/
SpatialDiffMerger.java
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/
SpatialDiffMerger.java
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/* Copyright (c) 2018 Boundless and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Distribution License v1.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/org/documents/edl-v10.html
*
* Contributors:
* Gabriel Roldan (Boundless) - initial implementation
*/
package org.locationtech.geogig.geotools.data.reader;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import org.eclipse.jdt.annotation.Nullable;
import org.locationtech.geogig.model.Bucket;
import org.locationtech.geogig.model.NodeRef;
import org.locationtech.geogig.model.RevTree;
import org.locationtech.geogig.plumbing.diff.PreOrderDiffWalk;
import org.locationtech.geogig.plumbing.diff.PreOrderDiffWalk.BucketIndex;
import org.locationtech.geogig.plumbing.diff.PreOrderDiffWalk.Consumer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Decorates the {@link PreOrderDiffWalk} {@link Consumer} when performing a diff between quad trees
* to merge delete and add feature events against the same feature as a single modification event.
* <p>
* Given quad trees are spatially clustered instead of following the canonical order, it could be
* that a feature modification is reported twice if the change made it fall into a different index
* quadrant.
* <p>
* This consumer wrapper merges such events into one modification event.
* <p>
* NOTE the order the add, delete, and merged modification events are reported is altered and hence
* this is not to be used whenever the diff events are expected to follow proper in-order traversal.
* It is useful though for the feature source to produce a stream of features with accurate
* reporting of feature changes.
*/
public class SpatialDiffMerger extends PreOrderDiffWalk.ForwardingConsumer {
private static final Logger log = LoggerFactory.getLogger(SpatialDiffMerger.class);
private long maxHeldFeatures, totalFeatureEvents, totalMerged;
private static class FeatureEvent {
private NodeRef left, right;
FeatureEvent(NodeRef left, NodeRef right) {
this.left = left;
this.right = right;
}
public String name() {
return SpatialDiffMerger.name(left, right);
}
//@formatter:off
public void setLeft(NodeRef l) {if (l != null) {left = l;}}
public void setRight(NodeRef r) {if (r != null) {right = r;}}
//@formatter:on
public boolean merge(FeatureEvent e) {
if ((left != null && left.equals(e.right)) || (right != null && right.equals(e.left))) {
return false;
}
setLeft(e.left);
setRight(e.right);
return true;
}
}
public SpatialDiffMerger() {
super();
}
public SpatialDiffMerger(Consumer delegate) {
super(delegate);
}
private Map<String, FeatureEvent> featureEvents = new LinkedHashMap<>();
private boolean flush() {
final int size = featureEvents.size();
if (size == 0) {
return true;
}
int adds = 0, removes = 0;
for (Iterator<FeatureEvent> it = featureEvents.values().iterator(); it.hasNext();) {//@formatter:off
FeatureEvent fe = it.next();
it.remove();
NodeRef left = fe.left;
NodeRef right = fe.right;
if(left == null) adds++;
if(right == null) removes++;//@formatter:on
if (!super.feature(left, right)) {
return false;
}
}
if (log.isInfoEnabled()) {
log.info(String.format(
"Flushed %,d of %,d feature events: +%,d -%,d ~%,d, max held features: %,d",
size, totalFeatureEvents, adds, removes, totalMerged, maxHeldFeatures));
}
return true;
}
private boolean treePassThru;
public @Override boolean tree(NodeRef left, NodeRef right) {
boolean passthru = RevTree.EMPTY_TREE_ID.equals(left.getObjectId())
|| RevTree.EMPTY_TREE_ID.equals(right.getObjectId());
treePassThru = passthru;
return super.tree(left, right);
}
public @Override void endTree(NodeRef left, NodeRef right) {
flush();
super.endTree(left, right);
}
public @Override boolean bucket(NodeRef leftParent, NodeRef rightParent,
BucketIndex bucketIndex, @Nullable Bucket left, @Nullable Bucket right) {
if (treePassThru || (left != null && right != null)) {
return super.bucket(leftParent, rightParent, bucketIndex, left, right);
}
return true;
}
public @Override void endBucket(NodeRef leftParent, NodeRef rightParent,
BucketIndex bucketIndex, @Nullable Bucket left, @Nullable Bucket right) {
if (treePassThru || (left != null && right != null)) {
super.endBucket(leftParent, rightParent, bucketIndex, left, right);
}
}
public @Override boolean feature(@Nullable NodeRef left, @Nullable NodeRef right) {
++totalFeatureEvents;
if (treePassThru) {
return super.feature(left, right);
}
if (left != null && right != null) {
return super.feature(left, right);
}
FeatureEvent featureEvent = new FeatureEvent(left, right);
FeatureEvent previous = featureEvents.putIfAbsent(featureEvent.name(), featureEvent);
maxHeldFeatures = Math.max(maxHeldFeatures, featureEvents.size());
if (previous != null) {
featureEvents.remove(previous.name());
if (previous.merge(featureEvent)) {
++totalMerged;
return super.feature(previous.left, previous.right);
} // else ignore, they're the same, represent no change
}
final int flushThreshold = 10_000_000;
if (featureEvents.size() == flushThreshold) {
treePassThru = true;
return flush();
}
return true;
}
private static String name(NodeRef left, NodeRef right) {
return left == null ? right.name() : left.name();
}
}