Add batch query support for drop step [tp-tests]

- Reuse multi-query optimization for TinkerPop DropStep
- Change restriction on eligible multi-query traversals and allow multi-query optimizations to be used for queries with steps which contain drop() step

Signed-off-by: Oleksandr Porunov <alexandr.porunov@gmail.com>

docs/changelog.md

@@ -128,6 +128,32 @@ Example: `storage.berkeleyje.ext.je.lock.timeout=5000 ms`
 For simplicity JSON schema initialization options has been added into JanusGraph.
 See [documentation](./schema/schema-init-strategies.md) to learn more about JSON schema initialization process.
 
+##### Batched Queries Enhancement: Introduction of `JanusGraphNoOpBarrierVertexOnlyStep`
+
+In previous versions, when a query that could benefit from batch-query optimization (multi-query) was executed without
+a user-defined barrier step, JanusGraph would inject a `NoOpBarrierStep` by default. This approach allowed batching
+for edges and properties, which do not gain advantages from multi-query optimization.
+
+Starting with JanusGraph 1.1.0, this behavior has been improved. The system now injects a
+`JanusGraphNoOpBarrierVertexOnlyStep` instead of the standard `NoOpBarrierStep` when no barrier steps are detected.
+This change ensures that batching is applied exclusively to vertices, which do benefit from batch queries,
+while excluding edges and properties from the batching process.
+
+If a user explicitly defines a `.barrier()` step in the query, the system will continue to use the `NoOpBarrierStep` as expected.
+
+##### Batch Query Optimizations Now Support Traversals Containing the `drop()` Step
+
+Starting with JanusGraph 1.1.0, batch optimizations for vertex removal have been introduced in the `drop()` step and
+are enabled by default. Previously, any batch optimization would be skipped for queries containing at least one
+`drop()` step. However, with this update, such queries are now eligible for batch query optimization (multi-query).
+
+Please note that the `LazyBarrierStrategy` (a TinkerPop strategy) is disabled for any query that includes at least one `drop()` step.
+
+To disable the `drop()` step optimization and maintain the previous behavior, users can set the following configuration:
+```
+query.batch.drop-step-mode=none
+```
+
 ### Version 1.0.1 (Release Date: ???)
 
 /// tab | Maven

docs/configs/janusgraph-cfg.md

@@ -366,6 +366,7 @@ Configuration options to configure batch queries optimization behavior
 
 | Name | Description | Datatype | Default Value | Mutability |
 | ---- | ---- | ---- | ---- | ---- |
+| query.batch.drop-step-mode | Batching mode for `drop()` step. Used only when `query.batch.enabled` is `true`.<br>Supported modes:<br>- `all` - Drops all vertices in a batch.<br>- `none` - Skips drop batching optimization.<br> | String | all | MASKABLE |
 | query.batch.enabled | Whether traversal queries should be batched when executed against the storage backend. This can lead to significant performance improvement if there is a non-trivial latency to the backend. If `false` then all other configuration options under `query.batch` namespace are ignored. | Boolean | true | MASKABLE |
 | query.batch.has-step-mode | Properties pre-fetching mode for `has` step. Used only when `query.batch.enabled` is `true`.<br>Supported modes:<br>- `all_properties` - Pre-fetch all vertex properties on any property access (fetches all vertex properties in a single slice query)<br>- `required_properties_only` - Pre-fetch necessary vertex properties for the whole chain of foldable `has` steps (uses a separate slice query per each required property)<br>- `required_and_next_properties` - Prefetch the same properties as with `required_properties_only` mode, but also prefetch<br>properties which may be needed in the next properties access step like `values`, `properties,` `valueMap`, `elementMap`, or `propertyMap`.<br>In case the next step is not one of those properties access steps then this mode behaves same as `required_properties_only`.<br>In case the next step is one of the properties access steps with limited scope of properties, those properties will be<br>pre-fetched together in the same multi-query.<br>In case the next step is one of the properties access steps with unspecified scope of property keys then this mode<br>behaves same as `all_properties`.<br>- `required_and_next_properties_or_all` - Prefetch the same properties as with `required_and_next_properties`, but in case the next step is not<br>`values`, `properties,` `valueMap`, `elementMap`, or `propertyMap` then acts like `all_properties`.<br>- `none` - Skips `has` step batch properties pre-fetch optimization.<br> | String | required_and_next_properties | MASKABLE |
 | query.batch.label-step-mode | Labels pre-fetching mode for `label()` step. Used only when `query.batch.enabled` is `true`.<br>Supported modes:<br>- `all` - Pre-fetch labels for all vertices in a batch.<br>- `none` - Skips vertex labels pre-fetching optimization.<br> | String | all | MASKABLE |

docs/operations/batch-processing.md

@@ -159,7 +159,7 @@ Batched query processing takes into account two types of steps:
 
