title_wip

[Edit this page](https://github.com/ClickHouse/ClickHouse/tree/master/docs/en/operations/system-tables/projection_parts_columns.md)

This table contains information about columns in projection parts for tables of the MergeTree family.

## Columns[​](#columns "Direct link to Columns")

- `partition` ([String](/docs/sql-reference/data-types)) — The partition name.
- `name` ([String](/docs/sql-reference/data-types)) — Name of the data part.
- `part_type` ([String](/docs/sql-reference/data-types)) — The data part storing format.
- `parent_name` ([String](/docs/sql-reference/data-types)) — The name of the source (parent) data part.
- `parent_uuid` ([UUID](/docs/sql-reference/data-types)) — The UUID of the source (parent) data part.
- `parent_part_type` ([String](/docs/sql-reference/data-types)) — The source (parent) data part storing format.
- `active` ([UInt8](/docs/sql-reference/data-types)) — Flag that indicates whether the data part is active
- `marks` ([UInt64](/docs/sql-reference/data-types)) — The number of marks.
- `rows` ([UInt64](/docs/sql-reference/data-types)) — The number of rows.
- `bytes_on_disk` ([UInt64](/docs/sql-reference/data-types)) — Total size of all the data part files in bytes.
- `data_compressed_bytes` ([UInt64](/docs/sql-reference/data-types)) — 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](/docs/sql-reference/data-types)) — Total size of uncompressed data in the data part. All the auxiliary files (for example, files with marks) are not included.
- `marks_bytes` ([UInt64](/docs/sql-reference/data-types)) — The size of the file with marks.
- `parent_marks` ([UInt64](/docs/sql-reference/data-types)) — The number of marks in the source (parent) part.
- `parent_rows` ([UInt64](/docs/sql-reference/data-types)) — The number of rows in the source (parent) part.
- `parent_bytes_on_disk` ([UInt64](/docs/sql-reference/data-types)) — Total size of all the source (parent) data part files in bytes.
- `parent_data_compressed_bytes` ([UInt64](/docs/sql-reference/data-types)) — Total size of compressed data in the source (parent) data part.
- `parent_data_uncompressed_bytes` ([UInt64](/docs/sql-reference/data-types)) — Total size of uncompressed data in the source (parent) data part.
- `parent_marks_bytes` ([UInt64](/docs/sql-reference/data-types)) — The size of the file with marks in the source (parent) data part.
- `modification_time` ([DateTime](/docs/sql-reference/data-types)) — The time the directory with the data part was modified. This usually corresponds to the time of data part creation.
- `remove_time` ([DateTime](/docs/sql-reference/data-types)) — The time when the data part became inactive.
- `refcount` ([UInt32](/docs/sql-reference/data-types)) — 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](/docs/sql-reference/data-types)) — The minimum value for the Date column if that is included in the partition key.
- `max_date` ([Date](/docs/sql-reference/data-types)) — The maximum value for the Date column if that is included in the partition key.
- `min_time` ([DateTime](/docs/sql-reference/data-types)) — The minimum value for the DateTime column if that is included in the partition key.
- `max_time` ([DateTime](/docs/sql-reference/data-types)) — The maximum value for the DateTime column if that is included in the partition key.
- `partition_id` ([String](/docs/sql-reference/data-types)) — ID of the partition.
- `min_block_number` ([Int64](/docs/sql-reference/data-types)) — The minimum number of data parts that make up the current part after merging.
- `max_block_number` ([Int64](/docs/sql-reference/data-types)) — The maximum number of data parts that make up the current part after merging.
- `level` ([UInt32](/docs/sql-reference/data-types)) — Depth of the merge tree. Zero means that the current part was created by insert rather than by merging other parts.
- `data_version` ([UInt64](/docs/sql-reference/data-types)) — 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](/docs/sql-reference/data-types)) — The amount of memory (in bytes) used by primary key values.
- `primary_key_bytes_in_memory_allocated` ([UInt64](/docs/sql-reference/data-types)) — The amount of memory (in bytes) reserved for primary key values.
- `database` ([String](/docs/sql-reference/data-types)) — Name of the database.
- `table` ([String](/docs/sql-reference/data-types)) — Name of the table.
- `engine` ([String](/docs/sql-reference/data-types)) — Name of the table engine without parameters.
- `disk_name` ([String](/docs/sql-reference/data-types)) — Name of a disk that stores the data part.
- `path` ([String](/docs/sql-reference/data-types)) — Absolute path to the folder with data part files.
- `column` ([String](/docs/sql-reference/data-types)) — Name of the column.
- `type` ([String](/docs/sql-reference/data-types)) — Column type.
- `column_position` ([UInt64](/docs/sql-reference/data-types)) — Ordinal position of a column in a table starting with 1.
- `default_kind` ([String](/docs/sql-reference/data-types)) — Expression type (DEFAULT, MATERIALIZED, ALIAS) for the default value, or an empty string if it is not defined.
- `default_expression` ([String](/docs/sql-reference/data-types)) — Expression for the default value, or an empty string if it is not defined.
- `column_bytes_on_disk` ([UInt64](/docs/sql-reference/data-types)) — Total size of the column in bytes.
- `column_data_compressed_bytes` ([UInt64](/docs/sql-reference/data-types)) — Total size of compressed data in the column, in bytes.
- `column_data_uncompressed_bytes` ([UInt64](/docs/sql-reference/data-types)) — Total size of the decompressed data in the column, in bytes.
- `column_marks_bytes` ([UInt64](/docs/sql-reference/data-types)) — The size of the column with marks, in bytes.
- `column_modification_time` ([Nullable(DateTime)](/docs/sql-reference/data-types)) — The last time the column was modified.

- [Columns](#columns)

Was this page helpful?