Aligning Connection#setTransactionIsolationLevel Behavior with r2dbc-spi Specification

[jchrys]

Issue

The current implementation of Connection#setTransactionIsolationLevel does not align with its specification. According to the specification(), this method should configure the isolation level for the connection, and the specified isolation level should apply to all subsequent transactions. However, the current behavior applies the isolation level only to the next transaction.

Proposal

Aligning the behavior of Connection#setTransactionIsolationLevel with its specification. The implementation should be adjusted so that the configured isolation level persists for all subsequent transactions until explicitly changed.

Action Items

• Modify the implementation of Connection#setTransactionIsolationLevel to align with the specification.(AbstractTransactionState could be utilized if needed )
• Verify and update the transaction isolation behavior in the entire project to ensure consistency and adherence to the proposed changes.

Refs

• r2dbc-spi specification: https://github.com/r2dbc/r2dbc-spi/blob/160cd2743f8ce8551618abcd96fa1d7ee37f8f38/r2dbc-spi/src/main/java/io/r2dbc/spi/Connection.java#L221C12-L221C12
• mysql-dev doc: https://dev.mysql.com/doc/refman/8.0/en/set-transaction.html#set-transaction-scope

[JohnNiang]

I'm willing to contribute this enhancement.

/assign

[jchrys]

I'm willing to contribute this enhancement.

/assign

Thanks!

[jchrys]

#202 resolved this issue