> ## Documentation Index > Fetch the complete documentation index at: https://private-7c7dfe99-fix-nav-issues.mintlify.site/llms.txt > Use this file to discover all available pages before exploring further. # ClickHouseでクエリキャッシュが使用されているかを確認する方法 > `clickhouse-client` のトレースログまたはSQLコマンドを使って、ClickHouseでクエリキャッシュが利用されているかどうかを確認する方法を紹介します。
## クエリで クエリキャッシュ が使用されているか確認するにはどうすればよいですか？
[clickhouse client](/ja/concepts/features/interfaces/cli) と ClickHouse Cloud service を使用する次の例を参照してください。 `query_cache_test` テーブルを作成します
## clickhouse client を使用する
```sql theme={null} clickhouse-cloud :) CREATE TABLE query_cache_test (name String, age UInt8) ENGINE =MergeTree ORDER BY name CREATE TABLE query_cache_test ( `name` String, `age` UInt8 ) ENGINE = MergeTree ORDER BY name Query id: 81c54f09-7de4-48ec-916f-c7c304a46931 Ok. 0 rows in set. Elapsed: 0.343 sec. ``` テーブルにいくつかのデータを挿入します: ```sql theme={null} clickhouse-cloud :) INSERT INTO query_cache_test SELECT * FROM generateRandom('name String, age UInt8',1,1) LIMIT 100000; INSERT INTO query_cache_test SELECT * FROM generateRandom('name String, age UInt8', 1, 1) LIMIT 100000 Query id: 90369105-bd67-494c-bdaf-d90dbfb6def9 Ok. 0 rows in set. Elapsed: 0.173 sec. Processed 327.05 thousand rows, 3.43 MB (1.89 million rows/s., 19.86 MB/s.) ``` トレースログを有効にします: ```sql theme={null} clickhouse-cloud :) SET send_logs_level = 'trace' SET send_logs_level = 'trace' Query id: d65490b0-7960-4a85-a343-787e70e5e293 Ok. 0 rows in set. Elapsed: 0.134 sec. ``` クエリキャッシュを使用するよう指定してクエリを実行します (クエリの末尾に `SETTINGS use_query_cache=true` を追加します) : ```sql theme={null} clickhouse-cloud :) SELECT name FROM query_cache_test WHERE age > 1000 FORMAT Null SETTINGS use_query_cache=true; SELECT name FROM query_cache_test WHERE age > 1000 FORMAT `Null` SETTINGS use_query_cache = 1 Query id: 3754a7fd-b786-47c1-a258-dfbc75e35a04 [c-red-qc-36-server-0] 2023.05.29 12:06:10.542408 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ executeQuery: (from 151.53.3.113:50412, user: tony) SELECT name FROM query_cache_test WHERE age > 1000 FORMAT Null SETTINGS use_query_cache=true; (stage: Complete) [c-red-qc-36-server-0] 2023.05.29 12:06:10.542744 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ InterpreterSelectQuery: MergeTreeWhereOptimizer: condition "age > 1000" moved to PREWHERE [c-red-qc-36-server-0] 2023.05.29 12:06:10.542900 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ InterpreterSelectQuery: MergeTreeWhereOptimizer: condition "age > 1000" moved to PREWHERE [c-red-qc-36-server-0] 2023.05.29 12:06:10.543020 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ ContextAccess (tony): Access granted: SELECT(name, age) ON tony.test [c-red-qc-36-server-0] 2023.05.29 12:06:10.543164 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ ContextAccess (tony): Access granted: SELECT(name, age) ON tony.test [c-red-qc-36-server-0] 2023.05.29 12:06:10.543226 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ InterpreterSelectQuery: FetchColumns -> Complete [c-red-qc-36-server-0] 2023.05.29 12:06:10.543337 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ tony.test (e61a107c-e7f8-4445-825f-88f85c72f7e9) (SelectExecutor): Key condition: unknown [c-red-qc-36-server-0] 2023.05.29 12:06:10.543395 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ tony.test (e61a107c-e7f8-4445-825f-88f85c72f7e9) (SelectExecutor): Selected 1/1 parts by partition key, 1 parts by primary key, 12/12 marks by primary key, 12 marks to read from 1 ranges [c-red-qc-36-server-0] 2023.05.29 12:06:10.543412 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ tony.test (e61a107c-e7f8-4445-825f-88f85c72f7e9) (SelectExecutor): Spreading mark ranges among streams (default reading) [c-red-qc-36-server-0] 2023.05.29 12:06:10.543461 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ MergeTreeBaseSelectProcessor: PREWHERE condition was split into 1 steps: "greater(age, 1000)" [c-red-qc-36-server-0] 2023.05.29 12:06:10.543484 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ MergeTreeInOrderSelectProcessor: Reading 1 ranges in order from part all_0_0_0, approx. 