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java.lang.Objectorg.apache.derby.impl.sql.execute.SystemAggregator
org.apache.derby.impl.sql.execute.OrderableAggregator
org.apache.derby.impl.sql.execute.MaxMinAggregator
public final class MaxMinAggregator
Aggregator for MAX()/MIN(). Defers most of its work to OrderableAggregator.
OrderableAggregator
,
Serialized FormField Summary | |
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private boolean |
isMax
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Fields inherited from class org.apache.derby.impl.sql.execute.OrderableAggregator |
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value |
Constructor Summary | |
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MaxMinAggregator()
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Method Summary | |
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protected void |
accumulate(DataValueDescriptor addend)
Accumulate |
int |
getTypeFormatId()
Get the formatID which corresponds to this class. |
ExecAggregator |
newAggregator()
Return a new initialized copy of this aggregator, any state set by the setup() method of the original Aggregator must be copied into the new aggregator. |
void |
readExternal(java.io.ObjectInput in)
|
void |
setup(java.lang.String aggregateName)
Set's up the aggregate for processing. |
void |
writeExternal(java.io.ObjectOutput out)
Although we are not expected to be persistent per se, we may be written out by the sorter temporarily. |
Methods inherited from class org.apache.derby.impl.sql.execute.OrderableAggregator |
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getResult, merge, toString |
Methods inherited from class org.apache.derby.impl.sql.execute.SystemAggregator |
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accumulate, didEliminateNulls |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Field Detail |
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private boolean isMax
Constructor Detail |
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public MaxMinAggregator()
Method Detail |
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public void setup(java.lang.String aggregateName)
ExecAggregator
setup
in interface ExecAggregator
setup
in class OrderableAggregator
protected void accumulate(DataValueDescriptor addend) throws StandardException
accumulate
in class SystemAggregator
addend
- value to be added in
StandardException
- on errorpublic ExecAggregator newAggregator()
ExecAggregator
public void writeExternal(java.io.ObjectOutput out) throws java.io.IOException
OrderableAggregator
Why would we be called to write ourselves out if we are null? For scalar aggregates, we don't bother setting up the aggregator since we only need a single row. So for a scalar aggregate that needs to go to disk, the aggregator might be null.
writeExternal
in interface java.io.Externalizable
writeExternal
in class OrderableAggregator
java.io.IOException
- on errorExternalizable.writeExternal(java.io.ObjectOutput)
public void readExternal(java.io.ObjectInput in) throws java.io.IOException, java.lang.ClassNotFoundException
readExternal
in interface java.io.Externalizable
readExternal
in class OrderableAggregator
java.io.IOException
- on error
java.lang.ClassNotFoundException
- on errorExternalizable.readExternal(java.io.ObjectInput)
public int getTypeFormatId()
|
Built on Thu 2011-03-10 11:54:14+0000, from revision ??? | ||||||||
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