question: public void ensureIndex ( String idxName , QueryIndexType idxType ) { QueryIndex idx = idxs . get ( idxName ) ; if ( idx == null ) { idx = new QueryIndex ( ) ; idx . setName ( idxName ) ; idx . setIndexType ( idxType ) ; idxs . put ( idxName , idx ) ; } else throw new IllegalArgumentException ( "An index with the same name and of a different type already exists " + "[idxName=" + idxName + ", existingIdxType=" + idx . getIndexType ( ) + ", newIdxType=" + idxType + ']' ) ; }
target:  Ensures that index with the given name exists.