system.query_cache

System table which shows the content of the query cache.

Querying in ClickHouse Cloud

The data in this system table is held locally on each node in ClickHouse Cloud. Obtaining a complete view of all data, therefore, requires the clusterAllReplicas function. See here for further details.

Description

Shows the content of the query cache.

Columns

• query (String) — Query string.
• query_id (String) — ID of the query.
• is_subquery (UInt8) — Whether the query cache entry is a subquery result.
• result_size (UInt64) — Size of the query cache entry.
• tag (LowCardinality(String)) — Tag of the query cache entry.
• stale (UInt8) — If the query cache entry is stale.
• shared (UInt8) — If the query cache entry is shared between multiple users.
• compressed (UInt8) — If the query cache entry is compressed.
• expires_at (DateTime) — When the query cache entry becomes stale.
• key_hash (UInt64) — A hash of the query string, used as a key to find query cache entries.

Example

SELECT * FROM system.query_cache FORMAT Vertical;

Row 1:
──────
query:       SELECT 1 SETTINGS use_query_cache = 1
query_id:    7c28bbbb-753b-4eba-98b1-efcbe2b9bdf6
result_size: 128
tag:
stale:       0
shared:      0
compressed:  1
expires_at:  2023-10-13 13:35:45
key_hash:    12188185624808016954

1 row in set. Elapsed: 0.004 sec.