DML sql execution time slow down PGv14 compared with PGv13

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Hi,

   We had some load test ( DML inserts/deletes/updates/ on tens of hash partition tables)  and found that PGV14 slow down 10-15% compared with PGV13.  Same test server, same schema tables and data. From pg_stat_statements, sql exec_time, we did found similar mean_exec_time increased from 5%-25% with same SQL statements. Both v14 and v13 give very fast sql response time, just compare the %diff from sql statements mean_exec_time.

   Now, I get a pgbench test in same server, the steps as below, it’s similar as our application workload test, small sql statement running very fast but did see v14 slow down 5-10% for DML,compared with v13.

   1.date;pgbench -i -s 6000 -F 85 -U pgbench --partition-method=hash --partitions=32

   2.reboot OS to refresh buffer

   3.run four rounds of test:  date;pgbench -c 10 -j 10 -n -T 180 -U pgbench -M prepared

 

Compare 14.6 and 13.9 on RHEL8.4,  the “add primary key” step 14.6 much fast than 13.9, but most of insert/updates slow down 5-10%.  The table is very simple and sql should be same, no idea what contribute to the sql exec_time difference?  Attached please find sql exec_time.

 

I copy the sql here too,

   

version

min_exec_time

max_exec_time

mean_exec_time

calls

SQL

13.9

0.002814

1.088559

0.004214798

3467468

INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES ($1, $2, $3, $4, CURRENT_TIMESTAMP)

14.6

0.003169

0.955241

0.004482497

3466665

INSERT INTO pgbench_history (tid, bid, aid, delta, mtime) VALUES ($1, $2, $3, $4, CURRENT_TIMESTAMP)

%diff

12.61549396

 

6.351410351

 

 

 

 

 

 

 

 

 

 

 

 

 

 

13.9

0.013449

15.638027

1.18372356

3467468

UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2

14.6

0.016109

133.106913

1.228978518

3466665

UPDATE pgbench_accounts SET abalance = abalance + $1 WHERE aid = $2

%diff

19.77842219

 

3.823101875

 

 

 

 

 

 

 

 

13.9

0.005433

2.051736

0.008532748

3467468

UPDATE pgbench_branches SET bbalance = bbalance + $1 WHERE bid = $2

14.6

0.00625

1.847688

0.009062454

3466665

UPDATE pgbench_branches SET bbalance = bbalance + $1 WHERE bid = $2

%diff

15.03773238

 

6.207914363

 

 

 

Thanks,

 

James

Attachment: sqlstats_v13_v14_pgbench.xlsx
Description: sqlstats_v13_v14_pgbench.xlsx


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