Ah ha! Thank you for the prompt and useful response :-)
The reverse timestamp key does the trick. Thank you!
So, Filters are not run on the Client. For example, a
SingleColumnValueFilter does its comparisons on the Server and is
reasonably efficient. Is this correct?
P
On 1/5/12 5:23 PM, Leonardo Gamas wrote:
1) Filters are applied direct in the RegionServer:
http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/filter/Filter.html
2) You can reverse the timestamp:
http://hbase.apache.org/book/rowkey.design.html#reverse.timestamp
So you will have the rowkey:<accountID><reverse timestamp>
In the scan you set the caching attribute to 100, so the matches will be
transfered to the client in a single trip, but you need to count the number
of times you call the next in the scanner to don't exceed the cache and
cause a new call to the regionserver.
2012/1/5 Peter Wolf<[email protected]>
Hello all,
I am a new HBase user with a familiar problem. I need to efficiently
return the last 100 rows from an account. I searched the archives, and
read the book, but did not find a complete answer.
I have a table of interactions with my users. One row per interaction.
I am using a composite Row Key of the form
<accountID><timestamp>
So using partial row key scans I can efficiently get all the rows for an
account.
Unfortunately, I do not know how to relate row count to timestamp, so I
have to get all the rows. I then use a PageFilter to get only the last 100.
However, I believe that Filters operate on the Client side, so all of the
rows get transmitted. I believe this is not efficient.
I have two questions--
1) Am I correct that my solution is not efficient, and I need to filter at
the Server?
2) If so, is there a "best practice" for this problem?
Thanks in advance
Peter
