Hi Michael, Thank you for the explanation and the patch! I'm happy, that I seem to be on the right way.
On Wednesday, December 25, 2024 08:04 MSK, Michael Paquier <mich...@paquier.xyz> wrote: > Vitaly, have you seen that in the wild as an effect of future 2PC files? I haven't heard about this problem in production, but I've encountered it when I did some development in two-phase functionality. I fixed it by swapping the if blocks and it solved my problem. It is pretty easy to reproduce it on the master branch: 1. Start an instance with enabled prepared transactions 2. Create a simple prepared transaction 3. Do checkpoint to write the transaction two-phase state into a file in pg_twophase subdirectory 4. Copy the created file, change its name to reflect a future xid (in my case: cp 00000000000002E8 00000000000FF2E8) 5. Commit the prepared transaction 6. Stop the instance with -m immediate 7. Start the instance After starting, you can get an error like "could not start server". In the log file you can find a message like: LOG: database system was not properly shut down; automatic recovery in progress FATAL: could not access status of transaction 1045224 DETAIL: Could not read from file "pg_xact/0000" at offset 253952: read too few bytes. 2024-12-25 18:38:30.606 MSK [795557] LOG: startup process (PID 795560) exited with exit code 1 I tried your patch and it seems the server is started successfully. But I've found another problem in my synthetic test - it can not remove the file with the following message: LOG: database system was not properly shut down; automatic recovery in progress WARNING: removing future two-phase state file for transaction 1045224 WARNING: could not remove file "pg_twophase/FFFFFFFF000FF2E8": No such file or directory LOG: redo starts at 0/1762978 The fill will never be removed automatically. I guess, it is because we incorrectly calculate the two-phase file name using TwoPhaseFilePath in RemoveTwoPhaseFile in this scenario. It can be fixed if to pass file path directly from RecoverPreparedTransactions or StandbyRecoverPreparedTransaction into ProcessTwoPhaseBuffer -> RemoveTwoPhaseFile. I did it in the proposed patch https://www.postgresql.org/message-id/cedbe-65e0c000-1-6db17700%40133269862 (it is incomplete now). With best regards, Vitaly
