org.datanucleus.store.rdbms.sql.method
Class CountFunction

java.lang.Object
  extended by org.datanucleus.store.rdbms.sql.method.AbstractSQLMethod
      extended by org.datanucleus.store.rdbms.sql.method.SimpleAggregateMethod
          extended by org.datanucleus.store.rdbms.sql.method.CountFunction
All Implemented Interfaces:
SQLMethod

public class CountFunction
extends SimpleAggregateMethod

Expression handler to invoke the SQL COUNT aggregation function. For use in evaluating COUNT({expr}) where the RDBMS supports this function. Returns a NumericExpression "COUNT({numericExpr})".


Field Summary
 
Fields inherited from class org.datanucleus.store.rdbms.sql.method.AbstractSQLMethod
clr, exprFactory, LOCALISER, stmt
 
Constructor Summary
CountFunction()
           
 
Method Summary
protected  java.lang.Class getClassForMapping()
           
 SQLExpression getExpression(SQLExpression expr, java.util.List args)
          Return the expression for this SQL function.
protected  java.lang.String getFunctionName()
           
 
Methods inherited from class org.datanucleus.store.rdbms.sql.method.AbstractSQLMethod
getMappingForClass, setStatement
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

CountFunction

public CountFunction()
Method Detail

getFunctionName

protected java.lang.String getFunctionName()
Specified by:
getFunctionName in class SimpleAggregateMethod

getExpression

public SQLExpression getExpression(SQLExpression expr,
                                   java.util.List args)
Description copied from interface: SQLMethod
Return the expression for this SQL function.

Specified by:
getExpression in interface SQLMethod
Overrides:
getExpression in class SimpleAggregateMethod
Parameters:
expr - The expression that it is invoked on
args - Arguments passed in
Returns:
The SQL expression using the SQL function

getClassForMapping

protected java.lang.Class getClassForMapping()
Specified by:
getClassForMapping in class SimpleAggregateMethod


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