RE: Postgres DB Slowness

From: Bhattacharjee, Soumik
Sent: Thursday, August 22, 2019 5:05 PM
To: 'Ron' <ronljohnsonjr(at)gmail(dot)com>; pgsql-admin(at)lists(dot)postgresql(dot)org
Subject: RE: Postgres DB Slowness

From: Ron <ronljohnsonjr(at)gmail(dot)com><mailto:ronljohnsonjr(at)gmail(dot)com>
Sent: Thursday, August 22, 2019 4:26 PM
To: pgsql-admin(at)lists(dot)postgresql(dot)org<mailto:pgsql-admin(at)lists(dot)postgresql(dot)org>
Subject: Re: Postgres DB Slowness

On 8/22/19 9:04 AM, soumik(dot)bhattacharjee(at)kpn(dot)com<mailto:soumik(dot)bhattacharjee(at)kpn(dot)com> wrote:

Hello Members,

We have the below PostgreSQL database recently migrated from Oracle.

The postgres DB parameters are attached here.

# DB Version: 10

# OS Type: Linux

# Total Memory (RAM): 30 GB
#CPU
nproc --all
2

There is huge slowness in the database now with any queries.

Oracle - Select * from TABLENAME- in takes 0.009 milliseconds
PostgreSQL - Same query takes more than 2 minutes.

Have you validated that the Postgres server has the same indexes?

If so, did you ANALYZE all the tables?

Yes Ron, we migrated from Oracle as per same structure and indexes.

I did the analyze for 2-3 tables now as per my SQL query I wrote and also ran for one particular table below –

VACUUM (FULL,ANALYZE) table_name.

What does the query plan for that query look like?

What's the table definition?

Is the hardware comparable? (Might it be a SAN or VM issue?)

Table definition is attached here.

EXPLAIN SELECT *
FROM npcurren.num_aangesloten_nr;

"Seq Scan on num_aangesloten_nr (cost=0.00..268192.46 rows=9649046 width=113)"

- Oracle 11gR2 was hosted on physical HP-UX server last updated 12 years back- legacy system

- Current postgres server- physical

$ cat /etc/redhat-release

Red Hat Enterprise Linux Server release 7.6 (Maipo)

$ uname -a

Linux slnc7r1513.db.gen.local 3.10.0-957.1.3.el7.x86_64 #1 SMP Thu Nov 15 17:36:42 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

The select * from query takes all of the 2 CPU’s.

top - 17:24:33 up 42 days, 5:12, 1 user, load average: 0.43, 0.54, 0.57
Tasks: 227 total, 4 running, 223 sleeping, 0 stopped, 0 zombie
%Cpu(s): 35.2 us, 6.9 sy, 0.0 ni, 51.9 id, 0.0 wa, 0.0 hi, 6.0 si, 0.0 st
KiB Mem : 32947032 total, 29998788 free, 375068 used, 2573176 buff/cache
KiB Swap: 2097148 total, 1953380 free, 143768 used. 30803956 avail Mem

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
11331 postgres 20 0 5976024 16036 13432 R 92.1 0.0 0:13.98 postgres
11163 postgres 20 0 5981000 16764 9088 S 1.3 0.1 0:01.24 postgres