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

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.

Regards,
Igor Neyman