Transaction replay

Overview

Open transactions can be replayed on a replacement server if the following criteria are met:

• Only SELECT ... FOR UPDATE reads have been done
• The contents of the SELECT ... FOR UPDATE statements are identical

This does not provide a 100% guarantee of an identical end result for the migration as the storage engine can alter the locking order of rows.

Task Details

• Track transaction contents
• Calculate checksum/hash for SELECT ... FOR UPDATE results
• Replay executed queries

Some of the session command code can be reused or re-purposed to handle the execution of the commands.