jeffw13 commented on code in PR #5821:
URL: https://github.com/apache/datafusion-comet/pull/5821#discussion_r4009110950
##########
spark/src/main/scala/org/apache/comet/serde/operator/CometDataWritingCommand.scala:
##########
@@ -59,6 +62,14 @@ object CometDataWritingCommand extends
CometOperatorSerde[DataWritingCommandExec
case cmd: InsertIntoHadoopFsRelationCommand =>
cmd.fileFormat match {
case _: ParquetFileFormat =>
+ // AQE can replace the write input with a zero-partition empty
relation. Keep
+ // Spark's writer, which creates an empty task to preserve the
output file schema.
+ // The native writer only maps existing partitions and cannot do
that yet.
+ if (hasEmptyRelationInput(op.child)) {
Review Comment:
Yes, I've documented the trade-off we're making here further (that an empty
relation could ultimately produce a non zero-partition count) more and linked
to that open issue.
##########
docs/source/user-guide/latest/compatibility/operators.md:
##########
@@ -19,6 +19,19 @@ under the License.
# Operator Compatibility
+## Empty Relations
Review Comment:
I've added this documentation + the spark version note in
https://github.com/apache/datafusion-comet/pull/5821/changes/1296afd34d6caa8e19b53bd7b6d7ef3e8fcac441
##########
spark/src/main/spark-4.x/org/apache/spark/sql/comet/shims/ShimCometEmptyRelation.scala:
##########
@@ -0,0 +1,31 @@
+/*
+ * 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.
+ */
+
+package org.apache.spark.sql.comet.shims
+
+import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
+import org.apache.spark.sql.execution.{EmptyRelationExec, SparkPlan}
+
+/** EmptyRelationExec is available starting in Spark 4.0. */
+object ShimCometEmptyRelation {
+
+ def emptyRelationClass: Option[Class[_ <: SparkPlan]] =
Some(classOf[EmptyRelationExec])
+
+ def create(logical: LogicalPlan): Option[SparkPlan] =
Some(EmptyRelationExec(logical))
Review Comment:
Yes, this makes sense. I've moved them over to the spark-4.x location and
registered them, and removed the version conditional. I also split them into
three separate test suites.
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