[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #2486: Add SQL planner support for `grouping()` aggregate expressions

[GitBox <gi...@apache.org>]

alamb commented on code in PR #2486:
URL: https://github.com/apache/arrow-datafusion/pull/2486#discussion_r869660880


##########
datafusion/physical-expr/src/aggregate/grouping.rs:
##########
@@ -0,0 +1,93 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+//! Defines physical expressions that can evaluated at runtime during query execution
+
+use std::any::Any;
+use std::sync::Arc;
+
+use crate::{AggregateExpr, PhysicalExpr};
+use arrow::datatypes::DataType;
+use arrow::datatypes::Field;
+use datafusion_common::{DataFusionError, Result};
+use datafusion_expr::Accumulator;
+
+use crate::expressions::format_state_name;
+
+/// GROUPING aggregate expression
+/// Returns the amount of non-null values of the given expression.
+#[derive(Debug)]
+pub struct Grouping {
+    name: String,
+    data_type: DataType,
+    nullable: bool,
+    expr: Arc<dyn PhysicalExpr>,
+}
+
+impl Grouping {
+    /// Create a new GROUPING aggregate function.
+    pub fn new(
+        expr: Arc<dyn PhysicalExpr>,
+        name: impl Into<String>,
+        data_type: DataType,
+    ) -> Self {
+        Self {
+            name: name.into(),
+            expr,
+            data_type,
+            nullable: true,
+        }
+    }
+}
+
+impl AggregateExpr for Grouping {
+    /// Return a reference to Any that can be used for downcasting
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+
+    fn field(&self) -> Result<Field> {
+        Ok(Field::new(
+            &self.name,
+            self.data_type.clone(),
+            self.nullable,
+        ))
+    }
+
+    fn state_fields(&self) -> Result<Vec<Field>> {
+        Ok(vec![Field::new(
+            &format_state_name(&self.name, "grouping"),
+            self.data_type.clone(),
+            true,
+        )])
+    }
+
+    fn expressions(&self) -> Vec<Arc<dyn PhysicalExpr>> {
+        vec![self.expr.clone()]
+    }
+
+    fn create_accumulator(&self) -> Result<Box<dyn Accumulator>> {
+        Err(DataFusionError::NotImplemented(

Review Comment:
   👍 
   I see -- I was going to suggest adding a test to `sql_integ` but it isn't ready yet 👍 



-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: github-unsubscribe@arrow.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org