Force another plan. - Mailing list pgsql-performance
From | Fredrik Olsson |
---|---|
Subject | Force another plan. |
Date | |
Msg-id | 43F74592.7010701@treyst.se Whole thread Raw |
Responses |
Re: Force another plan.
|
List | pgsql-performance |
I have some quite huge queries, inside functions, so debugging is kind of hard. But I have located the query that for some reason gets 4 times as slow after an analyze. Before analyze the plan for the query is this: Nested Loop (cost=16.80..34.33 rows=1 width=28) Join Filter: (ischildof(2, "outer".calendar) OR (hashed subplan)) -> Nested Loop (cost=0.00..11.66 rows=1 width=32) -> Index Scan using t_events_eventype on t_events e (cost=0.00..5.82 rows=1 width=28) Index Cond: (eventtype = 1) Filter: (rrfreq IS NOT NULL) -> Index Scan using t_entities_pkey on t_entities te (cost=0.00..5.83 rows=1 width=4) Index Cond: (te."ID" = "outer".entity) Filter: (partof = 'events'::name) -> Index Scan using t_entities_pkey on t_entities (cost=0.00..5.85 rows=1 width=4) Index Cond: (t_entities."ID" = "outer".entity) Filter: ((haveaccess(createdby, responsible, "class", false) OR CASE WHEN (partof = 'contacts'::name) THEN ischildof(ancestorof(me()), "ID") ELSE false END) AND (subplan)) SubPlan -> Function Scan on alleventoccurances (cost=0.00..12.50 rows=1000 width=8) SubPlan -> Seq Scan on t_attendees (cost=0.00..16.38 rows=170 width=4) Filter: ischildof(2, contact) In reality this takes approximately 1.0s in the general case. After an analyze the plan becomes: Nested Loop (cost=2.09..4.82 rows=1 width=28) Join Filter: ("inner"."ID" = "outer"."ID") -> Hash Join (cost=2.09..3.59 rows=1 width=32) Hash Cond: ("outer"."ID" = "inner".entity) Join Filter: (ischildof(2, "inner".calendar) OR (hashed subplan)) -> Seq Scan on t_entities (cost=0.00..1.46 rows=6 width=4) Filter: ((haveaccess(createdby, responsible, "class", false) OR CASE WHEN (partof = 'contacts'::name) THEN ischildof(ancestorof(me()), "ID") ELSE false END) AND (subplan)) SubPlan -> Function Scan on alleventoccurances (cost=0.00..12.50 rows=1000 width=8) -> Hash (cost=1.06..1.06 rows=2 width=28) -> Seq Scan on t_events e (cost=0.00..1.06 rows=2 width=28) Filter: ((rrfreq IS NOT NULL) AND (eventtype = 1)) SubPlan -> Seq Scan on t_attendees (cost=0.00..1.02 rows=1 width=4) Filter: ischildof(2, contact) -> Seq Scan on t_entities te (cost=0.00..1.16 rows=5 width=4) Filter: (partof = 'events'::name) This takes on approximately 4.5s. So obviously it has degraded. I count myself as a newbie here, so any hints on what goes on, why a plan might be chosen, and how I can make is better is appreciated. Naturally the I can provide scripts to set up all or parts of the database if anyone like. regards -- //Fredrik Olsson Treyst AB +46-(0)19-362182 fredrik.olsson@treyst.se
pgsql-performance by date: