The function takes as arguments a set of conditions from 1 to 32 arguments of type `UInt8` that indicate whether a certain condition was met for the event.
Any condition can be specified as an argument (as in [WHERE](../select.md#select-where)).
Any condition can be specified as an argument (as in [WHERE](../../query_language/select.md#select-where)).
The conditions, except the first, apply in pairs: the result of the second will be true if the first and second are true, of the third if the first and fird are true, etc.
- If ClickHouse parses the attribute successfully in the [attribute's data type](../dicts/external_dicts_dict_structure.md#ext_dict_structure-attributes), functions return the value of the dictionary attribute that corresponds to `id_expr`.
- If ClickHouse parses the attribute successfully in the [attribute's data type](../../query_language/dicts/external_dicts_dict_structure.md#ext_dict_structure-attributes), functions return the value of the dictionary attribute that corresponds to `id_expr`.
- If there is no the key, corresponding to `id_expr`, in the dictionary, then:
- `dictGet` returns the content of the `<null_value>` element specified for the attribute in the dictionary configuration.
- If ClickHouse parses the attribute successfully in the [attribute's data type](../dicts/external_dicts_dict_structure.md#ext_dict_structure-attributes), functions return the value of the dictionary attribute that corresponds to `id_expr`.
- If ClickHouse parses the attribute successfully in the [attribute's data type](../../query_language/dicts/external_dicts_dict_structure.md#ext_dict_structure-attributes), functions return the value of the dictionary attribute that corresponds to `id_expr`.
- If there is no requested `id_expr` in the dictionary then:
- `dictGet[Type]` returns the content of the `<null_value>` element specified for the attribute in the dictionary configuration.
@@ -704,7 +704,7 @@ For `ON`, `WHERE`, and `GROUP BY` clauses:
- Arbitrary expressions cannot be used in `ON`, `WHERE`, and `GROUP BY` clauses, but you can define an expression in a `SELECT` clause and then use it in these clauses via an alias.
### WHERE Clause
### WHERE Clause {#select-where}
If there is a WHERE clause, it must contain an expression with the UInt8 type. This is usually an expression with comparison and logical operators.
This expression will be used for filtering data before all other transformations.
تاریخ با ساعت 4 بایت به صورت Unix timestamp ذخیره می کند (unsigned). به شما اجازه ی ذخیره سازی در محدوده ی تایپ Date را می دهد. حداقل مقدار در خروجی 0000-00-00 00:00:00 می باشد. زمان با دقت تا یک ثانیه ذخیره می شود.
@@ -493,7 +493,7 @@ ClickHouse использует этот параметр при чтении д
Установка логирования запроса.
Запросы, переданные в ClickHouse с этой установкой, логируются согласно правилам конфигурационного параметра сервера [query_log](../server_settings/settings.md#server_settings-query-log).
Запросы, переданные в ClickHouse с этой установкой, логируются согласно правилам конфигурационного параметра сервера [query_log](../../operations/server_settings/settings.md#server_settings-query-log).
Sets the period for a real clock timer of the [query profiler](../../operations/performance/sampling_query_profiler.md). Real clock timer counts wall-clock time.
Possible values:
- Positive integer number, in nanoseconds.
Recommended values:
- 10000000 (100 times a second) nanoseconds and less for single queries.
- 1000000000 (once a second) for cluster-wide profiling.
- 0 for turning off the timer.
Type: [UInt64](../../data_types/int_uint.md).
Default value: 1000000000 nanoseconds (once a second).
See also:
- System table [trace_log](../../operations/system_tables.md#system_tables-trace_log)
@@ -474,6 +474,91 @@ ClickHouse создаёт таблицу только в том случае, к
Можно указать произвольный ключ партиционирования для таблицы `system.query_log` в конфигурации [query_log](server_settings/settings.md#server_settings-query-log)(параметр`partition_by`).
## system.query_log {#system_tables-query_log}
Contains information about execution of queries. For each query, you can see processing start time, duration of processing, error messages and other information.
!!! note "Note"
The table doesn't contain input data for `INSERT` queries.
ClickHouse creates this table only if the [query_log](server_settings/settings.md#server_settings-query-log) server parameter is specified. This parameter sets the logging rules, such as the logging interval or the name of the table the queries will be logged in.
To enable query logging, set the [log_queries](settings/settings.md#settings-log-queries) parameter to 1. For details, see the [Settings](settings/settings.md) section.
The `system.query_log` table registers two kinds of queries:
1. Initial queries that were run directly by the client.
2. Child queries that were initiated by other queries (for distributed query execution). For these types of queries, information about the parent queries is shown in the `initial_*` columns.
Columns:
-`type` (`Enum8`) — Type of 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` (Date) — Query starting date.
-`event_time` (DateTime) — Query starting time.
-`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.
-`result_rows` (UInt64) — Number of rows in the result.
-`result_bytes` (UInt64) — Number of bytes in the result.
-`memory_usage` (UInt64) — Memory consumption by the query.
-`query` (String) — Query string.
-`exception` (String) — Exception message.
-`stack_trace` (String) — Stack trace (a list of methods called before the error occurred). An empty string, if the query is completed successfully.
-`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](../interfaces/cli.md).
-`client_hostname` (String) — Hostname of the client machine where the [clickhouse-client](../interfaces/cli.md) or another TCP client is run.
