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Subject svn commit: r1239400 - /incubator/accumulo/branches/1.4/docs/examples/README.mapred
Date Wed, 01 Feb 2012 23:29:27 GMT
Author: kturner
Date: Wed Feb  1 23:29:27 2012
New Revision: 1239400

ACCUMULO-278 updated mapred example to use combiners instead of aggregators


Modified: incubator/accumulo/branches/1.4/docs/examples/README.mapred
--- incubator/accumulo/branches/1.4/docs/examples/README.mapred (original)
+++ incubator/accumulo/branches/1.4/docs/examples/README.mapred Wed Feb  1 23:29:27 2012
@@ -18,7 +18,7 @@ Notice:    Licensed to the Apache Softwa
 This example uses mapreduce and accumulo to compute word counts for a set of
 documents.  This is accomplished using a map-only mapreduce job and a
-accumulo table with aggregators.
+accumulo table with combiners.
 To run this example you will need a directory in HDFS containing text files.
 The accumulo readme will be used to show how to run this example.
@@ -28,7 +28,7 @@ The accumulo readme will be used to show
     Found 1 items
     -rw-r--r--   2 username supergroup       9359 2009-07-15 17:54 /user/username/wc/Accumulo.README
-The first part of running this example is to create a table with aggregation
+The first part of running this example is to create a table with a combiner
 for the column family count.
     $ ./bin/accumulo shell -u username -p password
@@ -39,7 +39,13 @@ for the column family count.
     - type 'help' for a list of available commands
-    username@instance> createtable wordCount -a count=org.apache.accumulo.core.iterators.aggregation.StringSummation

+    username@instance> createtable wordCount
+    username@instance wordCount> setiter -class org.apache.accumulo.core.iterators.user.SummingCombiner
-p 10 -t wordCount -majc -minc -scan
+    SummingCombiner interprets Values as Longs and adds them together.  A variety of encodings
(variable length, fixed length, or string) are available
+    ----------> set SummingCombiner parameter all, set to true to apply Combiner to every
column, otherwise leave blank. if true, columns option will be ignored.: false
+    ----------> set SummingCombiner parameter columns, <col fam>[:<col qual>]{,<col
fam>[:<col qual>]} escape non-alphanum chars using %<hex>.: count
+    ----------> set SummingCombiner parameter lossy, if true, failed decodes are ignored.
Otherwise combiner will error on failed decodes (default false): <TRUE|FALSE>: false

+    ----------> set SummingCombiner parameter type, <VARLEN|FIXEDLEN|STRING|fullClassName>:
     username@instance wordCount> quit
 After creating the table, run the word count map reduce job.

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