Why Only Repeatable Read Isolation Level is Supported in the Optimistic Transaction Model

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This topic has been translated from a Chinese forum by GPT and might contain errors.

Original topic: 为什么在乐观事务模型下，仅支持可重复读隔离级别

| username: Raymond

May I ask why TiDB only supports the repeatable read isolation level under the optimistic transaction model?

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| username: 突破边界 | Original post link

Read the submitted support

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| username: alfred | Original post link

Are transaction isolation levels related to pessimistic transactions and optimistic transactions?

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| username: Raymond | Original post link

Relevant,

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| username: alfred | Original post link

Are you saying that the optimistic transaction model supports a higher level of transaction isolation: the repeatable read isolation level?

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| username: forever | Original post link

Setting the transaction isolation level to Read Committed in optimistic transaction mode will not take effect; the transaction will still use the Repeatable Read isolation level.

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| username: alfred | Original post link

TiDB defaults to the pessimistic transaction model, right? Can it be adjusted to the optimistic transaction model?

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| username: Billmay表妹 | Original post link

By default, it is a pessimistic transaction, but it can be adjusted to an optimistic transaction.

Thanks to @jiyf and @OnTheRoad for providing the answers~

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| username: alfred | Original post link

It seems to say that pessimistic locks will consume more network IO and disk IO?

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| username: system | Original post link

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