planner: add new cascades planner document #20470
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Signed-off-by: AilinKid <[email protected]>
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system-variables.md
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| - 类型：布尔型 | ||
| - 默认值：`OFF` | ||
| - 这个变量用于控制是否开启 cascades planner。 | ||
| - 目前 cascades 优化器默认为 `OFF`, 我们将在临近几个 DMR 版本之内收敛新优化器的相关问题，并且在下个 LTS 默认开启 cascades planner。 |
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| - 目前 cascades 优化器默认为 `OFF`, 我们将在临近几个 DMR 版本之内收敛新优化器的相关问题，并且在下个 LTS 默认开启 cascades planner。 | |
| - 目前 cascades 优化器默认为 `OFF`。在未来几个 DMR 版本之内会收敛新优化器的相关问题，并且在下个 LTS 版本默认开启 cascades planner。 |
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Generally, do not pre-announce features in official documentation. I suggest keeping the original wording.
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Co-authored-by: xixirangrang <[email protected]>
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[APPROVALNOTIFIER] This PR is NOT APPROVED This pull-request has been approved by: The full list of commands accepted by this bot can be found here.
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| > **注意：** | ||
| > | ||
| > 目前 cascades planner 为实验特性，不建议在生产环境中使用。 | ||
| > 目前 cascades planner 为全新的优化器框架实现，其在设计之初就是为了兼容性出发考虑的，其可以在最大程度上保证和原有优化器逻辑的兼容性，并且在逻辑层面能够给到一定的扩展空间，此外还能够在多重逻辑计划之间进行 CBO 决策。目前 cascades planner 开启之后由于逻辑 rule 的数量目前还比较有限，其做 plan 的能力不一定会显现出很大的提升，但是随着后续 [TiDB Cascades Rule Evolution Project](https://github.com/pingcap/tidb/issues/61528) 项目的不断深入，cascades planner 将会展现更大的灵活性和适用性。 |
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| > 目前 cascades planner 为全新的优化器框架实现，其在设计之初就是为了兼容性出发考虑的，其可以在最大程度上保证和原有优化器逻辑的兼容性，并且在逻辑层面能够给到一定的扩展空间，此外还能够在多重逻辑计划之间进行 CBO 决策。目前 cascades planner 开启之后由于逻辑 rule 的数量目前还比较有限，其做 plan 的能力不一定会显现出很大的提升，但是随着后续 [TiDB Cascades Rule Evolution Project](https://github.com/pingcap/tidb/issues/61528) 项目的不断深入，cascades planner 将会展现更大的灵活性和适用性。 | |
| > Cascades planner 是 TiDB 引入的一种全新的优化器框架。该框架充分考虑了与现有优化器逻辑的兼容性，并在逻辑层面预留了扩展空间。借助这一框架，优化器能够在多个候选逻辑执行计划之间进行基于代价的优化 (Cost-Based Optimization, CBO) 决策。 | |
| > | |
| > 目前，当开启 cascades planner 时，由于逻辑规则 (rule) 数量有限，生成的执行计划在性能上未必有显著提升。但随着 [TiDB Cascades Rule Evolution Project](https://github.com/pingcap/tidb/issues/61528) 的推进，cascades planner 将逐步展现更大的灵活性和适用性，为复杂查询场景提供更好的优化能力。 |
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lilin90
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Sep 15, 2025
| ### `tidb_enable_cascades_planner` | ||
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| > **警告：** | ||
| > **注意：** |
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Since "Cascades Planner" is listed in TiDB 功能概览 | TiDB 文档中心, please confirm whether we need to update the status in that table. Till v8.5, the feature status is experimental. Is it GA in v9.0?
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First-time contributors' checklist
What is changed, added or deleted? (Required)
This PR updates documentation for the cascades planner.
EN PR: pingcap/docs#21773
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