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java.lang.Objectorg.apache.derby.impl.sql.execute.SystemAggregator
org.apache.derby.impl.sql.execute.CountAggregator
Aggregator for COUNT()/COUNT(*).
Field Summary | |
private boolean |
isCountStar
|
private long |
value
|
Constructor Summary | |
CountAggregator()
|
Method Summary | |
protected void |
accumulate(DataValueDescriptor addend)
|
void |
accumulate(DataValueDescriptor addend,
java.lang.Object ga)
Accumulate for count(). |
boolean |
didEliminateNulls()
Return true if the aggregation eliminated at least one null from the input data set. |
DataValueDescriptor |
getResult()
Return the result of the aggregation. |
int |
getTypeFormatId()
Get the formatID which corresponds to this class. |
boolean |
isCountStar()
|
void |
merge(ExecAggregator addend)
Merges one aggregator into a another aggregator. |
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 java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
private long value
private boolean isCountStar
Constructor Detail |
public CountAggregator()
Method Detail |
public void setup(java.lang.String aggregateName)
ExecAggregator
public void merge(ExecAggregator addend) throws StandardException
ExecAggregator
An example of a merge would be: given two COUNT() aggregators, C1 and C2, a merge of C1 into C2 would set C1.count += C2.count. So, given a CountAggregator with a getCount() method that returns its counts, its merge method might look like this:
public void merge(ExecAggregator inputAggregator) throws StandardException { count += ((CountAccgregator)inputAggregator).getCount(); }
addend
- the other Aggregator
(input partial aggregate)
StandardException
- on errorExecAggregator.merge(org.apache.derby.iapi.sql.execute.ExecAggregator)
public DataValueDescriptor getResult()
public void accumulate(DataValueDescriptor addend, java.lang.Object ga) throws StandardException
accumulate
in interface ExecAggregator
accumulate
in class SystemAggregator
addend
- value to be added inga
- the generic aggregator that is calling me
StandardException
ExecAggregator.accumulate(org.apache.derby.iapi.types.DataValueDescriptor, java.lang.Object)
protected final void accumulate(DataValueDescriptor addend)
accumulate
in class SystemAggregator
public ExecAggregator newAggregator()
ExecAggregator
public boolean isCountStar()
public final void writeExternal(java.io.ObjectOutput out) throws java.io.IOException
writeExternal
in interface java.io.Externalizable
writeExternal
in class SystemAggregator
java.io.IOException
- thrown on errorpublic final void readExternal(java.io.ObjectInput in) throws java.io.IOException, java.lang.ClassNotFoundException
readExternal
in interface java.io.Externalizable
readExternal
in class SystemAggregator
java.io.IOException
- io exception
java.lang.ClassNotFoundException
- on errorExternalizable.readExternal(java.io.ObjectInput)
public int getTypeFormatId()
public boolean didEliminateNulls()
ExecAggregator
didEliminateNulls
in interface ExecAggregator
|
Built on Mon 2007-06-04 09:58:47+0400, from revision ??? | |||||||||
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