/**************************************************************************************
* 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.view.std;
import com.espertech.esper.client.EPException;
import com.espertech.esper.client.EventBean;
import com.espertech.esper.client.EventType;
import com.espertech.esper.collection.MultiKeyUntyped;
import com.espertech.esper.collection.Pair;
import com.espertech.esper.core.context.util.AgentInstanceViewFactoryChainContext;
import com.espertech.esper.epl.expression.ExprEvaluator;
import com.espertech.esper.epl.expression.ExprNode;
import com.espertech.esper.epl.expression.ExprNodeUtility;
import com.espertech.esper.event.EventBeanUtility;
import com.espertech.esper.view.CloneableView;
import com.espertech.esper.view.View;
import com.espertech.esper.view.ViewSupport;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import java.util.*;
/**
* The group view splits the data in a stream to multiple subviews, based on a key index.
* The key is one or more fields in the stream. Any view that follows the GROUP view will be executed
* separately on each subview, one per unique key.
*
* The view takes a single parameter which is the field name returning the key value to group.
*
* This view can, for example, be used to calculate the average price per symbol for a list of symbols.
*
* The view treats its child views and their child views as prototypes. It dynamically instantiates copies
* of each child view and their child views, and the child view's child views as so on. When there are
* no more child views or the special merge view is encountered, it ends. The view installs a special merge
* view unto each leaf child view that merges the value key that was grouped by back into the stream
* using the group-by field name.
*/
public class GroupByViewImpl extends ViewSupport implements CloneableView, GroupByView
{
private final ExprNode[] criteriaExpressions;
private final ExprEvaluator[] criteriaEvaluators;
protected final AgentInstanceViewFactoryChainContext agentInstanceContext;
private EventBean[] eventsPerStream = new EventBean[1];
protected String[] propertyNames;
protected final Map<Object, Object> subViewsPerKey = new HashMap<Object, Object>();
private final HashMap<Object, Pair<Object, Object>> groupedEvents = new HashMap<Object, Pair<Object, Object>>();
/**
* Constructor.
* @param criteriaExpressions is the fields from which to pull the values to group by
* @param agentInstanceContext contains required view services
*/
public GroupByViewImpl(AgentInstanceViewFactoryChainContext agentInstanceContext, ExprNode[] criteriaExpressions, ExprEvaluator[] criteriaEvaluators)
{
this.agentInstanceContext = agentInstanceContext;
this.criteriaExpressions = criteriaExpressions;
this.criteriaEvaluators = criteriaEvaluators;
propertyNames = new String[criteriaExpressions.length];
for (int i = 0; i < criteriaExpressions.length; i++)
{
propertyNames[i] = criteriaExpressions[i].toExpressionString();
}
}
public View cloneView()
{
return new GroupByViewImpl(agentInstanceContext, criteriaExpressions, criteriaEvaluators);
}
/**
* Returns the field name that provides the key valie by which to group by.
* @return field name providing group-by key.
*/
public ExprNode[] getCriteriaExpressions()
{
return criteriaExpressions;
}
public final EventType getEventType()
{
// The schema is the parent view's schema
return parent.getEventType();
}
public final void update(EventBean[] newData, EventBean[] oldData)
{
// Algorithm for single new event
if ((newData != null) && (oldData == null) && (newData.length == 1))
{
EventBean theEvent = newData[0];
EventBean[] newDataToPost = new EventBean[] {theEvent};
Object groupByValuesKey = getGroupKey(theEvent);
// Get child views that belong to this group-by value combination
Object subViews = this.subViewsPerKey.get(groupByValuesKey);
// If this is a new group-by value, the list of subviews is null and we need to make clone sub-views
if (subViews == null)
{
subViews = makeSubViews(this, propertyNames, groupByValuesKey, agentInstanceContext);
subViewsPerKey.put(groupByValuesKey, subViews);
}
updateChildViews(subViews, newDataToPost, null);
}
else
{
// Algorithm for dispatching multiple events
if (newData != null)
{
for (EventBean newValue : newData)
{
handleEvent(newValue, true);
}
}
if (oldData != null)
{
for (EventBean oldValue : oldData)
{
handleEvent(oldValue, false);
}
}
// Update child views
for (Map.Entry<Object, Pair<Object, Object>> entry : groupedEvents.entrySet())
{
EventBean[] newEvents = convertToArray(entry.getValue().getFirst());
EventBean[] oldEvents = convertToArray(entry.getValue().getSecond());
updateChildViews(entry.getKey(), newEvents, oldEvents);
}
groupedEvents.clear();
}
}
public final Iterator<EventBean> iterator()
{
throw new UnsupportedOperationException("Cannot iterate over group view, this operation is not supported");
}
public final String toString()
{
return this.getClass().getName() + " groupFieldNames=" + Arrays.toString(criteriaExpressions);
}
/**
* Instantiate subviews for the given group view and the given key value to group-by.
* Makes shallow copies of each child view and its subviews up to the merge point.
* Sets up merge data views for merging the group-by key value back in.
* @param groupView is the parent view for which to copy subviews for
* @param groupByValues is the key values to group-by
* @param agentInstanceContext is the view services that sub-views may need
* @param propertyNames names of expressions or properties
* @return a single view or a list of views that are copies of the original list, with copied children, with
* data merge views added to the copied child leaf views.
