Release 9.6Release Date2016-09-29Overview
Major enhancements in PostgreSQL> 9.6 include:
Parallel execution of sequential scans, joins and aggregates
Avoid scanning pages unnecessarily during vacuum freeze operations
Synchronous replication now allows multiple standby servers for
increased reliability
Full-text search can now search for phrases (multiple adjacent words)
postgres_fdw> now supports remote joins, sorts,
UPDATE>s, and DELETE>s
Substantial performance improvements, especially in the area of
scalability on multi-CPU>-socket servers
The above items are explained in more detail in the sections below.
Migration to Version 9.6
A dump/restore using , or use of , is required for those wishing to migrate data
from any previous release.
Version 9.6 contains a number of changes that may affect compatibility
with previous releases. Observe the following incompatibilities:
Improve the pg_stat_activity>
view's information about what a process is waiting for (Amit
Kapila, Ildus Kurbangaliev)
Historically a process has only been shown as waiting if it was
waiting for a heavyweight lock. Now waits for lightweight locks
and buffer pins are also shown in pg_stat_activity>.
Also, the type of lock being waited for is now visible.
These changes replace the waiting> column with
wait_event_type> and wait_event>.
In to_char()>>,
do not count a minus sign (when needed) as part of the field
width for time-related fields (Bruce Momjian)
For example, to_char('-4 years'::interval, 'YY')>
now returns -04>, rather than -4>.
Make extract()>> behave
more reasonably with infinite inputs (Vitaly Burovoy)
Historically the extract()> function just returned
zero given an infinite timestamp, regardless of the given
field name. Make it return infinity
or -infinity as appropriate when the
requested field is one that is monotonically increasing (e.g,
year>, epoch>), or NULL> when
it is not (e.g., day>, hour>). Also,
throw the expected error for bad field names.
Remove PL/pgSQL's feature> that suppressed the
innermost line of CONTEXT> for messages emitted by
RAISE> commands (Pavel Stehule)
This ancient backwards-compatibility hack was agreed to have
outlived its usefulness.
Fix the default text search parser to allow leading digits
in email> and host> tokens (Artur Zakirov)
In most cases this will result in few changes in the parsing of
text. But if you have data where such addresses occur frequently,
it may be worth rebuilding dependent tsvector> columns
and indexes so that addresses of this form will be found properly
by text searches.
Extend contrib/unaccent>>'s
standard unaccent.rules> file to handle all diacritics
known to Unicode, and to expand ligatures correctly (Thomas Munro,
Léonard Benedetti)
The previous version neglected to convert some less-common letters
with diacritic marks. Also, ligatures are now expanded into
separate letters. Installations that use this rules file may wish
to rebuild tsvector> columns and indexes that depend on the
result.
Remove the long-deprecated
CREATEUSER>/NOCREATEUSER> options from
CREATE ROLE> and allied commands (Tom Lane)
CREATEUSER> actually meant SUPERUSER>,
for ancient backwards-compatibility reasons. This has been a
constant source of confusion for people who (reasonably) expect
it to mean CREATEROLE>. It has been deprecated for
ten years now, so fix the problem by removing it.
Treat role names beginning with pg_> as reserved
(Stephen Frost)
User creation of such role names is now disallowed. This prevents
conflicts with built-in roles created by initdb>.
Change a column name in the
information_schema>.routines>
view from result_cast_character_set_name>
to result_cast_char_set_name> (Clément
Prévost)
The SQL:2011 standard specifies the longer name, but that appears
to be a mistake, because adjacent column names use the shorter
style, as do other information_schema> views.
psql>'s option no longer implies
(Pavel Stehule, Catalin Iacob)
Write (or its
abbreviation ) explicitly to obtain the old
behavior. Scripts so modified will still work with old
versions of psql>.
Improve pg_restore>'s option to
match all types of relations, not only plain tables (Craig Ringer)
Change the display format used for NextXID> in
pg_controldata> and related places (Joe Conway,
Bruce Momjian)
Display epoch-and-transaction-ID values in the format
number>:>number>.
The previous format
number>/>number> was
confusingly similar to that used for LSN>s.
Update extension functions to be marked parallel-safe where
appropriate (Andreas Karlsson)
Many of the standard extensions have been updated to allow their
functions to be executed within parallel query worker processes.
These changes will not take effect in
databases pg_upgrade>'d from prior versions unless
you apply ALTER EXTENSION UPDATE> to each such extension
(in each database of a cluster).
Changes
Below you will find a detailed account of the changes between
PostgreSQL 9.6 and the previous major
release.
ServerParallel Queries
Parallel queries (Robert Haas, Amit Kapila, David Rowley,
many others)
With 9.6, PostgreSQL> introduces initial support
for parallel execution of large queries. Only strictly read-only
queries where the driving table is accessed via a sequential scan
can be parallelized. Hash joins and nested loops can be performed
in parallel, as can aggregation (for supported aggregates).
Much remains to be done, but this is already a useful set of
features.
Parallel query execution is not (yet) enabled by default.
To allow it, set the new configuration
parameter to a
value larger than zero. Additional control over use of parallelism
is available through other new configuration parameters
,
, , and .
Provide infrastructure for marking the parallel-safety status of
functions (Robert Haas, Amit Kapila)
Indexes
Allow GIN>> index builds to
make effective use of
settings larger than 1 GB (Robert Abraham, Teodor Sigaev)
Add pages deleted from a GIN index's pending list to the free space
map immediately
(Jeff Janes, Teodor Sigaev)
This reduces bloat if the table is not vacuumed often.
Add gin_clean_pending_list()>>
function to allow manual invocation of pending-list cleanup for a
GIN index (Jeff Janes)
Formerly, such cleanup happened only as a byproduct of vacuuming or
analyzing the parent table.
Improve handling of dead index tuples in GiST> indexes (Anastasia Lubennikova)
Dead index tuples are now marked as such when an index scan notices
that the corresponding heap tuple is dead. When inserting tuples,
marked-dead tuples will be removed if needed to make space on
the page.
Add an SP-GiST operator class for
type box> (Alexander Lebedev)
Sorting
Improve sorting performance by using quicksort, not replacement
selection sort, when performing external sort steps (Peter
Geoghegan)
The new approach makes better use of the CPU> cache
for typical cache sizes and data volumes. Where necessary,
the behavior can be adjusted via the new configuration parameter
.
Speed up text sorts where the same string occurs multiple times
(Peter Geoghegan)
Speed up sorting of uuid>, bytea>, and
char(n)> fields by using abbreviated> keys
(Peter Geoghegan)
Support for abbreviated keys has also been
added to the non-default operator classes text_pattern_ops>>,
varchar_pattern_ops>, and
bpchar_pattern_ops>. Processing of ordered-set
aggregates can also now exploit abbreviated keys.
Speed up CREATE INDEX CONCURRENTLY> by treating
TID>s as 64-bit integers during sorting (Peter
Geoghegan)
Locking
Reduce contention for the ProcArrayLock> (Amit Kapila,
Robert Haas)
Improve performance by moving buffer content locks into the buffer
descriptors (Andres Freund, Simon Riggs)
Replace shared-buffer header spinlocks with atomic operations to
improve scalability (Alexander Korotkov, Andres Freund)
Use atomic operations, rather than a spinlock, to protect an
LWLock>'s wait queue (Andres Freund)
Partition the shared hash table freelist to reduce contention on
multi-CPU>-socket servers (Aleksander Alekseev)
Reduce interlocking on standby servers during the replay of btree
index vacuuming operations (Simon Riggs)
This change avoids substantial replication delays that sometimes
occurred while replaying such operations.
Optimizer Statistics
Improve ANALYZE>'s estimates for columns with many nulls
(Tomas Vondra, Alex Shulgin)
Previously ANALYZE> tended to underestimate the number
of non-NULL> distinct values in a column with many
NULL>s, and was also inaccurate in computing the
most-common values.
Improve planner's estimate of the number of distinct values in
a query result (Tomas Vondra)
Use foreign key relationships to infer selectivity for join
predicates (Tomas Vondra, David Rowley)
If a table t> has a foreign key restriction, say
(a,b) REFERENCES r (x,y)>, then a WHERE>
condition such as t.a = r.x AND t.b = r.y> cannot
select more than one r> row per t> row.
The planner formerly considered these AND> conditions
to be independent and would often drastically misestimate
selectivity as a result. Now it compares the WHERE>
conditions to applicable foreign key constraints and produces
better estimates.
VACUUM>
Avoid re-vacuuming pages containing only frozen tuples (Masahiko
Sawada, Robert Haas, Andres Freund)
Formerly, anti-wraparound vacuum had to visit every page of
a table, even pages where there was nothing to do. Now, pages
containing only already-frozen tuples are identified in the table's
visibility map, and can be skipped by vacuum even when doing
transaction wraparound prevention. This should greatly reduce the
cost of maintaining large tables containing mostly-unchanging data.
