Hbase quickly count number of rows

Question

Right now I implement row count over ResultScanner like this

for (Result rs = scanner.next(); rs != null; rs = scanner.next()) {
    number++;
}         


        

Answer 1

You can use the count method in hbase to count the number of rows. But yes, counting rows of a large table can be slow.count 'tablename' [interval]

Return value is the number of rows.

This operation may take a LONG time (Run ‘$HADOOP_HOME/bin/hadoop jar hbase.jar rowcount’ to run a counting mapreduce job). Current count is shown every 1000 rows by default. Count interval may be optionally specified. Scan caching is enabled on count scans by default. Default cache size is 10 rows. If your rows are small in size, you may want to increase this parameter.

Examples:

hbase> count 't1'

hbase> count 't1', INTERVAL => 100000

hbase> count 't1', CACHE => 1000

hbase> count 't1', INTERVAL => 10, CACHE => 1000

The same commands also can be run on a table reference. Suppose you had a reference to table 't1', the corresponding commands would be:

hbase> t.count

hbase> t.count INTERVAL => 100000

hbase> t.count CACHE => 1000

hbase> t.count INTERVAL => 10, CACHE => 1000