Re: [COMMITTERS] pgsql: Reset btpo.xact following recovery of btree delete page.

sriggs(at)postgresql(dot)org (Simon Riggs) writes:
> Log Message:
> -----------
> Reset btpo.xact following recovery of btree delete page. Add btpo_xact
> field into WAL record and reset it from there, rather than using
> FrozenTransactionId which can lead to some corner case bugs.

Simon, you can't just whack WAL record contents around without a care.
This commit breaks on-disk WAL compatibility and will result in possibly
unrecoverable databases as soon as someone applies it; not to mention
what will happen if an HS slave is not running the same code as its
master. This must be treated as an initdb-forcing, or at least
pg_resetxlog-forcing, change.

The correct thing to do when committing such a change is to change the
WAL-file magic number XLOG_PAGE_MAGIC.

regards, tom lane