LZ4File_write() did not advance the input pointer on subsequent invocations of
LZ4F_compressUpdate(). As a result the generated compressed output would be a
compressed version of the same input chunk.
Tests failed to catch this error because the data would comfortably fit
within the default buffer size, as a single chunk. Tests have been added
to provide adequate coverage of multi-chunk compression.
WriteDataToArchiveLZ4() which is also using LZ4F_compressUpdate() did
not suffer from this omission.
Author: Georgios Kokolatos <gkokolatos@pm.me>
Reported-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/ZFhCyn4Gm2eu60rB%40paquier.xyz
Prior to the introduction of the compression API in e9960732a9, pg_dump
would use the ZLIB_IN_SIZE/ZLIB_OUT_SIZE to size input/output buffers.
Commit 0da243fed0 introduced similar constants for LZ4, but while gzip
defined both buffers to be 4kB, LZ4 used 4kB and 16kB without any clear
reasoning why that's desirable.
Furthermore, parts of the code unaware of which compression is used
(e.g. pg_backup_directory.c) continued to use ZLIB_OUT_SIZE directly.
Simplify by replacing the various constants with DEFAULT_IO_BUFFER_SIZE,
set to 4kB. The compression implementations still have an option to use
a custom value, but considering 4kB was fine for 20+ years, I find that
unlikely (and we'd probably just increase the default buffer size).
Author: Georgios Kokolatos
Reviewed-by: Tomas Vondra, Justin Pryzby
Discussion: https://postgr.es/m/33496f7c-3449-1426-d568-63f6bca2ac1f@gmail.com
After 0da243fed0 got committed, we've received a report about a compiler
warning, related to the new LZ4File_gets() function:
compress_lz4.c: In function 'LZ4File_gets':
compress_lz4.c:492:19: warning: comparison of unsigned expression in
'< 0' is always false [-Wtype-limits]
492 | if (dsize < 0)
The reason is very simple - dsize is declared as size_t, which is an
unsigned integer, and thus the check is pointless and we might fail to
notice an error in some cases (or fail in a strange way a bit later).
The warning could have been silenced by simply changing the type, but we
realized the API mostly assumes all the libraries use the same types and
report errors the same way (e.g. by returning 0 and/or negative value).
But we can't make this assumption - the gzip/lz4 libraries already
disagree on some of this, and even if they did a library added in the
future might not.
The right solution is to define what the API does, and translate the
library-specific behavior in consistent way (so that the internal errors
are not exposed to users of our compression API). So this adjusts the
data types in a couple places, so that we don't miss library errors, and
simplifies and unifies the error reporting to simply return true/false
(instead of e.g. size_t).
While at it, make sure LZ4File_open_write() does not clobber errno in
case open_func() fails.
Author: Georgios Kokolatos
Reported-by: Alexander Lakhin
Reviewed-by: Tomas Vondra, Justin Pryzby
Discussion: https://postgr.es/m/33496f7c-3449-1426-d568-63f6bca2ac1f@gmail.com
Switch pg_dump to use the Compression API, implemented by bf9aa490db.
The CompressFileHandle replaces the cfp* family of functions with a
struct of callbacks for accessing (compressed) files. This allows adding
new compression methods simply by introducing a new struct instance with
appropriate implementation of the callbacks.
Archives compressed using custom compression methods store an identifier
of the compression algorithm in their header instead of the compression
level. The header version is bumped.
Author: Georgios Kokolatos
Reviewed-by: Michael Paquier, Rachel Heaton, Justin Pryzby, Tomas Vondra
Discussion: https://postgr.es/m/faUNEOpts9vunEaLnmxmG-DldLSg_ql137OC3JYDmgrOMHm1RvvWY2IdBkv_CRxm5spCCb_OmKNk2T03TMm0fBEWveFF9wA1WizPuAgB7Ss%3D%40protonmail.com
Commit bf9aa490db introduced a compression API in compress_io.{c,h} to
make reuse easier, and allow adding more compression algorithms.
However, pg_backup_archiver.c was not switched to this API and continued
to call the compression directly.
