Description
Contains information about parts and columns of MergeTree tables.
Each row describes one data part.
Columns
partition (String) — The partition name.name (String) — Name of the data part.uuid (UUID) — The parts UUID.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.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 does not 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 for the Date column if that is included in the partition key.max_date (Date) — The maximum value for the Date column if that is included in the partition key.min_time (DateTime) — The minimum value for the DateTime column if that is included in the partition key.max_time (DateTime) — The maximum value for the DateTime column if that is included in the partition key.partition_id (String) — ID of the partition.min_block_number (Int64) — The minimum number of data parts that make up the current part after merging.max_block_number (Int64) — 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.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.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 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 (UInt64) — Total size of the column in bytes.column_data_compressed_bytes (UInt64) — Total size of the compressed data in the column, in bytes.column_data_uncompressed_bytes (UInt64) — Total size of the decompressed data in the column, in bytes.column_marks_bytes (UInt64) — The size of the marks for column, in bytes.column_modification_time (Nullable(DateTime)) — The last time the column was modified.column_ttl_min (Nullable(DateTime)) — The minimum value of the calculated TTL expression of the column.column_ttl_max (Nullable(DateTime)) — The maximum value of the calculated TTL expression of the column.statistics (Array(String)) — The statistics of the column.estimates.min (Nullable(String)) — Estimated minimum value of the column.estimates.max (Nullable(String)) — Estimated maximum value of the column.estimates.cardinality (Nullable(UInt64)) — Estimated cardinality of the column.estimates.null_count (Nullable(UInt64)) — Estimated number of NULL values in the column.serialization_kind (String) — Kind of serialization of a columnsubstreams (Array(String)) — Names of substreams to which column is serializedfilenames (Array(String)) — Names of files for each substream of a column respectivelysubcolumns.names (Array(String)) — Names of subcolumns of a columnsubcolumns.types (Array(String)) — Types of subcolumns of a columnsubcolumns.serializations (Array(String)) — Kinds of serialization of subcolumns of a columnsubcolumns.bytes_on_disk (Array(UInt64)) — Sizes in bytes for each subcolumnsubcolumns.data_compressed_bytes (Array(UInt64)) — Sizes of the compressed data for each subcolumn, in bytessubcolumns.data_uncompressed_bytes (Array(UInt64)) — Sizes of the decompressed data for each subcolumn, in bytessubcolumns.marks_bytes (Array(UInt64)) — Sizes of the marks for each subcolumn of a column, in 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
Last modified on June 8, 2026