 1.  Batch compatible step. This is the step which will execute batch requests. Currently, the list of such steps
     is the next: `out()`, `in()`, `both()`, `inE()`, `outE()`, `bothE()`, `has()`, `values()`, `properties()`, `valueMap()`,
-    `propertyMap()`, `elementMap()`, `label()`.
+    `propertyMap()`, `elementMap()`, `label()`, `drop()`.
 2.  Parent step. This is a parent step which has local traversals with the same start. Such parent steps also implement the 
     interface `TraversalParent`. There are many such steps, but as for an example those could be: `and(...)`, `or(...)`, 
     `not(...)`, `order().by(...)`, `project("valueA", "valueB", "valueC").by(...).by(...).by(...)`, `union(..., ..., ...)`,
@@ -331,3 +331,4 @@ See configuration option `query.batch.has-step-mode` to control properties pre-f
 See configuration option `query.batch.properties-mode` to control properties pre-fetching behaviour for `values`, 
 `properties`, `valueMap`, `propertyMap`, and `elementMap` steps.  
 See configuration option `query.batch.label-step-mode` to control labels pre-fetching behaviour for `label` step.  
+See configuration option `query.batch.drop-step-mode` to control drop batching behaviour for `drop` step.  

janusgraph-backend-testutils/src/main/java/org/janusgraph/graphdb/JanusGraphTest.java

@@ -31,6 +31,7 @@
 import org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.GraphTraversal;
 import org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.GraphTraversalSource;
 import org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.__;
+import org.apache.tinkerpop.gremlin.process.traversal.step.filter.DropStep;
 import org.apache.tinkerpop.gremlin.process.traversal.step.filter.HasStep;
 import org.apache.tinkerpop.gremlin.process.traversal.step.util.WithOptions;
 import org.apache.tinkerpop.gremlin.process.traversal.strategy.decoration.SubgraphStrategy;
@@ -60,6 +61,7 @@
 import org.janusgraph.core.PropertyKey;
 import org.janusgraph.core.RelationType;
 import org.janusgraph.core.SchemaViolationException;
+import org.janusgraph.core.Transaction;
 import org.janusgraph.core.VertexLabel;
 import org.janusgraph.core.VertexList;
 import org.janusgraph.core.attribute.Cmp;
@@ -138,10 +140,12 @@
 import org.janusgraph.graphdb.relations.StandardVertexProperty;
 import org.janusgraph.graphdb.serializer.SpecialInt;
 import org.janusgraph.graphdb.serializer.SpecialIntSerializer;
+import org.janusgraph.graphdb.tinkerpop.optimize.step.JanusGraphDropStep;
 import org.janusgraph.graphdb.tinkerpop.optimize.step.JanusGraphElementMapStep;
 import org.janusgraph.graphdb.tinkerpop.optimize.step.JanusGraphHasStep;
 import org.janusgraph.graphdb.tinkerpop.optimize.step.JanusGraphPropertiesStep;
 import org.janusgraph.graphdb.tinkerpop.optimize.step.JanusGraphPropertyMapStep;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.MultiQueryDropStepStrategyMode;
 import org.janusgraph.graphdb.tinkerpop.optimize.strategy.MultiQueryHasStepStrategyMode;
 import org.janusgraph.graphdb.tinkerpop.optimize.strategy.MultiQueryLabelStepStrategyMode;
 import org.janusgraph.graphdb.tinkerpop.optimize.strategy.MultiQueryPropertiesStrategyMode;
@@ -220,6 +224,7 @@
 import static org.janusgraph.graphdb.configuration.GraphDatabaseConfiguration.DB_CACHE;
 import static org.janusgraph.graphdb.configuration.GraphDatabaseConfiguration.DB_CACHE_CLEAN_WAIT;
 import static org.janusgraph.graphdb.configuration.GraphDatabaseConfiguration.DB_CACHE_TIME;
+import static org.janusgraph.graphdb.configuration.GraphDatabaseConfiguration.DROP_STEP_BATCH_MODE;
 import static org.janusgraph.graphdb.configuration.GraphDatabaseConfiguration.FORCE_INDEX_USAGE;
 import static org.janusgraph.graphdb.configuration.GraphDatabaseConfiguration.HARD_MAX_LIMIT;
 import static org.janusgraph.graphdb.configuration.GraphDatabaseConfiguration.HAS_STEP_BATCH_MODE;
@@ -10074,11 +10079,7 @@ public void testMultiQueryDropsVertices() {
 
         int verticesAmount = 42;
 
