MySQL 是多线程的，客户端可以通过多个线程同时针对同一表发出查询。因此，MySQL 可以为每个会话单独打开表。同时打开的表的数量由 table_open_cache 管理。如果缓存已满并且打开了其他表，MySQL 会关闭最近最少使用的表。如果缓存中的所有表当前正在使用，则 MySQL 会临时扩展缓存，并在表未使用后立即关闭表。
GET https://recommender.googleapis.com/v1beta1/projects/PROJECT-ID/locations/LOCATION/recommenders/google.cloudsql.instance.PerformanceRecommender.MySqlHighNumberOfTablesBestPractice/recommendations
GET https://recommender.googleapis.com/v1beta1/projects/PROJECT-ID/locations/LOCATION/insightTypes/google.cloudsql.instance.PerformanceRecommender.MySqlHighNumberOfOpenTables/insights
请替换以下内容：
PROJECT_ID：您的项目 ID。
LOCATION：区域，例如 us-central1。
下表列出了 Cloud SQL 大量打开的表 Recommender 生成的数据分析和建议，以帮助您提高性能。gcloud CLI 和 API 结果中显示子类型。
[[["易于理解","easyToUnderstand","thumb-up"],["解决了我的问题","solvedMyProblem","thumb-up"],["其他","otherUp","thumb-up"]],[["很难理解","hardToUnderstand","thumb-down"],["信息或示例代码不正确","incorrectInformationOrSampleCode","thumb-down"],["没有我需要的信息/示例","missingTheInformationSamplesINeed","thumb-down"],["翻译问题","translationIssue","thumb-down"],["其他","otherDown","thumb-down"]],["最后更新时间 (UTC)：2025-08-28。"],[],[],null,["# Increase the table open cache size\n\n\u003cbr /\u003e\n\nMySQL \\| PostgreSQL \\| SQL Server\n\n\u003cbr /\u003e\n\n\u003cbr /\u003e\n\n|\n| **Preview**\n|\n|\n| This feature is subject to the \"Pre-GA Offerings Terms\" in the General Service Terms section\n| of the [Service Specific Terms](/terms/service-terms#1).\n|\n| Pre-GA features are available \"as is\" and might have limited support.\n|\n| For more information, see the\n| [launch stage descriptions](/products#product-launch-stages).\n\nThe Cloud SQL high-number-of-open-tables [recommender](/recommender/docs/overview) helps you detect instances\nwhose number of concurrently opened tables is equal to the value of `table_open_cache`. It then\nprovides recommendations on how to optimize such instances to improve performance.\n\nThis page describes how the high-number-of-open-tables recommender works and how\nyou can use it.\n\nHow it works\n------------\n\nMySQL is multi-threaded, and clients can simultaneously issue a query on the same table from multiple\nthreads. Thus, MySQL can have independently open tables for each session.\nThe number of simultaneously opened tables is managed by `table_open_cache`.\nIf the cache is full and additional tables are opened, MySQL closes the least recently used\ntable. If all the tables in cache are currently being used, MySQL extends the cache\ntemporarily and closes the tables as soon as they become unused.\n\nIf the number of open tables exceeds the`table_open_cache` value, database performance\ncan be adversely affected during high workload. This is because more threads are created and table handlers\nhave to open and close the tables more frequently.\n\nThe Cloud SQL high-number-of-open-tables recommender analyzes metrics for the number\nof opened tables on a Cloud SQL MySQL instance daily. If the number of opened tables increases\nby 1 every 2 seconds or faster in the preceding 24 hours, and the number of open\ntables is equal to or more than the `table_open_cache` value, the recommender advises you to\nadjust the `table_open_cache` flag.\n| **Note:** Recommendations are generated daily.\n\nPricing\n-------\n\nThe Cloud SQL high-number-of-open-tables recommender is in the *Standard* [Recommender pricing tier](/recommender/pricing).\n\nBefore you begin\n----------------\n\nBefore you can view recommendations and insights, do the following:\n\n- To get the permissions to view and work with insights and recommendations, ensure that you have the required [roles](/sql/docs/mysql/project-access-control#roles).\n\n For more information about roles, see [understanding roles](/iam/docs/understanding-roles) and [granting IAM permissions](/iam/docs/granting-changing-revoking-access).\n-\n\n\n Enable the Recommender API.\n\n\n [Enable the API](https://console.cloud.google.com/flows/enableapi?apiid=recommender.googleapis.com)\n\nList instance performance recommendations\n-----------------------------------------\n\nYou can list the instance performance recommendations by\nusing the Google Cloud console, [gcloud CLI](/sdk/gcloud), or the Recommender API.\n\nThe improve instance performance recommendations are shown only if you have instances that\nare nearing performance threshold limits. \n\n### Console\n\nTo list recommendations about instance performance by using the\nGoogle Cloud console, follow these steps:\n\n1. Go to the **Cloud SQL Instances** page.\n\n [Go to Cloud SQL Instances](https://console.cloud.google.com/sql/instances)\n2. Click **View all** on the Increase table open cache recommendations banner.\n\nAlternatively, follow these steps:\n\n1. Go to the **Recommendation Hub** . See also [Getting started with Recommendation Hub](/recommender/docs/recommendation-hub/identify-configuration-problems).\n\n [Go to the Recommendation Hub](https://console.cloud.google.com/home/recommendations/)\n2. In the **Improve Cloud SQL Instance Performance** card, click **View all**.\n\n3. Select the instances with **Increase table open cache** recommendation.