-----------------------------------------------------------​----------------
 Aggregate  (cost=188.76..188.77 rows=1 width=8)
   -&gt;  Append  (cost=0.00..181.05 rows=3085 width=0)
         -&gt;  Seq Scan on measurement_y2006m02  (cost=0.00..33.12 rows=617 width=0)
               Filter: (logdate &gt;= '2008-01-01'::date)
         -&gt;  Seq Scan on measurement_y2006m03  (cost=0.00..33.12 rows=617 width=0)
               Filter: (logdate &gt;= '2008-01-01'::date)
...
         -&gt;  Seq Scan on measurem