Thank you for the clarification about archiving. I now fully understand why writing a missing contrecord into an already-archived timeline is unsafe.
Could this be avoided by having the standby check the WAL archive before promotion? Specifically, if the standby detects an incomplete contrecord at the end of its WAL stream, it attempts to fetch the contrecord from the archive, and only if the contrecord is not found in the archive, it proceeds with writing a missing contrecord and starting a new timeline. What do you think?
I plan to reproduce your described scenario to test both my original patch and this revised approach.
P.S. I'm attaching my notes just so I don’t lose them =)
