query using partitions explicitly ("1"):
explain analyze
select nome1,
thv3tralacc,
dltbfpgpdch
FROM cell_bsc_60_0610 as cell_bsc
left outer join teststscell73_0610_1 as data on data.ne_id=cell_bsc.nome1
left outer join teststscell13_0610_1 as data1 on data1.ne_id=cell_bsc.nome1 and data1.time=data.time
where
data.time >=cell_bsc.starttime and data.time <=cell_bsc.endtime and
data.time between '2006-10-01 00:00:00' and '2006-10-06 00:00:00'
and data1.time >=cell_bsc.starttime and data1.time <=cell_bsc.endtime
and data1.time between '2006-10-01 00:00:00' and '2006-10-06 00:00:00'
and cell_bsc.nome2=2
explain analyze:
http://explain-analyze.info/query_plans/3805-query-plan-2509
same query, but using postgresql's partition pruning ("2"):
explain analyze
select nome1,
thv3tralacc,
dltbfpgpdch
FROM cell_bsc_60_0610 as cell_bsc
left outer join teststscell73 as data on data.ne_id=cell_bsc.nome1
left outer join teststscell13 as data1 on data1.ne_id=cell_bsc.nome1 and data1.time=data.time
where
data.time >=cell_bsc.starttime and data.time <=cell_bsc.endtime and
data.time between '2006-10-01 00:00:00' and '2006-10-06 00:00:00'
and data1.time >=cell_bsc.starttime and data1.time <=cell_bsc.endtime
and data1.time between '2006-10-01 00:00:00' and '2006-10-06 00:00:00'
and cell_bsc.nome2=2
explain analyze:
http://explain-analyze.info/query_plans/3807-query-plan-2511
The second version is A LOT slower (10x). But the 2 queries should be identical... why the two totally different
plans???
As you can see in query "1" I just put the used table, in query "2" postgres uses exactly the table I put in "1" (plus
theempty tables that are the "father" of the other tables); so I don't understand why the 2 plans...