100000 rows starting from 0 [c-red-qc-36-server-0] 2023.05.29 12:06:10.543559 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ QueryCache: No entry found for query SELECT name FROM query_cache_test WHERE age > 1000 FORMAT `Null` SETTINGS [c-red-qc-36-server-0] 2023.05.29 12:06:10.547760 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ QueryCache: Stored result of query SELECT name FROM query_cache_test WHERE age > 1000 FORMAT `Null` SETTINGS [c-red-qc-36-server-0] 2023.05.29 12:06:10.547827 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ executeQuery: Read 100000 rows, 97.66 KiB in 0.005508 sec., 18155410.31227306 rows/sec., 17.31 MiB/sec. [c-red-qc-36-server-0] 2023.05.29 12:06:10.547913 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ MemoryTracker: Peak memory usage (for query): 451.89 KiB. [c-red-qc-36-server-0] 2023.05.29 12:06:10.547933 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ TCPHandler: Processed in 0.005911032 sec. Ok. 0 rows in set. Elapsed: 0.006 sec. Processed 100.00 thousand rows, 100.00 KB (17.56 million rows/s., 17.56 MB/s.) ``` 同じクエリをもう一度実行します: ```sql theme={null} clickhouse-cloud :) SELECT name FROM query_cache_test WHERE age > 1000 FORMAT Null SETTINGS use_query_cache=true; SELECT name FROM query_cache_test WHERE age > 1000 FORMAT `Null` SETTINGS use_query_cache = 1 Query id: a047527c-9d55-4e6b-9747-0ccad8787515 [c-red-qc-36-server-0] 2023.05.29 12:06:17.931007 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ executeQuery: (from 151.53.3.113:50412, user: tony) SELECT name FROM query_cache_test WHERE age > 1000 FORMAT Null SETTINGS use_query_cache=true; (stage: Complete) [c-red-qc-36-server-0] 2023.05.29 12:06:17.931331 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ InterpreterSelectQuery: MergeTreeWhereOptimizer: condition "age > 1000" moved to PREWHERE [c-red-qc-36-server-0] 2023.05.29 12:06:17.931468 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ InterpreterSelectQuery: MergeTreeWhereOptimizer: condition "age > 1000" moved to PREWHERE [c-red-qc-36-server-0] 2023.05.29 12:06:17.931585 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ ContextAccess (tony): Access granted: SELECT(name, age) ON tony.test [c-red-qc-36-server-0] 2023.05.29 12:06:17.931696 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ ContextAccess (tony): Access granted: SELECT(name, age) ON tony.test [c-red-qc-36-server-0] 2023.05.29 12:06:17.931749 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ InterpreterSelectQuery: FetchColumns -> Complete [c-red-qc-36-server-0] 2023.05.29 12:06:17.931857 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ tony.test (e61a107c-e7f8-4445-825f-88f85c72f7e9) (SelectExecutor): Key condition: unknown [c-red-qc-36-server-0] 2023.05.29 12:06:17.931891 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ tony.test (e61a107c-e7f8-4445-825f-88f85c72f7e9) (SelectExecutor): Selected 1/1 parts by partition key, 1 parts by primary key, 12/12 marks by primary key, 12 marks to read from 1 ranges [c-red-qc-36-server-0] 2023.05.29 12:06:17.931913 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ tony.test (e61a107c-e7f8-4445-825f-88f85c72f7e9) (SelectExecutor): Spreading mark ranges among streams (default reading) [c-red-qc-36-server-0] 2023.05.29 12:06:17.931952 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ MergeTreeBaseSelectProcessor: PREWHERE condition was split into 1 steps: "greater(age, 1000)" [c-red-qc-36-server-0] 2023.05.29 12:06:17.931975 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ MergeTreeInOrderSelectProcessor: Reading 1 ranges in order from part all_0_0_0, approx. 