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java.lang.Objectcom.ebay.erl.mobius.core.function.base.Projectable
com.ebay.erl.mobius.core.function.base.GroupFunction
com.ebay.erl.mobius.core.function.base.AggregateFunction
com.ebay.erl.mobius.core.function.base.SingleInputAggregateFunction
com.ebay.erl.mobius.core.function.Counts
public class Counts
Counts the number of records of the given inputColumn
in a group. Used only if the value of the given
inputColumn
is not null.
This product is licensed under the Apache License, Version 2.0, available at http://www.apache.org/licenses/LICENSE-2.0. This product contains portions derived from Apache hadoop which is licensed under the Apache License, Version 2.0, available at http://hadoop.apache.org. © 2007 – 2012 eBay Inc., Evan Chiu, Woody Zhou, Neel Sundaresan
Field Summary |
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Fields inherited from class com.ebay.erl.mobius.core.function.base.SingleInputAggregateFunction |
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inputColumnName |
Fields inherited from class com.ebay.erl.mobius.core.function.base.AggregateFunction |
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aggregateResult |
Fields inherited from class com.ebay.erl.mobius.core.function.base.GroupFunction |
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rowsToBeOutputted |
Fields inherited from class com.ebay.erl.mobius.core.function.base.Projectable |
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conf, hashCode, inputs, outputSchema, reporter, requireDataFromMultiDatasets |
Constructor Summary | |
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Counts(Column inputColumn)
Create an instance of Counts that
counting the number of occurrence of
inputColumn in a group. |
Method Summary | |
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void |
consume(Tuple tuple)
consume a value within a group, to be implemented by sub-class. |
protected Tuple |
getComputedResult()
Return the computed result in a Tuple . |
boolean |
isCombinable()
Determine this function can be run in a combiner or not, default is false. |
void |
reset()
Empty previous result ( rowsToBeOutputted ), reset is
called when the values within a group have been all iterated. |
Methods inherited from class com.ebay.erl.mobius.core.function.base.AggregateFunction |
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getResult, newBigTupleList, output |
Methods inherited from class com.ebay.erl.mobius.core.function.base.GroupFunction |
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getNoMatchResult, getRowsToBeOutputted |
Methods inherited from class com.ebay.erl.mobius.core.function.base.Projectable |
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calledByCombiner, equals, getConf, getInputColumns, getOutputSchema, getParticipatedDataset, hashCode, init, requireDataFromMultiDatasets, setCalledByCombiner, setConf, setOutputSchema, setReporter, toString, useGroupKeyOnly |
Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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public Counts(Column inputColumn)
Counts
that
counting the number of occurrence of
inputColumn
in a group.
If the value of inputColumn
,
the count won't increase.
Method Detail |
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public void consume(Tuple tuple)
GroupFunction
consume
in class GroupFunction
protected Tuple getComputedResult()
SingleInputAggregateFunction
Tuple
.
By default, the returned Tuple
contains only
one column, the name of the column is the first
element in the Projectable.getOutputSchema()
.
Override this method if there is a need to output a
Tuple
with more than one column.
getComputedResult
in class SingleInputAggregateFunction
public void reset()
GroupFunction
rowsToBeOutputted
), reset is
called when the values within a group have been all iterated.
It is important to call super.reset() when override this method in a sub-class, fail to do so, will result in wrong result.
reset
in class AggregateFunction
public final boolean isCombinable()
Projectable
isCombinable
in class Projectable
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