Lucene does not support index on char property

[InverseIntegral]

I'm currently using JanusGraph InMemory with Lucene as an index backend. When I want to create a mixed index on a char property, I get the following exception:

Exception in thread "main" org.janusgraph.core.JanusGraphException: Could not register new index field 'p' with index backend as the data type, cardinality or parameter combination is not supported.
	at org.janusgraph.graphdb.database.management.ManagementSystem.addIndexKey(ManagementSystem.java:714)
	at org.janusgraph.graphdb.database.management.ManagementSystem$IndexBuilder.buildMixedIndex(ManagementSystem.java:833)

I think the Number.class.isAssignableFrom(dataType) in

janusgraph/janusgraph-lucene/src/main/java/org/janusgraph/diskstorage/lucene/LuceneIndex.java

Line 1012 in 543632f

if (Number.class.isAssignableFrom(dataType) || dataType == Date.class || dataType == Instant.class || dataType == Boolean.class || dataType == UUID.class) {

evaluates to false. Is this intended behaviour? I would expect a char to be an integer which can be indexed but maybe Lucene does not support this.

[vtslab]

I guess it is intended behaviour. char/Character is more of a java thing that is not easily transferrable to other programming languages. So, it is the responsibility of the application to convert the char to a string or integer.

[InverseIntegral]

Lucene is written in Java though, that's why I would expect them to support it in some way or another. But I will convert it to an integer for now on my side and maybe make a feature request later on.