ClickHouse/docs/en/operations/system-tables/part_log.md

system.part_log

The system.part_log table is created only if the part_log server setting is specified.

This table contains information about events that occurred with data parts in the MergeTree family tables, such as adding or merging data.

The system.part_log table contains the following columns:

• event_type (Enum) — Type of the event that occurred with the data part. Can have one of the following values:
  • NEW_PART — Inserting of a new data part.
  • MERGE_PARTS — Merging of data parts.
  • DOWNLOAD_PART — Downloading a data part.
  • REMOVE_PART — Removing or detaching a data part using DETACH PARTITION.
  • MUTATE_PART — Mutating of a data part.
  • MOVE_PART — Moving the data part from the one disk to another one.
• event_date (Date) — Event date.
• event_time (DateTime) — Event time.
• duration_ms (UInt64) — Duration.
• database (String) — Name of the database the data part is in.
• table (String) — Name of the table the data part is in.
• part_name (String) — Name of the data part.
• partition_id (String) — ID of the partition that the data part was inserted to. The column takes the ‘all’ value if the partitioning is by tuple().
• rows (UInt64) — The number of rows in the data part.
• size_in_bytes (UInt64) — Size of the data part in bytes.
• merged_from (Array(String)) — An array of names of the parts which the current part was made up from (after the merge).
• bytes_uncompressed (UInt64) — Size of uncompressed bytes.
• read_rows (UInt64) — The number of rows was read during the merge.
• read_bytes (UInt64) — The number of bytes was read during the merge.
• error (UInt16) — The code number of the occurred error.
• exception (String) — Text message of the occurred error.

The system.part_log table is created after the first inserting data to the MergeTree table.