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ClickHouse/docs/en/operations/system-tables/tables.md

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[docs] split aggregate function and system table references (#11742) * prefer relative links from root * wip * split aggregate function reference * split system tables
2020-06-18 08:24:31 +00:00
# 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.
Implement lifetime_rows/lifetime_bytes for Buffer engine Buffer engine is usually used on INSERTs, but right now there is no way to track number of INSERTed rows per-table, since only summary metrics exists: - StorageBufferRows - StorageBufferBytes But it can be pretty useful to track INSERTed rows rate (and it can be exposed via http_handlers for i.e. prometheus)
2020-07-11 12:26:53 +00:00
- `lifetime_rows` (Nullable(UInt64)) - Total number of rows INSERTed since server start (only for `Buffer` tables).
Add lifetime_rows/lifetime_bytes interface (exported via system.tables)
2020-07-11 12:19:06 +00:00
Implement lifetime_rows/lifetime_bytes for Buffer engine Buffer engine is usually used on INSERTs, but right now there is no way to track number of INSERTed rows per-table, since only summary metrics exists: - StorageBufferRows - StorageBufferBytes But it can be pretty useful to track INSERTed rows rate (and it can be exposed via http_handlers for i.e. prometheus)
2020-07-11 12:26:53 +00:00
- `lifetime_bytes` (Nullable(UInt64)) - Total number of bytes INSERTed since server start (only for `Buffer` tables).
Add lifetime_rows/lifetime_bytes interface (exported via system.tables)
2020-07-11 12:19:06 +00:00
[docs] split aggregate function and system table references (#11742) * prefer relative links from root * wip * split aggregate function reference * split system tables
2020-06-18 08:24:31 +00:00
The `system.tables` table is used in `SHOW TABLES` query implementation.
DOCSUP-1915: Split system-table.md into separate files. (#13160) * Corrected en files * Split system-tables.md into separate files * Fixed links. * Fixed links. * Fixed links. * Fixed links. * Add ref to original article * Fixed links * Add toc_folder_title and translate * Add stack_trace.md, correct toc-title * Fixed links * Hypothesis testing * Hypothesis testing * Update run.sh, thanks @azat Co-authored-by: Anna Devyatova <annadevyatova@yandex-team.ru> Co-authored-by: Sergei Shtykov <bayonet@yandex-team.ru> Co-authored-by: alexey-milovidov <milovidov@yandex-team.ru>
2020-08-06 08:50:29 +00:00
[Original article](https://clickhouse.tech/docs/en/operations/system_tables/tables) <!--hide-->
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