If necessary, vacuum can be forced to process all-frozen
pages using the new DISABLE_PAGE_SKIPPING> option.
Normally this should never be needed, but it might help in
recovering from visibility-map corruption.
Avoid useless heap-truncation attempts during VACUUM>
(Jeff Janes, Tom Lane)
This change avoids taking an exclusive table lock in some cases
where no truncation is possible. The main benefit comes from
avoiding unnecessary query cancellations on standby servers.
General Performance
Allow old MVCC> snapshots to be invalidated after a
configurable timeout (Kevin Grittner)
Normally, deleted tuples cannot be physically removed by
vacuuming until the last transaction that could see>
them is gone. A transaction that stays open for a long
time can thus cause considerable table bloat because
space cannot be recycled. This feature allows setting
a time-based limit, via the new configuration parameter
, on how long an
MVCC> snapshot is guaranteed to be valid. After that,
dead tuples are candidates for removal. A transaction using an
outdated snapshot will get an error if it attempts to read a page
that potentially could have contained such data.
Ignore GROUP BY> columns that are
functionally dependent on other columns (David Rowley)
If a GROUP BY> clause includes all columns of a
non-deferred primary key, as well as other columns of the same
table, those other columns are redundant and can be dropped
from the grouping. This saves computation in many common cases.
Allow use of an index-only
scan on a partial index when the index's WHERE>
clause references columns that are not indexed (Tomas Vondra,
Kyotaro Horiguchi)
For example, an index defined by CREATE INDEX tidx_partial
ON t(b) WHERE a > 0> can now be used for an index-only scan by
a query that specifies WHERE a > 0> and does not
otherwise use a>. Previously this was disallowed
because a> is not listed as an index column.
Perform checkpoint writes in sorted order (Fabien Coelho,
Andres Freund)
Previously, checkpoints wrote out dirty pages in whatever order
they happen to appear in shared buffers, which usually is nearly
random. That performs poorly, especially on rotating media.
This change causes checkpoint-driven writes to be done in order
by file and block number, and to be balanced across tablespaces.
Where feasible, trigger kernel writeback after a configurable
number of writes, to prevent accumulation of dirty data in kernel
disk buffers (Fabien Coelho, Andres Freund)
PostgreSQL> writes data to the kernel's disk cache,
from where it will be flushed to physical storage in due time.
Many operating systems are not smart about managing this and allow
large amounts of dirty data to accumulate before deciding to flush
it all at once, causing long delays for new I/O requests until the
flushing finishes.
This change attempts to alleviate this problem by explicitly
requesting data flushes after a configurable interval.
On Linux, sync_file_range()> is used for this purpose,
and the feature is on by default on Linux because that function has
few downsides. This flushing capability is also available on other
platforms if they have msync()>
or posix_fadvise()>, but those interfaces have some
undesirable side-effects so the feature is disabled by default on
non-Linux platforms.
The new configuration parameters , , , and control this behavior.
Improve aggregate-function performance by sharing calculations
across multiple aggregates if they have the same arguments and
transition functions (David Rowley)
For example, SELECT AVG(x), VARIANCE(x) FROM tab> can use
a single per-row computation for both aggregates.
Speed up visibility tests for recently-created tuples by checking
the current transaction's snapshot, not pg_clog>, to
decide if the source transaction should be considered committed
(Jeff Janes, Tom Lane)
Allow tuple hint bits to be set sooner than before (Andres Freund)
Improve performance of short-lived prepared transactions (Stas
Kelvich, Simon Riggs, Pavan Deolasee)
Two-phase commit information is now written only to WAL>
during PREPARE TRANSACTION>, and will be read back from
WAL> during COMMIT PREPARED> if that happens
soon thereafter. A separate state file is created only if the
pending transaction does not get committed or aborted by the time
of the next checkpoint.
Improve performance of memory context destruction (Jan Wieck)
Improve performance of resource owners with many tracked objects
(Aleksander Alekseev)
Improve speed of the output functions for timestamp>,
time>, and date> data types (David Rowley,
Andres Freund)
Avoid some unnecessary cancellations of hot-standby queries
during replay of actions that take AccessExclusive>
locks (Jeff Janes)
Extend relations multiple blocks at a time when there is contention
for the relation's extension lock (Dilip Kumar)
This improves scalability by decreasing contention.
