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system-variables: add tidb_paging_size_bytes (internal use) #21752

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system-variables: add tidb_paging_size_bytes (internal use) #21752

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system-variables: add tidb_paging_size_bytes (internal use)
JmPotato Jul 1, 2026
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system-variables: update tidb_paging_size_bytes default and refine wo…
JmPotato Jul 17, 2026
201b47f
system-variables: restore tidb_paging_size_bytes default to 0
JmPotato Jul 24, 2026
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12 changes: 12 additions & 0 deletions system-variables.md
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Expand Up @@ -4745,6 +4745,18 @@ SHOW WARNINGS;
- 范围：`[0, 2147483647]`
- 控制优化器估算逻辑的更迭。更改该变量值后，优化器的估算逻辑会产生较大的改变。目前该变量的有效值只有 `0`，不建议设为其它值。

### `tidb_paging_size_bytes` <span class="version-mark">从 v9.0.0 版本开始引入</span>

- 作用域：SESSION | GLOBAL
- 是否持久化到集群：是
- 是否受 Hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value) 控制：是
- 类型：整数型
- 默认值：`0`
- 范围：`[0, 9223372036854775807]`
Comment on lines +4753 to +4755

@coderabbitai coderabbitai Bot Jul 24, 2026

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🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

将变量类型标注为无符号整数型。

PR 目标明确该变量为 unsigned，但当前文档写成“整数型”，容易让读者误以为支持负值；这也与 [0, 9223372036854775807] 的范围不一致。

Suggested change
- 类型：整数型
- 默认值：`0`
- 范围：`[0, 9223372036854775807]`
- 类型：无符号整数型

- 单位：字节
- 控制 coprocessor 协议中单个分页响应的字节数上限，用于在 [`tidb_max_paging_size`](#tidb_max_paging_size-从-v630-版本开始引入) 所提供的按行数分页机制之外，额外提供按字节数分页的能力。默认值为 `0`，表示关闭按字节数分页。该功能仅在开启[资源管控](/tidb-resource-control-ru-groups.md)且当前语句所属资源组具有固定的 RU 配额时生效，供 PD 的资源管控模块在执行语句前根据扫描数据量预估并预扣 RU。如需启用，可考虑设置为 `4194304`（即 4 MiB）。
- 该变量为 TiDB 内部变量，**不推荐**修改该变量的值。

### `tidb_partition_prune_mode` <span class="version-mark">从 v5.1 版本开始引入</span>

> **警告：**
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