Monitoring ClickHouse Query Parser Performance

Table of Contents


To monitor the Parser performance in ClickHouse, you can use the system.query_log system table, which contains information about all queries executed in the cluster.

Here’s an example SQL code that you can use to monitor the Parser performance:

FROM system.query_log
WHERE type = 1
ORDER BY event_time DESC

In this code, we select several columns from the system.query_log table, including the query text, query duration, parse duration, and the approximate number of total, read, and written rows for the query. We filter the results using the type = 1 condition, corresponding to queries parsed successfully. Finally, we sort the results by event time in descending order and limit the output to the last 100 queries.


By monitoring the Parser performance in this way, you can gain insights into the efficiency of the parsing process and identify any performance bottlenecks or issues. For example, if you notice that the parse duration is consistently high for certain queries, you may need to investigate and optimize the query structure or workload to improve performance.

To know more about Query Profiler and Parser, do consider reading the below articles

About Shiv Iyer 227 Articles
Open Source Database Systems Engineer with a deep understanding of Optimizer Internals, Performance Engineering, Scalability and Data SRE. Shiv currently is the Founder, Investor, Board Member and CEO of multiple Database Systems Infrastructure Operations companies in the Transaction Processing Computing and ColumnStores ecosystem. He is also a frequent speaker in open source software conferences globally.