# system.query_thread_log {#system_tables-query_thread_log} Contains information about threads that execute queries, for example, thread name, thread start time, duration of query processing. To start logging: 1. Configure parameters in the [query_thread_log](../../operations/server-configuration-parameters/settings.md#server_configuration_parameters-query_thread_log) section. 2. Set [log_query_threads](../../operations/settings/settings.md#settings-log-query-threads) to 1. The flushing period of data is set in `flush_interval_milliseconds` parameter of the [query_thread_log](../../operations/server-configuration-parameters/settings.md#server_configuration_parameters-query_thread_log) server settings section. To force flushing, use the [SYSTEM FLUSH LOGS](../../sql-reference/statements/system.md#query_language-system-flush_logs) query. ClickHouse does not delete data from the table automatically. See [Introduction](../../operations/system-tables/index.md#system-tables-introduction) for more details. Columns: - `event_date` ([Date](../../sql-reference/data-types/date.md)) — The date when the thread has finished execution of the query. - `event_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — The date and time when the thread has finished execution of the query. - `event_time_microsecinds` ([DateTime](../../sql-reference/data-types/datetime.md)) — The date and time when the thread has finished execution of the query with microseconds precision. - `query_start_time` ([DateTime](../../sql-reference/data-types/datetime.md)) — Start time of query execution. - `query_start_time_microseconds` ([DateTime64](../../sql-reference/data-types/datetime64.md)) — Start time of query execution with microsecond precision. - `query_duration_ms` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Duration of query execution. - `read_rows` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Number of read rows. - `read_bytes` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Number of read bytes. - `written_rows` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — For `INSERT` queries, the number of written rows. For other queries, the column value is 0. - `written_bytes` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — For `INSERT` queries, the number of written bytes. For other queries, the column value is 0. - `memory_usage` ([Int64](../../sql-reference/data-types/int-uint.md)) — The difference between the amount of allocated and freed memory in context of this thread. - `peak_memory_usage` ([Int64](../../sql-reference/data-types/int-uint.md)) — The maximum difference between the amount of allocated and freed memory in context of this thread. - `thread_name` ([String](../../sql-reference/data-types/string.md)) — Name of the thread. - `thread_number` ([UInt32](../../sql-reference/data-types/int-uint.md)) — Internal thread ID. - `thread_id` ([Int32](../../sql-reference/data-types/int-uint.md)) — thread ID. - `master_thread_id` ([UInt64](../../sql-reference/data-types/int-uint.md#uint-ranges)) — OS initial ID of initial thread. - `query` ([String](../../sql-reference/data-types/string.md)) — Query string. - `is_initial_query` ([UInt8](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Query type. Possible values: - 1 — Query was initiated by the client. - 0 — Query was initiated by another query for distributed query execution. - `user` ([String](../../sql-reference/data-types/string.md)) — Name of the user who initiated the current query. - `query_id` ([String](../../sql-reference/data-types/string.md)) — ID of the query. - `address` ([IPv6](../../sql-reference/data-types/domains/ipv6.md)) — IP address that was used to make the query. - `port` ([UInt16](../../sql-reference/data-types/int-uint.md#uint-ranges)) — The client port that was used to make the query. - `initial_user` ([String](../../sql-reference/data-types/string.md)) — Name of the user who ran the initial query (for distributed query execution). - `initial_query_id` ([String](../../sql-reference/data-types/string.md)) — ID of the initial query (for distributed query execution). - `initial_address` ([IPv6](../../sql-reference/data-types/domains/ipv6.md)) — IP address that the parent query was launched from. - `initial_port` ([UInt16](../../sql-reference/data-types/int-uint.md#uint-ranges)) — The client port that was used to make the parent query. - `interface` ([UInt8](../../sql-reference/data-types/int-uint.md#uint-ranges)) — Interface that the query was initiated from. Possible values: - 1 — TCP. - 2 — HTTP. - `os_user` ([String](../../sql-reference/data-types/string.md)) — OS’s username who runs [clickhouse-client](../../interfaces/cli.md). - `client_hostname` ([String](../../sql-reference/data-types/string.md)) — Hostname of the client machine where the [clickhouse-client](../../interfaces/cli.md) or another TCP client is run. - `client_name` ([String](../../sql-reference/data-types/string.md)) — The [clickhouse-client](../../interfaces/cli.md) or another TCP client name. - `client_revision` ([UInt32](../../sql-reference/data-types/int-uint.md)) — Revision of the [clickhouse-client](../../interfaces/cli.md) or another TCP client. - `client_version_major` ([UInt32](../../sql-reference/data-types/int-uint.md)) — Major version of the [clickhouse-client](../../interfaces/cli.md) or another TCP client. - `client_version_minor` ([UInt32](../../sql-reference/data-types/int-uint.md)) — Minor version of the [clickhouse-client](../../interfaces/cli.md) or another TCP client. - `client_version_patch` ([UInt32](../../sql-reference/data-types/int-uint.md)) — Patch component of the [clickhouse-client](../../interfaces/cli.md) or another TCP client version. - `http_method` ([UInt8](../../sql-reference/data-types/int-uint.md#uint-ranges)) — 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](../../sql-reference/data-types/string.md)) — The `UserAgent` header passed in the HTTP request. - `quota_key` ([String](../../sql-reference/data-types/string.md)) — The “quota key” specified in the [quotas](../../operations/quotas.md) setting (see `keyed`). - `revision` ([UInt32](../../sql-reference/data-types/int-uint.md)) — ClickHouse revision. - `ProfileEvents` ([Map(String, UInt64)](../../sql-reference/data-types/array.md)) — ProfileEvents that measure different metrics for this thread. The description of them could be found in the table [system.events](#system_tables-events). **Example** ``` sql SELECT * FROM system.query_thread_log LIMIT 1 \G ``` ``` text 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: {'Query':1,'SelectQuery':1,'ReadCompressedBytes':36,'CompressedReadBufferBlocks':1,'CompressedReadBufferBytes':10,'IOBufferAllocs':1,'IOBufferAllocBytes':89,'ContextLock':15,'RWLockAcquiredReadLocks':1} ``` **See Also** - [system.query_log](../../operations/system-tables/query_log.md#system_tables-query_log) — Description of the `query_log` system table which contains common information about queries execution. [Original article](https://clickhouse.tech/docs/en/operations/system-tables/query_thread_log)