> ## Documentation Index > Fetch the complete documentation index at: https://private-7c7dfe99-fix-nav-issues.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. > System table containing information about threads that execute queries, for example, thread name, thread start time, duration of query processing. # system.query_thread_log **Querying in ClickHouse Cloud** The data in this system table is held locally on each node in ClickHouse Cloud. Obtaining a complete view of all data, therefore, requires the `clusterAllReplicas` function. See [here](/reference/system-tables/overview#system-tables-in-clickhouse-cloud) for further details.

Description

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](/reference/settings/server-settings/settings#query_thread_log) section. 2. Set [log\_query\_threads](/reference/settings/session-settings#log_query_threads) to 1. The flushing period of data is set in `flush_interval_milliseconds` parameter of the [query\_thread\_log](/reference/settings/server-settings/settings#query_thread_log) server settings section. To force flushing, use the [SYSTEM FLUSH LOGS](/reference/statements/system#flush-logs) query. ClickHouse does not delete data from the table automatically. See [Introduction](/reference/system-tables/overview#system-tables-introduction) for more details. You can use the [log\_queries\_probability](/reference/settings/session-settings#log_queries_probability)) setting to reduce the number of queries, registered in the `query_thread_log` table.

Columns

* `hostname` ([LowCardinality(String)](/reference/data-types/lowcardinality)) — Hostname of the server executing the query. * `event_date` ([Date](/reference/data-types/date)) — The date when the thread has finished execution of the query. * `event_time` ([DateTime](/reference/data-types/datetime)) — The date and time when the thread has finished execution of the query. * `event_time_microseconds` ([DateTime64(6)](/reference/data-types/datetime64)) — The date and time when the thread has finished execution of the query with microseconds precision. * `query_start_time` ([DateTime](/reference/data-types/datetime)) — Start time of query execution. * `query_start_time_microseconds` ([DateTime64(6)](/reference/data-types/datetime64)) — Start time of query execution with microsecond precision. * `query_duration_ms` ([UInt64](/reference/data-types/int-uint)) — Duration of query execution. * `read_rows` ([UInt64](/reference/data-types/int-uint)) — Number of read rows. * `read_bytes` ([UInt64](/reference/data-types/int-uint)) — Number of read bytes. * `written_rows` ([UInt64](/reference/data-types/int-uint)) — For INSERT queries, the number of written rows. For other queries, the column value is 0. * `written_bytes` ([UInt64](/reference/data-types/int-uint)) — For INSERT queries, the number of written bytes. For other queries, the column value is 0. * `memory_usage` ([Int64](/reference/data-types/int-uint)) — The difference between the amount of allocated and freed memory in context of this thread. * `peak_memory_usage` ([Int64](/reference/data-types/int-uint)) — The maximum difference between the amount of allocated and freed memory in context of this thread. * `thread_name` ([LowCardinality(String)](/reference/data-types/lowcardinality)) — Name of the thread. * `thread_id` ([UInt64](/reference/data-types/int-uint)) — Internal thread ID. * `master_thread_id` ([UInt64](/reference/data-types/int-uint)) — OS initial ID of initial thread. * `current_database` ([LowCardinality(String)](/reference/data-types/lowcardinality)) — Name of the current database. * `query` ([String](/reference/data-types/string)) — Query string. * `normalized_query_hash` ([UInt64](/reference/data-types/int-uint)) — The hash of normalized query - with wiped constants, etc. * `is_initial_query` ([UInt8](/reference/data-types/int-uint)) — Query type. Possible values: 1 — Query was initiated by the client, 0 — Query was initiated by another query for distributed query execution. * `connection_address` ([IPv6](/reference/data-types/ipv6)) — The client IP address from which the connection was made. When connected through a proxy, this will be the address of the proxy. * `connection_port` ([UInt16](/reference/data-types/int-uint)) — The client port from which the connection was made. When connected through a proxy, this will be the port of the proxy. * `user` ([LowCardinality(String)](/reference/data-types/lowcardinality)) — Name of the user who initiated the current query. * `query_id` ([String](/reference/data-types/string)) — ID of the query. * `address` ([IPv6](/reference/data-types/ipv6)) — IP address that was used to make the