mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-08 08:35:20 +00:00
108 lines
4.3 KiB
Markdown
108 lines
4.3 KiB
Markdown
# system.tables {#system-tables}
|
||
|
||
Contains metadata of each table that the server knows about. Detached tables are not shown in `system.tables`.
|
||
|
||
This table contains the following columns (the column type is shown in brackets):
|
||
|
||
- `database` (String) — The name of the database the table is in.
|
||
|
||
- `name` (String) — Table name.
|
||
|
||
- `engine` (String) — Table engine name (without parameters).
|
||
|
||
- `is_temporary` (UInt8) - Flag that indicates whether the table is temporary.
|
||
|
||
- `data_path` (String) - Path to the table data in the file system.
|
||
|
||
- `metadata_path` (String) - Path to the table metadata in the file system.
|
||
|
||
- `metadata_modification_time` (DateTime) - Time of latest modification of the table metadata.
|
||
|
||
- `dependencies_database` (Array(String)) - Database dependencies.
|
||
|
||
- `dependencies_table` (Array(String)) - Table dependencies ([MaterializedView](../../engines/table-engines/special/materializedview.md) tables based on the current table).
|
||
|
||
- `create_table_query` (String) - The query that was used to create the table.
|
||
|
||
- `engine_full` (String) - Parameters of the table engine.
|
||
|
||
- `partition_key` (String) - The partition key expression specified in the table.
|
||
|
||
- `sorting_key` (String) - The sorting key expression specified in the table.
|
||
|
||
- `primary_key` (String) - The primary key expression specified in the table.
|
||
|
||
- `sampling_key` (String) - The sampling key expression specified in the table.
|
||
|
||
- `storage_policy` (String) - The storage policy:
|
||
|
||
- [MergeTree](../../engines/table-engines/mergetree-family/mergetree.md#table_engine-mergetree-multiple-volumes)
|
||
- [Distributed](../../engines/table-engines/special/distributed.md#distributed)
|
||
|
||
- `total_rows` (Nullable(UInt64)) - Total number of rows, if it is possible to quickly determine exact number of rows in the table, otherwise `Null` (including underying `Buffer` table).
|
||
|
||
- `total_bytes` (Nullable(UInt64)) - Total number of bytes, if it is possible to quickly determine exact number of bytes for the table on storage, otherwise `Null` (**does not** includes any underlying storage).
|
||
|
||
- If the table stores data on disk, returns used space on disk (i.e. compressed).
|
||
- If the table stores data in memory, returns approximated number of used bytes in memory.
|
||
|
||
- `lifetime_rows` (Nullable(UInt64)) - Total number of rows INSERTed since server start (only for `Buffer` tables).
|
||
|
||
- `lifetime_bytes` (Nullable(UInt64)) - Total number of bytes INSERTed since server start (only for `Buffer` tables).
|
||
|
||
The `system.tables` table is used in `SHOW TABLES` query implementation.
|
||
|
||
```sql
|
||
:) SELECT * FROM system.tables LIMIT 2 FORMAT Vertical;
|
||
```
|
||
|
||
```text
|
||
Row 1:
|
||
──────
|
||
database: system
|
||
name: aggregate_function_combinators
|
||
uuid: 00000000-0000-0000-0000-000000000000
|
||
engine: SystemAggregateFunctionCombinators
|
||
is_temporary: 0
|
||
data_paths: []
|
||
metadata_path: /var/lib/clickhouse/metadata/system/aggregate_function_combinators.sql
|
||
metadata_modification_time: 1970-01-01 03:00:00
|
||
dependencies_database: []
|
||
dependencies_table: []
|
||
create_table_query:
|
||
engine_full:
|
||
partition_key:
|
||
sorting_key:
|
||
primary_key:
|
||
sampling_key:
|
||
storage_policy:
|
||
total_rows: ᴺᵁᴸᴸ
|
||
total_bytes: ᴺᵁᴸᴸ
|
||
|
||
Row 2:
|
||
──────
|
||
database: system
|
||
name: asynchronous_metrics
|
||
uuid: 00000000-0000-0000-0000-000000000000
|
||
engine: SystemAsynchronousMetrics
|
||
is_temporary: 0
|
||
data_paths: []
|
||
metadata_path: /var/lib/clickhouse/metadata/system/asynchronous_metrics.sql
|
||
metadata_modification_time: 1970-01-01 03:00:00
|
||
dependencies_database: []
|
||
dependencies_table: []
|
||
create_table_query:
|
||
engine_full:
|
||
partition_key:
|
||
sorting_key:
|
||
primary_key:
|
||
sampling_key:
|
||
storage_policy:
|
||
total_rows: ᴺᵁᴸᴸ
|
||
total_bytes: ᴺᵁᴸᴸ
|
||
|
||
2 rows in set. Elapsed: 0.004 sec.
|
||
```
|
||
|
||
[Original article](https://clickhouse.tech/docs/en/operations/system_tables/tables) <!--hide-->
|