RE: Postgres DB Slowness

-----Original Message-----
From: Juan José Santamaría Flecha <juanjo(dot)santamaria(at)gmail(dot)com>
Sent: Friday, August 23, 2019 1:08 PM
To: Bhattacharjee, Soumik <soumik(dot)bhattacharjee(at)kpn(dot)com>
Cc: eddy(dot)adarsh(at)gmail(dot)com; pgsql-admin(at)lists(dot)postgresql(dot)org
Subject: Re: Postgres DB Slowness

On Fri, Aug 23, 2019 at 10:17 AM <soumik(dot)bhattacharjee(at)kpn(dot)com<mailto:soumik(dot)bhattacharjee(at)kpn(dot)com>> wrote:

>

> Query

> ===========

> SELECT

> i.*

> FROM

> npcurren.num_cps_instelling i,

> npcurren.num_aangesloten_nr n

> WHERE

> n.fk_exploit_nop_int_oper_id = 'PTT'

> AND i.telefoonnummer != n.anr_nummer_hoog

> AND i.telefoonnummer != n.anr_nummer_laag;

>

> Explain Plan

> ======================

> "Nested Loop (cost=2068.47..1769226624.33 rows=101090505159 width=73)"

>

This query looks wrong, resulting in a cartesian join.

As other people have pointed out, the execution times do not seem reasonable, could you change the 'SELECT *' into a 'SELECT count(1)'

for the comparison?

Regards,

Juan José Santamaría Flecha

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Hi Juan,

The query plan is below -

numbes_test=# explain analyze select i.* from npcurren.NUM_CPS_INSTELLING i, npcurren.NUM_AANGESLOTEN_NR n where n.FK_EXPLOIT_NOP_INT_OPER_ID = 'PTT' and i.TELEFOONNUMMER != n.ANR_NUMMER_HOOG and i.TELEFOONNUMMER != n.ANR_NUMMER_LAAG;Â

QUERY PLAN

--------------------------------------------------------------------------------------------------------------------------------------------------------

Nested Loop (cost=2071.86..1817248003.24 rows=103834572306 width=73) (actual time=68.512..28074371.506 rows=98046804138 loops=1)

Join Filter: (((i.telefoonnummer)::text <> (n.anr_nummer_hoog)::text) AND ((i.telefoonnummer)::text <> (n.anr_nummer_laag)::text))

Rows Removed by Join Filter: 36398

-> Seq Scan on num_cps_instelling i (cost=0.00..12485.52 rows=539852 width=73) (actual time=0.069..403.077 rows=539852 loops=1)

-> Materialize (cost=2071.86..130606.58 rows=192339 width=22) (actual time=0.002..16.490 rows=181618 loops=539852)

-> Bitmap Heap Scan on num_aangesloten_nr n (cost=2071.86..129644.88 rows=192339 width=22) (actual time=68.425..555.068 rows=181618 loops=1)

Recheck Cond: ((fk_exploit_nop_int_oper_id)::text = 'PTT'::text)

Heap Blocks: exact=51470

-> Bitmap Index Scan on anr_idx6 (cost=0.00..2023.78 rows=192339 width=0) (actual time=59.276..59.276 rows=181618 loops=1)

Index Cond: ((fk_exploit_nop_int_oper_id)::text = 'PTT'::text)

Planning time: 4.702 ms

Execution time: 31536903.127 ms

(12 rows)

Does this also looks bad for performance with Data types- as there is varchar in a number records field ? - The table DDL is attached

anr_nummer_laag character varying(20) COLLATE pg_catalog."default" NOT NULL,

anr_nummer_hoog character varying(20) COLLATE pg_catalog."default" NOT NULL,