Deduplication reduces the storage overhead of duplicates in indexes that
use the standard nbtree index access method. The deduplication process
is applied lazily, after the point where opportunistic deletion of
LP_DEAD-marked index tuples occurs. Deduplication is only applied at
the point where a leaf page split would otherwise be required. New
posting list tuples are formed by merging together existing duplicate
tuples. The physical representation of the items on an nbtree leaf page
is made more space efficient by deduplication, but the logical contents
of the page are not changed. Even unique indexes make use of
deduplication as a way of controlling bloat from duplicates whose TIDs
point to different versions of the same logical table row.
The lazy approach taken by nbtree has significant advantages over a GIN
style eager approach. Most individual inserts of index tuples have
exactly the same overhead as before. The extra overhead of
deduplication is amortized across insertions, just like the overhead of
page splits. The key space of indexes works in the same way as it has
since commit dd299df8 (the commit that made heap TID a tiebreaker
column).
Testing has shown that nbtree deduplication can generally make indexes
with about 10 or 15 tuples for each distinct key value about 2.5X - 4X
smaller, even with single column integer indexes (e.g., an index on a
referencing column that accompanies a foreign key). The final size of
single column nbtree indexes comes close to the final size of a similar
contrib/btree_gin index, at least in cases where GIN's posting list
compression isn't very effective. This can significantly improve
transaction throughput, and significantly reduce the cost of vacuuming
indexes.
A new index storage parameter (deduplicate_items) controls the use of
deduplication. The default setting is 'on', so all new B-Tree indexes
automatically use deduplication where possible. This decision will be
reviewed at the end of the Postgres 13 beta period.
There is a regression of approximately 2% of transaction throughput with
synthetic workloads that consist of append-only inserts into a table
with several non-unique indexes, where all indexes have few or no
repeated values. The underlying issue is that cycles are wasted on
unsuccessful attempts at deduplicating items in non-unique indexes.
There doesn't seem to be a way around it short of disabling
deduplication entirely. Note that deduplication of items in unique
indexes is fairly well targeted in general, which avoids the problem
there (we can use a special heuristic to trigger deduplication passes in
unique indexes, since we're specifically targeting "version bloat").
Bump XLOG_PAGE_MAGIC because xl_btree_vacuum changed.
No bump in BTREE_VERSION, since the representation of posting list
tuples works in a way that's backwards compatible with version 4 indexes
(i.e. indexes built on PostgreSQL 12). However, users must still
REINDEX a pg_upgrade'd index to use deduplication, regardless of the
Postgres version they've upgraded from. This is the only way to set the
new nbtree metapage flag indicating that deduplication is generally
safe.
Author: Anastasia Lubennikova, Peter Geoghegan
Reviewed-By: Peter Geoghegan, Heikki Linnakangas
Discussion:
https://postgr.es/m/55E4051B.7020209@postgrespro.ruhttps://postgr.es/m/4ab6e2db-bcee-f4cf-0916-3a06e6ccbb55@postgrespro.ru
Invent the concept of a B-Tree equalimage ("equality implies image
equality") support function, registered as support function 4. This
indicates whether it is safe (or not safe) to apply optimizations that
assume that any two datums considered equal by an operator class's order
method must be interchangeable without any loss of semantic information.
This is static information about an operator class and a collation.
Register an equalimage routine for almost all of the existing B-Tree
opclasses. We only need two trivial routines for all of the opclasses
that are included with the core distribution. There is one routine for
opclasses that index non-collatable types (which returns 'true'
unconditionally), plus another routine for collatable types (which
returns 'true' when the collation is a deterministic collation).
This patch is infrastructure for an upcoming patch that adds B-Tree
deduplication.
Author: Peter Geoghegan, Anastasia Lubennikova
Discussion: https://postgr.es/m/CAH2-Wzn3Ee49Gmxb7V1VJ3-AC8fWn-Fr8pfWQebHe8rYRxt5OQ@mail.gmail.com
The documentation included some outdated instructions to change the
architecture, build type or target OS of a build done with MSVC. This
commit updates the documentation to include the modern options
available, down to Visual Studio 2013.
