QAN - increase query length and examples/explain

Percona Monitoring and Management (PMM) PMM 2.x
1

Is there a way when running PMM with a MySQL node to increase the length of the queries displayed in Query Analytics?

Currently they are getting truncated for our longer queries I am trying to review and they also don’t show any information in Examples or Explain.

2

Hi @agrowe,

You can hover the icon next to the query to see the full query:

full_query_1.png
full_query_1.png718×389 69 KB

full_query_2.png
full_query_2.png718×389 77.2 KB

If that doesn’t work for you please check the comments in the following feature request to see if it matches your problem: https://jira.percona.com/browse/PMM-6692.

Thank you for the question and hope this helps!

3

Hi @tiagomotasantos

Thanks for linking that Jira ticket, it looks to be what I was seeing with the performance schema.

When hovering over the (i) icon, the full query isn’t available which then also causes issues for the examples/explain tabs as they can’t show anything.

According to that ticket, I need to update “max_digest_length” and “performance_schema_max_digest_length” which are the normalised values seen in the query popup.

To also get the examples column working, it looks like I also need to update “performance_schema_max_sql_text_length”, is that correct?

Are there also any performance considerations to take into account when raising these? the ticket had values of 4000 up from 1024 and also the docs mention a 10:1 ratio of queries to sessions. With only a few hundred sessions at a time, it only looks to add around 8MB total memory requirements.

Thanks

4

Hi,

as posted in another thread, the examples/explain tabs worked for me after enabling the events_statements_current and events_statements_history consumers.

max_digest_length configures the max length for the normalized version (as shown in the screenshot)

max_sql_text_length configures the max length for the SQL_TEXT column, it is used as example (which is then used for the explain)

https://forums.percona.com/discussion/comment/57538/#Comment_57538

5

Did you increase the values from default 1024 to 4000 and checked the performance?