-`client_name` (String) — The [clickhouse-client](../interfaces/cli.md) or another TCP client name.
-`client_revision` (UInt32) — Revision of the [clickhouse-client](../interfaces/cli.md) or another TCP client.
-`client_version_major` (UInt32) — Major version of the [clickhouse-client](../interfaces/cli.md) or another TCP client.
-`client_version_minor` (UInt32) — Minor version of the [clickhouse-client](../interfaces/cli.md) or another TCP client.
-`client_version_patch` (UInt32) — Patch component of the [clickhouse-client](../interfaces/cli.md) 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](quotas.md) setting (see `keyed`).
-`revision` (UInt32) — ClickHouse revision.
-`thread_numbers` (Array(UInt32)) — Number of threads that are participating in query execution.
-`ProfileEvents.Names` (Array(String)) — Counters that measure different metrics. The description of them could be found in the table [system.events](#system_tables-events)
-`ProfileEvents.Values` (Array(UInt64)) — Values of metrics that are listed in the `ProfileEvents.Names` column.
-`Settings.Names` (Array(String)) — Names of settings that were changed when the client ran the query. To enable logging changes to settings, set the `log_query_settings` parameter to 1.
-`Settings.Values` (Array(String)) — Values of settings that are listed in the `Settings.Names` column.
Each query creates one or two rows in the `query_log` table, depending on the status of the query:
1. If the query execution is successful, two events with types 1 and 2 are created (see the `type` column).
2. If an error occurred during query processing, two events with types 1 and 4 are created.
3. If an error occurred before launching the query, a single event with type 3 is created.
By default, logs are added to the table at intervals of 7.5 seconds. You can set this interval in the [query_log](server_settings/settings.md#server_settings-query-log) server setting (see the `flush_interval_milliseconds` parameter). To flush the logs forcibly from the memory buffer into the table, use the `SYSTEM FLUSH LOGS` query.
When the table is deleted manually, it will be automatically created on the fly. Note that all the previous logs will be deleted.
!!! note
The storage period for logs is unlimited. Logs aren't automatically deleted from the table. You need to organize the removal of outdated logs yourself.
You can specify an arbitrary partitioning key for the `system.query_log` table in the [query_log](server_settings/settings.md#server_settings-query-log) server setting (see the `partition_by` parameter).
Содержит информацию о каждом потоке выполняемых запросов.
...
...
@@ -538,6 +623,48 @@ ClickHouse создаёт таблицу только в том случае, к
Можно указать произвольный ключ партиционирования для таблицы `system.query_log` в конфигурации [query_thread_log](server_settings/settings.md#server_settings-query-thread-log)(параметр`partition_by`).
## system.trace_log {#system_tables-trace_log}
Contains stack traces collected by the sampling query profiler.
ClickHouse creates this table when the [trace_log](server_settings/settings.md#server_settings-trace_log) server configuration section is set. Also the [query_profiler_real_time_period_ns](settings/settings.md#query_profiler_real_time_period_ns) and [query_profiler_cpu_time_period_ns](settings/settings.md#query_profiler_cpu_time_period_ns) settings should be set.
To analyze logs, use the `addressToLine`, `addressToSymbol` and `demangle` introspection functions.
Columns:
-`event_date`([Date](../data_types/date.md)) — Date of sampling moment.
-`event_time`([DateTime](../data_types/datetime.md)) — Timestamp of sampling moment.
-`revision`([UInt32](../data_types/int_uint.md)) — ClickHouse server build revision.
When connecting to server by `clickhouse-client`, you see the string similar to `Connected to ClickHouse server version 19.18.1 revision 54429.`. This field contains the `revision`, but not the `version` of a server.
-`query_id`([String](../data_types/string.md)) — Query identifier that can be used to get details about a query that was running from the [query_log](#system_tables-query_log) system table.
-`trace`([Array(UInt64)](../data_types/array.md)) — Stack trace at the moment of sampling. Each element is a virtual memory address inside ClickHouse server process.
-`startdate` — Первая дата. [Date](../../data_types/date.md) или [DateTime](../../data_types/datetime.md).
-`enddate` — Вторая дата. [Date](../../data_types/date.md) или [DateTime](../../data_types/datetime.md).
-`timezone` — Опциональный параметр. Если определен, применяется к обоим значениям: `startdate` и `enddate`. Если не определен, используются часовые пояса `startdate` и `enddate`. Если часовые пояса не совпадают, вернется неожидаемый результат.[Часовые пояса](../../data_types/datetime.md#time-zones).
-`timezone` — Опциональный параметр. Если определен, применяется к обоим значениям: `startdate` и `enddate`. Если не определен, используются часовые пояса `startdate` и `enddate`. Если часовые пояса не совпадают, вернется неожидаемый результат.
@@ -104,7 +104,7 @@ Defines storage time for values. Can be specified only for MergeTree-family tabl
### Column Compression Codecs {#codecs}
By default, ClickHouse applies the compression method, defined in [server settings](../operations/server_settings/settings.md#compression), to columns. You can also define the compression method for each individual column in the `CREATE TABLE` query.
By default, ClickHouse applies the compression method, defined in [server settings](../operations/server_settings/settings.md#server-settings-compression), to columns. You can also define the compression method for each individual column in the `CREATE TABLE` query.
