AggregationService.java

/**************************************************************************************
 * Copyright (C) 2008 EsperTech, Inc. All rights reserved.                            *
 * http://esper.codehaus.org                                                          *
 * http://www.espertech.com                                                           *
 * ---------------------------------------------------------------------------------- *
 * The software in this package is published under the terms of the GPL license       *
 * a copy of which has been included with this distribution in the license.txt file.  *
 **************************************************************************************/
package com.espertech.esper.epl.agg.service;

import com.espertech.esper.client.EventBean;
import com.espertech.esper.epl.expression.ExprEvaluatorContext;

/**
 * Service for maintaining aggregation state. Processes events entering (a window, a join etc,) and
 * events leaving. Answers questions about current aggregation state for a given row.
 */
public interface AggregationService extends AggregationResultFuture
{
    /**
     * Apply events as entering a window (new events).
     * @param eventsPerStream - events for each stream entering window
     * @param optionalGroupKeyPerRow - can be null if grouping without keys is desired, else the keys
     * to use for grouping, each distinct key value results in a new row of aggregation state.
     * @param exprEvaluatorContext context for expression evaluatiom
     */
    public void applyEnter(EventBean[] eventsPerStream, Object optionalGroupKeyPerRow, ExprEvaluatorContext exprEvaluatorContext);

    /**
     * Apply events as leaving a window (old events).
     * @param eventsPerStream - events for each stream entering window
     * @param optionalGroupKeyPerRow - can be null if grouping without keys is desired, else the keys
     * to use for grouping, each distinct key value results in a new row of aggregation state.
     * @param exprEvaluatorContext context for expression evaluatiom
     */
    public void applyLeave(EventBean[] eventsPerStream, Object optionalGroupKeyPerRow, ExprEvaluatorContext exprEvaluatorContext);

    /**
     * Set the current aggregation state row - for use when evaluation nodes are asked to evaluate.
     * @param groupKey - key identify the row of aggregation states
     * @param agentInstanceId context partition id
     */
    public void setCurrentAccess(Object groupKey, int agentInstanceId);

    /**
     * Clear current aggregation state.
     * @param exprEvaluatorContext
     */
    public void clearResults(ExprEvaluatorContext exprEvaluatorContext);

    public void setRemovedCallback(AggregationRowRemovedCallback callback);
}