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

java.lang.Object
  org.datanucleus.store.rdbms.sql.method.AbstractSQLMethod
      org.datanucleus.store.rdbms.sql.method.SimpleAggregateMethod
          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