Re: Fix XLogFileReadAnyTLI silently applying divergent WAL from wrong timeline

Hi Andrey,

Thanks for v4. I applied it to the current master (86f7c82cf10) it applies
and builds cleanly. The xlogfname split and the 057/058 renumbering both
look right.

Fair enough on keeping it at DEBUG1, announcing a declined action at LOG
does sit oddly.

What I'd still raise is narrower. Where a parent timeline exists the
message is accurate. But in a single-timeline case, where there is no
parent to fall back to, so the message describes something that cannot
happen and it still fires on every retry. On an idle archive-only standby
with no history files I measured about five a second at
wal_retrieve_retry_interval = 200ms, all of them reading "not searching
older timelines ... The whole segment must be read from timeline 1".

Gating it on there actually being an older timeline to abandon i.e. only
when the eligible entry isn't the last in expectedTLEs would confine the
message to the case where it's true, and the tests would still get their
hook since they exercise the multi-timeline case.

Not a blocker from my side. v4 looks good to me and I think it's ready for
a committer.

Regards,
Surya Poondla