> ## Documentation Index > Fetch the complete documentation index at: https://private-7c7dfe99-vortex-format.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. > System table containing information about parts of MergeTree # system.parts

Description

Contains information about parts of [MergeTree](/reference/engines/table-engines/mergetree-family/mergetree) tables. Each row describes one data part.

Columns

* `partition` ([String](/reference/data-types/string)) — Partition identifier (string representation derived from the table partition key expression). * `name` ([String](/reference/data-types/string)) — Name of the data part. The part naming structure can be used to determine many aspects of the data, ingest, and merge patterns. The part naming format is the following: ```text theme={null} ____ ``` * Definitions: * `partition_id` - identifies the partition key * `minimum_block_number` - identifies the minimum block number in the part. ClickHouse always merges continuous blocks * `maximum_block_number` - identifies the maximum block number in the part * `level` - incremented by one with each additional merge on the part. A level of 0 indicates this is a new part that has not been merged. It is important to remember that all parts in ClickHouse are always immutable * `data_version` - optional value, incremented when a part is mutated (again, mutated data is always only written to a new part, since parts are immutable) * `uuid` ([UUID](/reference/data-types/uuid)) — The UUID of data part. * `part_type` ([String](/reference/data-types/string)) — The data part storing format. Possible values: `Wide` — each column is stored in a separate file, `Compact` — all columns are stored in one file. Data storing format is controlled by the `min_bytes_for_wide_part` and `min_rows_for_wide_part` settings of the MergeTree table. * `part_storage_type` ([String](/reference/data-types/string)) — The type of `DataPartStorage`. Possible values: `Packed` - most part files are stored in a single archive (projections and a few service files such as `txn_version.txt` are written separately), `Full` - each file is stored separately. * `active` ([UInt8](/reference/data-types/int-uint)) — Flag that indicates whether the data part is active. If a data part is active, it's used in a table. Otherwise, it's about to be deleted. Inactive data parts appear after merging and mutating operations. * `marks` ([UInt64](/reference/data-types/int-uint)) — 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](/reference/data-types/int-uint)) — The number of rows. * `files` ([UInt64](/reference/data-types/int-uint)) — The number of files in the data part. * `bytes_on_disk` ([UInt64](/reference/data-types/int-uint)) — Total size of all the data part files in bytes. * `data_compressed_bytes` ([UInt64](/reference/data-types/int-uint)) — 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](/reference/data-types/int-uint)) — Total size of uncompressed data in the data part. All the auxiliary files (for example, files with marks) are not included. * `primary_key_size` ([UInt64](/reference/data-types/int-uint)) — The amount of memory (in bytes) used by primary key values in the primary.idx/cidx file on disk. * `marks_bytes` ([UInt64](/reference/data-types/int-uint)) — The size of the file with marks. * `secondary_indices_compressed_bytes` ([UInt64](/reference/data-types/int-uint)) — Total size of compressed data for secondary indices in the data part. All the auxiliary files (for example, files with marks) are not included. * `secondary_indices_uncompressed_bytes` ([UInt64](/reference/data-types/int-uint)) — Total size of uncompressed data for secondary indices in the data part. All the auxiliary files (for example, files with marks) are not included. * `secondary_indices_marks_bytes` ([UInt64](/reference/data-types/int-uint)) — The size of the file with marks for secondary indices. * `modification_time` ([DateTime](/reference/data-types/datetime)) — The time the directory with the data part was modified. This usually corresponds to the time of data part creation. * `remove_time` ([DateTime](/reference/data-types/datetime)) — The time when the data part became inactive. * `refcount` ([UInt32](/reference/data-types/int-uint)) — 