Bug 123840 Incorrect use of static fields in NEvaluator and FilterPassController
Data Engine classes org.eclipse.birt.data.engine.script.NEvaluator and FilterPassController (used for top-n and bottom-n filter process) use static class fields to store proessing data. This is not multi-thread safe. If there are concurrent requests running in the same JVM (even if they use different instances of DataEngine), data corruption will occur since multiple requests may get/set the static fields at the same time. These classes should keep all per-request data in instance fields. Each report query need to have its own instance.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/script/NEvaluator.java
{
	protected Object doCompare( Object value1, Object value2 ) throws DataException
	{
		return ScriptEvalUtil.evalConditionalExpr2( value1, IConditionalExpression.OP_GT, value2, null);
	}
}
/**
 * The class that provides "Bottom N" calculation service
 *
 */
class BottomNEvaluator extends NEvaluator
{
	protected Object doCompare( Object value1, Object value2 ) throws DataException
	{
		return ScriptEvalUtil.evalConditionalExpr2( value1, IConditionalExpression.OP_LT, value2, null);
	}
}