Increase the number of clog buffers for better scalability (Amit
Kapila, Andres Freund)
Speed up expression evaluation in PL/pgSQL> by
keeping ParamListInfo> entries for simple variables
valid at all times (Tom Lane)
Avoid reducing the SO_SNDBUF> setting below its default
on recent Windows versions (Chen Huajun)
Disable by default on
Windows (Takayuki Tsunakawa)
The overhead of updating the process title is much larger on Windows
than most other platforms, and it is also less useful to do it since
most Windows users do not have tools that can display process titles.
Monitoring
Add pg_stat_progress_vacuum>
system view to provide progress reporting for VACUUM>
operations (Amit Langote, Robert Haas, Vinayak Pokale, Rahila Syed)
Add pg_control_system()>>,
pg_control_checkpoint()>,
pg_control_recovery()>, and
pg_control_init()> functions to expose fields of
pg_control> to SQL> (Joe Conway, Michael
Paquier)
Add pg_config>
system view (Joe Conway)
This view exposes the same information available from
the pg_config> comand-line utility,
namely assorted compile-time configuration information for
PostgreSQL>.
Add a confirmed_flush_lsn> column to the pg_replication_slots>
system view (Marko Tiikkaja)
Add pg_stat_wal_receiver>
system view to provide information about the state of a hot-standby
server's WAL> receiver process (Michael Paquier)
Add pg_blocking_pids()>>
function to reliably identify which sessions block which others
(Tom Lane)
This function returns an array of the process IDs of any
sessions that are blocking the session with the given process ID.
Historically users have obtained such information using a self-join
on the pg_locks> view. However, it is unreasonably
tedious to do it that way with any modicum of correctness, and
the addition of parallel queries has made the old approach entirely
impractical, since locks might be held or awaited by child worker
processes rather than the session's main process.
Add function pg_current_xlog_flush_location()>>
to expose the current transaction log flush location (Tomas Vondra)
Add function pg_notification_queue_usage()>>
to report how full the NOTIFY> queue is (Brendan Jurd)
Limit the verbosity of memory context statistics dumps (Tom Lane)
The memory usage dump that is output to the postmaster log during an
out-of-memory failure now summarizes statistics when there are a
large number of memory contexts, rather than possibly generating
a very large report. There is also a grand total>
summary line now.
Authentication>
Add a BSD> authentication
method to allow use of
the BSD> Authentication service for
PostgreSQL> client authentication (Marisa Emerson)
BSD Authentication is currently only available on OpenBSD>.
When using PAM>
authentication, provide the client IP address or host name
to PAM> modules via the PAM_RHOST> item
(Grzegorz Sampolski)
Provide detail in the postmaster log for more types of password
authentication failure (Tom Lane)
All ordinarily-reachable password authentication failure cases
should now provide specific DETAIL> fields in the log.
Support RADIUS> passwords>
up to 128 characters long (Marko Tiikkaja)
Add new SSPI>
authentication parameters
compat_realm> and upn_username> to control
whether NetBIOS> or Kerberos>
realm names and user names are used during SSPI>
authentication (Christian Ullrich)
Server Configuration
Allow sessions to be terminated automatically if they are in
idle-in-transaction state for too long (Vik Fearing)
This behavior is controlled by the new configuration parameter
. It can
be useful to prevent forgotten transactions from holding locks
or preventing vacuum cleanup for too long.
Raise the maximum allowed value
of to 24 hours (Simon Riggs)
Allow effective_io_concurrency> to be set per-tablespace
to support cases where different tablespaces have different I/O
characteristics (Julien Rouhaud)
Add option %n> to
print the current time in Unix epoch form, with milliseconds (Tomas
Vondra, Jeff Davis)
Add and configuration parameters
to provide more control over the message format when logging to
syslog> (Peter Eisentraut)
Merge the archive> and hot_standby> values
of the configuration parameter
into a single new value replica> (Peter Eisentraut)
Making a distinction between these settings is no longer useful,
and merging them is a step towards a planned future simplification
of replication setup. The old names are still accepted but are
converted to replica> internally.
Add configure option
This allows the use of systemd> service units of
type notify>, which greatly simplifies the management
of PostgreSQL> under systemd>.
Allow the server's SSL> key file to have group read
access if it is owned by root> (Christoph Berg)
Formerly, we insisted the key file be owned by the
user running the PostgreSQL> server, but
that is inconvenient on some systems (such as Debian>) that are configured to manage
certificates centrally. Therefore, allow the case where the key
file is owned by root> and has group read access.
It is up to the operating system administrator to ensure that
the group does not include any untrusted users.
