Re: About Query Performaces Problem

[Pavel Stehule <pavel.stehule@xxxxxxxxx>]

st 12. 1. 2022 v 9:23 odesílatel Hüseyin Ellezer <ellezerh@xxxxxxxxx> napsal:

I mean, despite the execution times shown here PostgreSQL 10 is working faster compared to PostgreSQL 14. Is this speed performance about the cached or disk data? How can we see where the data comes from?

use EXPLAIN (ANALYZE, BUFFERS) SELECT ...

https://www.postgresql.org/docs/current/sql-explain.html

Regards

Pavel

Best regards

Pavel Stehule <pavel.stehule@xxxxxxxxx>, 11 Oca 2022 Sal, 16:31 tarihinde şunu yazdı:

út 11. 1. 2022 v 9:41 odesílatel Hüseyin Ellezer <ellezerh@xxxxxxxxx> napsal:

Hello everyone,

I am currently running queries with the same table structures in 2 different virtual machines and 2 different versions. and I get results like below.


Execution Query:

select d.device_id from ats_devices d inner join ats_device_detays dd on dd.device_id=d.device_id;

RESULTS:

postgres v10
                                                                               QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------------------------------------
 Nested Loop  (cost=0.69..7398.76 rows=2325 width=8) (actual time=0.023..5.877 rows=2325 loops=1)
 
 
 
   ->  Index Only Scan using ats_device_detays_device_id_idx on ats_device_detays det  (cost=0.28..91.16 rows=2325 width=8) (actual time=0.006..0.483 rows=2325
         Heap Fetches: 373
   ->  Index Only Scan using ats_devices_pkey1 on ats_devices d  (cost=0.41..3.14 rows=1 width=8) (actual time=0.002..0.002 rows=1 loops=2325)
         Index Cond: (device_id = det.device_id)
         Heap Fetches: 528
 Planning time: 0.180 ms
 Execution time: 6.006 ms
(8 rows)

###########################################################################################################################################################

postgres v14
                                                                           QUERY PLAN
----------------------------------------------------------------------------------------------------------------------------------------------------------------
 Merge Join  (cost=0.56..174.59 rows=2279 width=8) (actual time=0.065..2.264 rows=2304 loops=1)
   Merge Cond: (d.device_id = det.device_id)
   ->  Index Only Scan using ats_devices_pkey1 on ats_devices d  (cost=0.28..70.18 rows=2260 width=8) (actual time=0.033..0.603 rows=2304 loops=1)
         Heap Fetches: 0
   ->  Index Only Scan using ats_device_detays_pkey on ats_device_detays det  (cost=0.28..70.47 rows=2279 width=8) (actual time=0.024..0.506 rows=2304 loops=1)
         Heap Fetches: 0
 Planning Time: 0.666 ms
 Execution Time: 2.519 ms

As a result of that;

According to the result og explain analyzer, Although the performance of the machine on which Postgres v14 is installed is better than the performance of the machine on which v10 is installed and their configurations are the same, in reality it seems to be the opposite. I would appreciate it if you could let me know what could be the cause of this and which parameters I should look?

???

PostgreSQL 10 - execution time 6 ms

PostgreSQL 14 - execution time 2.5 ms

Postgres 14 is about 2x faster

Regards

Pavel