system.parts
Contains information about parts of MergeTree tables.
Each row describes one data part.
Columns:
-
partition(String) – The partition name. To learn what a partition is, see the description of the ALTER query.Formats:
YYYYMMfor automatic partitioning by month.any_stringwhen partitioning manually.
-
name(String) – Name of the data part. -
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.
Data storing format is controlled by the
min_bytes_for_wide_partandmin_rows_for_wide_partsettings of the MergeTree table. -
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, multiplymarksby 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 of the date key in the data part. -
max_date(Date) – The maximum value of the date key in the data part. -
min_time(DateTime) – The minimum value of the date and time key in the data part. -
max_time(DateTime) – The maximum value of the date and time 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 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 thandata_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. -
is_frozen(UInt8) – Flag that shows that a partition data backup exists. 1, the backup exists. 0, the backup does not exist. For more details, see FREEZE PARTITION -
database(String) – Name of the database. -
table(String) – Name of the table. -
engine(String) – Name of the table engine without parameters. -
path(String) – Absolute path to the folder with data part files. -
disk(String) – Name of a disk that stores the data part. -
hash_of_all_files(String) – sipHash128 of compressed files. -
hash_of_uncompressed_files(String) – sipHash128 of uncompressed files (files with marks, index file etc.). -
uncompressed_hash_of_compressed_files(String) – sipHash128 of data in the compressed files as if they were uncompressed. -
delete_ttl_info_min(DateTime) — The minimum value of the date and time key for TTL DELETE rule. -
delete_ttl_info_max(DateTime) — The maximum value of the date and time key for TTL DELETE rule. -
move_ttl_info.expression(Array(String)) — Array of expressions. Each expression defines a TTL MOVE rule.Warning
The
move_ttl_info.expressionarray is kept mostly for backward compatibility, now the simpliest way to checkTTL MOVErule is to use themove_ttl_info.minandmove_ttl_info.maxfields. -
move_ttl_info.min(Array(DateTime)) — Array of date and time values. Each element describes the minimum key value for a TTL MOVE rule. -
move_ttl_info.max(Array(DateTime)) — Array of date and time values. Each element describes the maximum key value for a TTL MOVE rule. -
bytes(UInt64) – Alias forbytes_on_disk. -
marks_size(UInt64) – Alias formarks_bytes.
Example
SELECT * FROM system.parts LIMIT 1 FORMAT Vertical;
Row 1:
──────
partition: tuple()
name: all_1_4_1_6
part_type: Wide
active: 1
marks: 2
rows: 6
bytes_on_disk: 310
data_compressed_bytes: 157
data_uncompressed_bytes: 91
marks_bytes: 144
modification_time: 2020-06-18 13:01:49
remove_time: 1970-01-01 00:00:00
refcount: 1
min_date: 1970-01-01
max_date: 1970-01-01
min_time: 1970-01-01 00:00:00
max_time: 1970-01-01 00:00:00
partition_id: all
min_block_number: 1
max_block_number: 4
level: 1
data_version: 6
primary_key_bytes_in_memory: 8
primary_key_bytes_in_memory_allocated: 64
is_frozen: 0
database: default
table: months
engine: MergeTree
disk_name: default
path: /var/lib/clickhouse/data/default/months/all_1_4_1_6/
hash_of_all_files: 2d0657a16d9430824d35e327fcbd87bf
hash_of_uncompressed_files: 84950cc30ba867c77a408ae21332ba29
uncompressed_hash_of_compressed_files: 1ad78f1c6843bbfb99a2c931abe7df7d
delete_ttl_info_min: 1970-01-01 00:00:00
delete_ttl_info_max: 1970-01-01 00:00:00
move_ttl_info.expression: []
move_ttl_info.min: []
move_ttl_info.max: []
See Also