Replica Transactions

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Feature Description

Vitess currently supports transactions through vtgate only on MASTER tablets. We would like to extend transaction support to REPLICA (or other tablet types).

Use Case(s)

  • Consistent reads
  • Sqoop integration

Proposed Solution

  • When vtgate chooses a tablet to execute a query on, it should return the tablet alias.
  • tablet alias and transactionID will be stored on the shard session struct.
  • if the session object has a tablet alias set, then the query will target the specific tablet.
  • if the transaction is committed or rolled back, the session should end.

In order to use this feature, a client will need to issue use @replica followed by BEGIN.

Prerequisite: #5750

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