he point here is that there
    is no need to scan the older partitions at all to answer this query.
    When we enable partition pruning, we get a significantly
    cheaper plan that will deliver the same answer:
</p><pre class="programlisting">
SET enable_partition_pruning = on;
EXPLAIN SELECT count(*) FROM measurement WHERE logdate &gt;= DATE '2008-01-01';
                                    QUERY PLAN
-------------------------------------------------------------------​----------------
 Aggregate  (cos