Examples of cascading.pipe.assembly.MaxBy$MaxPartials

cascading.pipe.assembly.MaxBy

Class MaxBy is used to find the maximum value in a grouping.

Typically finding the max value of a field in a tuple stream relies on a {@link cascading.pipe.GroupBy} and a{@link cascading.operation.aggregator.MaxValue} {@link cascading.operation.Aggregator} operation.

This SubAssembly also uses the {@link cascading.pipe.assembly.MaxBy.MaxPartials} {@link cascading.pipe.assembly.AggregateBy.Functor}to track the maximum value before the GroupBy operator to reduce IO over the network.

This strategy is similar to using {@code combiners}, except no sorting or serialization is invoked and results in a much simpler mechanism.

The {@code threshold} value tells the underlying MaxPartials functions how many unique key sums to accumulatein the LRU cache, before emitting the least recently used entry.

By default, either the value of {@link #AGGREGATE_BY_THRESHOLD} System property or {@link AggregateBy#DEFAULT_THRESHOLD}will be used. @see AggregateBy

      else if( aggregationName.equals( "SUM" ) )
        aggregates.add( new SumBy( current, groupFields, argFields, aggResultFields ) );
      else if( aggregationName.equals( "MIN" ) )
        aggregates.add( new MinBy( current, groupFields, argFields, aggResultFields ) );
      else if( aggregationName.equals( "MAX" ) )
        aggregates.add( new MaxBy( current, groupFields, argFields, aggResultFields ) );
      else if( aggregationName.equals( "AVG" ) )
        aggregates.add( new AverageBy( current, groupFields, argFields, aggResultFields, AverageBy.Include.NO_NULLS ) );
      else
        throw new UnsupportedOperationException( "unimplemented aggregation: " + aggregationName );
      }

      else if( aggregationName.equals( "SUM" ) )
        aggregates.add( new SumBy( argFields, aggResultFields ) );
      else if( aggregationName.equals( "MIN" ) )
        aggregates.add( new MinBy( argFields, aggResultFields ) );
      else if( aggregationName.equals( "MAX" ) )
        aggregates.add( new MaxBy( argFields, aggResultFields ) );
      else if( aggregationName.equals( "AVG" ) )
        aggregates.add( new AverageBy( argFields, aggResultFields, AverageBy.Include.NO_NULLS ) );
      else
        throw new UnsupportedOperationException( "unimplemented aggregation: " + aggregationName );
      }

Examples of cascading.pipe.assembly.MaxBy$MaxPartials

Related Classes of cascading.pipe.assembly.MaxBy$MaxPartials