Attempting such an operation would already fail, but in various and
confusing ways. For example, while in recovery, some elog() messages
would be reported, but these should never be user-facing. This commit
restricts any write operations done on large objects in a read-only
context, so as the errors generated are more user-friendly. This is per
the discussion done with Tom Lane and Robert Haas.
Some regression tests are added to check the case of all the SQL
functions working on large objects (including an update of the test's
alternate output).
Author: Yugo Nagata
Discussion: https://postgr.es/m/20220527153028.61a4608f66abcd026fd3806f@sraoss.co.jp
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
libpq's error messages for connection failures pretty well stand on
their own, especially since commits 52a10224e/27a48e5a1. Prefixing
them with 'could not connect to database "foo"' or the like is just
redundant, and perhaps even misleading if the specific database name
isn't relevant to the failure. (When it is, we trust that the
backend's error message will include the DB name.) Indeed, psql
hasn't used any such prefix in a long time. So, make all our other
programs and documentation examples agree with psql's practice.
Discussion: https://postgr.es/m/1094524.1611266589@sss.pgh.pa.us
This patch eliminates a few more "exceed the available area" warnings
whose causes aren't particularly connected to anything else.
The only one really worthy of comment is that I increased the space
allowed for an <orderedlist>'s numbers, because the default of 1em
doesn't quite work for more than one digit. The rest are one-off
insertions of &zwsp; and suchlike tweaks, in places where they
shouldn't do any damage to the material. (In particular, although
I split some long identifiers with zwsp's, there are other nearby
occurrences of each one; so those changes shouldn't hurt greppability
of the document sources.)
This converts the contrib documentation to the new style, and mops up
a couple of function tables that were outside chapter 9 in the main
docs.
A few contrib modules choose not to present their functions in the
standard tabular format. There might be room to rethink those decisions
now that the standard format is more friendly to verbose descriptions.
But I have not undertaken to do that here; I just converted existing
tables.
Turn most mentions of libpq functions into links. At id attributes to
most libpq functions, where not existing yet, so that they can be
linked to. (In a handful of cases there were problems with the PDF
processing toolchain, so those instances were not changed.)
Author: Fabien COELHO <coelho@cri.ensmp.fr>
Reviewed-by: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/flat/alpine.DEB.2.21.1905121032330.27203@lancre
When these programs call pg_catalog.set_config, they need to check for
PGRES_TUPLES_OK instead of PGRES_COMMAND_OK. Fix for
5770172cb0.
Reported-by: Ideriha, Takeshi <ideriha.takeshi@jp.fujitsu.com>
The ability to create like-named objects in different schemas opens up
the potential for users to change the behavior of other users' queries,
maliciously or accidentally. When you connect to a PostgreSQL server,
you should remove from your search_path any schema for which a user
other than yourself or superusers holds the CREATE privilege. If you do
not, other users holding CREATE privilege can redefine the behavior of
your commands, causing them to perform arbitrary SQL statements under
your identity. "SET search_path = ..." and "SELECT
pg_catalog.set_config(...)" are not vulnerable to such hijacking, so one
can use either as the first command of a session. As special
exceptions, the following client applications behave as documented
regardless of search_path settings and schema privileges: clusterdb
createdb createlang createuser dropdb droplang dropuser ecpg (not
programs it generates) initdb oid2name pg_archivecleanup pg_basebackup
pg_config pg_controldata pg_ctl pg_dump pg_dumpall pg_isready
pg_receivewal pg_recvlogical pg_resetwal pg_restore pg_rewind pg_standby
pg_test_fsync pg_test_timing pg_upgrade pg_waldump reindexdb vacuumdb
vacuumlo. Not included are core client programs that run user-specified
SQL commands, namely psql and pgbench. PostgreSQL encourages non-core
client applications to do likewise.
Document this in the context of libpq connections, psql connections,
dblink connections, ECPG connections, extension packaging, and schema
usage patterns. The principal defense for applications is "SELECT
pg_catalog.set_config('search_path', '', false)", and the principal
defense for databases is "REVOKE CREATE ON SCHEMA public FROM PUBLIC".
Either one is sufficient to prevent attack. After a REVOKE, consider
auditing the public schema for objects named like pg_catalog objects.
Authors of SECURITY DEFINER functions use some of the same defenses, and
the CREATE FUNCTION reference page already covered them thoroughly.
This is a good opportunity to audit SECURITY DEFINER functions for
robust security practice.
Back-patch to 9.3 (all supported versions).
Reviewed by Michael Paquier and Jonathan S. Katz. Reported by Arseniy
Sharoglazov.
Security: CVE-2018-1058
Since some preparation work had already been done, the only source
changes left were changing empty-element tags like <xref linkend="foo">
to <xref linkend="foo"/>, and changing the DOCTYPE.
The source files are still named *.sgml, but they are actually XML files
now. Renaming could be considered later.
In the build system, the intermediate step to convert from SGML to XML
is removed. Everything is build straight from the source files again.
The OpenSP (or the old SP) package is no longer needed.
The documentation toolchain instructions are updated and are much
simpler now.
Peter Eisentraut, Alexander Lakhin, Jürgen Purtz
Commit 5ecc0d738 removed the hard-wired superuser checks in lo_import
and lo_export in favor of protecting them with SQL permissions, but
failed to adjust the documentation to match. Fix that, and add a
<caution> paragraph pointing out the nontrivial security hazards
involved with actually granting such permissions. (It's still better
than ALLOW_DANGEROUS_LO_FUNCTIONS, though.)
Also, commit ae20b23a9 caused large object read/write privilege to
be checked during lo_open() rather than in the actual read or write
calls. Document that.
