pg_combinebackup had various problems:
* strncpy was used in various places where strlcpy should be used
instead, to avoid any possibility of the result not being
\0-terminated.
* scan_for_existing_tablespaces() failed to close the directory,
and an error when opening the directory was reported with the
wrong pathname.
* write_reconstructed_file() contained some redundant and therefore
dead code.
* flush_manifest() didn't check the result of pg_checksum_update()
as we do in other places, and misused a local pathname variable
that shouldn't exist at all.
In pg_basebackup, the wrong variable name was used in one place,
due to a copy and paste that was not properly adjusted.
In blkreftable.c, the loop incorrectly doubled chunkno instead of
max_chunks. Fix that. Also remove a nearby assertion per repeated
off-list complaints from Tom Lane.
Per Coverity and subsequent code inspection by me and by Tom Lane.
Discussion: http://postgr.es/m/CA+Tgmobvqqj-DW9F7uUzT-cQqs6wcVb-Xhs=w=hzJnXSE-kRGw@mail.gmail.com
Recently-introduced code in reconstruct.c was using "unsigned"
to store the result of read(), pg_pread(), or write(). This is
completely bogus: it breaks subsequent tests for the result being
negative, as we're being reminded of by a chorus of buildfarm
warnings. Switch to "int" as was doubtless intended. (There are
several other uses of "unsigned" in this file that also look poorly
chosen to me, but for now I'm just trying to clean up the buildfarm.)
A larger problem is that "int" is not necessarily wide enough to hold
the result: per POSIX, all these functions return ssize_t. In places
where the requested read or write length clearly fits in int, that's
academic. It may be academic anyway as long as we constrain
individual data files to 1GB, since even a readv or writev-like
operation would then not be responsible for transferring more than
1GB. Nonetheless it seems like trouble waiting to happen, so I made
a pass over readv and writev calls and fixed the result variables
where that seemed appropriate. We might want to think about changing
some of the fd.c functions to return ssize_t too, for future-proofing;
but I didn't tackle that here.
Discussion: https://postgr.es/m/1672202.1703441340@sss.pgh.pa.us
To take an incremental backup, you use the new replication command
UPLOAD_MANIFEST to upload the manifest for the prior backup. This
prior backup could either be a full backup or another incremental
backup. You then use BASE_BACKUP with the INCREMENTAL option to take
the backup. pg_basebackup now has an --incremental=PATH_TO_MANIFEST
option to trigger this behavior.
An incremental backup is like a regular full backup except that
some relation files are replaced with files with names like
INCREMENTAL.${ORIGINAL_NAME}, and the backup_label file contains
additional lines identifying it as an incremental backup. The new
pg_combinebackup tool can be used to reconstruct a data directory
from a full backup and a series of incremental backups.
Patch by me. Reviewed by Matthias van de Meent, Dilip Kumar, Jakub
Wartak, Peter Eisentraut, and Álvaro Herrera. Thanks especially to
Jakub for incredibly helpful and extensive testing.
Discussion: http://postgr.es/m/CA+TgmoYOYZfMCyOXFyC-P+-mdrZqm5pP2N7S-r0z3_402h9rsA@mail.gmail.com
Peter Eisentraut
Robert Haas
Bruce Momjian
Tom Lane