log_queries_* session settings

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

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:

log_queries=1

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.

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)

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:

log_queries_min_type='EXCEPTION_WHILE_PROCESSING'

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.