Re: Strange workaround for slow query

Hi,

EXPLAIN SELECT * FROM events_events LEFT OUTER JOIN events_event_types ON
eventType_id=events_event_types.id WHERE severity=20 AND (eventType_id
IN (71)) ORDER BY datetime DESC limit 50;
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------------
Limit (cost=3.23..200.31 rows=50 width=131)
-> Nested Loop (cost=3.23..49139.16 rows=12466 width=131)
-> Index Scan Backward using
events_events_eventtype_id_datetime_ind on events_events
(cost=0.00..48886.61 rows=12466 width=93)
Index Cond: (eventtype_id = 71)
-> Materialize (cost=3.23..3.24 rows=1 width=38)
-> Seq Scan on events_event_types (cost=0.00..3.23 rows=1
width=38)
Filter: ((id = 71) AND (severity = 20))

EXPLAIN SELECT * FROM events_events LEFT OUTER JOIN events_event_types ON
eventType_id=events_event_types.id WHERE severity=70 AND (eventType_id
IN (71, 999)) ORDER BY datetime DESC LIMIT 50;

QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------------------------------------
Limit (cost=27290.24..27290.37 rows=50 width=131)
-> Sort (cost=27290.24..27303.15 rows=5164 width=131)
Sort Key: events_events.datetime
-> Nested Loop (cost=22.95..27118.70 rows=5164 width=131)
-> Seq Scan on events_event_types (cost=0.00..3.02 rows=17
width=38)
Filter: (severity = 70)
-> Bitmap Heap Scan on events_events (cost=22.95..1589.94
rows=408 width=93)
Recheck Cond: ((events_events.eventtype_id = ANY
('{71,999}'::bigint[])) AND (events_events.eventtype_id =
events_event_types.id))
-> Bitmap Index Scan on
test_events_events_eventtype_id_severity_ind (cost=0.00..22.85 rows=408
width=0)
Index Cond: ((events_events.eventtype_id = ANY
('{71,999}'::bigint[])) AND (events_events.eventtype_id =
events_event_types.id))

By the way, sorry for my colleague Kees re-posting my message, but I was
under the assumption that my post did not make it into the group (as we
experienced in the past as well).

Groeten, best regards,

Sander Verhagen