This commit teaches pg_backup_archiver.c about the compression API, so
that it can benefit from bf9aa490db (simpler code, easier addition of
new compression methods).
Author: Georgios Kokolatos
Reviewed-by: Michael Paquier, Rachel Heaton, Justin Pryzby, Tomas Vondra
Discussion: https://postgr.es/m/faUNEOpts9vunEaLnmxmG-DldLSg_ql137OC3JYDmgrOMHm1RvvWY2IdBkv_CRxm5spCCb_OmKNk2T03TMm0fBEWveFF9wA1WizPuAgB7Ss%3D%40protonmail.com
Compression specifications are currently used by pg_basebackup and
pg_receivewal, and are able to let the user control in an extended way
the method and level of compression used. As an effect of this commit,
pg_dump's -Z/--compress is now able to use more than just an integer, as
of the grammar "method[:detail]".
The method can be either "none" or "gzip", and can optionally take a
detail string. If the detail string is only an integer, it defines the
compression level. A comma-separated list of keywords can also be used
method allows for more options, the only keyword supported now is
"level".
The change is backward-compatible, hence specifying only an integer
leads to no compression for a level of 0 and gzip compression when the
level is greater than 0.
Most of the code changes are straight-forward, as pg_dump was relying on
an integer tracking the compression level to check for gzip or no
compression. These are changed to use a compression specification and
the algorithm stored in it.
As of this change, note that the dump format is not bumped because there
is no need yet to track the compression algorithm in the TOC entries.
Hence, we still rely on the compression level to make the difference
when reading them. This will be mandatory once a new compression method
is added, though.
In order to keep the code simpler when parsing the compression
specification, the code is changed so as pg_dump now fails hard when
using gzip on -Z/--compress without its support compiled, rather than
enforcing no compression without the user knowing about it except
through a warning. Like before this commit, archive and custom formats
are compressed by default when the code is compiled with gzip, and left
uncompressed without gzip.
Author: Georgios Kokolatos
Reviewed-by: Michael Paquier
Discussion: https://postgr.es/m/O4mutIrCES8ZhlXJiMvzsivT7ztAMja2lkdL1LJx6O5f22I2W8PBIeLKz7mDLwxHoibcnRAYJXm1pH4tyUNC4a8eDzLn22a6Pb1S74Niexg=@pm.me
Some error reports were reporting strerror(errno), which for some error
conditions coming from zlib are wrong, resulting in confusing reports
such as
pg_restore: [compress_io] could not read from input file: Success
which makes no sense. To correctly extract the error message we need to
use gzerror(), so let's do that.
This isn't as comprehensive or as neat as I would like, but at least it
should improve things in many common cases. The zlib abstraction in
compress_io does not seem to be applied consistently enough; we could
perhaps improve that, but it seems master-only material, not a bug fix
for back-patching.
This problem goes back all the way, but I decided to apply back to 9.4
only, because older branches don't contain commit 14ea89366 which this
change depends on.
Authors: Vladimir Kunschikov, Álvaro Herrera
Discussion: https://postgr.es/m/1498120508308.9826@infotecs.ru
Most pg_dump.c global variables, which were passed down individually to
dumping routines, are now grouped as members of the new DumpOptions
struct, which is used as a local variable and passed down into routines
that need it. This helps future development efforts; in particular it
is said to enable a mode in which a parallel pg_dump run can output
multiple streams, and have them restored in parallel.
Also take the opportunity to clean up the pg_dump header files somewhat,
to avoid circularity.
Author: Joachim Wieland, revised by Álvaro Herrera
Reviewed by Peter Eisentraut
to make it easier to reuse that code. There is no user-visible changes.
This is in preparation for the patch to add a new archive format, a directory,
to perform a custom-like dump but with each table being dumped to a separate
file (that in turn is a prerequisite for parallel pg_dump). This also makes it
easier to add new compression methods in the future, and makes the
pg_backup_custom.c code easier to read, when the compression-related code is
factored out.
Joachim Wieland, with heavy editorialization by me.
Bruce Momjian
Tomas Vondra
Michael Paquier
Tom Lane
Alvaro Herrera
Heikki Linnakangas