Class SystemAggregator
- java.lang.Object
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- org.apache.derby.impl.sql.execute.SystemAggregator
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- All Implemented Interfaces:
java.io.Externalizable
,java.io.Serializable
,Formatable
,TypedFormat
,ExecAggregator
- Direct Known Subclasses:
CountAggregator
,OrderableAggregator
abstract class SystemAggregator extends java.lang.Object implements ExecAggregator
Abstract aggregator that is extended by all internal (system) aggregators.
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Field Summary
Fields Modifier and Type Field Description private boolean
eliminatedNulls
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Constructor Summary
Constructors Constructor Description SystemAggregator()
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description protected abstract void
accumulate(DataValueDescriptor addend)
void
accumulate(DataValueDescriptor addend, java.lang.Object ga)
Iteratively accumulates the addend into the aggregator.boolean
didEliminateNulls()
Return true if the aggregation eliminated at least one null from the input data set.void
readExternal(java.io.ObjectInput in)
java.lang.String
toString()
void
writeExternal(java.io.ObjectOutput out)
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Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
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Methods inherited from interface org.apache.derby.iapi.sql.execute.ExecAggregator
getResult, merge, newAggregator, setup
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Methods inherited from interface org.apache.derby.iapi.services.io.TypedFormat
getTypeFormatId
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Method Detail
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didEliminateNulls
public boolean didEliminateNulls()
Description copied from interface:ExecAggregator
Return true if the aggregation eliminated at least one null from the input data set.- Specified by:
didEliminateNulls
in interfaceExecAggregator
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accumulate
public void accumulate(DataValueDescriptor addend, java.lang.Object ga) throws StandardException
Description copied from interface:ExecAggregator
Iteratively accumulates the addend into the aggregator. Called on each member of the set of values that is being aggregated.- Specified by:
accumulate
in interfaceExecAggregator
- Parameters:
addend
- the DataValueDescriptor addend (current input to the aggregation)ga
- a result set getter- Throws:
StandardException
- on error
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accumulate
protected abstract void accumulate(DataValueDescriptor addend) throws StandardException
- Throws:
StandardException
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writeExternal
public void writeExternal(java.io.ObjectOutput out) throws java.io.IOException
- Specified by:
writeExternal
in interfacejava.io.Externalizable
- Throws:
java.io.IOException
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readExternal
public void readExternal(java.io.ObjectInput in) throws java.io.IOException, java.lang.ClassNotFoundException
- Specified by:
readExternal
in interfacejava.io.Externalizable
- Throws:
java.io.IOException
java.lang.ClassNotFoundException
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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