Reported-by: Kyotaro Horiguchi
Author: Juan José Santamaría Flecha
Discussion: https://postgr.es/m/CAC+AXB0J7tAqW_2F1fCE4Dh2=Ccz96TcLpsGXOCvka7VvWG9Qw@mail.gmail.com
Backpatch-through: 12
Creating a bunch of non-overlapping partial indexes is generally
a bad idea, so add an example saying not to do that.
Back-patch to v10. Before that, the alternative of using (real)
partitioning wasn't available, so that the tradeoff isn't quite
so clear cut.
Discussion: https://postgr.es/m/CAKVFrvFY-f7kgwMRMiPLbPYMmgjc8Y2jjUGK_Y0HVcYAmU6ymg@mail.gmail.com
Andres Freund pointed out that allowing non-superusers to run
"CREATE EXTENSION ... FROM unpackaged" has security risks, since
the unpackaged-to-1.0 scripts don't try to verify that the existing
objects they're modifying are what they expect. Just attaching such
objects to an extension doesn't seem too dangerous, but some of them
do more than that.
We could have resolved this, perhaps, by still requiring superuser
privilege to use the FROM option. However, it's fair to ask just what
we're accomplishing by continuing to lug the unpackaged-to-1.0 scripts
forward. None of them have received any real testing since 9.1 days,
so they may not even work anymore (even assuming that one could still
load the previous "loose" object definitions into a v13 database).
And an installation that's trying to go from pre-9.1 to v13 or later
in one jump is going to have worse compatibility problems than whether
there's a trivial way to convert their contrib modules into extension
style.
Hence, let's just drop both those scripts and the core-code support
for "CREATE EXTENSION ... FROM".
Discussion: https://postgr.es/m/20200213233015.r6rnubcvl4egdh5r@alap3.anarazel.de
This fixes and updates a couple of comments related to outdated Windows
versions. Particularly, src/common/exec.c had a fallback implementation
to read a file's line from a pipe because stdin/stdout/stderr does not
exist in Windows 2000 that is removed to simplify src/common/ as there
are unlikely versions of Postgres running on such platforms.
Author: Michael Paquier
Reviewed-by: Kyotaro Horiguchi, Juan José Santamaría Flecha
Discussion: https://postgr.es/m/20191219021526.GC4202@paquier.xyz
This commit also updates wait event enum into alphabetical order.
Previously the enum entry for GSSOpenServer was added out-of-order.
Back-patch to v12 where commit b0b39f72b9 introduced
GSSOpenServer wait event. In v12, the commit doesn't include
the update of wait event enum, not to break ABI.
Author: Fujii Masao
Reviewed-by: Michael Paquier
Discussion: https://postgr.es/m/949931aa-4ed4-d867-a7b5-de9c02b2292b@oss.nttdata.com
The stylesheets used for the HTML documentation rendered on
postgresql.org have shifted, and no longer matched what was expected by
"make STYLE=website html" builds performed locally. Local doc builds
did not reflect other aspects of the website, including font and
margins.
This patch updates the references to use the current set of stylesheets
that are used by the documentation on postgresql.org. This also wraps
the documentation preview in a HTML container so it can keep the content
within similar margins to those found on the website.
The documentation on building the docs is updated to reflect this
change, and to let the documentation builder know that an external
network connection is required to properly preview documentation built
with "make STYLE=website html" (which was true prior to this patch too,
but not mentioned).
Author: Jonathan Katz
Reported-By: Tom Lane
Discussion: https://postgr.es/m/1375.1581446233@sss.pgh.pa.us
This allows these modules to be installed into a database without
superuser privileges (assuming that the DBA or sysadmin has installed
the module's files in the expected place). You only need CREATE
privilege on the current database, which by default would be
available to the database owner.
The following modules are marked trusted:
btree_gin
btree_gist
citext
cube
dict_int
earthdistance
fuzzystrmatch
hstore
hstore_plperl
intarray
isn
jsonb_plperl
lo
ltree
pg_trgm
pgcrypto
seg
tablefunc
tcn
tsm_system_rows
tsm_system_time
unaccent
uuid-ossp
In the future we might mark some more modules trusted, but there
seems to be no debate about these, and on the whole it seems wise
to be conservative with use of this feature to start out with.
