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Class JBMSTours.aggregates.MaxButOneDoubleAggregator
java.lang.Object
|
+----JBMSTours.aggregates.MaxButOneDoubleAggregator
- public class MaxButOneDoubleAggregator
- extends Object
- implements Externalizable, Aggregator
This class implements the aggregation for MaxButONE when the input type is
a double.
We implement Externalizable to save space in case we
are written out (Serialization tends to take up a lot
of space).
-
MaxButOneDoubleAggregator()
- Niladic constructor
-
accumulate(ResultSet)
- Iteratively accumulates the addend into the aggregator.
-
getResult()
- Produces the result to be returned by the query.
-
getSecondValue()
- Returns the second highest value in the column found so far.
-
getTopValue()
- Returns the highest value in the column found so far.
-
initialize()
- Initializes the aggregate for processing.
-
merge(Aggregator)
- Merges one aggregator into a another aggregator.
-
newInstance()
- Return a new instance of this class.
-
readExternal(ObjectInput)
- Read in our two fields.
-
writeExternal(ObjectOutput)
- Write out our two fields.
MaxButOneDoubleAggregator
public MaxButOneDoubleAggregator()
- Niladic constructor
initialize
public void initialize()
- Initializes the aggregate for processing.
accumulate
public void accumulate(ResultSet addend) throws Throwable
- Iteratively accumulates the addend into the aggregator.
Called on each member of the set of values that is being
aggregated.
- Parameters:
- addend - the ResultSet addend (current input to
the aggregation)
- Throws: Throwable
- on error
merge
public void merge(Aggregator inputAggregator) throws Throwable
- Merges one aggregator into a another aggregator. Used in Group by.
- Parameters:
- inputAggregator - the other Aggregator
(input partial aggregate)
- Throws: Throwable
- on error
getResult
public Object getResult()
- Produces the result to be returned by the query.
The last processing of the aggregate.
In this instance, returns the second highest value in the column.
See
COM.cloudscape.aggregates.AggregateDefinition.getResult().
- Returns:
- the result column.
newInstance
public Aggregator newInstance()
- Return a new instance of this class. Identical
to Class.newInstance() but much cheaper because
reflection is costly.
Just implement it to do new myClass().
- Returns:
- Aggregator
getTopValue
public Double getTopValue()
- Returns the highest value in the column found so far. This method
needs to be public because instances call each other during a
merge.
- Returns:
- topValue
getSecondValue
public Double getSecondValue()
- Returns the second highest value in the column found so far. This method
needs to be public because instances call each other during a
merge.
- Returns:
- secondValue
writeExternal
public void writeExternal(ObjectOutput out) throws IOException
- Write out our two fields.
- Parameters:
- out - the output stream
- Throws: IOException
- on error
readExternal
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
- Read in our two fields.
- Parameters:
- int - the input stream
- Throws: IOException
- on error
- Throws: ClassNotFoundException
- on error
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