Implementing JanusGraph aggregate queries using Java
JanusGraph is a distributed Graph database. Aggregate queries using Java and JanusGraph need to be operated through JanusGraph's Java driver. The following are the steps to implement various aggregation queries in JanusGraph using Java:
1. Add Dependency: Add the following dependencies in the pom.xml file of the Maven project:
<dependencies>
<dependency>
<groupId>org.janusgraph</groupId>
<artifactId>janusgraph-core</artifactId>
<version>0.4.3</version>
</dependency>
</dependencies>
2. Connect to JanusGraph: Create a JanusGraph instance and connect using the configuration information related to the connection.
import org.janusgraph.core.JanusGraph;
import org.janusgraph.core.JanusGraphFactory;
public class JanusGraphExample {
public static void main(String[] args) {
JanusGraph graph = JanusGraphFactory.build()
.set("storage.backend", "berkeleyje")
.set("storage.directory", "/tmp/janusgraph")
.open();
}
}
3. Create vertices and edges: Use the JanusGraph API to create vertices and edges.
TitanVertex person1 = graph.addVertex("person");
person1.property("name", "Alice");
person1.property("age", 25);
TitanVertex person2 = graph.addVertex("person");
person2.property("name", "Bob");
person2.property("age", 30);
TitanEdge knows = person1.addEdge("knows", person2);
knows.property("since", 2010);
graph.tx().commit();
4. Query data: Use JanusGraph's query API to execute various aggregated queries.
-Count query: Counts the number of vertices or edges.
long vertexCount = graph.traversal().V().count().next();
long edgeCount = graph.traversal().E().count().next();
-Sum query: Calculate the sum of a certain attribute.
double ageSum = graph.traversal().V().values("age").sum().next();
-Average query: Calculate the average value of a certain attribute.
double ageAvg = graph.traversal().V().values("age").mean().next();
-Maximum and minimum value query: Find the maximum and minimum values of a certain attribute.
int maxAge = graph.traversal().V().values("age").max().next();
int minAge = graph.traversal().V().values("age").min().next();
-Grouping query: Group according to a certain attribute and perform aggregation calculation.
Map<String, Long> ageGroupCount = graph.traversal().V()
.group().by("age").by(count())
.next();
-Sort query: Sort by a certain attribute.
List<String> sortedNames = graph.traversal().V()
.order().by("name").values("name")
.toList();
-Filter Query: Filter based on the value of a certain attribute.
List<String> filteredNames = graph.traversal().V()
.has("age", gt(25)).values("name")
.toList();
-Multi level query: Performs multiple aggregate query operations.
Map<String, Long> ageGroupCount = graph.traversal().V()
.group().by("age").by(count())
.order().by(select(values).sum(), decr)
.next();
This is a simple example of how to use Java to implement various data aggregation queries for JanusGraph. Based on your specific needs, you can use JanusGraph's rich query APIs to perform more complex query operations. Please configure and modify the corresponding operations according to your specific needs.