Discussion: https://postgr.es/m/32315.1580326876@sss.pgh.pa.us
Use a top-level "variablelist", with one item per B-Tree support
function. This structure matches the structure used by various
"Extensibility" sections in other documentation chapters for other index
access methods.
An explicit list makes it much clearer where each item begins and ends.
This wasn't really a problem before now, but an upcoming patch that adds
deduplication to nbtree will need to have its own new B-Tree support
function. Ease the burden of translators by tidying up btree.sgml ahead
of committing the deduplication patch.
The GRANTED BY clause in GRANT/REVOKE ROLE has been there since 2005
but was never documented. I'm not sure now whether that was just an
oversight or was intentional (given the limited capability of the
option). But seeing that pg_dumpall does emit code that uses this
option, it seems like not documenting it at all is a bad idea.
Also, when we upgraded the syntax to allow CURRENT_USER/SESSION_USER
as the privilege recipient, the role form of GRANT was incorrectly
not modified to show that, and REVOKE's docs weren't touched at all.
Although I'm not that excited about GRANTED BY, the other oversight
seems serious enough to justify a back-patch.
Discussion: https://postgr.es/m/3070.1581526786@sss.pgh.pa.us
%d can be used to track if the current connection is in a transaction
block or not, and adding it by default to the prompt has the advantage
to not need a modification of .psqlrc, something not possible depending
on the environment.
This discussion has happened across various sources, and there was a
strong consensus in favor of this change.
Author: Vik Fearing
Reviewed-by: Fabien Coelho
Discussion: https://postgr.es/m/09502c40-cfe1-bb29-10f9-4b3fa7b2bbb2@2ndquadrant.com
When running TRUNCATE CASCADE on a child of a partitioned table
referenced by another partitioned table, the truncate was not applied to
partitions of the referencing table; this could leave rows violating the
constraint in the referencing partitioned table. Repair by walking the
pg_constraint chain all the way up to the topmost referencing table.
Note: any partitioned tables containing FKs that reference other
partitioned tables should be checked for possible violating rows, if
TRUNCATE has occurred in partitions of the referenced table.
Reported-by: Christophe Courtois
Author: Jehan-Guillaume de Rorthais
Discussion: https://postgr.es/m/20200204183906.115f693e@firost
This new field tracks the PID of the group leader used with parallel
query. For parallel workers and the leader, the value is set to the
PID of the group leader. So, for the group leader, the value is the
same as its own PID. Note that this reflects what PGPROC stores in
shared memory, so as leader_pid is NULL if a backend has never been
involved in parallel query. If the backend is using parallel query or
has used it at least once, the value is set until the backend exits.
Author: Julien Rouhaud
Reviewed-by: Sergei Kornilov, Guillaume Lelarge, Michael Paquier, Tomas
Vondra
Discussion: https://postgr.es/m/CAOBaU_Yy5bt0vTPZ2_LUM6cUcGeqmYNoJ8-Rgto+c2+w3defYA@mail.gmail.com
The docs are ambiguous as to which tables would be copied over when the
copy_data parameter is true in ALTER SUBSCRIPTION ... REFRESH PUBLICATION.
Make it clear that it only applies to tables which are new in the
publication.
Author: David Christensen (reword by Álvaro Herrera)
Discussion: https://postgr.es/m/95339420-7F09-4F8C-ACC0-8F1CFAAD9CD7@endpoint.com
Advancing a physical replication slot with pg_replication_slot_advance()
did not mark the slot as dirty if any advancing was done, preventing the
follow-up checkpoint to flush the slot data to disk. This caused the
advancing to be lost even on clean restarts. This does not happen for
logical slots as any advancing marked the slot as dirty. Per
discussion, the original feature has been implemented so as in the event
of a crash the slot may move backwards to a past LSN. This property is
kept and more documentation is added about that.
This commit adds some new TAP tests to check the persistency of physical
and logical slots after advancing across clean restarts.
