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ticdc: update "safe-mode" description (#19785) #19791

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Feb 12, 2025
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ticdc: update "safe-mode" description (#19785) #19791

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Update ticdc-faq.md
flowbehappy Feb 12, 2025
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Refine wording and remove manual line break
lilin90 Feb 12, 2025
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lilin90 Feb 12, 2025
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4 changes: 3 additions & 1 deletion ticdc/ticdc-faq.md
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Expand Up @@ -344,7 +344,9 @@ mysql [email protected]:test> show create table test;

TiCDC 提供至少一次的数据同步保证，当下游有重复数据时，会引起写冲突。为了避免该问题，TiCDC 会将 `INSERT` 和 `UPDATE` 语句转成 `REPLACE INTO` 语句。该行为由 `safe-mode` 参数来控制。

在 v6.1.3 版本之前，`safe-mode` 默认为 `true`，即所有的 `INSERT` 和 `UPDATE` 语句都转成 `REPLACE INTO` 语句。在 v6.1.3 及之后版本，系统能自动判断下游是否存在重复数据，`safe-mode` 默认更改为 `false`，当系统判断下游无重复数据时，会直接同步 `INSERT` 和 `UPDATE` 语句。
在 v6.1.3 版本之前，`safe-mode` 的默认值为 `true`，即所有的 `INSERT` 和 `UPDATE` 语句都转成 `REPLACE INTO` 语句。

在 v6.1.3 及之后版本，`safe-mode` 的默认值更改为 `false`，而且 TiCDC 能自动判断下游是否存在重复数据。当 TiCDC 判断下游无重复数据时，会直接同步 `INSERT` 和 `UPDATE` 语句；否则，TiCDC 会将 `INSERT` 和 `UPDATE` 语句都转成 `REPLACE INTO` 语句再进行同步。

## 为什么 TiCDC 需要使用磁盘，什么时候会写磁盘，TiCDC 能否利用内存缓存提升同步性能？

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