# 目标列只读场景（A）

+ 无 ADD INDEX 操作时:
+ 有 ADD INDEX 操作，且 tidb_ddl_reorg_batch_size = 32 时:

![left](./student-guide/diagram/19-Read-only-scene-01-01.png)
![left](./student-guide/diagram/19-Read-only-scene-01-02.png)

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目标列只读场景
550.9
8812.8