Bug 136141 Prepared statements not properly cleaned up.
After designing a JDBC query in a report design, I opened the DataSetEditor and choose "Preview Results". There are a number of warnings that came up in the Console indicating there are prepared statements not properly managed or cleaned up. Apr 11, 2006 8:23:04 AM org.eclipse.birt.data.engine.executor.DataSource close WARNING: 1 statements still active. Apr 11, 2006 8:23:05 AM org.eclipse.birt.data.engine.executor.DataSource closeStatement WARNING: statement not found Tracing down the problem a little further, the root cause of the problem is because the DataSourceQuery (in data.engine.executor) is trying to close a dangling reference of a PreparedStatement. The PreparedStatement has been previously dropped from the statementMap of the DataSource when the DataSource.close() was called. But DataSourceQuery is still holding on to a reference of it. The sequence is as follows: 1) DataSourceQuery prepares a statement. This in turn makes DataSource prepare a statement, and creates a PreparedStatement object, adds it to the statementMap. 2) During DataEngineImpl.defineDataSource(), the existing DataSource is closed, replaced by the supplied DataSourceDesign. The DataSource still have statements in its map. And a warning is logged indicating this is a resource leak. It then cleans the statementMap and closes all its open connections. 3) When DataSourceQuery tries to close the dangling statement, it cannot find it. It logs a message "Statement not found". Then, it still proceeds to close it.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/odi/IDataSource.java
*/
	public IDataSourceQuery newQuery( String queryType, String queryText ) 
					throws DataException;
    /**
	 * Instantiates a new empty query for use with candidate result instances.
     * @return		A new query instance.
     */
    public ICandidateQuery newCandidateQuery();
    /**
     * Indicates whether this data source is already opened.
     * @return	true if this is already opened
     */
    
    
	/**
	 * Opens the data source connection. <br>
	 * Optional call.  Its call is implied when any associated query
	 * needs to access the underlying data source driver.
	 * If the data source is already opened, returns with no error.
     * @throws DataException	if opening data source has error(s).
	 */
    public void open() throws DataException;
	
	/**
     * Closes the data source and any associated resources.  
     * The data source and its query instances can no longer be used.
     */
    public void close();
}