Bug 146548 [regression]Data type convert in chart data binding doesn't work.
Description: Data type convert in chart data binding doesn't work. Steps to reproduce: 1. New sample data source and dataset from OFFICES. 2. Insert a chart, bind it to dataset 3. Edit data binding to change officecode from string type to integer type 4. Drag officecode to y-series Expected result: No errors. Actual result: Unable to use a text data to render a numerical/datetime axis. org.eclipse.birt.chart.exception.ChartException at: org.eclipse.birt.chart.factory.Generator.build(Generator.java:985) org.eclipse.birt.chart.ui.swt.wizard.internal.ChartPreviewPainter.updateBuffer(ChartPreviewPainter.java:152) org.eclipse.birt.chart.ui.swt.wizard.internal.ChartPreviewPainter.renderModel(ChartPreviewPainter.java:333) org.eclipse.birt.chart.ui.swt.wizard.TaskSelectData.doLivePreview(TaskSelectData.java:1043) org.eclipse.birt.chart.ui.swt.wizard.TaskSelectData.changeTask(TaskSelectData.java:984) org.eclipse.birt.chart.ui.swt.wizard.ChartAdapter.notifyChanged(ChartAdapter.java:68) org.eclipse.emf.common.notify.impl.BasicNotifierImpl.eNotify
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/expression/ColumnReferenceExpression.java
{
		return m_columnName;
	}
	public int getColumnindex( )
	{
		return m_columnIndex;
	}
	public boolean isIndexed( )
	{
		return ( m_columnIndex != -1 );
	}
	
	public boolean equals(Object other)
	{
		if ( other == null || ! (other instanceof ColumnReferenceExpression))
			return false;
		
		ColumnReferenceExpression expr2 = (ColumnReferenceExpression) other;
		
		if ( m_columnName != null )
			return ( m_columnName.equals( expr2.m_columnName)); 
		else 
			return m_columnIndex == expr2.m_columnIndex;
	}
	
	public int hashCode()
	{
		if ( m_columnName != null )
			return m_columnName.hashCode();
		else