\n\n### gcloud CLI\n\nTo list Improve Instance Performance recommendations by using `gcloud CLI`, run the\n[`gcloud recommender recommendations list`](/sdk/gcloud/reference/recommender/recommendations/list)\ncommand as follows: \n\n```\ngcloud recommender recommendations list \\\n--project=PROJECT_ID \\\n--location=LOCATION \\\n--recommender=google.cloudsql.instance.PerformanceRecommender \\\n--filter=recommenderSubtype=MYSQL_HIGH_NUMBER_OF_OPEN_TABLES_BEST_PRACTICE\n```\n\nReplace the following:\n\n- \u003cvar translate=\"no\"\u003ePROJECT_ID\u003c/var\u003e: Your project ID\n- \u003cvar translate=\"no\"\u003eLOCATION\u003c/var\u003e: A region, such as `us-central1`\n\n### API\n\nTo list Improve Instance Performance recommendations by using the\n[Recommendations API](/recommender/docs/using-api), call the\n[`recommendations.list`](/recommender/docs/reference/rest/v1beta1/projects.locations.recommenders.recommendations/list)\nmethod as follows: \n\n```\nGET https://recommender.googleapis.com/v1beta1/projects/PROJECT-ID/locations/LOCATION/recommenders/google.cloudsql.instance.PerformanceRecommender.MySqlHighNumberOfTablesBestPractice/recommendations\n```\n\nReplace the following:\n\n- \u003cvar translate=\"no\"\u003ePROJECT_ID\u003c/var\u003e: Your project ID.\n- \u003cvar translate=\"no\"\u003eLOCATION\u003c/var\u003e: A region, such as `us-central1`.\n\nIf the recommender detects instances that have a high-number-of-open-tables, it lists them in a table\nwith other performance recommendations.\nEach row shows the instance ID, a brief recommendation, database engine, the location, and the last refresh date.\n\nView insights and detailed recommendations\n------------------------------------------\n\nYou can view insights and detailed recommendations about instances\nthat have a high-number-of-open-tables by using the Google Cloud console,\n`gcloud CLI`, or the Recommender API. \n\n### Console\n\nTo view insights and detailed recommendations about instances that are close to\nthe performance threshold by using the Google Cloud console, click the recommendation\nlink in the list of instances.\n\n### gcloud CLI\n\nTo view insights and detailed recommendations about instances that are close to\nthe performance threshold by using `gcloud CLI`, run the\n[`gcloud recommender insights list`](/sdk/gcloud/reference/recommender/insights/list)\ncommand as follows: \n\n```\ngcloud recommender insights list \\\n--project=PROJECT_ID \\\n--location=LOCATION \\\n--insight-type=google.cloudsql.instance.PerformanceInsight \\\n--filter=insightSubtype=MYSQL_HIGH_NUMBER_OF_OPEN_TABLES\n```\n\nReplace the following:\n\n- \u003cvar translate=\"no\"\u003ePROJECT_ID\u003c/var\u003e: Your project ID.\n- \u003cvar translate=\"no\"\u003eLOCATION\u003c/var\u003e: A region, such as `us-central1`.\n\n### API\n\nTo view insights and detailed recommendations about instances that have a high-number-of-open-tables\nby using the [Recommendations API](/recommender/docs/using-api),\ncall the [`insights.list`](/recommender/docs/reference/rest/v1beta1/projects.locations.insightTypes.insights/list)\nmethod as follows: \n\n```\nGET https://recommender.googleapis.com/v1beta1/projects/PROJECT-ID/locations/LOCATION/insightTypes/google.cloudsql.instance.PerformanceRecommender.MySqlHighNumberOfOpenTables/insights\n```\n\nReplace the following:\n\n- \u003cvar translate=\"no\"\u003ePROJECT_ID\u003c/var\u003e: Your project ID.\n- \u003cvar translate=\"no\"\u003eLOCATION\u003c/var\u003e: A region, such as `us-central1`.\n\nThe following table lists the insight and recommendation that the Cloud SQL\nhigh-number-of-open-tables recommender generates to help you improve performance.\nThe subtypes are visible in the `gcloud CLI` and API results.\n\nApply recommendations\n---------------------\n\nEvaluate the recommendations carefully and do any of the following:\n\n- To examine the instance, click **View instance** . See [Optimize the performance of your instance](#optimize-performance) and follow the recommendations.\n\n- To dismiss the recommendation so that it's de-emphasized and appears dimmed,\n click **Dismiss**.\n\n- To close the panel without applying or dismissing the recommendation, click\n **Cancel**.\n\n### Optimize the performance of your instance\n\nTo optimize your instance's performance, do any of the following:\n\n1. Increase the value of `table_open_cache` by 500 until the recommendation disappears. The recommendation is updated daily, so after you increase the value of `table_open_cache`, wait for 24 hours before checking it again.\n\n2. If the value of `open_tables` is more than `table_open_cache`, increase the value of `table_open_cache`\n to the value of `open_tables`.\n\n For information on how to\n update a database flag, see [Configure database flags](/sql/docs/mysql/flags#config).\n | **Note:** Don't set the value of `table_open_cache` to be more than `524288`, which is [the maximum allowed value for this flag](/sql/docs/mysql/flags#table-open-cache).\n\nWhat's next\n-----------\n\n- [Manage high number of tables](/sql/docs/mysql/recommender-high-number-of-tables)\n- [Monitor disk availability](/sql/docs/mysql/using-ood-recommender)\n- [Identify idle Cloud SQL instances](/sql/docs/mysql/recommender-sql-idle)\n- [Reduce overprovisioned Cloud SQL instances](/sql/docs/mysql/recommender-sql-overprovisioned)\n- Explore [Google Cloud recommenders](/recommender/docs/recommenders)"]]
