RE: Postgres DB Slowness

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

On Fri, Aug 23, 2019 at 10:17 AM <soumik.bhattacharjee@kpn.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; 

                                                                       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,