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From Shay Assulin <SH...@il.ibm.com>
Subject Row cache
Date Thu, 30 Jun 2011 11:46:39 GMT
Hi,

I am running Cassandra 0.7.4 and I monitor the nodes using JConsole. 

I am trying to figure out  the location Cassandra read the returned rows 
and there are few strange things... 

1. I am reading few rows (using Hector) and the 
org.apache.cassandra.db.ColumnFamilies.<my-keyspace>.<my-cf>.ReadCount 
remains 0 -  It remains 0 with MEMTable and after flushing the MEMTable.
2. The column family  is configured to run with row-cache and key-cache 
and although I am reading the same row over and over the row-cache 
size/requests remains 0. The key-cache size/requests attributes are 
changed.





Why Cassandra does not cache a row that was requested few times?
What the ReadCount attribute in ColumnFamilies indicates and why it 
remains zero.
How can I know from where Cassandra read a row (from MEMTable,RowCache or 
SSTable)?
does the following correct? In read operation Cassandra looks for the row 
in the MEMTable - if not found it looks in the row-cache - if not found it 
looks in SSTable (after looking in the key-cache to optimize the access to 
the SSTable)? 

10x


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