org.apache.hadoop.hbase.mapreduce.GroupingTableMapper 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.hadoop.hbase.mapreduce;
import java.io.IOException;
import java.util.ArrayList;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.classification.InterfaceStability;
import org.apache.hadoop.conf.Configurable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.CellUtil;
import org.apache.hadoop.hbase.KeyValue;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.mapreduce.Job;
/**
* Extract grouping columns from input record.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public class GroupingTableMapper
extends TableMapper implements Configurable {
/**
* JobConf parameter to specify the columns used to produce the key passed to
* collect from the map phase.
*/
public static final String GROUP_COLUMNS =
"hbase.mapred.groupingtablemap.columns";
/** The grouping columns. */
protected byte [][] columns;
/** The current configuration. */
private Configuration conf = null;
/**
* Use this before submitting a TableMap job. It will appropriately set up
* the job.
*
* @param table The table to be processed.
* @param scan The scan with the columns etc.
* @param groupColumns A space separated list of columns used to form the
* key used in collect.
* @param mapper The mapper class.
* @param job The current job.
* @throws IOException When setting up the job fails.
*/
@SuppressWarnings("unchecked")
public static void initJob(String table, Scan scan, String groupColumns,
Class mapper, Job job) throws IOException {
TableMapReduceUtil.initTableMapperJob(table, scan, mapper,
ImmutableBytesWritable.class, Result.class, job);
job.getConfiguration().set(GROUP_COLUMNS, groupColumns);
}
/**
* Extract the grouping columns from value to construct a new key. Pass the
* new key and value to reduce. If any of the grouping columns are not found
* in the value, the record is skipped.
*
* @param key The current key.
* @param value The current value.
* @param context The current context.
* @throws IOException When writing the record fails.
* @throws InterruptedException When the job is aborted.
*/
@Override
public void map(ImmutableBytesWritable key, Result value, Context context)
throws IOException, InterruptedException {
byte[][] keyVals = extractKeyValues(value);
if(keyVals != null) {
ImmutableBytesWritable tKey = createGroupKey(keyVals);
context.write(tKey, value);
}
}
/**
* Extract columns values from the current record. This method returns
* null if any of the columns are not found.
*
* Override this method if you want to deal with nulls differently.
*
* @param r The current values.
* @return Array of byte values.
*/
protected byte[][] extractKeyValues(Result r) {
byte[][] keyVals = null;
ArrayList foundList = new ArrayList();
int numCols = columns.length;
if (numCols > 0) {
for (Cell value: r.listCells()) {
byte [] column = KeyValue.makeColumn(CellUtil.cloneFamily(value),
CellUtil.cloneQualifier(value));
for (int i = 0; i < numCols; i++) {
if (Bytes.equals(column, columns[i])) {
foundList.add(CellUtil.cloneValue(value));
break;
}
}
}
if(foundList.size() == numCols) {
keyVals = foundList.toArray(new byte[numCols][]);
}
}
return keyVals;
}
/**
* Create a key by concatenating multiple column values.
*
* Override this function in order to produce different types of keys.
*
* @param vals The current key/values.
* @return A key generated by concatenating multiple column values.
*/
protected ImmutableBytesWritable createGroupKey(byte[][] vals) {
if(vals == null) {
return null;
}
StringBuilder sb = new StringBuilder();
for(int i = 0; i < vals.length; i++) {
if(i > 0) {
sb.append(" ");
}
sb.append(Bytes.toString(vals[i]));
}
return new ImmutableBytesWritable(Bytes.toBytesBinary(sb.toString()));
}
/**
* Returns the current configuration.
*
* @return The current configuration.
* @see org.apache.hadoop.conf.Configurable#getConf()
*/
@Override
public Configuration getConf() {
return conf;
}
/**
* Sets the configuration. This is used to set up the grouping details.
*
* @param configuration The configuration to set.
* @see org.apache.hadoop.conf.Configurable#setConf(
* org.apache.hadoop.conf.Configuration)
*/
@Override
public void setConf(Configuration configuration) {
this.conf = configuration;
String[] cols = conf.get(GROUP_COLUMNS, "").split(" ");
columns = new byte[cols.length][];
for(int i = 0; i < cols.length; i++) {
columns[i] = Bytes.toBytes(cols[i]);
}
}
}