implement array_upper

diesel/src/pg/expression/functions.rs

@@ -1390,3 +1390,36 @@ define_sql_function! {
     /// ```
     fn array_ndims<Arr: ArrayOrNullableArray + SingleValue>(arr: Arr) -> Integer;
 }
+
+#[cfg(feature = "postgres_backend")]
+define_sql_function! {
+    /// Returns the upper bound of the requested array
+    ///
+    /// This function returns null for dimensions that do not exist
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// # include!("../../doctest_setup.rs");
+    /// #
+    /// # fn main() {
+    /// #     run_test().unwrap();
+    /// # }
+    /// #
+    /// # fn run_test() -> QueryResult<()> {
+    /// #     use diesel::dsl::array_upper;
+    /// #     use diesel::sql_types::{Integer, Array};
+    /// #     let connection = &mut establish_connection();
+    /// let result = diesel::select(array_upper::<Array<Integer>, _, _>(vec![1, 2, 3], 1))
+    ///     .get_result::<Option<i32>>(connection)?;
+    /// assert_eq!(Some(3), result);
+    ///
+    /// // the array has only one dimension
+    /// let result = diesel::select(array_upper::<Array<Integer>, _, _>(vec![1, 2, 3], 2))
+    ///     .get_result::<Option<i32>>(connection)?;
+    /// assert_eq!(None, result);
+    /// #     Ok(())
+    /// # }
+    /// ```
+    fn array_upper<Arr: ArrayOrNullableArray + SingleValue>(array: Arr, dimension: Integer) -> Nullable<Integer>;
+}

diesel/src/pg/expression/helper_types.rs

@@ -435,6 +435,11 @@ pub type array_fill_with_lower_bound<E, A1, A2> =
 #[cfg(feature = "postgres_backend")]
 pub type array_lower<A, D> = super::functions::array_lower<SqlTypeOf<A>, A, D>;
 
+/// Return type of [`array_upper(array, bound)`](super::functions::array_upper())
+#[allow(non_camel_case_types)]
+#[cfg(feature = "postgres_backend")]
+pub type array_upper<A, D> = super::functions::array_upper<SqlTypeOf<A>, A, D>;
+
 /// Return type of [`array_position(array,element)`](super::functions::array_position)
 #[allow(non_camel_case_types)]
 #[cfg(feature = "postgres_backend")]

diesel_derives/tests/auto_type.rs

@@ -427,6 +427,7 @@ fn postgres_functions() -> _ {
         array_fill(pg_extras::id, pg_extras::array),
         array_fill_with_lower_bound(pg_extras::id, pg_extras::array, pg_extras::array),
         array_lower(pg_extras::array, 1_i32),
+        array_upper(pg_extras::array, 1_i32),
         array_position(pg_extras::array, pg_extras::id),
         array_position_with_subscript(pg_extras::array, pg_extras::id, pg_extras::id),
         array_positions(pg_extras::array, pg_extras::id),