private static void assertCompatible(SelectResults sr1, SelectResults sr2) {
    Assert.assertTrue(
        sr1.getCollectionType().getElementType().equals(sr2.getCollectionType().getElementType()));
  }
Return a SelectResults that is the union of c1 and c2. May or may not return a modified c1 or
c2.
geode-core/src/main/java/org/apache/geode/cache/query/internal/QueryUtils.java