Author: Alexey Kondratov, Michael Paquier
Reviewed-by: Andres Freund, Kyotaro Horiguchi, Craig Ringer
Discussion: https://postgr.es/m/059cc53a-8b14-653a-a24d-5f867503b0ee@postgrespro.ru
Backpatch-through: 11
This patch creates a new extension property, "trusted". An extension
that's marked that way in its control file can be installed by a
non-superuser who has the CREATE privilege on the current database,
even if the extension contains objects that normally would have to be
created by a superuser. The objects within the extension will (by
default) be owned by the bootstrap superuser, but the extension itself
will be owned by the calling user. This allows replicating the old
behavior around trusted procedural languages, without all the
special-case logic in CREATE LANGUAGE. We have, however, chosen to
loosen the rules slightly: formerly, only a database owner could take
advantage of the special case that allowed installation of a trusted
language, but now anyone who has CREATE privilege can do so.
Having done that, we can delete the pg_pltemplate catalog, moving the
knowledge it contained into the extension script files for the various
PLs. This ends up being no change at all for the in-core PLs, but it is
a large step forward for external PLs: they can now have the same ease
of installation as core PLs do. The old "trusted PL" behavior was only
available to PLs that had entries in pg_pltemplate, but now any
extension can be marked trusted if appropriate.
This also removes one of the stumbling blocks for our Python 2 -> 3
migration, since the association of "plpythonu" with Python 2 is no
longer hard-wired into pg_pltemplate's initial contents. Exactly where
we go from here on that front remains to be settled, but one problem
is fixed.
Patch by me, reviewed by Peter Eisentraut, Stephen Frost, and others.
Discussion: https://postgr.es/m/5889.1566415762@sss.pgh.pa.us
Before, if a recovery target is configured, but the archive ended
before the target was reached, recovery would end and the server would
promote without further notice. That was deemed to be pretty wrong.
With this change, if the recovery target is not reached, it is a fatal
error.
Based-on-patch-by: Leif Gunnar Erlandsen <leif@lako.no>
Reviewed-by: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/993736dd3f1713ec1f63fc3b653839f5@lako.no
Commit 40d964ec99 allowed vacuum command to leverage multiple CPUs by
invoking parallel workers to process indexes. This commit provides a
'--parallel' option to specify the parallel degree used by vacuum command.
Author: Masahiko Sawada, with few modifications by me
Reviewed-by: Mahendra Singh and Amit Kapila
Discussion: https://postgr.es/m/CAD21AoDTPMgzSkV4E3SFo1CH_x50bf5PqZFQf4jmqjk-C03BWg@mail.gmail.com
These two new parameters, named sslminprotocolversion and
sslmaxprotocolversion, allow to respectively control the minimum and the
maximum version of the SSL protocol used for the SSL connection attempt.
The default setting is to allow any version for both the minimum and the
maximum bounds, causing libpq to rely on the bounds set by the backend
when negotiating the protocol to use for an SSL connection. The bounds
are checked when the values are set at the earliest stage possible as
this makes the checks independent of any SSL implementation.
Author: Daniel Gustafsson
Reviewed-by: Michael Paquier, Cary Huang
Discussion: https://postgr.es/m/4F246AE3-A7AE-471E-BD3D-C799D3748E03@yesql.se
This function allows us to fsync the specified file or directory.
It's useful, for example, when we want to sync the file that
pg_file_write() writes out or that COPY TO exports the data into,
for durability.
Author: Fujii Masao
Reviewed-By: Julien Rouhaud, Arthur Zakirov, Michael Paquier, Atsushi Torikoshi
Discussion: https://www.postgresql.org/message-id/CAHGQGwGY8uzZ_k8dHRoW1zDcy1Z7=5GQ+So4ZkVy2u=nLsk=hA@mail.gmail.com
Detection of WAL records having references to invalid pages
during recovery causes PostgreSQL to raise a PANIC-level error,
aborting the recovery. Setting ignore_invalid_pages to on causes
the system to ignore those WAL records (but still report a warning),
and continue recovery. This behavior may cause crashes, data loss,
propagate or hide corruption, or other serious problems.
However, it may allow you to get past the PANIC-level error,
to finish the recovery, and to cause the server to start up.
