This adds a new option to pg_verifybackup called -P/--progress, showing
every second some information about the progress of the checksum
verification based on the data of a backup manifest.
Similarly to what is done for pg_rewind and pg_basebackup, the
information printed in the progress report consists of the current
amount of data computed and the total amount of data that will be
computed. Note that files found with an incorrect size do not have
their checksum verified, hence their size is not appended to the total
amount of data estimated during the first scan of the manifest data
(such incorrect sizes could be overly high, for one, falsifying the
progress report).
Author: Masahiko Sawada
Discussion: https://postgr.es/m/CAD21AoC5+JOgMd4o3z_oxw0f8JDSsCYY7zSbhe-O9x7f33rw_A@mail.gmail.com
Whitespace between tags is significant, and in some cases it creates
extra vertical space in man pages. The fix is either to remove some
newlines or in some cases to reword slightly to avoid the awkward
markup layout.
