refine modify column #21110

wjhuang2016 · 2025-11-24T11:12:46Z

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sql-statements/sql-statement-modify-column.md

qiancai · 2025-11-26T09:13:03Z

add the do-not-merge/hold label as the change in this PR won't be included in v8.5.4

sql-statements/sql-statement-modify-column.md

Co-authored-by: Ruihao Chen <[email protected]> Co-authored-by: Grace Cai <[email protected]>

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sql-statements/sql-statement-modify-column.md

Co-authored-by: Grace Cai <[email protected]>

sql-statements/sql-statement-modify-column.md

Frank945946 · 2025-12-31T06:15:40Z

sql-statements/sql-statement-modify-column.md


+从 v8.5.5 和 v9.0.0 起，针对部分原本需要 Reorg-Data 的列类型变更，TiDB 优化了执行效率。如果当前会话的 [SQL 模式](/sql-mode.md)为严格模式（即 `sql_mode` 值包含 `STRICT_TRANS_TABLES` 或 `STRICT_ALL_TABLES`），TiDB 在进行以下类型变更时，会预先检查类型转换过程中是否存在数据截断风险，若不存在数据截断风险，TiDB 将不再进行表数据重建，仅重建受影响的索引：
+
+- 整数类型之间的变更（例如 `BIGINT` 到 `INT`）


这个场景下，是不是不需要重建索引？

不需要。之前需要

Oreoxmt · 2026-01-05T03:23:25Z

/cc @Oreoxmt

sql-statements/sql-statement-modify-column.md

qiancai · 2026-01-06T02:19:02Z

sql-statements/sql-statement-modify-column.md

 `ALTER TABLE .. MODIFY COLUMN` 语句用于修改已有表上的列，包括列的数据类型和属性。若要同时重命名，可改用 [`CHANGE COLUMN`](/sql-statements/sql-statement-change-column.md) 语句。

-从 v5.1.0 版本起，TiDB 开始支持 Reorg 类型变更，包括但不限于：
+从 v5.1.0 起，TiDB 支持需要 Reorg-Data 的列类型变更。这类变更在执行过程中会重建表中现有的所有数据，包括读取原始数据、按照新的数据格式进行处理，以及重新写入表中。由于需要处理全表数据，Reorg-Data 操作通常较为耗时，其执行时间与表中的数据量成正比。


#reorg-data-change 里只有一个 INT -> VARCHAR 的示例，不能成为 Reorg-Data 的定义，或者可以把 “需要 Reorg-Data 的列类型变更” 修改为 “需要 Reorg-Data（重新表数据）的列类型变更"?

Co-authored-by: Aolin <[email protected]>

sql-statements/sql-statement-modify-column.md

Synced from: pingcap/docs-cn#21110 Target PR: pingcap#22268 AI Provider: gemini Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

ti-chi-bot · 2026-01-06T03:04:50Z

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ti-chi-bot · 2026-01-06T07:38:50Z

[LGTM Timeline notifier]

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2026-01-06 07:38:50.067673289 +0000 UTC m=+687885.885981711: ☑️ agreed by Oreoxmt.

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refine modify column pingcap/docs#22268

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		从 v8.5.5 和 v9.0.0 起，针对部分原本需要 Reorg-Data 的列类型变更，TiDB 优化了执行效率。如果当前会话的 [SQL 模式](/sql-mode.md)为严格模式（即 `sql_mode` 值包含 `STRICT_TRANS_TABLES` 或 `STRICT_ALL_TABLES`），TiDB 在进行以下类型变更时，会预先检查类型转换过程中是否存在数据截断风险，若不存在数据截断风险，TiDB 将不再进行表数据重建，仅重建受影响的索引：

		- 整数类型之间的变更（例如 `BIGINT` 到 `INT`）

refine modify column #21110

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