public List<FixedPartitionAttributesImpl> getSecondaryFixedPartitionAttributes_TestsOnly() {
    List<FixedPartitionAttributesImpl> secondaryFixedPAttrs =
        new LinkedList<>();
    if (fixedPAttrs != null) {
      for (FixedPartitionAttributesImpl fpa : fixedPAttrs) {
        if (!fpa.isPrimary()) {
          secondaryFixedPAttrs.add(fpa);
        }
      }
    }
    return secondaryFixedPAttrs;
  }
This creates indexes on PR buckets.
geode-core/src/main/java/org/apache/geode/internal/cache/PartitionedRegion.java