implement array_shuffle

diesel/src/pg/expression/functions.rs

@@ -1423,3 +1423,30 @@ define_sql_function! {
     /// ```
     fn array_upper<Arr: ArrayOrNullableArray + SingleValue>(array: Arr, dimension: Integer) -> Nullable<Integer>;
 }
+
+#[cfg(feature = "postgres_backend")]
+define_sql_function! {
+    /// Randomly shuffles the first dimension of the array.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # include!("../../doctest_setup.rs");
+    /// #
+    /// # fn main() {
+    /// #     run_test().unwrap();
+    /// # }
+    /// #
+    /// # fn run_test() -> QueryResult<()> {
+    /// #     use diesel::dsl::array_shuffle;
+    /// #     use diesel::sql_types::{Array, Integer};
+    /// #     let connection = &mut establish_connection();
+    /// let shuffled = diesel::select(array_shuffle::<Array<Integer>, _>(vec![1, 2, 3, 4, 5]))
+    ///     .get_result::<Vec<i32>>(connection)?;
+    /// assert_eq!(5, shuffled.len());
+    /// assert!(shuffled != vec![1, 2, 3, 4, 5]);  // It's very unlikely to get the same order
+    /// #     Ok(())
+    /// # }
+    /// ```
+    fn array_shuffle<Arr: ArrayOrNullableArray + SingleValue>(array: Arr) -> Arr;
+}

diesel/src/pg/expression/helper_types.rs

@@ -461,3 +461,8 @@ pub type array_positions<A, E> =
 #[allow(non_camel_case_types)]
 #[cfg(feature = "postgres_backend")]
 pub type array_ndims<A> = super::functions::array_ndims<SqlTypeOf<A>, A>;
+
+/// Return type of [`array_shuffle(array)`](super::functions::array_shuffle())
+#[allow(non_camel_case_types)]
+#[cfg(feature = "postgres_backend")]
+pub type array_shuffle<A> = super::functions::array_shuffle<SqlTypeOf<A>, A>;

diesel_derives/tests/auto_type.rs

@@ -432,6 +432,7 @@ fn postgres_functions() -> _ {
         array_position_with_subscript(pg_extras::array, pg_extras::id, pg_extras::id),
         array_positions(pg_extras::array, pg_extras::id),
         array_ndims(pg_extras::array),
+        array_shuffle(pg_extras::array),
     )
 }