Author: Fujii Masao
Reviewed-by: Michael Paquier
Discussion: https://www.postgresql.org/message-id/CAHGQGwHCK6f77yeZD4MHOnN+PaTf6XiJfEB+Ce7SksSHjeAWtg@mail.gmail.com
Attempting to use CREATE INDEX, DROP INDEX or REINDEX with CONCURRENTLY
on a temporary relation with ON COMMIT actions triggered unexpected
errors because those operations use multiple transactions internally to
complete their work. Here is for example one confusing error when using
ON COMMIT DELETE ROWS:
ERROR: index "foo" already contains data
Issues related to temporary relations and concurrent indexing are fixed
in this commit by enforcing the non-concurrent path to be taken for
temporary relations even if using CONCURRENTLY, transparently to the
user. Using a non-concurrent path does not matter in practice as locks
cannot be taken on a temporary relation by a session different than the
one owning the relation, and the non-concurrent operation is more
effective.
The problem exists with REINDEX since v12 with the introduction of
CONCURRENTLY, and with CREATE/DROP INDEX since CONCURRENTLY exists for
those commands. In all supported versions, this caused only confusing
error messages to be generated. Note that with REINDEX, it was also
possible to issue a REINDEX CONCURRENTLY for a temporary relation owned
by a different session, leading to a server crash.
The idea to enforce transparently the non-concurrent code path for
temporary relations comes originally from Andres Freund.
Reported-by: Manuel Rigger
Author: Michael Paquier, Heikki Linnakangas
Reviewed-by: Andres Freund, Álvaro Herrera, Heikki Linnakangas
Discussion: https://postgr.es/m/CA+u7OA6gP7YAeCguyseusYcc=uR8+ypjCcgDDCTzjQ+k6S9ksQ@mail.gmail.com
Backpatch-through: 9.4
The behavior of something like
ALTER TABLE transactions
ADD COLUMN status varchar(30) DEFAULT 'old',
ALTER COLUMN status SET default 'current';
is to fill existing table rows with 'old', not 'current'. That's
intentional and desirable for a couple of reasons:
* It makes the behavior the same whether you merge the sub-commands
into one ALTER command or give them separately;
* If we applied the new default while filling the table, there would
be no way to get the existing behavior in one SQL command.
The same reasoning applies in cases that add a column and then
manipulate its GENERATED/IDENTITY status in a second sub-command,
since the generation expression is really just a kind of default.
However, that wasn't very obvious (at least not to me; earlier in
the referenced discussion thread I'd thought it was a bug to be
fixed). And it certainly wasn't documented.
Hence, add documentation, code comments, and a test case to clarify
that this behavior is all intentional.
In passing, adjust ATExecAddColumn's defaults-related relkind check
so that it matches up exactly with ATRewriteTables, instead of being
effectively (though not literally) the negated inverse condition.
The reasoning can be explained a lot more concisely that way, too
(not to mention that the comment now matches the code, which it
did not before).
Discussion: https://postgr.es/m/10365.1558909428@sss.pgh.pa.us
This feature allows the vacuum to leverage multiple CPUs in order to
process indexes. This enables us to perform index vacuuming and index
cleanup with background workers. This adds a PARALLEL option to VACUUM
command where the user can specify the number of workers that can be used
to perform the command which is limited by the number of indexes on a
table. Specifying zero as a number of workers will disable parallelism.
This option can't be used with the FULL option.
Each index is processed by at most one vacuum process. Therefore parallel
vacuum can be used when the table has at least two indexes.
The parallel degree is either specified by the user or determined based on
the number of indexes that the table has, and further limited by
max_parallel_maintenance_workers. The index can participate in parallel
vacuum iff it's size is greater than min_parallel_index_scan_size.
