Github user rdblue commented on a diff in the pull request:
https://github.com/apache/spark/pull/19269#discussion_r139836068
--- Diff:
sql/core/src/main/java/org/apache/spark/sql/sources/v2/writer/DataSourceV2Writer.java
---
@@ -0,0 +1,71 @@
+/*
+ * 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.sources.v2.writer;
+
+import org.apache.spark.annotation.InterfaceStability;
+import org.apache.spark.sql.Row;
+import org.apache.spark.sql.SaveMode;
+import org.apache.spark.sql.sources.v2.DataSourceV2Options;
+import org.apache.spark.sql.sources.v2.WriteSupport;
+import org.apache.spark.sql.types.StructType;
+
+/**
+ * A data source writer that is returned by
+ * {@link WriteSupport#createWriter(StructType, SaveMode,
DataSourceV2Options)}.
+ * It can mix in various writing optimization interfaces to speed up the
data saving. The actual
+ * writing logic is delegated to {@link WriteTask} that is returned by
{@link #createWriteTask()}.
+ *
+ * The writing procedure is:
+ * 1. Create a write task by {@link #createWriteTask()}, serialize and
send it to all the
+ * partitions of the input data(RDD).
+ * 2. For each partition, create a data writer with the write task, and
write the data of the
--- End diff --
How does this handle speculative execution? This description makes it sound
like attempts are only run serially. I'd like to have an interface that signals
support for concurrent tasks, for data sources that act like the direct
committer and can't handle speculation.
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