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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](/docs/operations/system-tables/overview#system-tables-in-clickhouse-cloud) for further details.

Contains information about the dependent views executed when running a query, for example, the view type or the execution time.

To start logging:

1. Configure parameters in the [query\_views\_log](/docs/operations/server-configuration-parameters/settings#query_views_log) section.
2. Set [log\_query\_views](/docs/operations/settings/settings#log_query_views) to 1.

The flushing period of data is set in `flush_interval_milliseconds` parameter of the [query\_views\_log](/docs/operations/server-configuration-parameters/settings#query_views_log) server settings section. To force flushing, use the [SYSTEM FLUSH LOGS](/docs/sql-reference/statements/system#flush-logs) query.

ClickHouse does not delete data from the table automatically. See [Introduction](/docs/operations/system-tables/overview#system-tables-introduction) for more details.

You can use the [log\_queries\_probability](/docs/operations/settings/settings#log_queries_probability)) setting to reduce the number of queries, registered in the `query_views_log` table.

Columns:

- `hostname` ([LowCardinality(String)](/docs/sql-reference/data-types/string)) — Hostname of the server executing the query.
- `event_date` ([Date](/docs/sql-reference/data-types/date)) — The date when the last event of the view happened.
- `event_time` ([DateTime](/docs/sql-reference/data-types/datetime)) — The date and time when the view finished execution.
- `event_time_microseconds` ([DateTime](/docs/sql-reference/data-types/datetime)) — The date and time when the view finished execution with microseconds precision.
- `view_duration_ms` ([UInt64](/docs/sql-reference/data-types/int-uint#integer-ranges)) — Duration of view execution (sum of its stages) in milliseconds.
- `initial_query_id` ([String](/docs/sql-reference/data-types/string)) — ID of the initial query (for distributed query execution).
- `view_name` ([String](/docs/sql-reference/data-types/string)) — Name of the view.
- `view_uuid` ([UUID](/docs/sql-reference/data-types/uuid)) — UUID of the view.
- `view_type` ([Enum8](/docs/sql-reference/data-types/enum)) — Type of the view. Values:
  - `'Default' = 1` — [Default views](/docs/sql-reference/statements/create/view#normal-view). Should not appear in this log.
  - `'Materialized' = 2` — [Materialized views](/docs/sql-reference/statements/create/view#materialized-view).
  - `'Live' = 3` — [Live views](/docs/sql-reference/statements/create/view#live-view).
- `view_query` ([String](/docs/sql-reference/data-types/string)) — The query executed by the view.
- `view_target` ([String](/docs/sql-reference/data-types/string)) — The name of the view target table.
- `read_rows` ([UInt64](/docs/sql-reference/data-types/int-uint#integer-ranges)) — Number of read rows.
- `read_bytes` ([UInt64](/docs/sql-reference/data-types/int-uint#integer-ranges)) — Number of read bytes.
- `written_rows` ([UInt64](/docs/sql-reference/data-types/int-uint#integer-ranges)) — Number of written rows.
- `written_bytes` ([UInt64](/docs/sql-reference/data-types/int-uint#integer-ranges)) — Number of written bytes.
- `peak_memory_usage` ([Int64](/docs/sql-reference/data-types/int-uint)) — The maximum difference between the amount of allocated and freed memory in context of this view.
- `ProfileEvents` ([Map(String, UInt64)](/docs/sql-reference/data-types/array)) — ProfileEvents that measure different metrics. The description of them could be found in the table [system.events](/docs/operations/system-tables/events).
- `status` ([Enum8](/docs/sql-reference/data-types/enum)) — Status of the view. Values:
  - `'QueryStart' = 1` — Successful start the view execution. Should not appear.
  - `'QueryFinish' = 2` — Successful end of the view execution.
  - `'ExceptionBeforeStart' = 3` — Exception before the start of the view execution.
  - `'ExceptionWhileProcessing' = 4` — Exception during the view execution.
- `exception_code` ([Int32](/docs/sql-reference/data-types/int-uint)) — Code of an exception.
- `exception` ([String](/docs/sql-reference/data-types/string)) — Exception message.
- `stack_trace` ([String](/docs/sql-reference/data-types/string)) — [Stack trace](https://en.wikipedia.org/wiki/Stack_trace). An empty string, if the query was completed successfully.

**Example**

Query:

```
SELECT * FROM system.query_views_log LIMIT 1 \G;
```

Result:

```
Row 1:
──────
hostname:                clickhouse.eu-central1.internal
event_date:              2021-06-22
event_time:              2021-06-22 13:23:07
event_time_microseconds: 2021-06-22 13:23:07.738221
view_duration_ms:        0
initial_query_id:        c3a1ac02-9cad-479b-af54-9e9c0a7afd70
view_name:               default.matview_inner
view_uuid:               00000000-0000-0000-0000-000000000000
view_type:               Materialized
view_query:              SELECT * FROM default.table_b
view_target:             default.`.inner.matview_inner`
read_rows:               4
read_bytes:              64
written_rows:            2
written_bytes:           32
peak_memory_usage:       4196188
ProfileEvents:           {'FileOpen':2,'WriteBufferFromFileDescriptorWrite':2,'WriteBufferFromFileDescriptorWriteBytes':187,'IOBufferAllocs':3,'IOBufferAllocBytes':3145773,'FunctionExecute':3,'DiskWriteElapsedMicroseconds':13,'InsertedRows':2,'InsertedBytes':16,'SelectedRows':4,'SelectedBytes':48,'ContextLock':16,'RWLockAcquiredReadLocks':1,'RealTimeMicroseconds':698,'SoftPageFaults':4,'OSReadChars':463}
status:                  QueryFinish
exception_code:          0
exception:
stack_trace:
```

**See Also**

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