-        for (int i = 0; i < verticesAmount; i++) {
-            Vertex vertex = tx.addVertex("id", i);
-            vertex.property("name", "name_test");
-            vertex.property("details", "details_" + i);
-        }
+        addVerticesForDropTest(verticesAmount, tx);
 
         clopen();
 
@@ -10090,20 +10091,161 @@ public void testMultiQueryDropsVertices() {
             .map(v -> (JanusGraphVertex) v)
             .collect(Collectors.toList());
 
-        int actualCount = tx.multiQuery(vertices).drop();
+        int actualCount = tx.multiQuery(vertices).drop().size();
         clopen();
 
         assertEquals(verticesAmount, actualCount);
 
-        int afterDropCount = tx.traversal()
-            .V()
-            .has("name", "name_test")
-            .toList()
-            .size();
+        long afterDropCount = getVerticesForDropTestCount(tx.traversal());
 
         assertEquals(0, afterDropCount);
     }
 
+    @Test
+    public void testMultiQueryDropsStrategyModes() {
+
+        mgmt.makePropertyKey("id").dataType(Integer.class).cardinality(Cardinality.SINGLE).make();
+        PropertyKey nameProp = mgmt.makePropertyKey("name").dataType(String.class).cardinality(Cardinality.SINGLE).make();
+        mgmt.makePropertyKey("details").dataType(String.class).cardinality(Cardinality.SINGLE).make();
+        mgmt.buildIndex("nameIndex", Vertex.class).addKey(nameProp).buildCompositeIndex();
+
+        finishSchema();
+
+        long verticesAmount = 42;
+
+        // Mode: NONE
+
+        addVerticesForDropTest(verticesAmount);
+        graph.tx().commit();
+        clopen(option(DROP_STEP_BATCH_MODE), MultiQueryDropStepStrategyMode.NONE.getConfigName());
+        assertEquals(verticesAmount, getVerticesForDropTestCount());
+        TraversalMetrics profileT = graph.traversal().V().drop().profile().next();
+        assertTrue(profileT.getMetrics().stream().anyMatch(metrics -> metrics.getName().equals(DropStep.class.getSimpleName())));
+        graph.tx().commit();
+        assertEquals(0, getVerticesForDropTestCount());
+
+        // Mode: ALL
+
+        addVerticesForDropTest(verticesAmount);
+        graph.tx().commit();
+        clopen(option(DROP_STEP_BATCH_MODE), MultiQueryDropStepStrategyMode.ALL.getConfigName());
+        assertEquals(verticesAmount, getVerticesForDropTestCount());
+        profileT = graph.traversal().V().drop().profile().next();
+        assertEquals("true", profileT.getMetrics().stream().filter(metrics -> metrics.getName().equals(JanusGraphDropStep.class.getSimpleName())).findAny().get().getAnnotation("multi"));
+        graph.tx().commit();
+        assertEquals(0, getVerticesForDropTestCount());
+
+        // `limit` with `drop` step.
+
+        addVerticesForDropTest(verticesAmount);
+        graph.tx().commit();
+        clopen(option(DROP_STEP_BATCH_MODE), MultiQueryDropStepStrategyMode.NONE.getConfigName());
+        assertEquals(verticesAmount, getVerticesForDropTestCount());
+        int limitSize = 2;
+        profileT = graph.traversal().V().limit(limitSize).drop().profile().next();
+        assertTrue(profileT.getMetrics().stream().anyMatch(metrics -> metrics.getName().equals(DropStep.class.getSimpleName())));
+        graph.tx().commit();
+        long afterDropCount = getVerticesForDropTestCount();
+        assertEquals(verticesAmount-limitSize, afterDropCount);
+        graph.traversal().V().drop().iterate();
+        graph.tx().commit();
+        addVerticesForDropTest(verticesAmount);
+        graph.tx().commit();
+        clopen(option(DROP_STEP_BATCH_MODE), MultiQueryDropStepStrategyMode.ALL.getConfigName());
+        assertEquals(verticesAmount, getVerticesForDropTestCount());
+        profileT = graph.traversal().V().limit(limitSize).drop().profile().next();
+        assertEquals("true", profileT.getMetrics().stream().filter(metrics -> metrics.getName().equals(JanusGraphDropStep.class.getSimpleName())).findAny().get().getAnnotation("multi"));
