M_query_time_p99 Always Zero

Hi Everyone,

Whenever I am seeing this m_query_time_p99 column in clickhouse-client, it is always showing 0, even in the production servers.
Can you please help me to understand what exactly this column means?

Hi @Asuwini_P thank you for posting to the Percona forums!

I just checked in my own instance and I too have no values for field m_query_time_p99. The field is described as ‘99 percentile of value of query_time in bucket’ but I suppose the QAN agent isn’t yet calculating this value.

Hi @Michael_Coburn ,

Thank you for your response

Is there any way to get this value? or could we calculate this value with the available columns in the metrics table?

Hi @Asuwini_P Can you tell me what the query source is for your MySQL queries? After taking a quick look at the code of the agent, It seems that if you are using the MySQL Slow Log as the source then the field should be populated

I don’t see the equivalent for perfschema, i think because perfschema is already aggregated data so we can’t calculate 99th percentile

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@Michael_Coburn ,
Thank you for the detailed explanation.
I am using performance schema as a query source. So that i couldn’t able to fetch the data

Hi @Asuwini_P
You may want to experiment with the slow log source and then you should start to see 99p calculations