Add SQL planner support for calling round function with two arguments (apache#2503)

* test

* specify correct signature for ROUND function

Can drop this after rebase on commit 8a29ed5 "Add SQL planner support for calling round function with two arguments (apache#2503)", first released in 8.0.0
(cherry picked from commit 8a29ed5)

# Conflicts:
#	datafusion/core/src/sql/planner.rs
#	datafusion/expr/src/function.rs

Author: andygrove

datafusion/core/src/sql/planner.rs

@@ -5052,6 +5052,10 @@ mod tests {
             name: TableReference,
         ) -> Option<Arc<dyn TableProvider>> {
             let schema = match name.table() {
+                "test_decimal" => Some(Schema::new(vec![
+                    Field::new("id", DataType::Int32, false),
+                    Field::new("price", DataType::Decimal(10, 2), false),
+                ])),
                 "person" => Some(Schema::new(vec![
                     Field::new("id", DataType::UInt32, false),
                     Field::new("first_name", DataType::Utf8, false),
@@ -5443,6 +5447,14 @@ mod tests {
         quick_test(sql, expected);
     }
 
+    #[tokio::test]
+    async fn round_decimal() {
+        let sql = "SELECT round(price/3, 2) FROM test_decimal";
+        let expected = "Projection: round(#test_decimal.price / Int64(3), Int64(2))\
+        \n  TableScan: test_decimal projection=None";
+        quick_test(sql, expected);
+    }
+
     #[ignore] // see https://github.com/apache/arrow-datafusion/issues/2469
     #[tokio::test]
     async fn aggregate_with_grouping_sets() {

datafusion/expr/src/function.rs

@@ -576,6 +576,8 @@ pub fn signature(fun: &BuiltinScalarFunction) -> Signature {
         ),
         BuiltinScalarFunction::Round => Signature::one_of(
             vec![
+                TypeSignature::Exact(vec![DataType::Float64, DataType::Int64]),
+                TypeSignature::Exact(vec![DataType::Float32, DataType::Int64]),
                 TypeSignature::Exact(vec![DataType::Float64]),
                 TypeSignature::Exact(vec![DataType::Float32]),
                 // NOTE: stub, won't execute