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Update the memory usage size of a transaction (#8316) #8523

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Mar 1, 2022
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Update the memory usage size of a transaction (#8316) #8523

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2 changes: 1 addition & 1 deletion transaction-overview.md
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Expand Up @@ -292,7 +292,7 @@ mysql> SELECT * FROM test;

TiDB 同时支持乐观事务与悲观事务，其中乐观事务是悲观事务的基础。由于乐观事务是先将修改缓存在私有内存中，因此，TiDB 对于单个事务的容量做了限制。

TiDB 中，单个事务的总大小默认不超过 100 MB，这个默认值可以通过配置文件中的配置项 `txn-total-size-limit` 进行修改，最大支持 10 GB。单个事务的实际大小限制还取决于服务器剩余可用内存的大小，执行事务时 TiDB 进程的内存消耗相对于事务大小会存在一定程度的放大，最大可能达到提交事务大小的 6 倍以上。
TiDB 中，单个事务的总大小默认不超过 100 MB，这个默认值可以通过配置文件中的配置项 `txn-total-size-limit` 进行修改，最大支持 10 GB。单个事务的实际大小限制还取决于服务器剩余可用内存的大小，执行事务时 TiDB 进程的内存消耗相对于事务大小会存在一定程度的放大，最大可能达到提交事务大小的 2 到 3 倍以上。

在 4.0 以前的版本，TiDB 限制了单个事务的键值对的总数量不超过 30 万条，从 4.0 版本起 TiDB 取消了这项限制。

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