*/
public static Object makeSubViews(GroupByView groupView, String[] propertyNames, Object groupByValues,
AgentInstanceViewFactoryChainContext agentInstanceContext)
{
if (!groupView.hasViews())
{
String message = "Unexpected empty list of child nodes for group view";
log.fatal(".copySubViews " + message);
throw new EPException(message);
}
Object subviewHolder;
if (groupView.getViews().size() == 1) {
subviewHolder = copyChildView(groupView, propertyNames, groupByValues, agentInstanceContext, groupView.getViews().get(0));
}
else {
// For each child node
ArrayList<View> subViewList = new ArrayList<View>(4);
subviewHolder = subViewList;
for (View originalChildView : groupView.getViews()) {
View copyChildView = copyChildView(groupView, propertyNames, groupByValues, agentInstanceContext, originalChildView);
subViewList.add(copyChildView);
}
}
return subviewHolder;
}
protected static void updateChildViews(Object subViews, EventBean[] newData, EventBean[] oldData) {
if (subViews instanceof List) {
List<View> viewList = (List<View>) subViews;
ViewSupport.updateChildren(viewList, newData, oldData);
}
else {
((View) subViews).update(newData, oldData);
}
}
private void handleEvent(EventBean theEvent, boolean isNew)
{
Object groupByValuesKey = getGroupKey(theEvent);
// Get child views that belong to this group-by value combination
Object subViews = this.subViewsPerKey.get(groupByValuesKey);
// If this is a new group-by value, the list of subviews is null and we need to make clone sub-views
if (subViews == null) {
subViews = makeSubViews(this, propertyNames, groupByValuesKey, agentInstanceContext);
subViewsPerKey.put(groupByValuesKey, subViews);
}
// Construct a pair of lists to hold the events for the grouped value if not already there
Pair<Object, Object> pair = groupedEvents.get(subViews);
if (pair == null) {
pair = new Pair<Object, Object>(null, null);
groupedEvents.put(subViews, pair);
}
// Add event to a child view event list for later child update that includes new and old events
if (isNew) {
pair.setFirst(addUpgradeToDequeIfPopulated(pair.getFirst(), theEvent));
}
else {
pair.setSecond(addUpgradeToDequeIfPopulated(pair.getSecond(), theEvent));
}
}
private static View copyChildView(GroupByView groupView, String[] propertyNames, Object groupByValues, AgentInstanceViewFactoryChainContext agentInstanceContext, View originalChildView) {
if (originalChildView instanceof MergeView)
{
String message = "Unexpected merge view as child of group-by view";
log.fatal(".copySubViews " + message);
throw new EPException(message);
}
if (!(originalChildView instanceof CloneableView))
{
throw new EPException("Unexpected error copying subview " + originalChildView.getClass().getName());
}
CloneableView cloneableView = (CloneableView) originalChildView;
// Copy child node
View copyChildView = cloneableView.cloneView();
copyChildView.setParent(groupView);
// Make the sub views for child copying from the original to the child
copySubViews(groupView.getCriteriaExpressions(), propertyNames, groupByValues, originalChildView, copyChildView,
agentInstanceContext);
return copyChildView;
}
private static void copySubViews(ExprNode[] criteriaExpressions, String[] propertyNames, Object groupByValues, View originalView, View copyView,
AgentInstanceViewFactoryChainContext agentInstanceContext)
{
for (View subView : originalView.getViews())
{
// Determine if view is our merge view
if (subView instanceof MergeViewMarker)
{
MergeViewMarker mergeView = (MergeViewMarker) subView;
if (ExprNodeUtility.deepEquals(mergeView.getGroupFieldNames(), criteriaExpressions))
{
// We found our merge view - install a new data merge view on top of it
AddPropertyValueView mergeDataView = new AddPropertyValueView(agentInstanceContext, propertyNames, groupByValues, mergeView.getEventType());
// Add to the copied parent subview the view merge data view
copyView.addView(mergeDataView);
// Add to the new merge data view the actual single merge view instance that clients may attached to
mergeDataView.addView(mergeView);
// Add a parent view to the single merge view instance
mergeView.addParentView(mergeDataView);
continue;
}
}
if (!(subView instanceof CloneableView))
{
throw new EPException("Unexpected error copying subview");
}
CloneableView cloneableView = (CloneableView) subView;
View copiedChild = cloneableView.cloneView();
copyView.addView(copiedChild);
// Make the sub views for child
copySubViews(criteriaExpressions, propertyNames, groupByValues, subView, copiedChild, agentInstanceContext);
}
}
private Object getGroupKey(EventBean theEvent)
{
eventsPerStream[0] = theEvent;
if (criteriaEvaluators.length == 1) {
return criteriaEvaluators[0].evaluate(eventsPerStream, true, agentInstanceContext);
}
Object[] values = new Object[criteriaEvaluators.length];
for (int i = 0; i < criteriaEvaluators.length; i++)
{
values[i] = criteriaEvaluators[i].evaluate(eventsPerStream, true, agentInstanceContext);
}
return new MultiKeyUntyped(values);
}
protected static Object addUpgradeToDequeIfPopulated(Object holder, EventBean theEvent) {
if (holder == null) {
return theEvent;
}
else if (holder instanceof Deque) {
ArrayDeque<EventBean> deque = (ArrayDeque<EventBean>) holder;
deque.add(theEvent);
return deque;
}
else {
ArrayDeque<EventBean> deque = new ArrayDeque<EventBean>(4);
deque.add((EventBean)holder);
deque.add(theEvent);
return deque;
}
}
protected static EventBean[] convertToArray(Object eventOrDeque) {
if (eventOrDeque == null) {
return null;
}
if (eventOrDeque instanceof EventBean) {
return new EventBean[] {(EventBean) eventOrDeque};
}
return EventBeanUtility.toArray((ArrayDeque<EventBean>) eventOrDeque);
}
private static final Log log = LogFactory.getLog(GroupByViewImpl.class);
}