Author: Masahiko Sawada and Amit Kapila
Reviewed-by: Dilip Kumar, Amit Kapila, Robert Haas, Tomas Vondra,
Mahendra Singh and Sergei Kornilov
Tested-by: Mahendra Singh and Prabhat Sahu
Discussion:
https://postgr.es/m/CAD21AoDTPMgzSkV4E3SFo1CH_x50bf5PqZFQf4jmqjk-C03BWg@mail.gmail.comhttps://postgr.es/m/CAA4eK1J-VoR9gzS5E75pcD-OH0mEyCdp8RihcwKrcuw7J-Q0+w@mail.gmail.com
Rather than intermixing the discussion of text-string and binary-string
functions, make a clean break, moving all discussion of binary-string
operations into section 9.5. This involves some duplication of
function descriptions between 9.4 and 9.5, but it seems cleaner on the
whole since the individual descriptions are clearer (and on the other
side of the coin, it gets rid of some duplicated descriptions, too).
Move the convert*/encode/decode functions to a separate table, because
they don't quite seem to fit under the heading of "binary string
functions".
Also provide full documentation of the textual formats supported by
encode() and decode() (which was the original goal of this patch
series, many moons ago).
Also move the table of built-in encoding conversions out of section 9.4,
where it no longer had any relevance whatsoever, and put it into section
23.3 about character sets. I chose to put both that and table 23.2
(multibyte-translation-table) into a new <sect2> so as not to break up
the flow of discussion in 23.3.3.
Also do a bunch of minor copy-editing on the function descriptions
in 9.4 and 9.5.
Karl Pinc, reviewed by Fabien Coelho, further hacking by me
Discussion: https://postgr.es/m/20190304163347.7bca4897@slate.meme.com
jsonb_set_lax() is the same as jsonb_set, except that it takes and extra
argument that specifies what to do if the value argument is NULL. The
default is 'use_json_null'. Other possibilities are 'raise_exception',
'return_target' and 'delete_key', all these behaviours having been
suggested as reasonable by various users.
Discussion: https://postgr.es/m/375873e2-c957-3a8d-64f9-26c43c2b16e7@2ndQuadrant.com
Reviewed by: Pavel Stehule
This uses the progress reporting infrastructure added by c16dc1aca5,
adding support for ANALYZE.
Co-authored-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Co-authored-by: Tatsuro Yamada <tatsuro.yamada.tf@nttcom.co.jp>
Reviewed-by: Julien Rouhaud, Robert Haas, Anthony Nowocien, Kyotaro Horiguchi,
Vignesh C, Amit Langote
Introduce new fields amusemaintenanceworkmem and amparallelvacuumoptions
in IndexAmRoutine for parallel vacuum. The amusemaintenanceworkmem tells
whether a particular IndexAM uses maintenance_work_mem or not. This will
help in controlling the memory used by individual workers as otherwise,
each worker can consume memory equal to maintenance_work_mem. The
amparallelvacuumoptions tell whether a particular IndexAM participates in
a parallel vacuum and if so in which phase (bulkdelete, vacuumcleanup) of
vacuum.
Author: Masahiko Sawada and Amit Kapila
Reviewed-by: Dilip Kumar, Amit Kapila, Tomas Vondra and Robert Haas
Discussion:
https://postgr.es/m/CAD21AoDTPMgzSkV4E3SFo1CH_x50bf5PqZFQf4jmqjk-C03BWg@mail.gmail.comhttps://postgr.es/m/CAA4eK1LmcD5aPogzwim5Nn58Ki+74a6Edghx4Wd8hAskvHaq5A@mail.gmail.com
If no permanent replication slot is configured using
primary_slot_name, the walreceiver now creates and uses a temporary
replication slot. A new setting wal_receiver_create_temp_slot can be
used to disable this behavior, for example, if the remote instance is
out of replication slots.
Reviewed-by: Masahiko Sawada <masahiko.sawada@2ndquadrant.com>
Discussion: https://www.postgresql.org/message-id/CA%2Bfd4k4dM0iEPLxyVyme2RAFsn8SUgrNtBJOu81YqTY4V%2BnqZA%40mail.gmail.com
This tells you about allocations that have been made from the main
shared memory segment. The original patch also tried to show information
about dynamic shared memory allocation as well, but I decided to
leave that problem for another time.
Andres Freund and Robert Haas, reviewed by Michael Paquier, Marti
Raudsepp, Tom Lane, Álvaro Herrera, and Kyotaro Horiguchi.
Discussion: http://postgr.es/m/20140504114417.GM12715@awork2.anarazel.de
Peter Geoghegan