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#[cfg(doc)]
use super::aggregate_expressions::{AggregateExpressionMethods, WindowExpressionMethods};
use crate::expression::functions::declare_sql_function;
use crate::sql_types::Foldable;
#[declare_sql_function]
extern "SQL" {
/// Represents a SQL `SUM` function. This function can only take types which are
/// Foldable.
///
/// ## Window Function Usage
///
/// This function can be used as window function. See [`WindowExpressionMethods`] for details
///
/// ## Aggregate Function Expression
///
/// This function can be used as aggregate expression. See [`AggregateExpressionMethods`] for details.
///
/// # Examples
///
/// ## Normal function usage
///
/// ```rust
/// # include!("../../doctest_setup.rs");
/// # use diesel::dsl::*;
/// #
/// # fn main() {
/// # use schema::animals::dsl::*;
/// # let connection = &mut establish_connection();
/// assert_eq!(Ok(Some(12i64)), animals.select(sum(legs)).first(connection));
/// # }
/// ```
///
/// ## Window function
///
/// ```rust
/// # include!("../../doctest_setup.rs");
/// # use diesel::dsl::*;
/// #
/// # fn main() {
/// # use schema::animals::dsl::*;
/// # let connection = &mut establish_connection();
/// let res = animals
/// .select((name, sum(legs).partition_by(id)))
/// .load::<(Option<String>, Option<i64>)>(connection);
///
/// assert_eq!(
/// Ok(vec![(Some("Jack".into()), Some(4)), (None, Some(8))]),
/// res
/// );
/// # }
/// ```
///
/// ## Aggregate function expression
///
/// ```rust
/// # include!("../../doctest_setup.rs");
/// # use diesel::dsl::*;
/// #
/// # fn main() {
/// # use schema::animals::dsl::*;
/// # let connection = &mut establish_connection();
/// # #[cfg(not(feature = "mysql"))]
/// assert_eq!(
/// Ok(Some(4i64)),
/// animals
/// .select(sum(legs).aggregate_filter(legs.lt(8)))
/// .first(connection)
/// );
/// # }
/// ```
#[aggregate]
#[window]
fn sum<ST: Foldable>(expr: ST) -> ST::Sum;
/// Represents a SQL `AVG` function. This function can only take types which are
/// Foldable.
///
/// ## Window Function Usage
///
/// This function can be used as window function. See [`WindowExpressionMethods`] for details
///
/// ## Aggregate Function Expression
///
/// This function can be used as aggregate expression. See [`AggregateExpressionMethods`] for details.
///
/// # Examples
///
/// ## Normal function usage
///
/// ```rust
/// # include!("../../doctest_setup.rs");
/// # use diesel::dsl::*;
/// # #[cfg(feature = "numeric")]
/// # extern crate bigdecimal;
/// #
/// # fn main() {
/// # run_test().unwrap();
/// # }
/// #
/// # table! {
/// # numbers (number) {
/// # number -> Integer,
/// # }
/// # }
/// #
/// # #[cfg(all(feature = "numeric", any(feature = "postgres", not(feature = "sqlite"))))]
/// # fn run_test() -> QueryResult<()> {
/// # use bigdecimal::BigDecimal;
/// # use self::numbers::dsl::*;
/// # let conn = &mut establish_connection();
/// # diesel::sql_query("CREATE TEMPORARY TABLE numbers (number INTEGER)").execute(conn)?;
/// diesel::insert_into(numbers)
/// .values(&vec![number.eq(1), number.eq(2)])
/// .execute(conn)?;
/// let average = numbers.select(avg(number)).get_result(conn)?;
/// let expected = "1.5".parse::<BigDecimal>().unwrap();
/// assert_eq!(Some(expected), average);
/// # Ok(())
/// # }
/// #
/// # #[cfg(not(all(feature = "numeric", any(feature = "postgres", not(feature = "sqlite")))))]
/// # fn run_test() -> QueryResult<()> {
/// # Ok(())
/// # }
/// ```
///
/// ## Window function
///
/// ```rust
/// # include!("../../doctest_setup.rs");
/// # use diesel::dsl::*;
/// #
/// # fn main() {
/// # run_test().unwrap();
/// # }
/// #
/// # #[cfg(not(all(feature = "numeric", feature = "postgres")))]
/// # fn run_test() -> QueryResult<()> {
/// # Ok(())
/// # }
/// # #[cfg(all(feature = "numeric", feature = "postgres"))]
/// fn run_test() -> QueryResult<()> {
/// # use schema::animals::dsl::*;
/// # use bigdecimal::BigDecimal;
/// # let connection = &mut establish_connection();
/// let res = animals.select((name, avg(legs).partition_by(id))).load::<(Option<String>, Option<BigDecimal>)>(connection)?;
///
/// assert_eq!(vec![
/// (Some("Jack".into()), "4".parse::<BigDecimal>().ok()),
/// (None, "8".parse::<BigDecimal>().ok()),
/// ], res);
/// # Ok(())
/// # }
/// ```
///
/// ## Aggregate function expression
///
/// ```rust
/// # include!("../../doctest_setup.rs");
/// # use diesel::dsl::*;
/// # #[cfg(feature = "numeric")]
/// # extern crate bigdecimal;
/// #
/// # fn main() {
/// # run_test().unwrap();
/// # }
/// #
/// # table! {
/// # numbers (number) {
/// # number -> Integer,
/// # }
/// # }
/// #
/// # #[cfg(all(feature = "numeric", feature = "postgres"))]
/// # fn run_test() -> QueryResult<()> {
/// # use bigdecimal::BigDecimal;
/// # use self::numbers::dsl::*;
/// # let conn = &mut establish_connection();
/// # diesel::sql_query("CREATE TEMPORARY TABLE numbers (number INTEGER)").execute(conn)?;
/// diesel::insert_into(numbers)
/// .values(&vec![number.eq(1), number.eq(2), number.eq(3)])
/// .execute(conn)?;
///
/// let average = numbers.select(avg(number).aggregate_filter(number.lt(3))).get_result(conn)?;
/// let expected = "1.5".parse::<BigDecimal>().unwrap();
/// assert_eq!(Some(expected), average);
/// # Ok(())
/// # }
/// #
/// # #[cfg(not(all(feature = "numeric", feature = "postgres")))]
/// # fn run_test() -> QueryResult<()> {
/// # Ok(())
/// # }
#[aggregate]
#[window]
fn avg<ST: Foldable>(expr: ST) -> ST::Avg;
}