hbase-shell/src/main/ruby/shell/commands/count.rb

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module Shell
  module Commands
    class Count < Command
      def help
        <<-EOF
Count the number of rows in a table.  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.
Examples:

 hbase> count 'ns1:t1'
 hbase> count 't1'
 hbase> count 't1', INTERVAL => 100000
 hbase> count 't1', FILTER => "
    (QualifierFilter (>=, 'binary:xyz')) AND (TimestampsFilter ( 123, 456))"
 hbase> count 't1', COLUMNS => ['c1', 'c2'], STARTROW => 'abc', STOPROW => 'xyz'

The same commands also can be run on a table reference. Suppose you had a reference
t to table 't1', the corresponding commands would be:

 hbase> t.count
 hbase> t.count INTERVAL => 100000
 hbase> t.count FILTER => "
    (QualifierFilter (>=, 'binary:xyz')) AND (TimestampsFilter ( 123, 456))"
 hbase> t.count COLUMNS => ['c1', 'c2'], STARTROW => 'abc', STOPROW => 'xyz'

By default, this operation does not cause any new blocks to be read into
the RegionServer block cache. This is typically the desired action; however,
if you want to force all blocks for a table to be loaded into the block cache
on-demand, you can pass the 'CACHE_BLOCKS' option with a value of 'true'. A value
of 'false' is the default and will result in no blocks being cached. This
command can be used in conjunction with all other options.

hbase> count 'ns1:t1', CACHE_BLOCKS => true
hbase> count 'ns1:t1', CACHE_BLOCKS => 'true'
hbase> count 'ns1:t1', INTERVAL => 100000, CACHE_BLOCKS => false
EOF
      end

      def command(table, params = {})
        count(table(table), params)
      end

      def count(table, params = {})
        # If the second parameter is an integer, then it is the old command syntax
        params = { 'INTERVAL' => params } if params.is_a?(Integer)

        # Try to be nice and convert a string to a bool
        if params.include?('CACHE_BLOCKS') and params['CACHE_BLOCKS'].is_a?(String)
          if params['CACHE_BLOCKS'].downcase == 'true'
            params['CACHE_BLOCKS'] = true
          elsif params['CACHE_BLOCKS'].downcase == 'false'
            params['CACHE_BLOCKS'] = false
          else
            raise(ArgumentError, "Expected CACHE_BLOCKS value to be a boolean or the string 'true' or 'false'")
          end
        end

        # Merge params with defaults
        params = {
          'INTERVAL' => 1000,
          'CACHE_BLOCKS' => false
        }.merge(params)

        scan = table._hash_to_scan(params)
        # Call the counter method
        @start_time = Time.now
        formatter.header
        count = table._count_internal(params['INTERVAL'].to_i, scan, params['CACHE_BLOCKS']) do |cnt, row|
          formatter.row(["Current count: #{cnt}, row: #{row}"])
        end
        formatter.footer(count)
        count
      end
    end
  end
end

# Add the method table.count that calls count.count
::Hbase::Table.add_shell_command('count')