system.query_views_log 

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 section.
  2. Set log_query_views to 1.

The flushing period of data is set in flush_interval_milliseconds parameter of the query_views_log server settings section. To force flushing, use the SYSTEM FLUSH LOGS query.

ClickHouse does not delete data from the table automatically. See Introduction for more details.

Columns:

  • event_date (Date) — The date when the last event of the view happened.
  • event_time (DateTime) — The date and time when the view finished execution.
  • event_time_microseconds (DateTime) — The date and time when the view finished execution with microseconds precision.
  • view_duration_ms (UInt64) — Duration of view execution (sum of its stages) in milliseconds.
  • initial_query_id (String) — ID of the initial query (for distributed query execution).
  • view_name (String) — Name of the view.
  • view_uuid (UUID) — UUID of the view.
  • view_type (Enum8) — Type of the view. Values:
  • view_query (String) — The query executed by the view.
  • view_target (String) — The name of the view target table.
  • read_rows (UInt64) — Number of read rows.
  • read_bytes (UInt64) — Number of read bytes.
  • written_rows (UInt64) — Number of written rows.
  • written_bytes (UInt64) — Number of written bytes.
  • peak_memory_usage (Int64) — The maximum difference between the amount of allocated and freed memory in context of this view.
  • ProfileEvents (Map(String, UInt64)) — ProfileEvents that measure different metrics. The description of them could be found in the table system.events.
  • status (Enum8) — 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) — Code of an exception.
  • exception (String) — Exception message.
  • stack_trace (String) — Stack trace. An empty string, if the query was completed successfully.

Example

 SELECT * FROM system.query_views_log LIMIT 1 \G
Row 1:
──────
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

  • system.query_log — Description of the query_log system table which contains common information about queries execution.
  • system.query_thread_log — This table contains information about each query execution thread.

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