rtitioning constraints should
      contain only comparisons of the partitioning column(s) to constants
      using B-tree-indexable operators, because only B-tree-indexable
      column(s) are allowed in the partition key.
     </p></li><li class="listitem"><p>
      All constraints on all children of the parent table are examined
      during constraint exclusion, so large numbers of children are likely
      to increase query planning time considerably.  So the legacy
      inheritance based partitioning