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Shaun Struwig
cb5903b1de
Move the page-level markers around each complete generated body and remove nested catalog markers. Preserve retired `system.events` anchors with compatibility stubs. Review: https://github.com/ClickHouse/ClickHouse/pull/116291#discussion_r3943539115 PR: https://github.com/ClickHouse/ClickHouse/pull/116291
53 lines
1.9 KiB
Plaintext
53 lines
1.9 KiB
Plaintext
---
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description: 'System table which shows the content of the query cache.'
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keywords: ['system table', 'query_cache']
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slug: /operations/system-tables/query_cache
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title: 'system.query_cache'
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doc_type: 'reference'
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---
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import SystemTableCloud from '/snippets/_system_table_cloud.mdx';
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<SystemTableCloud/>
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{/*AUTOGENERATED_START*/}
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## Description {#description}
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Shows the content of the [query cache](/concepts/features/performance/caches/query-cache).
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## Columns {#columns}
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- `query` ([String](/reference/data-types/string)) — Query string.
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- `query_id` ([String](/reference/data-types/string)) — ID of the query.
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- `is_subquery` ([UInt8](/reference/data-types/int-uint)) — Whether the query cache entry is a subquery result.
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- `result_size` ([UInt64](/reference/data-types/int-uint)) — Size of the query cache entry.
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- `tag` ([LowCardinality(String)](/reference/data-types/lowcardinality)) — Tag of the query cache entry.
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- `stale` ([UInt8](/reference/data-types/int-uint)) — If the query cache entry is stale.
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- `shared` ([UInt8](/reference/data-types/int-uint)) — If the query cache entry is shared between multiple users.
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- `compressed` ([UInt8](/reference/data-types/int-uint)) — If the query cache entry is compressed.
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- `expires_at` ([DateTime](/reference/data-types/datetime)) — When the query cache entry becomes stale.
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- `key_hash` ([UInt64](/reference/data-types/int-uint)) — A hash of the query string, used as a key to find query cache entries.
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## Example {#example}
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```sql
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SELECT * FROM system.query_cache FORMAT Vertical;
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```
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```text
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Row 1:
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──────
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query: SELECT 1 SETTINGS use_query_cache = 1
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query_id: 7c28bbbb-753b-4eba-98b1-efcbe2b9bdf6
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result_size: 128
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tag:
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stale: 0
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shared: 0
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compressed: 1
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expires_at: 2023-10-13 13:35:45
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key_hash: 12188185624808016954
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1 row in set. Elapsed: 0.004 sec.
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```
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{/*AUTOGENERATED_END*/}
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