org.apache.parquet.hadoop.api.WriteSupport 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, 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.parquet.hadoop.api;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import org.apache.hadoop.conf.Configuration;
import org.apache.parquet.io.api.RecordConsumer;
import org.apache.parquet.schema.MessageType;
/**
* Abstraction to use with {@link org.apache.parquet.hadoop.ParquetOutputFormat} to convert incoming records
*
* @param the type of the incoming records
*/
abstract public class WriteSupport {
/**
* information to be persisted in the file
*/
public static final class WriteContext {
private final MessageType schema;
private final Map extraMetaData;
/**
* @param schema the schema of the data
* @param extraMetaData application specific metadata to add in the file
*
* @throws NullPointerException if schema or extraMetaData is {@code null}
*/
public WriteContext(MessageType schema, Map extraMetaData) {
super();
this.schema = Objects.requireNonNull(schema, "schema cannot be null");
this.extraMetaData = Collections.unmodifiableMap(Objects
.requireNonNull(extraMetaData, "extraMetaData cannot be null"));
}
/**
* @return the schema of the file
*/
public MessageType getSchema() {
return schema;
}
/**
* @return application specific metadata
*/
public Map getExtraMetaData() {
return extraMetaData;
}
}
/**
* Information to be added in the file once all the records have been written
*/
public static final class FinalizedWriteContext {
private final Map extraMetaData;
// this class exists to facilitate evolution of the API
// we can add more fields later
/**
* @param extraMetaData application specific metadata to add in the file
*
* @throws NullPointerException if extraMetaData is {@code null}
*/
public FinalizedWriteContext(Map extraMetaData) {
super();
this.extraMetaData = Collections.unmodifiableMap(Objects
.requireNonNull(extraMetaData, "extraMetaData cannot be null"));
}
/**
* @return application specific metadata
*/
public Map getExtraMetaData() {
return extraMetaData;
}
}
/**
* called first in the task
* @param configuration the job's configuration
* @return the information needed to write the file
*/
public abstract WriteContext init(Configuration configuration);
/**
* This will be called once per row group
* @param recordConsumer the recordConsumer to write to
*/
public abstract void prepareForWrite(RecordConsumer recordConsumer);
/**
* called once per record
* @param record one record to write to the previously provided record consumer
*/
public abstract void write(T record);
/**
* Called to get a name to identify the WriteSupport object model.
* If not null, this is added to the file footer metadata.
*
* Defining this method will be required in a future API version.
*
* @return a String name for file metadata.
*/
public String getName() {
return null;
}
/**
* called once in the end after the last record was written
* @return information to be added in the file
*/
public FinalizedWriteContext finalizeWrite() {
return new FinalizedWriteContext(new HashMap());
}
}