Apache Accumulo Combiner Example
This tutorial uses the following Java class, which can be found in org.apache.accumulo.examples.simple.combiner in the simple-examples module:
- StatsCombiner.java - a combiner that calculates max, min, sum, and count
This is a simple combiner example. To build this example run maven and then copy the produced jar into the accumulo lib dir. This is already done in the tar distribution.
$ bin/accumulo shell -u username Enter current password for 'username'@'instance': *** Shell - Apache Accumulo Interactive Shell - - version: 1.4.x - instance name: instance - instance id: 00000000-0000-0000-0000-000000000000 - - type 'help' for a list of available commands - username@instance> createtable runners username@instance runners> setiter -t runners -p 10 -scan -minc -majc -n decStats -class org.apache.accumulo.examples.simple.combiner.StatsCombiner Combiner that keeps track of min, max, sum, and count ----------> set StatsCombiner parameter all, set to true to apply Combiner to every column, otherwise leave blank. if true, columns option will be ignored.: ----------> set StatsCombiner parameter columns, <col fam>[:<col qual>]{,<col fam>[:<col qual>]} escape non aplhanum chars using %<hex>.: stat ----------> set StatsCombiner parameter radix, radix/base of the numbers: 10 username@instance runners> setiter -t runners -p 11 -scan -minc -majc -n hexStats -class org.apache.accumulo.examples.simple.combiner.StatsCombiner Combiner that keeps track of min, max, sum, and count ----------> set StatsCombiner parameter all, set to true to apply Combiner to every column, otherwise leave blank. if true, columns option will be ignored.: ----------> set StatsCombiner parameter columns, <col fam>[:<col qual>]{,<col fam>[:<col qual>]} escape non aplhanum chars using %<hex>.: hstat ----------> set StatsCombiner parameter radix, radix/base of the numbers: 16 username@instance runners> insert 123456 name first Joe username@instance runners> insert 123456 stat marathon 240 username@instance runners> scan 123456 name:first [] Joe 123456 stat:marathon [] 240,240,240,1 username@instance runners> insert 123456 stat marathon 230 username@instance runners> insert 123456 stat marathon 220 username@instance runners> scan 123456 name:first [] Joe 123456 stat:marathon [] 220,240,690,3 username@instance runners> insert 123456 hstat virtualMarathon 6a username@instance runners> insert 123456 hstat virtualMarathon 6b username@instance runners> scan 123456 hstat:virtualMarathon [] 6a,6b,d5,2 123456 name:first [] Joe 123456 stat:marathon [] 220,240,690,3
In this example a table is created and the example stats combiner is applied to the column family stat and hstat. The stats combiner computes min,max,sum, and count. It can be configured to use a different base or radix. In the example above the column family stat is configured for base 10 and the column family hstat is configured for base 16.
