org.apache.spark.sql.execution.datasources.OutputWriter.scala Maven / Gradle / Ivy
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* 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,
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* See the License for the specific language governing permissions and
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*/
package org.apache.spark.sql.execution.datasources
import org.apache.hadoop.mapreduce.TaskAttemptContext
import org.apache.spark.sql.Row
import org.apache.spark.sql.catalyst.{CatalystTypeConverters, InternalRow}
import org.apache.spark.sql.types.StructType
/**
* A factory that produces [[OutputWriter]]s. A new [[OutputWriterFactory]] is created on driver
* side for each write job issued when writing to a [[HadoopFsRelation]], and then gets serialized
* to executor side to create actual [[OutputWriter]]s on the fly.
*/
abstract class OutputWriterFactory extends Serializable {
/** Returns the file extension to be used when writing files out. */
def getFileExtension(context: TaskAttemptContext): String
/**
* When writing to a [[HadoopFsRelation]], this method gets called by each task on executor side
* to instantiate new [[OutputWriter]]s.
*
* @param path Path to write the file.
* @param dataSchema Schema of the rows to be written. Partition columns are not included in the
* schema if the relation being written is partitioned.
* @param context The Hadoop MapReduce task context.
*/
def newInstance(
path: String,
dataSchema: StructType,
context: TaskAttemptContext): OutputWriter
}
/**
* [[OutputWriter]] is used together with [[HadoopFsRelation]] for persisting rows to the
* underlying file system. Subclasses of [[OutputWriter]] must provide a zero-argument constructor.
* An [[OutputWriter]] instance is created and initialized when a new output file is opened on
* executor side. This instance is used to persist rows to this single output file.
*/
abstract class OutputWriter {
/**
* Persists a single row. Invoked on the executor side. When writing to dynamically partitioned
* tables, dynamic partition columns are not included in rows to be written.
*/
def write(row: InternalRow): Unit
/**
* Closes the [[OutputWriter]]. Invoked on the executor side after all rows are persisted, before
* the task output is committed.
*/
def close(): Unit
}