+        graph.tx().commit();
+        afterDropCount = getVerticesForDropTestCount();
+        assertEquals(verticesAmount-limitSize, afterDropCount);
+    }
+
+    @Test
+    public void testMetaPropertiesDrop(){
+        mgmt.makePropertyKey("id").dataType(Integer.class).cardinality(Cardinality.SINGLE).make();
+        PropertyKey nameProp = mgmt.makePropertyKey("name").dataType(String.class).cardinality(Cardinality.SINGLE).make();
+        mgmt.makePropertyKey("details").dataType(String.class).cardinality(Cardinality.SINGLE).make();
+        mgmt.buildIndex("nameIndex", Vertex.class).addKey(nameProp).buildCompositeIndex();
+
+        finishSchema();
+
+        long verticesAmount = 42;
+
+        for (int i = 0; i < verticesAmount; i++) {
+            Vertex vertex = tx.addVertex("id", i);
+            VertexProperty<String> property = vertex.property("name", "name_test");
+            property.property("details", "details_" + i);
+        }
+        graph.tx().commit();
+
+        clopen(option(DROP_STEP_BATCH_MODE), MultiQueryDropStepStrategyMode.ALL.getConfigName());
+
+        assertEquals(verticesAmount, graph.traversal().V().properties("name").properties("details").count().next());
+
+        graph.traversal().V().properties("name").properties("details").drop().hasNext();
+
+        assertEquals(0, graph.traversal().V().properties("name").properties("details").count().next());
+
+        graph.tx().commit();
+
+        assertEquals(0, graph.traversal().V().properties("name").properties("details").count().next());
+        assertEquals(verticesAmount, graph.traversal().V().has("name").count().next());
+    }
+
+    @Test
+    public void testEdgePropertiesDrop(){
+        mgmt.makePropertyKey("id").dataType(Integer.class).cardinality(Cardinality.SINGLE).make();
+        mgmt.makePropertyKey("name").dataType(String.class).cardinality(Cardinality.SINGLE).make();
+        mgmt.makeEdgeLabel("relate").make();
+
+        finishSchema();
+
+        long verticesAmount = 42;
+
+        for (int i = 0; i < verticesAmount; i++) {
+            Vertex vertex = tx.addVertex("id", i);
+            Vertex vertex2 = tx.addVertex("id", i+verticesAmount);
+            vertex.addEdge("relate", vertex2).property("name", "name_"+i);
+        }
+
+        graph.tx().commit();
+
+        clopen(option(DROP_STEP_BATCH_MODE), MultiQueryDropStepStrategyMode.ALL.getConfigName());
+
+        assertEquals(verticesAmount, graph.traversal().E().properties("name").count().next());
+
+        graph.traversal().E().properties("name").drop().hasNext();
+
+        assertEquals(0, graph.traversal().E().properties("name").count().next());
+
+        graph.tx().commit();
+
+        assertEquals(0, graph.traversal().E().properties("name").count().next());
+        assertEquals(verticesAmount, graph.traversal().E().count().next());
+    }
+
+    private void addVerticesForDropTest(long verticesAmount){
+        addVerticesForDropTest(verticesAmount, graph);
+    }
+
+    private long getVerticesForDropTestCount(){
+        return getVerticesForDropTestCount(graph.traversal());
+    }
+
+    private void addVerticesForDropTest(long verticesAmount, Transaction tx){
+        for (int i = 0; i < verticesAmount; i++) {
+            Vertex vertex = tx.addVertex("id", i);
+            vertex.property("name", "name_test");
+            vertex.property("details", "details_" + i);
+        }
+    }
+
+    private long getVerticesForDropTestCount(GraphTraversalSource g){
+        return g.V()
+            .has("name", "name_test")
+            .count().next();
+    }
+
     @ParameterizedTest
     @ValueSource(booleans = {true, false})
     public void testParallelBackendOps(boolean parallelBackendOpsEnabled) {

janusgraph-benchmark/src/main/java/org/janusgraph/CQLMultiQueryDropBenchmark.java