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](/reference/data-types/date)) — The minimum value of the date key in the data part. * `max_date` ([Date](/reference/data-types/date)) — The maximum value of the date key in the data part. * `min_time` ([DateTime](/reference/data-types/datetime)) — The minimum value of the date and time key in the data part. * `max_time` ([DateTime](/reference/data-types/datetime)) — The maximum value of the date and time key in the data part. * `partition_id` ([String](/reference/data-types/string)) — ID of the partition. * `min_block_number` ([Int64](/reference/data-types/int-uint)) — The minimum number of data parts that make up the current part after merging. * `max_block_number` ([Int64](/reference/data-types/int-uint)) — The maximum number of data parts that make up the current part after merging. * `level` ([UInt32](/reference/data-types/int-uint)) — Depth of the merge tree. Zero means that the current part was created by insert rather than by merging other parts. * `data_version` ([UInt64](/reference/data-types/int-uint)) — 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](/reference/data-types/int-uint)) — The amount of memory (in bytes) used by primary key values. Will be 0 when `primary_key_lazy_load` is enabled and the key is not loaded. When non-zero the bytes live in the part itself and are accounted within `jemalloc.mergetree_arena.active_bytes`. They are NEVER counted in `PrimaryIndexCacheBytes` — those are mutually exclusive per part: an index lives either in the part (this metric) or in the shared `PrimaryIndexCache` (the other), depending on `primary_key_lazy_load` and `use_primary_key_cache`. * `primary_key_bytes_in_memory_allocated` ([UInt64](/reference/data-types/int-uint)) — The amount of memory (in bytes) reserved for primary key values. Will be 0 when `primary_key_lazy_load` is enabled and the key is not loaded. When non-zero, included in `jemalloc.mergetree_arena.active_bytes`. See the note on `primary_key_bytes_in_memory` for the relationship with `PrimaryIndexCacheBytes`. * `index_granularity_bytes_in_memory` ([UInt64](/reference/data-types/int-uint)) — The amount of memory (in bytes) used by index granularity values (will be 0 in case of primary\_key\_lazy\_load=1 and use\_primary\_key\_cache=1). When non-zero the bytes are part-owned and accounted within `jemalloc.mergetree_arena.active_bytes`. * `index_granularity_bytes_in_memory_allocated` ([UInt64](/reference/data-types/int-uint)) — The amount of memory (in bytes) reserved for index granularity values (will be 0 in case of primary\_key\_lazy\_load=1 and use\_primary\_key\_cache=1). When non-zero, included in `jemalloc.mergetree_arena.active_bytes`. * `is_frozen` ([UInt8](/reference/data-types/int-uint)) — 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](/reference/data-types/string)) — Name of the database. * `table` ([String](/reference/data-types/string)) — Name of the table. * `engine` ([String](/reference/data-types/string)) — Name of the table engine without parameters. * `disk_name` ([String](/reference/data-types/string)) — Name of a disk that stores the data part. * `path` ([String](/reference/data-types/string)) — Absolute path to the folder with data part files. * `hash_of_all_files` ([String](/reference/data-types/string)) — sipHash128 of compressed files. * `hash_of_uncompressed_files` ([String](/reference/data-types/string)) — sipHash128 of uncompressed files (files with marks, index file etc.). * `uncompressed_hash_of_compressed_files` ([String](/reference/data-types/string)) — sipHash128 of data in the compressed files as if they were uncompressed. * `delete_ttl_info_min` ([DateTime](/reference/data-types/datetime)) — The minimum value of the date and time key for TTL DELETE rule. * `delete_ttl_info_max` ([DateTime](/reference/data-types/datetime)) — The maximum value of the date and time key for TTL DELETE rule. * `move_ttl_info.expression` ([Array(String)](/reference/data-types/array)) — Array of expressions. Each expression defines a TTL MOVE rule. * `move_ttl_info.min` ([Array(DateTime)](/reference/data-types/array)) — Array of date and time values. Each element describes the minimum key value