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.
• event_time_microsecinds (DateTime) — The date and time when the thread has finished execution of the query with microseconds precision.
• query_start_time (DateTime) — Start time of query execution.
• query_start_time_microseconds (DateTime64) — Start time of query execution with microsecond precision.
• 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 \G

Row 1:
──────
event_date:                    2020-09-11
event_time:                    2020-09-11 10:08:17
event_time_microseconds:       2020-09-11 10:08:17.134042
query_start_time:              2020-09-11 10:08:17
query_start_time_microseconds: 2020-09-11 10:08:17.063150
query_duration_ms:             70
read_rows:                     0
read_bytes:                    0
written_rows:                  1
written_bytes:                 12
memory_usage:                  4300844
peak_memory_usage:             4300844
thread_name:                   TCPHandler
thread_id:                     638133
master_thread_id:              638133
query:                         INSERT INTO test1 VALUES
is_initial_query:              1
user:                          default
query_id:                      50a320fd-85a8-49b8-8761-98a86bcbacef
address:                       ::ffff:127.0.0.1
port:                          33452
initial_user:                  default
initial_query_id:              50a320fd-85a8-49b8-8761-98a86bcbacef
initial_address:               ::ffff:127.0.0.1
initial_port:                  33452
interface:                     1
os_user:                       bharatnc
client_hostname:               tower
client_name:                   ClickHouse 
client_revision:               54437
client_version_major:          20
client_version_minor:          7
client_version_patch:          2
http_method:                   0
http_user_agent:               
quota_key:                     
revision:                      54440
ProfileEvents.Names:           ['Query','InsertQuery','FileOpen','WriteBufferFromFileDescriptorWrite','WriteBufferFromFileDescriptorWriteBytes','ReadCompressedBytes','CompressedReadBufferBlocks','CompressedReadBufferBytes','IOBufferAllocs','IOBufferAllocBytes','FunctionExecute','CreatedWriteBufferOrdinary','DiskWriteElapsedMicroseconds','NetworkReceiveElapsedMicroseconds','NetworkSendElapsedMicroseconds','InsertedRows','InsertedBytes','SelectedRows','SelectedBytes','MergeTreeDataWriterRows','MergeTreeDataWriterUncompressedBytes','MergeTreeDataWriterCompressedBytes','MergeTreeDataWriterBlocks','MergeTreeDataWriterBlocksAlreadySorted','ContextLock','RWLockAcquiredReadLocks','RealTimeMicroseconds','UserTimeMicroseconds','SoftPageFaults','OSCPUVirtualTimeMicroseconds','OSWriteBytes','OSReadChars','OSWriteChars']
ProfileEvents.Values:          [1,1,11,11,591,148,3,71,29,6533808,1,11,72,18,47,1,12,1,12,1,12,189,1,1,10,2,70853,2748,49,2747,45056,422,1520]

See Also

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

Original article