org.apache.hadoop.hbase.client.coprocessor
Class AggregationClient

java.lang.Object
  org.apache.hadoop.hbase.client.coprocessor.AggregationClient

@InterfaceAudience.Public
@InterfaceStability.Evolving
public class AggregationClient
extends Object

This client class is for invoking the aggregate functions deployed on the Region Server side via the AggregateService. This class will implement the supporting functionality for summing/processing the individual results obtained from the AggregateService for each region.

This will serve as the client side handler for invoking the aggregate functions.

For all aggregate functions,
• start row < end row is an essential condition (if they are not HConstants.EMPTY_BYTE_ARRAY)
• Column family can't be null. In case where multiple families are provided, an IOException will be thrown. An optional column qualifier can also be defined.
• For methods to find maximum, minimum, sum, rowcount, it returns the parameter type. For average and std, it returns a double value. For row count, it returns a long value.

  Constructor Summary

  AggregationClient(org.apache.hadoop.conf.Configuration cfg)
  Constructor with Conf object

  Method Summary

  <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> double	avg(byte[] tableName, ColumnInterpreter<R,S,P,Q,T> ci, Scan scan) This is the client side interface/handle for calling the average method for a given cf-cq combination.
  <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> R	max(byte[] tableName, ColumnInterpreter<R,S,P,Q,T> ci, Scan scan) It gives the maximum value of a column for a given column family for the given range.
  <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> R	median(byte[] tableName, ColumnInterpreter<R,S,P,Q,T> ci, Scan scan) This is the client side interface/handler for calling the median method for a given cf-cq combination.
  <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> R	min(byte[] tableName, ColumnInterpreter<R,S,P,Q,T> ci, Scan scan) It gives the minimum value of a column for a given column family for the given range.
  <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> long	rowCount(byte[] tableName, ColumnInterpreter<R,S,P,Q,T> ci, Scan scan) It gives the row count, by summing up the individual results obtained from regions.
  <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> double	std(byte[] tableName, ColumnInterpreter<R,S,P,Q,T> ci, Scan scan) This is the client side interface/handle for calling the std method for a given cf-cq combination.
  <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> S	sum(byte[] tableName, ColumnInterpreter<R,S,P,Q,T> ci, Scan scan) It sums up the value returned from various regions.

  Methods inherited from class java.lang.Object

  clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  Constructor Detail

  AggregationClient

  public AggregationClient(org.apache.hadoop.conf.Configuration cfg)

  Constructor with Conf object

  Parameters:

  cfg -

  Method Detail

  max

  public <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> R max(byte[] tableName,
                                                                                                                                       ColumnInterpreter<R,S,P,Q,T> ci,
                                                                                                                                       Scan scan)
        throws Throwable

  It gives the maximum value of a column for a given column family for the given range. In case qualifier is null, a max of all values for the given family is returned.

  Parameters:

  tableName -

  ci -

  scan -

  Returns:

  max val

  Throws:

  Throwable - The caller is supposed to handle the exception as they are thrown & propagated to it.

  min

  public <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> R min(byte[] tableName,
                                                                                                                                       ColumnInterpreter<R,S,P,Q,T> ci,
                                                                                                                                       Scan scan)
        throws Throwable

  It gives the minimum value of a column for a given column family for the given range. In case qualifier is null, a min of all values for the given family is returned.

  Parameters:

  tableName -

  ci -

  scan -

  Returns:

  min val

  Throws:

  Throwable

  rowCount

  public <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> long rowCount(byte[] tableName,
                                                                                                                                               ColumnInterpreter<R,S,P,Q,T> ci,
                                                                                                                                               Scan scan)
                throws Throwable

  It gives the row count, by summing up the individual results obtained from regions. In case the qualifier is null, FirstKeyValueFilter is used to optimised the operation. In case qualifier is provided, I can't use the filter as it may set the flag to skip to next row, but the value read is not of the given filter: in this case, this particular row will not be counted ==> an error.

  Parameters:

  tableName -

  ci -

  scan -

  Returns:

  Throws:

  Throwable

  sum

  public <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> S sum(byte[] tableName,
                                                                                                                                       ColumnInterpreter<R,S,P,Q,T> ci,
                                                                                                                                       Scan scan)
        throws Throwable

  It sums up the value returned from various regions. In case qualifier is null, summation of all the column qualifiers in the given family is done.

  Parameters:

  tableName -

  ci -

  scan -

  Returns:

  sum

  Throws:

  Throwable

  avg

  public <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> double avg(byte[] tableName,
                                                                                                                                            ColumnInterpreter<R,S,P,Q,T> ci,
                                                                                                                                            Scan scan)
             throws Throwable

  This is the client side interface/handle for calling the average method for a given cf-cq combination. It was necessary to add one more call stack as its return type should be a decimal value, irrespective of what columninterpreter says. So, this methods collects the necessary parameters to compute the average and returs the double value.

  Parameters:

  tableName -

  ci -

  scan -

  Returns:

  Throws:

  Throwable

  std

  public <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> double std(byte[] tableName,
                                                                                                                                            ColumnInterpreter<R,S,P,Q,T> ci,
                                                                                                                                            Scan scan)
             throws Throwable

  This is the client side interface/handle for calling the std method for a given cf-cq combination. It was necessary to add one more call stack as its return type should be a decimal value, irrespective of what columninterpreter says. So, this methods collects the necessary parameters to compute the std and returns the double value.

  Parameters:

  tableName -

  ci -

  scan -

  Returns:

  Throws:

  Throwable

  median

  public <R,S,P extends com.google.protobuf.Message,Q extends com.google.protobuf.Message,T extends com.google.protobuf.Message> R median(byte[] tableName,
                                                                                                                                          ColumnInterpreter<R,S,P,Q,T> ci,
                                                                                                                                          Scan scan)
           throws Throwable

  This is the client side interface/handler for calling the median method for a given cf-cq combination. This method collects the necessary parameters to compute the median and returns the median.

  Parameters:

  tableName -

  ci -

  scan -

  Returns:

  R the median

  Throws:

  Throwable