system.tables

Description

Contains metadata of each table that the server knows about.

Detached tables are not shown in system.tables.

Temporary tables are visible in the system.tables only in those session where they have been created. They are shown with the empty database field and with the is_temporary flag switched on.

Columns

• database (String) — The name of the database the table is in.
• name (String) — Table name.
• uuid (UUID) — Table uuid (Atomic database).
• engine (String) — Table engine name (without parameters).
• is_temporary (UInt8) — Flag that indicates whether the table is temporary.
• data_paths (Array(String)) — Paths to the table data in the file systems.
• metadata_path (String) — Path to the table metadata in the file system.
• metadata_modification_time (DateTime) — Time of latest modification of the table metadata.
• metadata_version (Int32) — Metadata version for ReplicatedMergeTree table, 0 for non ReplicatedMergeTree table.
• dependencies_database (Array(String)) — Database dependencies.
• dependencies_table (Array(String)) — Table dependencies (materialized views the current table).
• create_table_query (String) — The query that was used to create the table.
• engine_full (String) — Parameters of the table engine.
• as_select (String) — SELECT query for view.
• parameterized_view_parameters (Array(Tuple(name String, type String))) — Parameters of parameterized view.
• 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. Relevant for tables using MergeTree and Distributed engines.
• 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 underlying 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.
• total_bytes_uncompressed (Nullable(UInt64)) — Total number of uncompressed bytes, if it's possible to quickly determine the exact number of bytes from the part checksums for the table on storage, otherwise NULL (does not take underlying storage (if any) into account).
• parts (Nullable(UInt64)) — The total number of parts in this table.
• active_parts (Nullable(UInt64)) — The number of active parts in this table.
• total_marks (Nullable(UInt64)) — The total number of marks in all parts in this table.
• active_on_fly_data_mutations (UInt64) — Total number of active data mutations (UPDATEs and DELETEs) suitable for applying on the fly.
• active_on_fly_alter_mutations (UInt64) — Total number of active alter mutations (MODIFY COLUMN) suitable for applying on the fly.
• active_on_fly_metadata_mutations (UInt64) — Total number of active metadata mutations (RENAMEs) suitable for applying on the fly.
• columns_descriptions_cache_size (UInt64) — Size of columns description cache for *MergeTree tables
• 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).
• comment (String) — The comment for the table.
• has_own_data (UInt8) — Flag that indicates whether the table itself stores some data on disk or only accesses some other source.
• loading_dependencies_database (Array(String)) — Database loading dependencies (list of objects which should be loaded before the current object).
• loading_dependencies_table (Array(String)) — Table loading dependencies (list of objects which should be loaded before the current object).
• loading_dependent_database (Array(String)) — Dependent loading database.
• loading_dependent_table (Array(String)) — Dependent loading table.
• definer (String) — SQL security definer's name used for the table.

Example

SELECT * FROM system.tables LIMIT 2 FORMAT Vertical;

Row 1:
──────
database:                   base
name:                       t1
uuid:                       81b1c20a-b7c6-4116-a2ce-7583fb6b6736
engine:                     MergeTree
is_temporary:               0
data_paths:                 ['/var/lib/clickhouse/store/81b/81b1c20a-b7c6-4116-a2ce-7583fb6b6736/']
metadata_path:              /var/lib/clickhouse/store/461/461cf698-fd0b-406d-8c01-5d8fd5748a91/t1.sql
metadata_modification_time: 2021-01-25 19:14:32
dependencies_database:      []
dependencies_table:         []
create_table_query:         CREATE TABLE base.t1 (`n` UInt64) ENGINE = MergeTree ORDER BY n
engine_full:                MergeTree ORDER BY n
as_select:                  SELECT database AS table_catalog
partition_key:
sorting_key:                n
primary_key:                n
sampling_key:
storage_policy:             default
total_rows:                 1
total_bytes:                99
lifetime_rows:              ᴺᵁᴸᴸ
lifetime_bytes:             ᴺᵁᴸᴸ
comment:
has_own_data:               0
loading_dependencies_database: []
loading_dependencies_table:    []
loading_dependent_database:    []
loading_dependent_table:       []

Row 2:
──────
database:                   default
name:                       53r93yleapyears
uuid:                       00000000-0000-0000-0000-000000000000
engine:                     MergeTree
is_temporary:               0
data_paths:                 ['/var/lib/clickhouse/data/default/53r93yleapyears/']
metadata_path:              /var/lib/clickhouse/metadata/default/53r93yleapyears.sql
metadata_modification_time: 2020-09-23 09:05:36
dependencies_database:      []
dependencies_table:         []
create_table_query:         CREATE TABLE default.`53r93yleapyears` (`id` Int8, `febdays` Int8) ENGINE = MergeTree ORDER BY id
engine_full:                MergeTree ORDER BY id
as_select:                  SELECT name AS catalog_name
partition_key:
sorting_key:                id
primary_key:                id
sampling_key:
storage_policy:             default
total_rows:                 2
total_bytes:                155
lifetime_rows:              ᴺᵁᴸᴸ
lifetime_bytes:             ᴺᵁᴸᴸ
comment:
has_own_data:               0
loading_dependencies_database: []
loading_dependencies_table:    []
loading_dependent_database:    []
loading_dependent_table:       []