best way to create in memory db? - neo4j

Question

Is it the correct way to create a in memory db using neo4j ? So that traverse query will hit only cache and not the disk .
approach - 1 : I tried with this :
package com.test;
import org.neo4j.graphdb.GraphDatabaseService;
import org.neo4j.graphdb.factory.GraphDatabaseFactory;
import org.neo4j.kernel.impl.util.FileUtils;
import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
public class CreateDBFactory {
private static GraphDatabaseService graphDb = null;
public static final String DB = "test/db";
public static GraphDatabaseService createInMemoryDB() {
System.out.println("- Inside createInMemoryDB() - ");
if (null == graphDb) {
synchronized (GraphDatabaseService.class) {
if (null == graphDb) {
System.out.println(" - Inside if clause -");
final Map<String, String> config = new HashMap<>();
config.put("neostore.nodestore.db.mapped_memory", "50M");
config.put("string_block_size", "60");
config.put("array_block_size", "300");
graphDb = new GraphDatabaseFactory()
.newEmbeddedDatabaseBuilder(DB).setConfig(config)
.newGraphDatabase();
registerShutdownHook(graphDb);
}
}
}
return graphDb;
}
private static void registerShutdownHook(final GraphDatabaseService graphDb) {
Runtime.getRuntime().addShutdownHook(new Thread() {
#Override
public void run() {
graphDb.shutdown();
}
});
}
public static void clearDb() {
try {
if (graphDb != null) {
graphDb.shutdown();
graphDb = null;
}
FileUtils.deleteRecursively(new File(DB));
} catch (final IOException e) {
throw new RuntimeException(e);
}
}
}
Approach -2 : Using Neo4jBasicDocTest class.
Here new ImpermanentDatabaseBuilder() is not creating the target/test-data/impermanent-db folder. So not able to test " Nancy" node is created or not .

Answer 1

Neo4j doesn't have an 'in memory' mode in the sense that all data always stored in memory and no disk storage is used. ImpermanentGraphDatabase is the closest you'll find to anything like that, but that just creates a data directory at random and will delete it when it is shutdown.
If you are okay with using disk, you can use the above ImpermanentGraphDatabase, and just set the cache of neo4j to be really high. This will make everything be stored in memory, as well as on disk.