How to use filters over atomic counter in hbase

Question

I'm using incr to increment a counter column in table.Now I need to filter certain records in scan so that counter is less than some value(say 1).get show the counter value(which is 4) for a particular row-key in hbase shell as below:

column=q:counter, timestamp=1419403701427, value=\x00\x00\x00\x00\x00\x00\x00\x04 

Now if use scan filter to filter exclude this record from scan as below

{FILTER=> "SingleColumnValueFilter('q','counter',<,'binary:1',true,true)" , COLUMNS=>['q:counter'] }

Above specify record with counter value 4 is still shown in scan result. I have tried true,false as third parameter of SingleColumnValueFilter.

Do I need to specify 1 in byte format or so?

Answer 1

For HBase the column value is just a byte[] so it's a bit tricky to make the query with the HBase Shell because the standard filter language will convert everything to strings: http://www.cloudera.com/content/cloudera/en/documentation/core/latest/topics/admin_hbase_filtering.html

To make it work with integers/longs we have to think of it as if we would do with JAVA: convert the value to a byte[] and feed it to a SingleColumnValueFilter with a CompareOp.

1. First you have to import the required libraries into HBase Shell

   import java.lang.Long
   import org.apache.hadoop.hbase.util.Bytes
   import org.apache.hadoop.hbase.filter.SingleColumnValueFilter
   import org.apache.hadoop.hbase.filter.CompareFilter
   import org.apache.hadoop.hbase.filter.BinaryComparator
   

2. To find rows with a value LESS than BINARY value of 20L \x00\x00\x00\x00\x00\x00\x00\x14

   scan "your_table", {LIMIT => 10, FILTER => SingleColumnValueFilter.new(Bytes.toBytes('Family'), Bytes.toBytes('Column'), CompareFilter::CompareOp.valueOf('LESS'), BinaryComparator.new(Bytes.toBytes(Long.parseLong("20"))))}

3. For integer columns the solution is a little easier (no Long parsing required). To find rows with a value LESS than BINARY value of 20 \x00\x00\x00\x14

   scan "your_table", {LIMIT => 10, FILTER => SingleColumnValueFilter.new(Bytes.toBytes('Family'), Bytes.toBytes('Column'), CompareFilter::CompareOp.valueOf('LESS'), BinaryComparator.new(Bytes.toBytes(20)))}

Valid compare operators:

• EQUAL
• GREATER
• GREATER_OR_EQUAL
• LESS
• LESS_OR_EQUAL
• NO_OP
• NOT_EQUAL