Re: Poor performance when deleting from entity-attribute-value type master-table

På mandag 09. februar 2015 kl. 22:36:55, skrev Igor Neyman <
ineyman(at)perceptron(dot)com <mailto:ineyman(at)perceptron(dot)com>>:  

From: pgsql-performance-owner(at)postgresql(dot)org
[mailto:pgsql-performance-owner(at)postgresql(dot)org]On Behalf Of Andreas Joseph Krogh
Sent: Monday, February 09, 2015 4:13 PM
To: pgsql-performance(at)postgresql(dot)org
Subject: [PERFORM] Poor performance when deleting from entity-attribute-value
type master-table

Hi all.

Using PG-9.4.0 I'm seeing this trying to delete from an "entity"-master table:

*# explain analyze     delete from onp_crm_entity where entity_id IN (select
tmp.delivery_id from temp_delete_delivery_id tmp);
                                                                    QUERY
PLAN                                                                     

---------------------------------------------------------------------------------------------------------------------------------------------------
 Delete on onp_crm_entity  (cost=0.43..5673.40 rows=1770 width=12) (actual
time=7.370..7.370 rows=0 loops=1)
   ->  Nested Loop  (cost=0.43..5673.40 rows=1770 width=12) (actual
time=0.050..1.374 rows=108 loops=1)
         ->  Seq Scan on temp_delete_delivery_id tmp  (cost=0.00..27.70
rows=1770 width=14) (actual time=0.014..0.080 rows=108 loops=1)
         ->  Index Scan using onp_crm_entity_pkey on onp_crm_entity 
(cost=0.43..3.18 rows=1 width=14) (actual time=0.010..0.011 rows=1 loops=108)
               Index Cond: (entity_id = tmp.delivery_id)
 Planning time: 0.314 ms
 Trigger for constraint onp_crm_activity_entity_id_fkey: time=4.141 calls=108

 Trigger for constraint ...

 Trigger for constraint ...

 Trigger for constraint ...

I have lots of tables referencing onp_crm_entity(entity_id) so I expect the
poor performance of deleting from it is caused by all the triggers firing to
check FKI-constraints.

Andreas, do you have indexes on FK columns in child tables?

If not – there is your problem.

  Yes, they have indexes, but deleting 1M rows still results in calling the
triggers 1M times * number of FKs...   -- Andreas Joseph Krogh CTO / Partner -
Visena AS Mobile: +47 909 56 963 andreas(at)visena(dot)com <mailto:andreas(at)visena(dot)com>
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