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.

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