http://www.datastax.com/support-forums/topic/range-query-with-reverse-true Software, Support, and Training for Apache Cassandra en-US Mon, 20 May 2013 01:58:47 +0000 http://bbpress.org/?v=1.0.3 q http://www.datastax.com/support-forums/search.php http://www.datastax.com/support-forums/topic/range-query-with-reverse-true#post-1041 Tue, 10 Jan 2012 20:34:33 +0000 Anonymous 1041@http://www.datastax.com/support-forums/ <p>I have 2 different flavors of CF with the same data</p> <p>create column family story_top_ten_covisited<br /> with column_type = 'Standard'<br /> and comparator = 'CompositeType(org.apache.cassandra.db.marshal.ReversedType(org.apache.cassandra.db.marshal.LongType),org.apache.cassandra.db.marshal.UTF8Type)'<br /> and default_validation_class = 'UTF8Type'</p> <p>create column family story_top_ten_covisited_increasing<br /> with column_type = 'Standard'<br /> and comparator = 'CompositeType(org.apache.cassandra.db.marshal.LongType,org.apache.cassandra.db.marshal.UTF8Type)'<br /> and default_validation_class = 'UTF8Type'<br /> and key_validation_class = 'UTF8Type'</p> <p>Both are similar in all respects , apart from the org.apache.cassandra.db.marshal.ReversedType(org.apache.cassandra.db.marshal.LongType) in the first CF.</p> <p>I run Hector code </p> <p>MultigetSliceQuery&lt;String,Composite,String&gt; multigetSliceQuery =<br /> HFactory.createMultigetSliceQuery(keyspace, StringSerializer.get(), cs,StringSerializer.get());<br /> multigetSliceQuery.setColumnFamily(CF_TT);<br /> multigetSliceQuery.setKeys(getKeysFromStories(recentStories));<br /> multigetSliceQuery.setRange(null, null , true , 10);<br /> QueryResult&lt;Rows&lt;String, Composite,String&gt;&gt; q = multigetSliceQuery.execute();</p> <p>with reverse true or false.</p> <p>I see that when reverse = true is outperforming reverse=false ( in both cases ) by a factor of 30 .... </p> <p>I am using version 1.0.5. I would have assumed and ( <a href="http://thelastpickle.com/2011/10/03/Reverse-Comparators/" rel="nofollow">http://thelastpickle.com/2011/10/03/Reverse-Comparators/</a> ) supports the natural intuition , that if I want my composite keys to be in descending , based on the first key, I would be better off using "reversed = true" in my CF creation script and than use "false" in my Hector range query.</p> <p>The tests show that assumption is incorrect. </p> <p>Is there a gap in my understanding here ? </p>