[GitHub] [arrow-datafusion] Dandandan commented on a change in pull request #543: Ballista: Implement map-side shuffle

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

Dandandan commented on a change in pull request #543:
URL: https://github.com/apache/arrow-datafusion/pull/543#discussion_r650512654



##########
File path: ballista/rust/core/src/execution_plans/query_stage.rs
##########
@@ -150,32 +159,150 @@ impl ExecutionPlan for QueryStageExec {
                     stats
                 );
 
-                let schema = Arc::new(Schema::new(vec![
-                    Field::new("path", DataType::Utf8, false),
-                    stats.arrow_struct_repr(),
-                ]));
+                let schema = result_schema();
 
                 // build result set with summary of the partition execution status
-                let mut c0 = StringBuilder::new(1);
-                c0.append_value(&path).unwrap();
-                let path: ArrayRef = Arc::new(c0.finish());
+                let mut part_builder = UInt32Builder::new(1);
+                part_builder.append_value(partition as u32)?;
+                let part: ArrayRef = Arc::new(part_builder.finish());
+
+                let mut path_builder = StringBuilder::new(1);
+                path_builder.append_value(&path).unwrap();
+                let path: ArrayRef = Arc::new(path_builder.finish());
 
                 let stats: ArrayRef = stats
                     .to_arrow_arrayref()
                     .map_err(|e| DataFusionError::Execution(format!("{:?}", e)))?;
-                let batch = RecordBatch::try_new(schema.clone(), vec![path, stats])
+                let batch = RecordBatch::try_new(schema.clone(), vec![part, path, stats])
                     .map_err(DataFusionError::ArrowError)?;
 
                 Ok(Box::pin(MemoryStream::try_new(vec![batch], schema, None)?))
             }
 
-            Some(Partitioning::Hash(_, _)) => {
-                //TODO re-use code from RepartitionExec to split each batch into
-                // partitions and write to one IPC file per partition
-                // See https://github.com/apache/arrow-datafusion/issues/456
-                Err(DataFusionError::NotImplemented(
-                    "Shuffle partitioning not implemented yet".to_owned(),
-                ))
+            Some(Partitioning::Hash(exprs, n)) => {
+                let num_output_partitions = *n;
+
+                // we won't necessary produce output for every possible partition, so we
+                // create writers on demand
+                let mut writers: Vec<Option<Arc<Mutex<ShuffleWriter>>>> = vec![];
+                for _ in 0..num_output_partitions {
+                    writers.push(None);
+                }
+
+                let hashes_buf = &mut vec![];
+                let random_state = ahash::RandomState::with_seeds(0, 0, 0, 0);
+                while let Some(result) = stream.next().await {
+                    let input_batch = result?;
+                    let arrays = exprs
+                        .iter()
+                        .map(|expr| {
+                            Ok(expr
+                                .evaluate(&input_batch)?
+                                .into_array(input_batch.num_rows()))
+                        })
+                        .collect::<Result<Vec<_>>>()?;
+                    hashes_buf.clear();

Review comment:
       Maybe we could reuse the code better at some moment?




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