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

[Andreas Joseph Krogh <andreas@xxxxxxxxxx>]

På mandag 09. februar 2015 kl. 22:36:55, skrev Igor Neyman <ineyman@xxxxxxxxxxxxxx>:

 

 

From: pgsql-performance-owner@xxxxxxxxxxxxxx [mailto:pgsql-performance-owner@xxxxxxxxxxxxxx] On Behalf Of Andreas Joseph Krogh
Sent: Monday, February 09, 2015 4:13 PM
To: pgsql-performance@xxxxxxxxxxxxxx
Subject: 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@xxxxxxxxxx

www.visena.com