Reliability
Force backends to exit if the postmaster dies (Rajeev Rastogi,
Robert Haas)
Under normal circumstances the postmaster should always outlive
its child processes. If for some reason the postmaster dies,
force backend sessions to exit with an error. Formerly, existing
backends would continue to run until their clients disconnect,
but that is unsafe and inefficient. It also prevents a new
postmaster from being started until the last old backend has
exited. Backends will detect postmaster death when waiting for
client I/O, so the exit will not be instantaneous, but it should
happen no later than the end of the current query.
Check for serializability conflicts before reporting
constraint-violation failures (Thomas Munro)
When using serializable transaction isolation, it is desirable
that any error due to concurrent transactions should manifest
as a serialization failure, thereby cueing the application that
a retry might succeed. Unfortunately, this does not reliably
happen for duplicate-key failures caused by concurrent insertions.
This change ensures that such an error will be reported as a
serialization error if the application explicitly checked for
the presence of a conflicting key (and did not find it) earlier
in the transaction.
Ensure that invalidation messages are recorded in WAL>
even when issued by a transaction that has no XID>
assigned (Andres Freund)
This fixes some corner cases in which transactions on standby
servers failed to notice changes, such as new indexes.
Prevent multiple processes from trying to clean a GIN>
index's pending list concurrently (Teodor Sigaev, Jeff Janes)
This had been intentionally allowed, but it causes race conditions
that can result in vacuum missing index entries it needs to delete.
Replication and Recovery
Allow synchronous replication to support multiple simultaneous
synchronous standby servers, not just one (Masahiko Sawada,
Beena Emerson, Michael Paquier, Fujii Masao, Kyotaro Horiguchi)
The number of standby servers that must acknowledge a commit
before it is considered complete is now configurable as part of
the parameter.
Add new setting remote_apply> for configuration
parameter (Thomas Munro)
In this mode, the master waits for the transaction to be
applied> on the standby server, not just written
to disk. That means that you can count on a transaction started
on the standby to see all commits previously acknowledged by
the master.
Add a feature to the replication
protocol, and a corresponding option to pg_create_physical_replication_slot()>>,
to allow reserving WAL> immediately when creating a
replication slot (Gurjeet Singh, Michael Paquier)
This allows the creation of a replication slot to guarantee
that all the WAL> needed for a base backup will be
available.
Add a option to
pg_basebackup>>
(Peter Eisentraut)
This lets pg_basebackup> use a replication
slot defined for WAL> streaming. After the base
backup completes, selecting the same slot for regular streaming
replication allows seamless startup of the new standby server.
Extend pg_start_backup()>>
and pg_stop_backup()> to support non-exclusive backups
(Magnus Hagander)
Queries
Allow functions that return sets of tuples to return simple
NULL>s (Andrew Gierth, Tom Lane)
In the context of SELECT FROM function(...)>, a function
that returned a set of composite values was previously not allowed
to return a plain NULL> value as part of the set.
Now that is allowed and interpreted as a row of NULL>s.
This avoids corner-case errors with, for example, unnesting an
array of composite values.
Fully support array subscripts and field selections in the
target column list of an INSERT> with multiple
VALUES> rows (Tom Lane)
Previously, such cases failed if the same target column was
mentioned more than once, e.g., INSERT INTO tab (x[1],
x[2]) VALUES (...)>.
When appropriate, postpone evaluation of SELECT>
output expressions until after an ORDER BY> sort
(Konstantin Knizhnik)
This change ensures that volatile or expensive functions in the
output list are executed in the order suggested by ORDER
BY>, and that they are not evaluated more times than required
when there is a LIMIT> clause. Previously, these
properties held if the ordering was performed by an index scan or
pre-merge-join sort, but not if it was performed by a top-level
sort.
Widen counters recording the number of tuples processed to 64 bits
(Andreas Scherbaum)
This change allows command tags, e.g. SELECT>, to
correctly report tuple counts larger than 4 billion. This also
applies to PL/pgSQL's GET DIAGNOSTICS ... ROW_COUNT>
command.
Avoid doing encoding conversions by converting through the
MULE_INTERNAL> encoding (Tom Lane)
Previously, many conversions for Cyrillic and Central
European single-byte encodings were done by converting to a
related MULE_INTERNAL> coding scheme and then to the
destination encoding. Aside from being inefficient, this meant
that when the conversion encountered an untranslatable character,
the error message would confusingly complain about failure to
convert to or from MULE_INTERNAL>, rather than the
user-visible encoding.
