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https://issues.apache.org/jira/browse/TINKERPOP-2681?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17486407#comment-17486407
]
ASF GitHub Bot commented on TINKERPOP-2681:
-------------------------------------------
spmallette commented on a change in pull request #1555:
URL: https://github.com/apache/tinkerpop/pull/1555#discussion_r798486220
##########
File path:
gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/MergeVertexStep.java
##########
@@ -0,0 +1,293 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.tinkerpop.gremlin.process.traversal.step.map;
+
+import org.apache.tinkerpop.gremlin.process.traversal.Merge;
+import org.apache.tinkerpop.gremlin.process.traversal.Step;
+import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
+import org.apache.tinkerpop.gremlin.process.traversal.Traverser;
+import org.apache.tinkerpop.gremlin.process.traversal.TraverserGenerator;
+import org.apache.tinkerpop.gremlin.process.traversal.lambda.ConstantTraversal;
+import org.apache.tinkerpop.gremlin.process.traversal.lambda.IdentityTraversal;
+import org.apache.tinkerpop.gremlin.process.traversal.step.Mutating;
+import
org.apache.tinkerpop.gremlin.process.traversal.step.TraversalOptionParent;
+import org.apache.tinkerpop.gremlin.process.traversal.step.util.Parameters;
+import
org.apache.tinkerpop.gremlin.process.traversal.step.util.event.CallbackRegistry;
+import org.apache.tinkerpop.gremlin.process.traversal.step.util.event.Event;
+import
org.apache.tinkerpop.gremlin.process.traversal.step.util.event.ListCallbackRegistry;
+import
org.apache.tinkerpop.gremlin.process.traversal.strategy.decoration.EventStrategy;
+import
org.apache.tinkerpop.gremlin.process.traversal.traverser.TraverserRequirement;
+import org.apache.tinkerpop.gremlin.process.traversal.util.TraversalUtil;
+import org.apache.tinkerpop.gremlin.structure.Graph;
+import org.apache.tinkerpop.gremlin.structure.Property;
+import org.apache.tinkerpop.gremlin.structure.T;
+import org.apache.tinkerpop.gremlin.structure.Vertex;
+import org.apache.tinkerpop.gremlin.structure.VertexProperty;
+import org.apache.tinkerpop.gremlin.structure.util.StringFactory;
+import org.apache.tinkerpop.gremlin.util.iterator.IteratorUtils;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Stream;
+
+/**
+ * Implementation for the {@code mergeV()} step covering both the start step
version and the one used mid-traversal.
+ */
+public class MergeVertexStep<S> extends FlatMapStep<S, Vertex> implements
Mutating<Event>,
+ TraversalOptionParent<Merge, S, Vertex> {
+
+ private final boolean isStart;
+ private boolean first = true;
+ private Traversal.Admin<S,Map<Object, Object>> searchCreateTraversal;
+ private Traversal.Admin<S, Map<Object, Object>> onCreateTraversal = null;
+ private Traversal.Admin<S, Map<String, Object>> onMatchTraversal = null;
+
+ protected CallbackRegistry<Event> callbackRegistry;
+
+ public MergeVertexStep(final Traversal.Admin traversal, final boolean
isStart) {
+ this(traversal, isStart, new IdentityTraversal());
+ }
+
+ public MergeVertexStep(final Traversal.Admin traversal, final boolean
isStart, final Map<Object, Object> searchCreate) {
+ this(traversal, isStart, new ConstantTraversal<>(searchCreate));
+ }
+
+ public MergeVertexStep(final Traversal.Admin traversal, final boolean
isStart, final Traversal.Admin<S,Map<Object, Object>> searchCreateTraversal) {
+ super(traversal);
+ this.isStart = isStart;
+ this.searchCreateTraversal = integrateChild(searchCreateTraversal);
+ }
+
+ public Traversal.Admin<S, Map<Object, Object>> getSearchCreateTraversal() {
+ return searchCreateTraversal;
+ }
+
+ public Traversal.Admin<S, Map<Object, Object>> getOnCreateTraversal() {
+ return onCreateTraversal;
+ }
+
+ public Traversal.Admin<S, Map<String, Object>> getOnMatchTraversal() {
+ return onMatchTraversal;
+ }
+
+ /**
+ * Determines if this is a start step.
