hyracks/hyracks-storage-am-common/src/main/java/edu/uci/ics/hyracks/storage/am/common/api/ISearchOperationCallback.java

package edu.uci.ics.hyracks.storage.am.common.api;

import edu.uci.ics.hyracks.api.exceptions.HyracksDataException;
import edu.uci.ics.hyracks.dataflow.common.data.accessors.ITupleReference;

/**
 * This operation callback allows for arbitrary actions to be taken while traversing 
 * an index structure. The {@link ISearchOperationCallback} will be called on 
 * all search operations for ordered indexes only.
 * 
 * @author zheilbron
 */
public interface ISearchOperationCallback {

    /**
     * During an index search operation, this method will be called on tuples as they are 
     * passed by with a search cursor. This call will be invoked while a leaf page is latched 
     * and pinned. If the call returns false, then the page will be unlatched and unpinned and 
     * {@link #reconcile(ITupleReference)} will be called with the tuple that was not proceeded 
     * on.
     * 
     * @param tuple the tuple that is being passed over by the search cursor
     * @return true to proceed otherwise false to unlatch and unpin, leading to reconciliation
     */
    public boolean proceed(ITupleReference tuple) throws HyracksDataException;

    /**
     * This method is only called on a tuple that was not 'proceeded' on 
     * (see {@link #proceed(ITupleReference)}). This method allows an opportunity to reconcile 
     * by performing any necessary actions before resuming the search (e.g. a try-lock may have 
     * failed in the proceed call, and now in reconcile we should take a full (blocking) lock).
     * 
     * @param tuple the tuple that failed to proceed
     */
    public void reconcile(ITupleReference tuple) throws HyracksDataException;

    /**
     * This method is only called on a tuple that was reconciled on, but not found after 
     * retraversing. This method allows an opportunity to cancel some action that was taken in 
     * {@link #reconcile(ITupleReference))}.
     * 
     * @param tuple the tuple that was previously reconciled
     */
    public void cancel(ITupleReference tuple) throws HyracksDataException;
    
    /**
     * This method is only called on a tuple that was reconciled on, and found after
     * retraversing. This method allows an opportunity to do some subsequent action that was 
     * taken in {@link #reconcile(ITupleReference))}.
     * 
     * @param tuple
     *            the tuple that was previously reconciled
     */
    public void complete(ITupleReference tuple) throws HyracksDataException;
}