Index: src/docbkx/performance.xml
===================================================================
--- src/docbkx/performance.xml (revision 1098694)
+++ src/docbkx/performance.xml (working copy)
@@ -189,6 +189,16 @@
have the cache value be large because it costs more in memory for both
client and RegionServer, so bigger isn't always better.
+
+ Scan Attribute Selection
+
+ Whenever a Scan is used to process large numbers of rows (and especially when used
+ as a MapReduce source), be aware of which attributes are selected. If scan.addFamily is called
+ then all of the attributes in the specified ColumnFamily will be returned to the client.
+ If only a small number of the available attributes are to be processed, then only those attributes should be specified
+ in the input scan because attribute over-selection is a non-trivial performance penalty over large datasets.
+
+