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use super::Expression;
use backend::Backend;
use query_builder::*;
use result::QueryResult;
use sql_types::BigInt;
sql_function! {
/// Creates a SQL `COUNT` expression
///
/// As with most bare functions, this is not exported by default. You can import
/// it specifically as `diesel::dsl::count`, or glob import
/// `diesel::dsl::*`
///
/// # Examples
///
/// ```rust
/// # #[macro_use] extern crate diesel;
/// # include!("../doctest_setup.rs");
/// # use diesel::dsl::*;
/// #
/// # fn main() {
/// # use schema::animals::dsl::*;
/// # let connection = establish_connection();
/// assert_eq!(Ok(1), animals.select(count(name)).first(&connection));
/// # }
/// ```
#[aggregate]
fn count<T>(expr: T) -> BigInt;
}
/// Creates a SQL `COUNT(*)` expression
///
/// For selecting the count of a query, and nothing else, you can just call
/// [`count`](../query_dsl/trait.QueryDsl.html#method.count)
/// on the query instead.
///
/// As with most bare functions, this is not exported by default. You can import
/// it specifically as `diesel::dsl::count_star`, or glob import
/// `diesel::dsl::*`
///
/// # Examples
///
/// ```rust
/// # #[macro_use] extern crate diesel;
/// # include!("../doctest_setup.rs");
/// # use diesel::dsl::*;
/// #
/// # fn main() {
/// # use schema::users::dsl::*;
/// # let connection = establish_connection();
/// assert_eq!(Ok(2), users.select(count_star()).first(&connection));
/// # }
/// ```
pub fn count_star() -> CountStar {
CountStar
}
#[derive(Debug, Clone, Copy, QueryId, DieselNumericOps)]
#[doc(hidden)]
pub struct CountStar;
impl Expression for CountStar {
type SqlType = BigInt;
}
impl<DB: Backend> QueryFragment<DB> for CountStar {
fn walk_ast(&self, mut out: AstPass<DB>) -> QueryResult<()> {
out.push_sql("COUNT(*)");
Ok(())
}
}
impl_selectable_expression!(CountStar);