----
<pre>
var bulk = db.h1H6.initializeUnorderedBulkOp();
bulk.find({}).update(
[{"$set": { "_RaceId": { $concat: [ "$RaceId.Year", "-", "$RaceId.MonthDay", "-","$RaceId.JyoCD", "-","$RaceId.Kaiji", "-","$RaceId.Nichiji", "-","$RaceId.RaceNum" ] } } }]);bulk.execute();
</pre>