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Created_tmp_files value always showing huge- MySQL RDS performance issue

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Dear All,

I have been seeing below values for MySQL RDS instance of type ( db.r5.8xlarge - Managed MySQL RDS version 8.0.23), and sometime applicaton also reporting slow performance. Would liek to know what params I have to look into to find out real bottleneck wtih DB.

8.0.23

Created_tmp_disk_tables 0 Created_tmp_files 4390282772 <=== Is this value really matter of concern? Created_tmp_tables 15

Best regards, Ravi

asked 6 months ago39 views
1 Answer
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Hi

I was researching this online and I found this blog post might be related to your case: https://forums.percona.com/t/created-tmp-files-what-is-the-cause/1231

Looks like the increase in the Created_tmp_files resides in the memory and could be caused due to unindexed group by/order by.

From MySQL DOC: https://dev.mysql.com/doc/refman/5.7/en/server-status-variables.html#statvar_Created_tmp_files

Created_tmp_files: How many temporary files mysqld has created.

Most likely related to some queries. Might need your DBAs to take a deeper look.

--> Regarding to the performance, general troubleshooting need to make sure:

  1. Instance having enough resources (CPU, Memory, Throughput, these can be reviewed in CloudWatch, Performance Insight)
  2. If certain query having performance issue, then need to investigate the query plan, and tune the query.
  3. If you suspect something from AWS end causing the performance issue, you may open a support case with us for us to look into storage and host.
SUPPORT ENGINEER
answered 6 months ago

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