package org.eclipse.birt.report.engine.api;

import org.eclipse.birt.core.exception.BirtException;

/**
 * An iterator on a result set from a prepared and executed query.
 * Multiple IResultIterator objects could be associated with the same 
 * IExtractionResults object, if extraction is done at report level
*/
public interface IDataIterator
{
    /**
     * Returns {@link org.eclipse.birt.report.engine.api.IExtractionResults} 
     * from which this data iterator is obtained. 
     */
    public IExtractionResults getQueryResults();

    /**
     * Returns the metadata of this result set's detail row.
     * @return	The result metadata of a detail row.
     */
    public IResultMetaData getResultMetaData() throws BirtException;
    
    /**
     * Moves down one element from its current position of the iterator.
     * @return 	true if next element exists and 
     * 		has not reached the limit on the maximum number of rows 
     * 		that can be accessed. 
     * @throws 	BirtException if error occurs 
     */
    public boolean next() throws BirtException;

    /**
     * Returns the value of a column. 
     * @param columnName 	the name of the column
     * @return			The value of the given column. It could be null.
     * @throws 			BirtException if error occurs 
     */
    public Object getValue( String columnName ) throws BirtException;
    
    /**
     * @param index column index. It is 1 based 
     * @throws BirtException if error occurs
     */
    public Object getValue( int index ) throws BirtException;

    /** 
     * Closes this result and provide a hint that the consumer is done with 
     * this result,
     * whose resources can be safely released as appropriate.  
     */
    public void close();
}
