Github user rdblue commented on a diff in the pull request: https://github.com/apache/spark/pull/19269#discussion_r140371372 --- 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 -- Maybe Spark should be able to disable speculative tasks at runtime instead of requiring data sources to rollback. I'd prefer that, but I don't think it is something that needs to change now. We can always add an interface if/when it is supported that allows data sources to communicate a lack of support for speculation.
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