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These settings are available in system.settings and are autogenerated from source.

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log_queries

Setting up query logging. Queries sent to ClickHouse with this setup are logged according to the rules in the query_log server configuration parameter. Example:

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log_queries_cut_to_length

If query length is greater than a specified threshold (in bytes), then cut query when writing to query log. Also limit the length of printed query in ordinary text log.

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log_queries_min_query_duration_ms

If enabled (non-zero), queries faster than the value of this setting will not be logged (you can think about this as a long_query_time for MySQL Slow Query Log), and this basically means that you will not find them in the following tables:
  • system.query_log
  • system.query_thread_log
Only the queries with the following type will get to the log:
  • QUERY_FINISH
  • EXCEPTION_WHILE_PROCESSING
  • Type: milliseconds
  • Default value: 0 (any query)

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log_queries_min_type

query_log minimal type to log. Possible values:
  • QUERY_START (=1)
  • QUERY_FINISH (=2)
  • EXCEPTION_BEFORE_START (=3)
  • EXCEPTION_WHILE_PROCESSING (=4)
Can be used to limit which entities will go to query_log, say you are interested only in errors, then you can use EXCEPTION_WHILE_PROCESSING:

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log_queries_probability

Allows a user to write to query_log, query_thread_log, and query_views_log system tables only a sample of queries selected randomly with the specified probability. It helps to reduce the load with a large volume of queries in a second. Possible values:
  • 0 — Queries are not logged in the system tables.
  • Positive floating-point number in the range [0..1]. For example, if the setting value is 0.5, about half of the queries are logged in the system tables.
  • 1 — All queries are logged in the system tables.
Last modified on July 23, 2026