for a TTL MOVE rule. * `move_ttl_info.max` ([Array(DateTime)](/reference/data-types/array)) — Array of date and time values. Each element describes the maximum key value for a TTL MOVE rule. * `default_compression_codec` ([String](/reference/data-types/string)) — The name of the codec used to compress this data part when a column has no explicit codec or uses `CODEC(Default)`. With `allow_experimental_adaptive_codec_selection`, individual blocks of such columns may use other codecs; see [`mergeTreeCodecBlockCounts`](/reference/functions/table-functions/mergeTreeCodecBlockCounts). * `recompression_ttl_info.expression` ([Array(String)](/reference/data-types/array)) — The TTL expression. * `recompression_ttl_info.min` ([Array(DateTime)](/reference/data-types/array)) — The minimum value of the calculated TTL expression within this part. Used to understand whether we have at least one row with expired TTL. * `recompression_ttl_info.max` ([Array(DateTime)](/reference/data-types/array)) — The maximum value of the calculated TTL expression within this part. Used to understand whether we have all rows with expired TTL. * `group_by_ttl_info.expression` ([Array(String)](/reference/data-types/array)) — The TTL expression. * `group_by_ttl_info.min` ([Array(DateTime)](/reference/data-types/array)) — The minimum value of the calculated TTL expression within this part. Used to understand whether we have at least one row with expired TTL. * `group_by_ttl_info.max` ([Array(DateTime)](/reference/data-types/array)) — The maximum value of the calculated TTL expression within this part. Used to understand whether we have all rows with expired TTL. * `rows_where_ttl_info.expression` ([Array(String)](/reference/data-types/array)) — The TTL expression. * `rows_where_ttl_info.min` ([Array(DateTime)](/reference/data-types/array)) — The minimum value of the calculated TTL expression within this part. Used to understand whether we have at least one row with expired TTL. * `rows_where_ttl_info.max` ([Array(DateTime)](/reference/data-types/array)) — The maximum value of the calculated TTL expression within this part. Used to understand whether we have all rows with expired TTL. * `projections` ([Array(String)](/reference/data-types/array)) — The list of projection names calculated for this part. * `visible` ([UInt8](/reference/data-types/int-uint)) — Flag which indicated whether this part is visible for SELECT queries. * `creation_tid` ([Tuple(UInt64, UInt64, UUID)](/reference/data-types/tuple)) — ID of transaction that has created/is trying to create this object. * `removal_tid_lock` ([UInt64](/reference/data-types/int-uint)) — Hash of removal\_tid, used to lock an object for removal. * `removal_tid` ([Tuple(UInt64, UInt64, UUID)](/reference/data-types/tuple)) — ID of transaction that has removed/is trying to remove this object * `creation_csn` ([UInt64](/reference/data-types/int-uint)) — CSN of transaction that has created this object * `removal_csn` ([UInt64](/reference/data-types/int-uint)) — CSN of transaction that has removed this object * `has_lightweight_delete` ([UInt8](/reference/data-types/int-uint)) — The flag which indicated whether the part has lightweight delete mask. * `last_removal_attempt_time` ([DateTime](/reference/data-types/datetime)) — The last time the server tried to delete this part. * `removal_state` ([String](/reference/data-types/string)) — The current state of part removal process. **Aliases:** * `bytes` — Alias for `bytes_on_disk`. * `marks_size` — Alias for `marks_bytes`. * `part_name` — Alias for `name`.

Example

```sql theme={null} SELECT * FROM system.parts LIMIT 1 FORMAT Vertical; ``` ```text theme={null} Row 1: ────── partition: tuple() name: all_1_4_1_6 part_type: Wide part_storage_type: Full active: 1 marks: 2 rows: 6 bytes_on_disk: 310 data_compressed_bytes: 157 data_uncompressed_bytes: 91 secondary_indices_compressed_bytes: 58 secondary_indices_uncompressed_bytes: 6 secondary_indices_marks_bytes: 48 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

* [MergeTree family](/reference/engines/table-engines/mergetree-family/mergetree) * [TTL for Columns and Tables](/reference/engines/table-engines/mergetree-family/mergetree#table_engine-mergetree-ttl)