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Original topic: TiFlash的一致性读怎么理解？读取的是最新数据吗？是基于什么原理实现的？
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Consistency
TiFlash provides snapshot isolation support similar to TiKV and ensures that the latest data can be read (ensuring that previously written data can be read). This consistency is achieved through replication progress verification of the data.
Each time a read request is received, the Region replica in TiFlash initiates a progress check with the Leader replica (a very lightweight RPC request). The read response is only given when the progress ensures that the data covered by the read request timestamp is included.
The data read conforms to your current isolation level.
It will pull data from TiKV and then read the correct data that matches your isolation level.
This means that there will be a proofreading of the replication progress, and if the delay is significant, it will not use TiFlash.
It depends on the parameter settings.
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