> Why is it necessary to replay the operation only on the slave? Can we
> just use XLOG_HEAP_NEWPAGE?
Uh, I don't know why but I thought I shouldn't log a page on the master,
since all the pages are already there and fsync-ed. But if it makes no harm,
I can easily use XLOG_HEAP_NEWPAGE (of course, only in the wal_level != minimal case).