@@ -27,6 +27,7 @@
 import org.janusgraph.diskstorage.configuration.WriteConfiguration;
 import org.janusgraph.diskstorage.cql.CQLConfigOptions;
 import org.janusgraph.graphdb.configuration.GraphDatabaseConfiguration;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.MultiQueryDropStepStrategyMode;
 import org.openjdk.jmh.annotations.Benchmark;
 import org.openjdk.jmh.annotations.BenchmarkMode;
 import org.openjdk.jmh.annotations.Fork;
@@ -65,6 +66,7 @@ public WriteConfiguration getConfiguration() {
         config.set(GraphDatabaseConfiguration.STORAGE_BACKEND,"cql");
         config.set(CQLConfigOptions.LOCAL_DATACENTER, "dc1");
         config.set(GraphDatabaseConfiguration.USE_MULTIQUERY, true);
+        config.set(GraphDatabaseConfiguration.DROP_STEP_BATCH_MODE, MultiQueryDropStepStrategyMode.NONE.getConfigName());
         return config.getConfiguration();
     }
 
@@ -103,7 +105,7 @@ public Integer dropVertices() {
                 .map(v -> (JanusGraphVertex) v)
                 .collect(Collectors.toList());
 
-            dropCount = tx.multiQuery(vertices).drop();
+            dropCount = tx.multiQuery(vertices).drop().size();
         } else {
             dropCount = tx.traversal()
                 .V()
@@ -117,6 +119,27 @@ public Integer dropVertices() {
         return dropCount;
     }
 
+    @Benchmark
+    public Integer dropVerticesGremlinQuery() {
+
+        JanusGraphTransaction tx;
+        if (isMultiDrop) {
+            tx = graph.buildTransaction().setDropStepStrategyMode(MultiQueryDropStepStrategyMode.ALL).start();
+        } else {
+            tx = graph.buildTransaction().setDropStepStrategyMode(MultiQueryDropStepStrategyMode.NONE).start();
+        }
+
+        Integer dropCount = tx.traversal()
+            .V()
+            .has("name", "name_test")
+            .drop()
+            .toList()
+            .size();
+
+        tx.rollback();
+        return dropCount;
+    }
+
     private void addVertices() {
         for (int i = 0; i < verticesAmount; i++) {
             Vertex vertex = graph.addVertex("id", i);

janusgraph-core/src/main/java/org/janusgraph/core/JanusGraphMultiVertexQuery.java

@@ -60,7 +60,6 @@ public interface JanusGraphMultiVertexQuery<Q extends JanusGraphMultiVertexQuery
      */
     JanusGraphMultiVertexQuery addAllVertices(Collection<? extends Vertex> vertices);
 
-
     @Override
     Q adjacent(Vertex vertex);
 
@@ -156,7 +155,8 @@ public interface JanusGraphMultiVertexQuery<Q extends JanusGraphMultiVertexQuery
     /**
      * Drops all vertices that match this query
      *
-     * @return Count of dropped vertices
+     * @return Map of vertices and their relations which were dropped
      */
-    Integer drop();
+    Map<JanusGraphVertex, Iterable<JanusGraphRelation>> drop();
+
 }

janusgraph-core/src/main/java/org/janusgraph/core/TransactionBuilder.java

@@ -15,6 +15,7 @@
 package org.janusgraph.core;
 
 import org.janusgraph.graphdb.configuration.GraphDatabaseConfiguration;
+import org.janusgraph.graphdb.tinkerpop.optimize.strategy.MultiQueryDropStepStrategyMode;
 import org.janusgraph.graphdb.tinkerpop.optimize.strategy.MultiQueryHasStepStrategyMode;
 import org.janusgraph.graphdb.tinkerpop.optimize.strategy.MultiQueryLabelStepStrategyMode;
 import org.janusgraph.graphdb.tinkerpop.optimize.strategy.MultiQueryPropertiesStrategyMode;
@@ -186,6 +187,15 @@ public interface TransactionBuilder {
      */
     TransactionBuilder setLabelsStepStrategyMode(MultiQueryLabelStepStrategyMode labelStepStrategyMode);
 
+    /**
+     * Sets `drop` step strategy mode.
+     * <p>
+     * Doesn't have any effect if multi-query was disabled via config `query.batch.enabled = false`.
+     *
+     * @return Object with the set drop strategy mode settings
+     */
+    TransactionBuilder setDropStepStrategyMode(MultiQueryDropStepStrategyMode dropStepStrategyMode);
+
     /**
      * Sets the group name for this transaction which provides a way for gathering
      * reporting on multiple transactions into one group.