Apache Accumulo™

Title: Apache Accumulo Regex Example Notice: 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.

This example uses mapreduce and accumulo to find items using regular expressions. This is accomplished using a map-only mapreduce job and a scan-time iterator.

To run this example you will need some data in a table. The following will put a trivial amount of data into accumulo using the accumulo shell:

$ ./bin/accumulo shell -u username -p password
Shell - Apache Accumulo Interactive Shell
- version: 1.5.0
- instance name: instance
- instance id: 00000000-0000-0000-0000-000000000000
- type 'help' for a list of available commands
username@instance> createtable input
username@instance> insert dogrow dogcf dogcq dogvalue
username@instance> insert catrow catcf catcq catvalue
username@instance> quit

The RegexExample class sets an iterator on the scanner. This does pattern matching against each key/value in accumulo, and only returns matching items. It will do this in parallel and will store the results in files in hdfs.

The following will search for any rows in the input table that starts with “dog”:

$ bin/tool.sh lib/accumulo-examples-simple.jar org.apache.accumulo.examples.simple.mapreduce.RegexExample -u user -p passwd -i instance -t input --rowRegex 'dog.*' --output /tmp/output

$ hadoop fs -ls /tmp/output
Found 3 items
-rw-r--r--   1 username supergroup          0 2013-01-10 14:11 /tmp/output/_SUCCESS
drwxr-xr-x   - username supergroup          0 2013-01-10 14:10 /tmp/output/_logs
-rw-r--r--   1 username supergroup         51 2013-01-10 14:10 /tmp/output/part-m-00000

We can see the output of our little map-reduce job:

$ hadoop fs -text /tmp/output/part-m-00000
dogrow dogcf:dogcq [] 1357844987994 false	dogvalue