system.parts

Contains information about parts of MergeTree tables.

Each row describes one data part.

Columns:

  • partition (String) – The partition name. To learn what a partition is, see the description of the ALTER query.

    Formats:

    • YYYYMM for automatic partitioning by month.
    • any_string when partitioning manually.

  • name (String) – Name of the data part.

  • part_type (String) — The data part storing format.

    Possible Values:

    • Wide — Each column is stored in a separate file in a filesystem.
    • Compact — All columns are stored in one file in a filesystem.

    Data storing format is controlled by the min_bytes_for_wide_part and min_rows_for_wide_part settings of the MergeTree table.

  • active (UInt8) – Flag that indicates whether the data part is active. If a data part is active, it’s used in a table. Otherwise, it’s deleted. Inactive data parts remain after merging.

  • marks (UInt64) – The number of marks. To get the approximate number of rows in a data part, multiply marks by the index granularity (usually 8192) (this hint doesn’t work for adaptive granularity).

  • rows (UInt64) – The number of rows.

  • bytes_on_disk (UInt64) – Total size of all the data part files in bytes.

  • data_compressed_bytes (UInt64) – Total size of compressed data in the data part. All the auxiliary files (for example, files with marks) are not included.

  • data_uncompressed_bytes (UInt64) – Total size of uncompressed data in the data part. All the auxiliary files (for example, files with marks) are not included.

  • marks_bytes (UInt64) – The size of the file with marks.

  • modification_time (DateTime) – The time the directory with the data part was modified. This usually corresponds to the time of data part creation.

  • remove_time (DateTime) – The time when the data part became inactive.

  • refcount (UInt32) – The number of places where the data part is used. A value greater than 2 indicates that the data part is used in queries or merges.

  • min_date (Date) – The minimum value of the date key in the data part.

  • max_date (Date) – The maximum value of the date key in the data part.

  • min_time (DateTime) – The minimum value of the date and time key in the data part.

  • max_time(DateTime) – The maximum value of the date and time key in the data part.

  • partition_id (String) – ID of the partition.

  • min_block_number (UInt64) – The minimum number of data parts that make up the current part after merging.

  • max_block_number (UInt64) – The maximum number of data parts that make up the current part after merging.

  • level (UInt32) – Depth of the merge tree. Zero means that the current part was created by insert rather than by merging other parts.

  • data_version (UInt64) – Number that is used to determine which mutations should be applied to the data part (mutations with a version higher than data_version).

  • primary_key_bytes_in_memory (UInt64) – The amount of memory (in bytes) used by primary key values.

  • primary_key_bytes_in_memory_allocated (UInt64) – The amount of memory (in bytes) reserved for primary key values.

  • is_frozen (UInt8) – Flag that shows that a partition data backup exists. 1, the backup exists. 0, the backup doesn’t exist. For more details, see FREEZE PARTITION

  • database (String) – Name of the database.

  • table (String) – Name of the table.

  • engine (String) – Name of the table engine without parameters.

  • path (String) – Absolute path to the folder with data part files.

  • disk (String) – Name of a disk that stores the data part.

  • hash_of_all_files (String) – sipHash128 of compressed files.

  • hash_of_uncompressed_files (String) – sipHash128 of uncompressed files (files with marks, index file etc.).

  • uncompressed_hash_of_compressed_files (String) – sipHash128 of data in the compressed files as if they were uncompressed.

  • delete_ttl_info_min (DateTime) — The minimum value of the date and time key for TTL DELETE rule.

  • delete_ttl_info_max (DateTime) — The maximum value of the date and time key for TTL DELETE rule.

  • move_ttl_info.expression (Array(String)) — Array of expressions. Each expression defines a TTL MOVE rule.

    Warning

    The move_ttl_info.expression array is kept mostly for backward compatibility, now the simpliest way to check TTL MOVE rule is to use the move_ttl_info.min and move_ttl_info.max fields.

  • move_ttl_info.min (Array(DateTime)) — Array of date and time values. Each element describes the minimum key value for a TTL MOVE rule.

  • move_ttl_info.max (Array(DateTime)) — Array of date and time values. Each element describes the maximum key value for a TTL MOVE rule.

  • bytes (UInt64) – Alias for bytes_on_disk.

  • marks_size (UInt64) – Alias for marks_bytes.

Example

  1. SELECT * FROM system.parts LIMIT 1 FORMAT Vertical;
  1. Row 1:
  2. ──────
  3. partition:                             tuple()
  4. name:                                  all_1_4_1_6
  5. part_type:                             Wide
  6. active:                                1
  7. marks:                                 2
  8. rows:                                  6
  9. bytes_on_disk:                         310
  10. data_compressed_bytes:                 157
  11. data_uncompressed_bytes:               91
  12. marks_bytes:                           144
  13. modification_time:                     2020-06-18 13:01:49
  14. remove_time:                           1970-01-01 00:00:00
  15. refcount:                              1
  16. min_date:                              1970-01-01
  17. max_date:                              1970-01-01
  18. min_time:                              1970-01-01 00:00:00
  19. max_time:                              1970-01-01 00:00:00
  20. partition_id:                          all
  21. min_block_number:                      1
  22. max_block_number:                      4
  23. level:                                 1
  24. data_version:                          6
  25. primary_key_bytes_in_memory:           8
  26. primary_key_bytes_in_memory_allocated: 64
  27. is_frozen:                             0
  28. database:                              default
  29. table:                                 months
  30. engine:                                MergeTree
  31. disk_name:                             default
  32. path:                                  /var/lib/clickhouse/data/default/months/all_1_4_1_6/
  33. hash_of_all_files:                     2d0657a16d9430824d35e327fcbd87bf
  34. hash_of_uncompressed_files:            84950cc30ba867c77a408ae21332ba29
  35. uncompressed_hash_of_compressed_files: 1ad78f1c6843bbfb99a2c931abe7df7d
  36. delete_ttl_info_min:                   1970-01-01 00:00:00
  37. delete_ttl_info_max:                   1970-01-01 00:00:00
  38. move_ttl_info.expression:              []
  39. move_ttl_info.min:                     []
  40. move_ttl_info.max:                     []

See Also

Original article