Hey everyone,

I'm currently running janusgraph-inmemory with janusgraph-lucence both version 0.6.2
And I'm experiencing strange behaviour when creating an index that contains an underscore in its name.
Whenever I run the following code:

PropertiesConfiguration conf = ConfigurationUtil.loadPropertiesConfig("conf/test.properties");
JanusGraph graph = JanusGraphFactory.open(conf);
String name = "some_name";

graph.tx().rollback();
JanusGraphManagement management = graph.openManagement();

management.makePropertyKey("name").dataType(String.class).make();
management.commit();

management = graph.openManagement();

management.buildIndex(name, Vertex.class)
        .addKey(management.getPropertyKey("name"))
        .buildMixedIndex("search");
management.commit();

ManagementSystem.awaitGraphIndexStatus(graph, name).
        status(SchemaStatus.REGISTERED)
        .call();

management = graph.openManagement();
management.updateIndex(management.getGraphIndex(name), SchemaAction.REINDEX).get();
management.commit();

management = graph.openManagement();
System.out.println(management.printIndexes());

graph.traversal().addV().property("name", "Test").next();
graph.tx().commit();

I get the following output:

I get the following output:

INFO  o.j.g.d.management.ManagementSystem - Index update job successful for [some_name]
------------------------------------------------------------------------------------------------
Graph Index (Vertex)           | Type        | Unique    | Backing        | Key:           Status |
---------------------------------------------------------------------------------------------------
some_name                      | Mixed       | false     | search         | name:         ENABLED |
---------------------------------------------------------------------------------------------------
Graph Index (Edge)             | Type        | Unique    | Backing        | Key:           Status |
---------------------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------------------
Relation Index (VCI)           | Type        | Direction | Sort Key       | Order    |     Status |
---------------------------------------------------------------------------------------------------

ERROR o.j.g.database.StandardJanusGraph - Error while committing index mutations for transaction [5] on index: search
org.janusgraph.core.JanusGraphException: Could not execute operation due to backend exception
	at org.janusgraph.diskstorage.util.BackendOperation.execute(BackendOperation.java:54)
	at org.janusgraph.diskstorage.indexing.IndexTransaction.flushInternal(IndexTransaction.java:158)
	at org.janusgraph.diskstorage.indexing.IndexTransaction.commit(IndexTransaction.java:139)
	at org.janusgraph.diskstorage.BackendTransaction.commitIndexes(BackendTransaction.java:143)
	at org.janusgraph.graphdb.database.StandardJanusGraph.commit(StandardJanusGraph.java:804)
	at org.janusgraph.graphdb.transaction.StandardJanusGraphTx.commit(StandardJanusGraphTx.java:1525)
	at org.janusgraph.graphdb.tinkerpop.JanusGraphBlueprintsGraph$GraphTransaction.doCommit(JanusGraphBlueprintsGraph.java:322)
	at org.apache.tinkerpop.gremlin.structure.util.AbstractTransaction.commit(AbstractTransaction.java:104)
	at org.janusgraph.graphdb.tinkerpop.JanusGraphBlueprintsGraph$GraphTransaction.commit(JanusGraphBlueprintsGraph.java:300)
	at Scratch.main(scratch.java:48)
Caused by: org.janusgraph.diskstorage.PermanentBackendException: Permanent exception while executing backend operation IndexMutation
	at org.janusgraph.diskstorage.util.BackendOperation.executeDirect(BackendOperation.java:79)
	at org.janusgraph.diskstorage.util.BackendOperation.execute(BackendOperation.java:52)
	... 9 common frames omitted
Caused by: java.lang.IllegalArgumentException: Invalid store name: some_name
	at com.google.common.base.Preconditions.checkArgument(Preconditions.java:217)
	at org.janusgraph.diskstorage.lucene.LuceneIndex.getStoreDirectory(LuceneIndex.java:194)
	at org.janusgraph.diskstorage.lucene.LuceneIndex.getWriter(LuceneIndex.java:216)
	at org.janusgraph.diskstorage.lucene.LuceneIndex.mutateStores(LuceneIndex.java:289)
	at org.janusgraph.diskstorage.lucene.LuceneIndex.mutate(LuceneIndex.java:275)
	at org.janusgraph.diskstorage.indexing.IndexTransaction$1.call(IndexTransaction.java:161)
	at org.janusgraph.diskstorage.indexing.IndexTransaction$1.call(IndexTransaction.java:158)
	at org.janusgraph.diskstorage.util.BackendOperation.executeDirect(BackendOperation.java:66)
	... 10 common frames omitted

Wouldn't it be better to disallow the creation of the index in the first place? After the creation all queries seem to fail with the same PermanentBackendException.