Are all data written to memory first during the execution of TiDB DML?

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

Original topic: TiDB DML执行过程中的所有数据都是先写到内存吗？

| username: alfred

[TiDB Usage Environment] Production Environment / Testing / POC
[TiDB Version]
[Encountered Issues]
[Reproduction Path] What operations were performed to encounter the issue
[Issue Phenomenon and Impact]

[Attachments]

Please provide the version information of each component, such as cdc/tikv, which can be obtained by executing cdc version/tikv-server --version.

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| username: xfworld | Original post link

Yes, TiDB nodes rely on memory for temporary storage and then schedule transactions. Once the transactions are committed, the memory is released.

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| username: ddhe9527 | Original post link

Write operations are first written to the memory (membuffer) of the TiDB instance, and then written to the memory of TiKV (RocksDB’s memtable) upon commit.

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| username: alfred | Original post link

Lock information is written directly to the disk, right?

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| username: ddhe9527 | Original post link

Locks are the same; there is a WAL when writing to the memtable.

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| username: alfred | Original post link

Yes, writing the WAL first is a must.

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| username: system | Original post link

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