Bug 180842 Config memory buffer size in data engine execution.
To tuning the performance, it is necessary for DtE to expose API for clients to config the size of memory it used to store the final result set. A new AppContext string, "org.eclipse.birt.data.cache.memory.size" is proposed. The new appcontext entry only accept positive integer as input, the unit of which would be MB.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/QueryExecutor.java
}
		return false;
	}
	/*
	 * @see org.eclipse.birt.data.engine.impl.IQueryExecutor#getResultMetaData()
	 */
	public IResultMetaData getResultMetaData( ) throws DataException
	{
		assert odiQuery instanceof IPreparedDSQuery
				|| odiQuery instanceof ICandidateQuery
				|| odiQuery instanceof JointDataSetQuery;
		if ( odiQuery instanceof IPreparedDSQuery )
		{
			if ( ( (IPreparedDSQuery) odiQuery ).getResultClass( ) != null )
				return new ResultMetaData( ( (IPreparedDSQuery) odiQuery ).getResultClass( ) );
			else
				return null;
		}
		else if ( odiQuery instanceof JointDataSetQuery )
		{
			return new ResultMetaData( ( (JointDataSetQuery) odiQuery ).getResultClass( ) );
		}
		else
		{
			return new ResultMetaData( ( (ICandidateQuery) odiQuery ).getResultClass( ) );
		}
	}
	/*
	 * @see org.eclipse.birt.data.engine.impl.IQueryExecutor#execute()
	 */