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
andmin_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, itβs used in a table. Otherwise, itβs 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, multiplymarks
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 thandata_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 forbytes_on_disk
.marks_size
(UInt64) β Alias formarks_bytes
.
Example
SELECT * FROM system.parts_columns LIMIT 1 FORMAT Vertical;
Row 1:
ββββββ
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