Forcing Janusgraph to use indices when performing traversal with Union step



I need to execute Janusgraph traversals, using a Union step, which contains multiple 'has' steps, each of which tests an indexed property for equality to a value.  Prior to the Union step, there is another 'has' step, which also tests an indexec property.

For example:

    g.V().has('indexed-prop1', 'value1').union(has('indexed-prop2', 'value2'), has('indexed-prop3', 'value3'))

How can I verify whether or not the traversal is using indices 'indexed-prop2' and 'indexed-prop3'?  I suspect that it is not.  The traversal seems to take a long time to run; however, when I simplify the traversal, by having only one 'has' step within the union, it runs very quickly.

What is the best way to execute this type of traversal.  My application is written in Java.

Thanks in advance,

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