RE: Postgres DB Slowness

 

 

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

 

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

 

On 8/22/19 9:04 AM, soumik.bhattacharjee@kpn.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