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* prefer relative links from root * wip * split aggregate function reference * split system tables
81 lines
4.2 KiB
Markdown
81 lines
4.2 KiB
Markdown
# system.parts {#system_tables-parts}
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Contains information about parts of [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md) tables.
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Each row describes one data part.
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Columns:
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- `partition` (String) – The partition name. To learn what a partition is, see the description of the [ALTER](../../sql-reference/statements/alter.md#query_language_queries_alter) query.
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Formats:
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- `YYYYMM` for automatic partitioning by month.
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- `any_string` when partitioning manually.
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- `name` (`String`) – Name of the data part.
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- `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.
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- `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 doesn’t work for adaptive granularity).
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- `rows` (`UInt64`) – The number of rows.
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- `bytes_on_disk` (`UInt64`) – Total size of all the data part files in bytes.
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- `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.
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- `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.
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- `marks_bytes` (`UInt64`) – The size of the file with marks.
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- `modification_time` (`DateTime`) – The time the directory with the data part was modified. This usually corresponds to the time of data part creation.\|
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- `remove_time` (`DateTime`) – The time when the data part became inactive.
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- `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.
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- `min_date` (`Date`) – The minimum value of the date key in the data part.
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- `max_date` (`Date`) – The maximum value of the date key in the data part.
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- `min_time` (`DateTime`) – The minimum value of the date and time key in the data part.
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- `max_time`(`DateTime`) – The maximum value of the date and time key in the data part.
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- `partition_id` (`String`) – ID of the partition.
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- `min_block_number` (`UInt64`) – The minimum number of data parts that make up the current part after merging.
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- `max_block_number` (`UInt64`) – The maximum number of data parts that make up the current part after merging.
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- `level` (`UInt32`) – Depth of the merge tree. Zero means that the current part was created by insert rather than by merging other parts.
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- `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`).
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- `primary_key_bytes_in_memory` (`UInt64`) – The amount of memory (in bytes) used by primary key values.
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- `primary_key_bytes_in_memory_allocated` (`UInt64`) – The amount of memory (in bytes) reserved for primary key values.
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- `is_frozen` (`UInt8`) – Flag that shows that a partition data backup exists. 1, the backup exists. 0, the backup doesn’t exist. For more details, see [FREEZE PARTITION](../../sql-reference/statements/alter.md#alter_freeze-partition)
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- `database` (`String`) – Name of the database.
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- `table` (`String`) – Name of the table.
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- `engine` (`String`) – Name of the table engine without parameters.
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- `path` (`String`) – Absolute path to the folder with data part files.
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- `disk` (`String`) – Name of a disk that stores the data part.
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- `hash_of_all_files` (`String`) – [sipHash128](../../sql-reference/functions/hash-functions.md#hash_functions-siphash128) of compressed files.
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- `hash_of_uncompressed_files` (`String`) – [sipHash128](../../sql-reference/functions/hash-functions.md#hash_functions-siphash128) of uncompressed files (files with marks, index file etc.).
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- `uncompressed_hash_of_compressed_files` (`String`) – [sipHash128](../../sql-reference/functions/hash-functions.md#hash_functions-siphash128) of data in the compressed files as if they were uncompressed.
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- `bytes` (`UInt64`) – Alias for `bytes_on_disk`.
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- `marks_size` (`UInt64`) – Alias for `marks_bytes`.
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