system.query_log包含有关已执行查询的信息，例如，开始时间、处理持续时间、错误消息。

!!! note "注"
此表不包含以下内容的摄取数据 INSERT 查询。

您可以更改查询日志记录的设置 [query_log] 服务器配置部分。

您可以通过设置禁用查询日志记录 [log_queries=0]. 我们不建议关闭日志记录，因为此表中的信息对于解决问题很重要。

数据的冲洗周期设置在 flush_interval_milliseconds 的参数 [query_log] 服务器设置部分。 要强制冲洗，请使用 [SYSTEM FLUSH LOGS] 查询。

ClickHouse不会自动从表中删除数据。 看 [导言] 欲了解更多详情。

该 system.query_log 表注册两种查询:

1. 客户端直接运行的初始查询。
2. 由其他查询启动的子查询（用于分布式查询执行）。 对于这些类型的查询，有关父查询的信息显示在 initial_* 列。

每个查询创建一个或两个行中 query_log 表，这取决于状态（见 type 列）的查询:

1. 如果查询执行成功，则两行具有 QueryStart 和 QueryFinish 创建类型。
2. 如果在查询处理过程中发生错误，两个事件与 QueryStart 和 ExceptionWhileProcessing 创建类型。
3. 如果在启动查询之前发生错误，则单个事件具有 ExceptionBeforeStart 创建类型。

列:

• type ([枚举8]) — Type of an event that occurred when executing the query. Values:
  • 'QueryStart' = 1 — Successful start of query execution.
  • 'QueryFinish' = 2 — Successful end of query execution.
  • 'ExceptionBeforeStart' = 3 — Exception before the start of query execution.
  • 'ExceptionWhileProcessing' = 4 — Exception during the query execution.
• event_date ([日期]) — Query starting date.
• event_time ([日期时间]) — Query starting time.
• query_start_time ([日期时间]) — Start time of query execution.
• query_duration_ms ([UInt64]) — Duration of query execution in milliseconds.
• read_rows ([UInt64]) — Total number or rows read from all tables and table functions participated in query. It includes usual subqueries, subqueries for IN 和 JOIN. 对于分布式查询 read_rows 包括在所有副本上读取的行总数。 每个副本发送它的 read_rows 值，并且查询的服务器-发起方汇总所有接收到的和本地的值。 缓存卷不会影响此值。
• read_bytes ([UInt64]) — Total number or bytes read from all tables and table functions participated in query. It includes usual subqueries, subqueries for IN 和 JOIN. 对于分布式查询 read_bytes 包括在所有副本上读取的行总数。 每个副本发送它的 read_bytes 值，并且查询的服务器-发起方汇总所有接收到的和本地的值。 缓存卷不会影响此值。
• written_rows ([UInt64]) — For INSERT 查询，写入的行数。 对于其他查询，列值为0。
• written_bytes ([UInt64]) — For INSERT 查询时，写入的字节数。 对于其他查询，列值为0。
• result_rows ([UInt64]) — Number of rows in a result of the SELECT 查询，或者在一些行 INSERT 查询。
• result_bytes ([UInt64]) — RAM volume in bytes used to store a query result.
• memory_usage ([UInt64]) — Memory consumption by the query.
• query ([字符串]) — Query string.
• exception ([字符串]) — Exception message.
• exception_code ([Int32]) — Code of an exception.
• stack_trace ([字符串]) — 堆栈跟踪. 如果查询成功完成，则为空字符串。
• is_initial_query ([UInt8]) — Query type. Possible values:
  • 1 — Query was initiated by the client.
  • 0 — Query was initiated by another query as part of distributed query execution.
• user ([字符串]) — Name of the user who initiated the current query.
• query_id ([字符串]) — 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 ([字符串]) — Name of the user who ran the initial query (for distributed query execution).
• initial_query_id ([字符串]) — 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 ([字符串]) — Operating system username who runs [ﾂ环板clientｮﾂ嘉ｯﾂ偲].
• client_hostname ([字符串]) — Hostname of the client machine where the [ﾂ环板clientｮﾂ嘉ｯﾂ偲] 或者运行另一个TCP客户端。
• client_name ([字符串]) — The [ﾂ环板clientｮﾂ嘉ｯﾂ偲] 或另一个TCP客户端名称。
• client_revision ([UInt32]) — Revision of the [ﾂ环板clientｮﾂ嘉ｯﾂ偲] 或另一个TCP客户端。
• client_version_major ([UInt32]) — Major version of the [ﾂ环板clientｮﾂ嘉ｯﾂ偲] 或另一个TCP客户端。
• client_version_minor ([UInt32]) — Minor version of the [ﾂ环板clientｮﾂ嘉ｯﾂ偲] 或另一个TCP客户端。
• client_version_patch ([UInt32]) — Patch component of the [ﾂ环板clientｮﾂ嘉ｯﾂ偲] 或另一个TCP客户端版本。
• http_method (UInt8) — HTTP method that initiated the query. Possible values:
  • 0 — The query was launched from the TCP interface.
  • 1 — GET 方法被使用。
  • 2 — POST 方法被使用。
• http_user_agent ([字符串]) — The UserAgent http请求中传递的标头。
• quota_key ([字符串]) — The “quota key” 在指定 [配额] 设置（见 keyed).
• revision ([UInt32]) — ClickHouse revision.
• thread_numbers ([数组(UInt32)]) — Number of threads that are participating in query execution.
• ProfileEvents.Names ([数组（字符串)]) — Counters that measure different metrics. The description of them could be found in the table [系统。活动]
• ProfileEvents.Values ([数组(UInt64)]) — Values of metrics that are listed in the ProfileEvents.Names 列。
• Settings.Names ([数组（字符串)]) — Names of settings that were changed when the client ran the query. To enable logging changes to settings, set the log_query_settings 参数为1。
• Settings.Values ([数组（字符串)]) — Values of settings that are listed in the Settings.Names 列。

示例

SELECT * FROM system.query_log LIMIT 1 FORMAT Vertical;

Row 1:
──────
type:                 QueryStart
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:            0
read_bytes:           0
written_rows:         0
written_bytes:        0
result_rows:          0
result_bytes:         0
memory_usage:         0
query:                SELECT 1
exception_code:       0
exception:
stack_trace:
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
thread_ids:           []
ProfileEvents.Names:  []
ProfileEvents.Values: []
Settings.Names:       ['use_uncompressed_cache','load_balancing','log_queries','max_memory_usage']
Settings.Values:      ['0','random','1','10000000000']