Discussion: https://postgr.es/m/CAB7nPqRHmNOYbETnc_2EjsuzSM00Z+BWKv9sy6tnvSd5gWT_JA@mail.gmail.com
IDs in SGML are case insensitive, and we have accumulated a mix of upper
and lower case IDs, including different variants of the same ID. In
XML, these will be case sensitive, so we need to fix up those
differences. Going to all lower case seems most straightforward, and
the current build process already makes all anchors and lower case
anyway during the SGML->XML conversion, so this doesn't create any
difference in the output right now. A future XML-only build process
would, however, maintain any mixed case ID spellings in the output, so
that is another reason to clean this up beforehand.
Author: Alexander Lakhin <exclusion@gmail.com>
For DocBook XML compatibility, don't use SGML empty tags (</>) anymore,
replace by the full tag name. Add a warning option to catch future
occurrences.
Alexander Lakhin, Jürgen Purtz
The previous naming broke the query that libpq's lo_initialize() uses
to collect the OIDs of the server-side functions it requires, because
that query effectively assumes that there is only one function named
lo_create in the pg_catalog schema (and likewise only one lo_open, etc).
While we should certainly make libpq more robust about this, the naive
query will remain in use in the field for the foreseeable future, so it
seems the only workable choice is to use a different name for the new
function. lo_from_bytea() won a small straw poll.
Back-patch into 9.4 where the new function was introduced.
We don't need two index entries for lo_create pointing at the same section.
It's a bit pedantic for the toolchain to warn about this, but warn it does.
With these, one need no longer manipulate large object descriptors and
extract numeric constants from header files in order to read and write
large object contents from SQL.
Pavel Stehule, reviewed by Rushabh Lathia.
libpq defines these functions as accepting "size_t" lengths ... but the
underlying backend functions expect signed int32 length parameters, and so
will misinterpret any value exceeding INT_MAX. Fix the libpq side to throw
error rather than possibly doing something unexpected.
This is a bug of long standing, but I doubt it's worth back-patching. The
problem is really pretty academic anyway with lo_read/lo_write, since any
caller expecting sane behavior would have to have provided a multi-gigabyte
buffer. It's slightly more pressing with lo_truncate, but still we haven't
supported large objects over 2GB until now.
Copy-editing for previous patch, plus fixing some longstanding markup
issues and oversights (like not mentioning that failures will set the
PQerrorMessage string).
4TB large objects (standard 8KB BLCKSZ case). For this purpose new
libpq API lo_lseek64, lo_tell64 and lo_truncate64 are added. Also
corresponding new backend functions lo_lseek64, lo_tell64 and
lo_truncate64 are added. inv_api.c is changed to handle 64-bit
offsets.
Patch contributed by Nozomi Anzai (backend side) and Yugo Nagata
(frontend side, docs, regression tests and example program). Reviewed
by Kohei Kaigai. Committed by Tatsuo Ishii with minor editings.
Until now, our Serializable mode has in fact been what's called Snapshot
Isolation, which allows some anomalies that could not occur in any
serialized ordering of the transactions. This patch fixes that using a
method called Serializable Snapshot Isolation, based on research papers by
Michael J. Cahill (see README-SSI for full references). In Serializable
Snapshot Isolation, transactions run like they do in Snapshot Isolation,
but a predicate lock manager observes the reads and writes performed and
aborts transactions if it detects that an anomaly might occur. This method
produces some false positives, ie. it sometimes aborts transactions even
though there is no anomaly.
To track reads we implement predicate locking, see storage/lmgr/predicate.c.
Whenever a tuple is read, a predicate lock is acquired on the tuple. Shared
memory is finite, so when a transaction takes many tuple-level locks on a
page, the locks are promoted to a single page-level lock, and further to a
single relation level lock if necessary. To lock key values with no matching
tuple, a sequential scan always takes a relation-level lock, and an index
scan acquires a page-level lock that covers the search key, whether or not
there are any matching keys at the moment.
A predicate lock doesn't conflict with any regular locks or with another
predicate locks in the normal sense. They're only used by the predicate lock
manager to detect the danger of anomalies. Only serializable transactions
participate in predicate locking, so there should be no extra overhead for
for other transactions.
Predicate locks can't be released at commit, but must be remembered until
all the transactions that overlapped with it have completed. That means that
we need to remember an unbounded amount of predicate locks, so we apply a
lossy but conservative method of tracking locks for committed transactions.
If we run short of shared memory, we overflow to a new "pg_serial" SLRU
pool.
We don't currently allow Serializable transactions in Hot Standby mode.
That would be hard, because even read-only transactions can cause anomalies
that wouldn't otherwise occur.
Serializable isolation mode now means the new fully serializable level.
Repeatable Read gives you the old Snapshot Isolation level that we have
always had.
Kevin Grittner and Dan Ports, reviewed by Jeff Davis, Heikki Linnakangas and
Anssi Kääriäinen
The endterm attribute is mainly useful when the toolchain does not support
automatic link target text generation for a particular situation. In the
past, this was required by the man page tools for all reference page links,
but that is no longer the case, and it now actually gets in the way of
proper automatic link text generation. The only remaining use cases are
currently xrefs to refsects.
Rewrite the documentation in more idiomatic English, and in the process make
it somewhat more succinct. Move the discussion of specific large object
privileges out of the "server-side functions" section, where it certainly
doesn't belong, and into "implementation features". That might not be
exactly right either, but it doesn't seem worth creating a new section for
this amount of information. Fix a few spelling and layout problems, too.
Bruce Momjian
Michael Paquier
Tom Lane
Alvaro Herrera
Peter Eisentraut
Magnus Hagander
Peter Eisentraut
Noah Misch
Robert Haas
Tatsuo Ishii
Heikki Linnakangas