+ */
+ public boolean isStart() {
+ return isStart;
+ }
+
+ public boolean isFirst() {
+ return first;
+ }
+
+ public CallbackRegistry<Event> getCallbackRegistry() {
+ return callbackRegistry;
+ }
+
+ @Override
+ public void addChildOption(final Merge token, final Traversal.Admin<S,
Vertex> traversalOption) {
+ if (token == Merge.onCreate) {
+ this.onCreateTraversal = this.integrateChild(traversalOption);
+ } else if (token == Merge.onMatch) {
+ this.onMatchTraversal = this.integrateChild(traversalOption);
+ } else {
+ throw new UnsupportedOperationException(String.format("Option %s
for Merge is not supported", token.name()));
+ }
+ }
+
+ @Override
+ public <S, E> List<Traversal.Admin<S, E>> getLocalChildren() {
+ final List<Traversal.Admin<S, E>> children = new ArrayList<>();
+ if (searchCreateTraversal != null) children.add((Traversal.Admin<S,
E>) searchCreateTraversal);
+ if (onMatchTraversal != null) children.add((Traversal.Admin<S, E>)
onMatchTraversal);
+ if (onCreateTraversal != null) children.add((Traversal.Admin<S, E>)
onCreateTraversal);
+ return children;
+ }
+
+ @Override
+ public void configure(final Object... keyValues) {
+ // this is a Mutating step but property() should not be folded into
this step. this exception should not
+ // end up visible to users really
+ }
+
+ @Override
+ public Parameters getParameters() {
+ // merge doesn't take fold ups of property() calls. those need to get
treated as regular old PropertyStep
+ // instances. not sure if this should support with() though.....none
of the other Mutating steps do.
+ return null;
+ }
+
+ @Override
+ protected Traverser.Admin<Vertex> processNextStart() {
+ // when it's a start step a traverser needs to be created to kick off
the traversal.
+ if (isStart && first) {
+ first = false;
+ final TraverserGenerator generator =
this.getTraversal().getTraverserGenerator();
+ this.addStart(generator.generate(false, (Step) this, 1L));
+ }
+ return super.processNextStart();
+ }
+
+ /**
+ * Use the {@code Map} of search criteria to most efficiently return a
{@code Stream<Vertex>} of matching elements.
+ * Providers might override this method when extending this step to
provide their own optimized mechanisms for
+ * matching the list of vertices. This implementation is only optimized
for the {@link T#id} so any other usage
+ * will simply be in-memory filtering which could be slow.
+ */
+ protected Stream<Vertex> createSearchStream(final Map<Object,Object>
search) {
+ final Graph graph = this.getTraversal().getGraph().get();
+
+ Stream<Vertex> stream;
+ // prioritize lookup by id
+ if (search.containsKey(T.id))
+ stream = IteratorUtils.stream(graph.vertices(search.get(T.id)));
+ else
+ stream = IteratorUtils.stream(graph.vertices());
+
+ // in-memory filter is not going to be nice here. it will be up to
graphs to optimize this step as they do
+ // for other Mutation steps
+ stream = stream.filter(v -> {
+ // try to match on all search criteria skipping T.id as it was
handled above
+ return search.entrySet().stream().filter(kv -> kv.getKey() !=
T.id).allMatch(kv -> {
+ if (kv.getKey() == T.label) {
+ return v.label().equals(kv.getValue());
+ } else {
+ final VertexProperty<Object> vp =
v.property(kv.getKey().toString());
+ return vp.isPresent() && kv.getValue().equals(vp.value());
+ }
+ });
+ });
+
+ return stream;
+ }
+
+ @Override
+ protected Iterator<Vertex> flatMap(final Traverser.Admin<S> traverser) {
+ final Map<Object,Object> searchCreate = TraversalUtil.apply(traverser,
searchCreateTraversal);
+
+ Stream<Vertex> stream = createSearchStream(searchCreate);
+ stream = stream.map(v -> {
+ // if no onMatch is defined then there is no update - return the
vertex unchanged
+ if (null == onMatchTraversal) return v;
+
+ // assume good input from GraphTraversal - folks might drop in a T
here even though it is immutable
+ final Map<String, Object> onMatchMap =
TraversalUtil.apply(traverser, onMatchTraversal);
+ onMatchMap.forEach((key, value) -> {
+ // trigger callbacks for eventing - in this case, it's a
VertexPropertyChangedEvent. if there's no
+ // registry/callbacks then just set the property
+ if (this.callbackRegistry != null &&
!callbackRegistry.getCallbacks().isEmpty()) {
+ final EventStrategy eventStrategy =
getTraversal().getStrategies().getStrategy(EventStrategy.class).get();
+ final Property<?> p = v.property(key);
+ final Property<Object> oldValue = p.isPresent() ?
eventStrategy.detach(v.property(key)) : null;
+ final Event.VertexPropertyChangedEvent vpce = new
Event.VertexPropertyChangedEvent(eventStrategy.detach(v), oldValue, value);
+ this.callbackRegistry.getCallbacks().forEach(c ->
c.accept(vpce));
+ }
+ v.property(key, value);
Review comment:
ok - we can try to detect it with `getCardinality()` off of graph
features.
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> Create merge() step to codify best practice for upsert pattern
> --------------------------------------------------------------
>
> Key: TINKERPOP-2681
> URL: https://issues.apache.org/jira/browse/TINKERPOP-2681
> Project: TinkerPop
> Issue Type: Improvement
> Components: language, process
> Affects Versions: 3.5.1
> Reporter: Dave Bechberger
> Assignee: Stephen Mallette
> Priority: Major
>
> Create a step that codifies the best practice for the upsert functionality
> into a single step to make it easier to use, more discoverable, and easier
> for implementers to optimize.
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