query. When connected through a proxy and `auth_use_forwarded_address` is set, this will be the address of the client instead of the proxy. * `port` ([UInt16](/reference/data-types/int-uint)) — The client port that was used to make the query. When connected through a proxy and `auth_use_forwarded_address` is set, this will be the port of the client instead of the proxy. * `initial_user` ([LowCardinality(String)](/reference/data-types/lowcardinality)) — Name of the user who ran the initial query (for distributed query execution). * `initial_query_id` ([String](/reference/data-types/string)) — ID of the initial query (for distributed query execution). * `initial_address` ([IPv6](/reference/data-types/ipv6)) — IP address that the parent query was launched from. * `initial_port` ([UInt16](/reference/data-types/int-uint)) — The client port that was used to make the parent query. * `initial_query_start_time` ([DateTime](/reference/data-types/datetime)) — Start time of the initial query execution. * `initial_query_start_time_microseconds` ([DateTime64(6)](/reference/data-types/datetime64)) — Start time of the initial query execution * `authenticated_user` ([LowCardinality(String)](/reference/data-types/lowcardinality)) — Name of the user who was authenticated in the session. * `interface` ([UInt8](/reference/data-types/int-uint)) — Interface that the query was initiated from. Possible values: 1 — TCP, 2 — HTTP. * `is_secure` ([UInt8](/reference/data-types/int-uint)) — The flag which shows whether the connection was secure. * `os_user` ([LowCardinality(String)](/reference/data-types/lowcardinality)) — OSs username who runs clickhouse-client. * `client_hostname` ([LowCardinality(String)](/reference/data-types/lowcardinality)) — Hostname of the client machine where the clickhouse-client or another TCP client is run. * `client_name` ([LowCardinality(String)](/reference/data-types/lowcardinality)) — The clickhouse-client or another TCP client name. * `client_agent` ([LowCardinality(String)](/reference/data-types/lowcardinality)) — The AI coding agent that invoked the client (for example, `claude-code` or `cursor`), detected from environment variables. Empty if no agent was detected. * `client_revision` ([UInt32](/reference/data-types/int-uint)) — Revision of the clickhouse-client or another TCP client. * `client_version_major` ([UInt32](/reference/data-types/int-uint)) — Major version of the clickhouse-client or another TCP client. * `client_version_minor` ([UInt32](/reference/data-types/int-uint)) — Minor version of the clickhouse-client or another TCP client. * `client_version_patch` ([UInt32](/reference/data-types/int-uint)) — Patch component of the clickhouse-client or another TCP client version. * `script_query_number` ([UInt32](/reference/data-types/int-uint)) — A sequential query number in a multi-query script. * `script_line_number` ([UInt32](/reference/data-types/int-uint)) — A line number in a multi-query script where the current query starts. * `http_method` ([UInt8](/reference/data-types/int-uint)) — 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` ([LowCardinality(String)](/reference/data-types/lowcardinality)) — The UserAgent header passed in the HTTP request. * `http_referer` ([String](/reference/data-types/string)) — HTTP header `Referer` passed in the HTTP query (contains an absolute or partial address of the page making the query). * `forwarded_for` ([String](/reference/data-types/string)) — HTTP header `X-Forwarded-For` passed in the HTTP query. * `quota_key` ([String](/reference/data-types/string)) — The 'quota key' specified in the quotas setting. * `distributed_depth` ([UInt64](/reference/data-types/int-uint)) — How many times a query was forwarded between servers. * `revision` ([UInt32](/reference/data-types/int-uint)) — ClickHouse revision. * `ProfileEvents` ([Map(LowCardinality(String), UInt64)](/reference/data-types/map)) — ProfileEvents that measure different metrics for this thread. The description of them could be found in the table system.events. **Aliases:** * `ProfileEvents.Names` — Alias for `mapKeys(ProfileEvents)`. * `ProfileEvents.Values` — Alias for `mapValues(ProfileEvents)`.

Example

```sql theme={null} SELECT * FROM system.query_thread_log LIMIT 1 \G ``` ```text theme={null} Row 1: ────── hostname: clickhouse.eu-central1.internal 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](/reference/system-tables/query_log) — Description of the `query_log` system table which contains common information about queries execution. * [system.query\_views\_log](/reference/system-tables/query_views_log) — This table contains information about each view executed during a query.