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parts_columns

Contains information about parts and columns of MergeTree tables.

Each row describes one data part.

Columns:

  • partition (String) β€” 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) β€” Name of the data part.

  • part_type (String) β€” The data part storing format.

    Possible values:

    • Wide β€” Each column is stored in a separate file in a filesystem.
    • Compact β€” 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) β€” 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) β€” 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 does not work for adaptive granularity).

  • rows (UInt64) β€” The number of rows.

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

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

  • marks_bytes (UInt64) β€” The size of the file with marks.

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

  • remove_time (DateTime) β€” The time when the data part became inactive.

  • refcount (UInt32) β€” 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) β€” The minimum value of the date key in the data part.

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

  • partition_id (String) β€” ID of the partition.

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

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

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

  • data_version (UInt64) β€” 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) β€” The amount of memory (in bytes) used by primary key values.

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

  • database (String) β€” Name of the database.

  • table (String) β€” Name of the table.

  • engine (String) β€” Name of the table engine without parameters.

  • disk_name (String) β€” Name of a disk that stores the data part.

  • path (String) β€” Absolute path to the folder with data part files.

  • column (String) β€” Name of the column.

  • type (String) β€” Column type.

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

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

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

  • column_bytes_on_disk (UInt64) β€” Total size of the column in bytes.

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

  • column_data_uncompressed_bytes (UInt64) β€” Total size of the decompressed data in the column, in bytes.

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

  • bytes (UInt64) β€” Alias for bytes_on_disk.

  • marks_size (UInt64) β€” Alias for marks_bytes.

Example

SELECT * FROM system.parts_columns LIMIT 1 FORMAT Vertical;
Row 1:
──────
partition: tuple()
name: all_1_2_1
part_type: Wide
active: 1
marks: 2
rows: 2
bytes_on_disk: 155
data_compressed_bytes: 56
data_uncompressed_bytes: 4
marks_bytes: 96
modification_time: 2020-09-23 10:13:36
remove_time: 2106-02-07 06:28:15
refcount: 1
min_date: 1970-01-01
max_date: 1970-01-01
partition_id: all
min_block_number: 1
max_block_number: 2
level: 1
data_version: 1
primary_key_bytes_in_memory: 2
primary_key_bytes_in_memory_allocated: 64
database: default
table: 53r93yleapyears
engine: MergeTree
disk_name: default
path: /var/lib/clickhouse/data/default/53r93yleapyears/all_1_2_1/
column: id
type: Int8
column_position: 1
default_kind:
default_expression:
column_bytes_on_disk: 76
column_data_compressed_bytes: 28
column_data_uncompressed_bytes: 2
column_marks_bytes: 48

See Also

Original article