system.parts_columns

    Each row describes one data part.

    Columns:

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

      Formats:

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

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

    • part_type () — 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 () — 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 () — The number of rows.

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

    • data_compressed_bytes () — 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.

    • modification_time () — 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 () — 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 () — The maximum value of the date key in the data part.

    • partition_id (String) — ID of the partition.

    • min_block_number () — 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 () — 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 () — The amount of memory (in bytes) used by primary key values.

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

    • table () — Name of the table.

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

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

    • column (String) — Name of the column.

    • type () — Column type.

    • column_position (UInt64) — Ordinal position of a column in a table starting with 1.

    • default_kind () — Expression type (DEFAULT, MATERIALIZED, ALIAS) for the default value, or an empty string if it is not defined.

    • default_expression (String) — Expression for the default value, or an empty string if it is not defined.

    • column_bytes_on_disk () — Total size of the column in bytes.

    • column_data_compressed_bytes (UInt64) — Total size of compressed data in the column, in bytes.

    • column_data_uncompressed_bytes () — Total size of the decompressed data in the column, in bytes.

    • column_marks_bytes (UInt64) — The size of the column with marks, in bytes.

    • bytes () — Alias for bytes_on_disk.

    • marks_size (UInt64) — Alias for marks_bytes.

    Example

    1. Row 1:
    2. ──────
    3. partition:                             tuple()
    4. name:                                  all_1_2_1
    5. part_type:                             Wide
    6. active:                                1
    7. marks:                                 2
    9. bytes_on_disk:                         155
    10. data_compressed_bytes:                 56
    11. data_uncompressed_bytes:               4
    12. modification_time:                     2020-09-23 10:13:36
    13. remove_time:                           2106-02-07 06:28:15
    14. refcount:                              1
    15. min_date:                              1970-01-01
    16. max_date:                              1970-01-01
    17. partition_id:                          all
    18. min_block_number:                      1
    19. max_block_number:                      2
    20. level:                                 1
    21. data_version:                          1
    22. primary_key_bytes_in_memory:           2
    23. primary_key_bytes_in_memory_allocated: 64
    24. database:                              default
    25. table:                                 53r93yleapyears
    26. engine:                                MergeTree
    27. disk_name:                             default
    28. path:                                  /var/lib/clickhouse/data/default/53r93yleapyears/all_1_2_1/
    29. column:                                id
    30. type:                                  Int8
    31. column_position:                       1
    32. default_kind:
    33. default_expression:
    34. column_bytes_on_disk:                  76
    35. column_data_compressed_bytes:          28
    37. column_marks_bytes:                    48