| Title: Apache Accumulo Table-to-File 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 to extract specified columns from an existing table. |
| |
| 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 dog cf cq dogvalue |
| username@instance> insert cat cf cq catvalue |
| username@instance> insert junk family qualifier junkvalue |
| username@instance> quit |
| |
| The TableToFile class configures a map-only job to read the specified columns and |
| write the key/value pairs to a file in HDFS. |
| |
| The following will extract the rows containing the column "cf:cq": |
| |
| $ bin/tool.sh lib/accumulo-examples-simple.jar org.apache.accumulo.examples.simple.mapreduce.TableToFile -u user -p passwd -i instance -t input --columns cf:cq --output /tmp/output |
| |
| $ hadoop fs -ls /tmp/output |
| -rw-r--r-- 1 username supergroup 0 2013-01-10 14:44 /tmp/output/_SUCCESS |
| drwxr-xr-x - username supergroup 0 2013-01-10 14:44 /tmp/output/_logs |
| drwxr-xr-x - username supergroup 0 2013-01-10 14:44 /tmp/output/_logs/history |
| -rw-r--r-- 1 username supergroup 9049 2013-01-10 14:44 /tmp/output/_logs/history/job_201301081658_0011_1357847072863_username_TableToFile%5F1357847071434 |
| -rw-r--r-- 1 username supergroup 26172 2013-01-10 14:44 /tmp/output/_logs/history/job_201301081658_0011_conf.xml |
| -rw-r--r-- 1 username supergroup 50 2013-01-10 14:44 /tmp/output/part-m-00000 |
| |
| We can see the output of our little map-reduce job: |
| |
| $ hadoop fs -text /tmp/output/output/part-m-00000 |
| catrow cf:cq [] catvalue |
| dogrow cf:cq [] dogvalue |
| $ |
| |
