On Thu, Mar 3, 2016 at 6:58 PM, lannis <msp548546(at)163(dot)com> wrote:
> So in the replay scenario, before we read the page from wal segment file,
> using the specical RecPtr which point to the next page header address, can
> we predicat the page header is a long or short?
I am not sure I am getting what you are looking for, but if you mean
if we can predict it or not, the answer is yes. A long header is used
at the beginning of a WAL segment, by default 16MB, and the short
header at the beginning of a WAL page, or XLOG_BLCKSZ, 8kB by default.
--
Michael