Github user rdblue commented on a diff in the pull request:
https://github.com/apache/spark/pull/19269#discussion_r140017014
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/WriteToDataSourceV2Command.scala
---
@@ -0,0 +1,114 @@
+/*
+ * 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
+ *
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+ */
+
+package org.apache.spark.sql.execution.datasources.v2
+
+import org.apache.spark.{SparkException, TaskContext}
+import org.apache.spark.internal.Logging
+import org.apache.spark.sql.{Row, SparkSession}
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.encoders.{ExpressionEncoder,
RowEncoder}
+import org.apache.spark.sql.catalyst.expressions.UnsafeRow
+import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
+import org.apache.spark.sql.execution.SparkPlan
+import org.apache.spark.sql.execution.command.RunnableCommand
+import org.apache.spark.sql.sources.v2.writer._
+import org.apache.spark.sql.types.StructType
+import org.apache.spark.util.Utils
+
+case class WriteToDataSourceV2Command(writer: DataSourceV2Writer, query:
LogicalPlan)
+ extends RunnableCommand {
--- End diff --
It isn't just the UI though. I've seen cases where
InsertIntoHadoopFsRelationCommand is run inside a
CreateDatasourceTableAsSelectCommand, and their enforcement of write modes
depend on one another. Our internal S3 committer updates partition information
and handles partition-level conflicts, but that requires that the table exists
before the write (to check what partitions already exist). When we moved table
creation in the CTAS command, it broke the insert into command, when these two
should be separate.
While it's convenient to have a logical plan and a physical plan together,
I think this ends up getting misused. That's why I'm advocating to change how
we use RunnableCommand. To fix it, we should introduce a node with a command
and logical plan, so we can optimize the entire plan and run the command at the
right time.
Clearly, this isn't a blocker for this PR, I just want to mention that I
see this pattern causing a lot of problems every time we pull in a new Spark
version.
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