mut out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
125        out.push_sql("*");
126        Ok(())
127    }
128}
129
130impl<DB: Backend> QueryFragment<DB> for CountStar {
131    fn walk_ast<'b>(&'b self, mut out: AstPass<'_, 'b, DB>) -> QueryResult<()> {
132        out.push_sql("COUNT(*)");
133        Ok(())
134    }
135}
136
137impl<Partition, Order, Frame, DB: Backend> WindowFunctionFragment<CountStar, DB>
138    for OverClause<Partition, Order, Frame>
139{
140}
141
142impl IsWindowFunction for CountStar {
143    type ArgTypes = ();
144}
145
146impl_selectable_expression!(CountStar);
147
148#[doc(hidden)]
149#[cfg(all(feature = "with-deprecated", not(feature = "without-deprecated")))]
150#[deprecated(note = "Use `AggregateExpressionMethods::aggregate_distinct` instead")]
151pub fn count_distinct<T, E>(expr: E) -> CountDistinct<T, E::Expression>
152where
153    T: SqlType + SingleValue,
154    E: crate::expression::AsExpression<T>,
155{
156    use crate::AggregateExpressionMethods;
157
158    count(expr).aggregate_distinct()
159}
160
161#[doc(hidden)]
162#[cfg(all(feature = "with-deprecated", not(feature = "without-deprecated")))]
163pub type CountDistinct<T, E> = crate::dsl::AggregateDistinct<self::count<T, E>>;
diesel/expression/count.rs

diesel/expression/
count.rs
