ClickHouse/docs/en/operations/system-tables/query_thread_log.md

system.query_thread_log

Contains information about threads which execute queries, for example, thread name, thread start time, duration of query processing.

To start logging:

1. Configure parameters in the query_thread_log section.
2. Set log_query_threads to 1.

The flushing period of data is set in flush_interval_milliseconds parameter of the query_thread_log server settings section. To force flushing, use the SYSTEM FLUSH LOGS query.

ClickHouse doesn’t delete data from the table automatically. See Introduction for more details.

Columns:

• event_date (Date) — The date when the thread has finished execution of the query.
• event_time (DateTime) — The date and time when the thread has finished execution of the query.
• query_start_time (DateTime) — Start time of query execution.
• query_duration_ms (UInt64) — Duration of query execution.
• read_rows (UInt64) — Number of read rows.
• read_bytes (UInt64) — Number of read bytes.
• written_rows (UInt64) — For INSERT queries, the number of written rows. For other queries, the column value is 0.
• written_bytes (UInt64) — For INSERT queries, the number of written bytes. For other queries, the column value is 0.
• memory_usage (Int64) — The difference between the amount of allocated and freed memory in context of this thread.
• peak_memory_usage (Int64) — The maximum difference between the amount of allocated and freed memory in context of this thread.
• thread_name (String) — Name of the thread.
• thread_number (UInt32) — Internal thread ID.
• thread_id (Int32) — thread ID.
• master_thread_id (UInt64) — OS initial ID of initial thread.
• query (String) — Query string.
• is_initial_query (UInt8) — Query type. Possible values:
  • 1 — Query was initiated by the client.
  • 0 — Query was initiated by another query for distributed query execution.
• user (String) — Name of the user who initiated the current query.
• query_id (String) — ID of the query.
• address (IPv6) — IP address that was used to make the query.
• port (UInt16) — The client port that was used to make the query.
• initial_user (String) — Name of the user who ran the initial query (for distributed query execution).
• initial_query_id (String) — ID of the initial query (for distributed query execution).
• initial_address (IPv6) — IP address that the parent query was launched from.
• initial_port (UInt16) — The client port that was used to make the parent query.
• interface (UInt8) — Interface that the query was initiated from. Possible values:
  • 1 — TCP.
  • 2 — HTTP.
• os_user (String) — OS’s username who runs clickhouse-client.
• client_hostname (String) — Hostname of the client machine where the clickhouse-client or another TCP client is run.
• client_name (String) — The clickhouse-client or another TCP client name.
• client_revision (UInt32) — Revision of the clickhouse-client or another TCP client.
• client_version_major (UInt32) — Major version of the clickhouse-client or another TCP client.
• client_version_minor (UInt32) — Minor version of the clickhouse-client or another TCP client.
• client_version_patch (UInt32) — Patch component of the clickhouse-client or another TCP client version.
• http_method (UInt8) — HTTP method that initiated the query. Possible values:
  • 0 — The query was launched from the TCP interface.
  • 1 — GET method was used.
  • 2 — POST method was used.
• http_user_agent (String) — The UserAgent header passed in the HTTP request.
• quota_key (String) — The “quota key” specified in the quotas setting (see keyed).
• revision (UInt32) — ClickHouse revision.
• ProfileEvents.Names (Array(String)) — Counters that measure different metrics for this thread. The description of them could be found in the table system.events.
• ProfileEvents.Values (Array(UInt64)) — Values of metrics for this thread that are listed in the ProfileEvents.Names column.

Example

 SELECT * FROM system.query_thread_log LIMIT 1 FORMAT Vertical

Row 1:
──────
event_date:           2020-05-13
event_time:           2020-05-13 14:02:28
query_start_time:     2020-05-13 14:02:28
query_duration_ms:    0
read_rows:            1
read_bytes:           1
written_rows:         0
written_bytes:        0
memory_usage:         0
peak_memory_usage:    0
thread_name:          QueryPipelineEx
thread_id:            28952
master_thread_id:     28924
query:                SELECT 1
is_initial_query:     1
user:                 default
query_id:             5e834082-6f6d-4e34-b47b-cd1934f4002a
address:              ::ffff:127.0.0.1
port:                 57720
initial_user:         default
initial_query_id:     5e834082-6f6d-4e34-b47b-cd1934f4002a
initial_address:      ::ffff:127.0.0.1
initial_port:         57720
interface:            1
os_user:              bayonet
client_hostname:      clickhouse.ru-central1.internal
client_name:          ClickHouse client
client_revision:      54434
client_version_major: 20
client_version_minor: 4
client_version_patch: 1
http_method:          0
http_user_agent:
quota_key:
revision:             54434
ProfileEvents.Names:  ['ContextLock','RealTimeMicroseconds','UserTimeMicroseconds','OSCPUWaitMicroseconds','OSCPUVirtualTimeMicroseconds']
ProfileEvents.Values: [1,97,81,5,81]
...

See Also

• system.query_log — Description of the query_log system table which contains common information about queries execution.

Original article