All the ERROR_* fields are removed in favor of a more simple layer
made of ERROR, FATAL, PANIC. The two last ones are not actually used
yet, thought there should be some code paths that would need more
polishing on this matter.
The error message emitted before leaving should be fine to let the
user know what is happening.
This commit improves the performance of page-level, or differential
backup, by not having to scan anymore all the pages of a relation file,
something that can be very long on large data sets, but by scanning the
list of blocks changed by WAL records since the last full or differential
backup.
As a restriction and to avoid potential data corruption should hint-bit
updates occur on a page, backups can only be taken from a server that has
wal_log_hints or data checksums enabled.
Base patch by Yury Zhuravlev, heavily modified by me.
--debug and --verbose had actually the same meaning as they were aimed
at giving to the user information regarding how the process is running,
hence both options are merged into --verbose and use elog(LOG) to decide
if a given message should be printed out depending on the verbosity of
the call. This makes a couple of routines more readable as they do not
depend on any boolean checks.
The "_()" have been removed from the code, those are aimed at being used
for translation but having them mandatorily in each log message is just
useless noise. If needed, pgut.c should be updated in consequence to
have a more portable facility.
At the same time this commit takes care of putting into correct shape
some code paths more in-line with PostgreSQL policy. There are surely
more of this kind of ugly stuff but at this stage things are more simple
and more manageable.
Performance of compression is quite questionable on many objects like
that and makes the routines aimed at managing file copy, backup and restore
more complicated than they should be.
This commit results in a largely simplified code in data.c, which will
be helpful when integrating differential backup using WAL file lookup.
