Disable autovacuum, because we don't want it to run against
intentionally corrupted tables. Also, before corrupting the tables,
run pg_amcheck and ensure that it passes. Otherwise, if something
unexpected happens when we check the corrupted tables, it's not so
clear whether it would have also happened before we corrupted
them.
Mark Dilger
Discussion: http://postgr.es/m/AA5506CE-7D2A-42E4-A51D-358635E3722D@enterprisedb.com
There is now a per-column COMPRESSION option which can be set to pglz
(the default, and the only option in up until now) or lz4. Or, if you
like, you can set the new default_toast_compression GUC to lz4, and
then that will be the default for new table columns for which no value
is specified. We don't have lz4 support in the PostgreSQL code, so
to use lz4 compression, PostgreSQL must be built --with-lz4.
In general, TOAST compression means compression of individual column
values, not the whole tuple, and those values can either be compressed
inline within the tuple or compressed and then stored externally in
the TOAST table, so those properties also apply to this feature.
Prior to this commit, a TOAST pointer has two unused bits as part of
the va_extsize field, and a compessed datum has two unused bits as
part of the va_rawsize field. These bits are unused because the length
of a varlena is limited to 1GB; we now use them to indicate the
compression type that was used. This means we only have bit space for
2 more built-in compresison types, but we could work around that
problem, if necessary, by introducing a new vartag_external value for
any further types we end up wanting to add. Hopefully, it won't be
too important to offer a wide selection of algorithms here, since
each one we add not only takes more coding but also adds a build
dependency for every packager. Nevertheless, it seems worth doing
at least this much, because LZ4 gets better compression than PGLZ
with less CPU usage.
It's possible for LZ4-compressed datums to leak into composite type
values stored on disk, just as it is for PGLZ. It's also possible for
LZ4-compressed attributes to be copied into a different table via SQL
commands such as CREATE TABLE AS or INSERT .. SELECT. It would be
expensive to force such values to be decompressed, so PostgreSQL has
never done so. For the same reasons, we also don't force recompression
of already-compressed values even if the target table prefers a
different compression method than was used for the source data. These
architectural decisions are perhaps arguable but revisiting them is
well beyond the scope of what seemed possible to do as part of this
project. However, it's relatively cheap to recompress as part of
VACUUM FULL or CLUSTER, so this commit adjusts those commands to do
so, if the configured compression method of the table happens not to
match what was used for some column value stored therein.
Dilip Kumar. The original patches on which this work was based were
written by Ildus Kurbangaliev, and those were patches were based on
even earlier work by Nikita Glukhov, but the design has since changed
very substantially, since allow a potentially large number of
compression methods that could be added and dropped on a running
system proved too problematic given some of the architectural issues
mentioned above; the choice of which specific compression method to
add first is now different; and a lot of the code has been heavily
refactored. More recently, Justin Przyby helped quite a bit with
testing and reviewing and this version also includes some code
contributions from him. Other design input and review from Tomas
Vondra, Álvaro Herrera, Andres Freund, Oleg Bartunov, Alexander
Korotkov, and me.
Discussion: http://postgr.es/m/20170907194236.4cefce96%40wp.localdomain
Discussion: http://postgr.es/m/CAFiTN-uUpX3ck%3DK0mLEk-G_kUQY%3DSNOTeqdaNRR9FMdQrHKebw%40mail.gmail.com
Don't complain about the last TOAST chunk number being different
from what we expected if there are no TOAST chunks at all.
In such a case, saying that the final chunk number is 0 is not
really accurate, and the fact the value is missing from the
TOAST table is reported separately anyway.
Mark Dilger
Discussion: http://postgr.es/m/AA5506CE-7D2A-42E4-A51D-358635E3722D@enterprisedb.com
Pipeline mode in libpq lets an application avoid the Sync messages in
the FE/BE protocol that are implicit in the old libpq API after each
query. The application can then insert Sync at its leisure with a new
libpq function PQpipelineSync. This can lead to substantial reductions
in query latency.
Co-authored-by: Craig Ringer <craig.ringer@enterprisedb.com>
Co-authored-by: Matthieu Garrigues <matthieu.garrigues@gmail.com>
Co-authored-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Aya Iwata <iwata.aya@jp.fujitsu.com>
Reviewed-by: Daniel Vérité <daniel@manitou-mail.org>
Reviewed-by: David G. Johnston <david.g.johnston@gmail.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Kirk Jamison <k.jamison@fujitsu.com>
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>
Reviewed-by: Nikhil Sontakke <nikhils@2ndquadrant.com>
Reviewed-by: Vaishnavi Prabakaran <VaishnaviP@fast.au.fujitsu.com>
Reviewed-by: Zhihong Yu <zyu@yugabyte.com>
Discussion: https://postgr.es/m/CAMsr+YFUjJytRyV4J-16bEoiZyH=4nj+sQ7JP9ajwz=B4dMMZw@mail.gmail.com
Discussion: https://postgr.es/m/CAJkzx4T5E-2cQe3dtv2R78dYFvz+in8PY7A8MArvLhs_pg75gg@mail.gmail.com
It's not immediately obvious what you have to do to get "make
installcheck" to work here, so document that along the same lines
as we've used elsewhere.
It does not work on all versions of perl across all platforms.
To avoid endian-ness issues, pick a new value for column a
that has the same upper 4 bytes as lower 4 bytes. Try to
make it something that isn't likely to occur anywhere nearby
in the page.
Discussion: http://postgr.es/m/29DA079B-0658-4E66-BDAA-0EFD7B64D9C6@enterprisedb.com
Commit 24189277f6 managed to remove
one of the two places where we were checking for a "no such user"
error while leaving the other one right next to it. So remove that
too. In fact, remove the entire test, because the whole point of
this test was to see which message we got on a failure.
It's hard to believe, but buildfarm results from the new pg_amcheck
suggest that command_checks_all() perform shell expansion on some
machines but not others, apparently due to an underlying behavior
difference in IPC::Run. Let's see if we can work around that - and
confirm that it is the real problem - by passing '-S*' as a single
argument rather than '-S' and '*' as two separate ones.
Failures were observed on jacana and hoverfly.
Mark Dilger
Discussion: http://postgr.es/m/9E76E46A-48B2-4869-BD0C-422204C1F767@enterprisedb.com
Test #12 overwrote a 1-byte varlena header to make it look like the
initial byte of a 4-byte varlena header, but the results were
endian-dependent. Also, the byte "abc" that followed the overwritten
byte would be interpreted differently depending on endian-ness.
Overwrite 4 bytes instead, in an endian-aware manner.
Test #13 accidentally managed to depend on TOAST_MAX_CHUNK_SIZE,
which varies slightly depending on MAXIMUM_ALIGNOF. That's not
the point anyway, so make the regexp insensitive to the expected
number of chunks.
Mark Dilger
Discussion: http://postgr.es/m/A80D68F6-E38F-482D-9522-E2FB6AAFE8A1@enterprisedb.com
Robert Haas
Alvaro Herrera
Tom Lane