100000 rows starting from 0 [c-red-qc-36-server-0] 2023.05.29 12:06:17.932043 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ QueryCache: Entry found for query SELECT name FROM query_cache_test WHERE age > 1000 FORMAT `Null` SETTINGS [c-red-qc-36-server-0] 2023.05.29 12:06:17.932551 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ MemoryTracker: Peak memory usage (for query): 5.19 KiB. [c-red-qc-36-server-0] 2023.05.29 12:06:17.932581 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ TCPHandler: Processed in 0.001961411 sec. Ok. 0 rows in set. Elapsed: 0.002 sec. ``` それでは、`QueryCache` に関連する `TRACE` ログの違いを見てみましょう。 1回目の実行: ``` [c-red-qc-36-server-0] 2023.05.29 12:06:10.543559 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ QueryCache: No entry found for query SELECT name FROM query_cache_test WHERE age > 1000 FORMAT `Null` SETTINGS [c-red-qc-36-server-0] 2023.05.29 12:06:10.547760 [ 454 ] {3754a7fd-b786-47c1-a258-dfbc75e35a04} \ QueryCache: Stored result of query SELECT name FROM query_cache_test WHERE age > 1000 FORMAT `Null` SETTINGS ``` 2回目の実行時: ``` [c-red-qc-36-server-0] 2023.05.29 12:06:17.932043 [ 454 ] {a047527c-9d55-4e6b-9747-0ccad8787515} \ QueryCache: Entry found for query SELECT name FROM query_cache_test WHERE age > 1000 FORMAT `Null` SETTINGS ``` 1 回目の実行では、当然ながらエントリは見つからなかったため (`No entry found for query SELECT...`) 、ClickHouse がそのエントリを保存しました (`Stored result of query SELECT...`) 。 2 回目の実行では、すでに保存されているエントリが見つかったため (`Entry found for query SELECT...`) 、クエリキャッシュ が使われました。
## SQLだけを使う
`clickhouse client` のトレースログを確認しなくても、SQLコマンドを実行するだけで、 関連する `system` テーブルを確認して、クエリキャッシュ が使用されているかどうかを検証できます: ```sql theme={null} clickhouse-cloud :) SELECT 1 SETTINGS use_query_cache=true; SELECT 1 SETTINGS use_query_cache = 1 Query id: a5a078c7-61e5-4036-a6f0-4d602d5b72d2 ┌─1─┐ │ 1 │ └───┘ 1 row in set. Elapsed: 0.001 sec. clickhouse-cloud :) SELECT 1 SETTINGS use_query_cache=true; SELECT 1 SETTINGS use_query_cache = 1 Query id: 322ae001-b1ab-463f-ac8d-dc5ba346f3f9 ┌─1─┐ │ 1 │ └───┘ 1 row in set. Elapsed: 0.001 sec. clickhouse-cloud :) SELECT * FROM clusterAllReplicas(default,system.query_cache); SELECT * FROM clusterAllReplicas(default, system.query_cache) Query id: c9b57eac-ba64-430e-8d51-8f865a13cc25 ┌─query──────────────┬─result_size─┬─stale─┬─shared─┬─compressed─┬──────────expires_at─┬─────────────key_hash─┐ │ SELECT 1 SETTINGS │ 136 │ 0 │ 1 │ 1 │ 2023-08-02 15:08:23 │ 12188185624808016954 │ └────────────────────┴─────────────┴───────┴────────┴────────────┴─────────────────────┴──────────────────────┘ 1 row in set. Elapsed: 0.005 sec. clickhouse-cloud :) SELECT * FROM clusterAllReplicas(default,system.events) WHERE event LIKE 'QueryCache%' SELECT * FROM clusterAllReplicas(default, system.events) WHERE event LIKE 'QueryCache%' Query id: d536555e-b8ab-4cd4-9741-c04e95612bec ┌─event────────────┬─value─┬─description────────────────────────────────────────────────────────────────────────────────────────────┐ │ QueryCacheHits │ 1 │ Number of times a query result has been found in the query cache (and query computation was avoided). │ │ QueryCacheMisses │ 1 │ Number of times a query result has not been found in the query cache (and required query computation). │ └──────────────────┴───────┴────────────────────────────────────────────────────────────────────────────────────────────────────────┘ 2 rows in set. Elapsed: 0.006 sec. ``` 直前の結果では、クエリ `SELECT 1 SETTINGS use_query_cache=true;` を初めて実行した際に `QueryCacheMisses` が 1 回発生し、2 回目の実行に対応する `QueryCacheHits` イベントも確認できます。 また、デフォルトの cache の最大エントリサイズは 1048576 バイト (= 1 MiB) で、結果はデフォルトでは 60 秒間しか cache に保存されない点にも注意してください (たとえば `SETTINGS` で `query_cache_ttl=300` を指定すると、クエリキャッシュの結果を 5 分間保存できます) 。 ClickHouse クエリキャッシュ の詳細については、[こちら](/ja/concepts/features/performance/caches/query-cache)を参照してください。