system.parts_columns

Contains information about parts and columns of MergeTree tables. Each row describes one data part.

Column	Type	Description
`partition`	String	The partition name. Formats: `YYYYMM` for automatic partitioning by month, or `any_string` when partitioning manually.
`name`	String	Name of the data part.
`part_type`	String	The data part storing format. Values: `Wide` (each column in separate file) or `Compact` (all columns in one file). Controlled by `min_bytes_for_wide_part` and `min_rows_for_wide_part` settings.
`active`	UInt8	Flag indicating whether the data part is active. Active parts are used in the table; inactive parts are deleted or remain after merging.
`marks`	UInt64	The number of marks. Multiply by index granularity (usually 8192) to get approximate row count.
`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 (excludes auxiliary files like marks).
`data_uncompressed_bytes`	UInt64	Total size of uncompressed data in the data part (excludes auxiliary files like marks).
`marks_bytes`	UInt64	The size of the file with marks.
`modification_time`	DateTime	The time the directory with the data part was modified (usually corresponds to creation time).
`remove_time`	DateTime	The time when the data part became inactive.
`refcount`	UInt32	The number of places where the data part is used. Value > 2 indicates use 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.
`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 created by insert, not by merging.
`data_version`	UInt64	Number used to determine which mutations should be applied (mutations with 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.
`database`	String	Name of the database.
`table`	String	Name of the table.
`engine`	String	Name of the table engine without parameters.
`disk_name`	String	Name of a disk that stores the data part.
`path`	String	Absolute path to the folder with data part files.
`column`	String	Name of the column.
`type`	String	Column type.
`statistics`	String	Statistics created for the column.
`estimates.min`	String	Estimated minimum value of the column.
`estimates.max`	String	Estimated maximum value of the column.
`estimates.cardinality`	String	Estimated cardinality of the column.
`column_position`	UInt64	Ordinal position of a column in a table starting with 1.
`default_kind`	String	Expression type (`DEFAULT`, `MATERIALIZED`, `ALIAS`) for the default value, or empty string if not defined.
`default_expression`	String	Expression for the default value, or empty string if not defined.
`column_bytes_on_disk`	UInt64	Total size of the column in bytes.
`column_data_compressed_bytes`	UInt64	Total size of compressed data in the column, in bytes. Note: this is not calculated for compact parts.
`column_data_uncompressed_bytes`	UInt64	Total size of the decompressed data in the column, in bytes. Note: this is not calculated for compact parts.
`column_marks_bytes`	UInt64	The size of the column with marks, in bytes.
`bytes`	UInt64	Alias for `bytes_on_disk`.
`marks_size`	UInt64	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