Consider performing joins of foreign tables remotely only when the
tables will be accessed under the same role ID (Shigeru Hanada,
Ashutosh Bapat, Etsuro Fujita)
Previously, the foreign join pushdown infrastructure left the
question of security entirely up to individual foreign data
wrappers, but that made it too easy for an FDW> to
inadvertently create subtle security holes. So, make it the core
code's job to determine which role ID will access each table,
and do not attempt join pushdown unless the role is the same for
all relevant relations.
Utility Commands
Allow COPY> to copy the output of an
INSERT>/UPDATE>/DELETE>
... RETURNING> query (Marko Tiikkaja)
Previously, an intermediate CTE> had to be written to
get this result.
Introduce ALTER object> DEPENDS ON
EXTENSION (Abhijit Menon-Sen)
This command allows a database object to be marked as depending
on an extension, so that it will be dropped automatically if
the extension is dropped (without needing CASCADE>).
However, the object is not part of the extension, and thus will
be dumped separately by pg_dump>.
Make ALTER object> SET SCHEMA> do nothing
when the object is already in the requested schema, rather than
throwing an error as it historically has for most object types
(Marti Raudsepp)
Add options to ALTER OPERATOR to allow changing
the selectivity functions associated with an existing operator
(Yury Zhuravlev)
Add an
Reduce the lock strength needed by ALTER TABLE>
when setting fillfactor and autovacuum-related relation options
(Fabrízio de Royes Mello, Simon Riggs)
Introduce CREATE
ACCESS METHOD>> to allow extensions to create index access
methods (Alexander Korotkov, Petr Jelínek)
Add a CASCADE> option to CREATE
EXTENSION to automatically create any extensions the
requested one depends on (Petr Jelínek)
Make CREATE TABLE ... LIKE> include an OID>
column if any source table has one (Bruce Momjian)
If a CHECK> constraint is declared NOT VALID>
in a table creation command, automatically mark it as valid
(Amit Langote, Amul Sul)
This is safe because the table has no existing rows. This matches
the longstanding behavior of FOREIGN KEY> constraints.
Fix DROP OPERATOR> to clear
pg_operator>.oprcom> and
pg_operator>.oprnegate> links to
the dropped operator (Roma Sokolov)
Formerly such links were left as-is, which could pose a problem
in the somewhat unlikely event that the dropped operator's
OID> was reused for another operator.
Do not show the same subplan twice in EXPLAIN> output
(Tom Lane)
In certain cases, typically involving SubPlan nodes in index
conditions, EXPLAIN> would print data for the same
subplan twice.
Disallow creation of indexes on system columns, except for
OID> columns (David Rowley)
Such indexes were never considered supported, and would very
possibly misbehave since the system might change the system-column
fields of a tuple without updating indexes. However, previously
there were no error checks to prevent them from being created.
Permissions Management
Use the privilege system to manage access to sensitive functions
(Stephen Frost)
Formerly, many security-sensitive functions contained hard-wired
checks that would throw an error if they were called by a
non-superuser. This forced the use of superuser roles for
some relatively pedestrian tasks. The hard-wired error checks
are now gone in favor of making initdb> revoke the
default public EXECUTE> privilege on these functions.
This allows installations to choose to grant usage of such
functions to trusted roles that do not need all superuser
privileges.
Create some built-in roles
that can be used to grant access to what were previously
superuser-only functions (Stephen Frost)
Currently the only such role is pg_signal_backend>,
but more are expected to be added in future.
Data Types
Improve full-text search> to support
searching for phrases, that is, lexemes appearing adjacent to each
other in a specific order, or with a specified distance between
them (Teodor Sigaev, Oleg Bartunov, Dmitry Ivanov)
A phrase-search query can be specified in tsquery>
input using the new operators <->> and
<N>>. The former means
that the lexemes before and after it must appear adjacent to
each other in that order. The latter means they must be exactly
N> lexemes apart.
Allow omitting one or both boundaries in an array slice specifier,
e.g. array_col[3:]> (Yury Zhuravlev)
Omitted boundaries are taken as the upper or lower limit of the
corresponding array subscript. This allows simpler specification
for many common use-cases.
Be more careful about out-of-range dates and timestamps (Vitaly
Burovoy)
This change prevents unexpected out-of-range errors for
timestamp with time zone> values very close to the
implementation limits. Previously, the same> value might
be accepted or not depending on the timezone> setting,
meaning that a dump and reload could fail on a value that had been
accepted when presented. Now the limits are enforced according
to the equivalent UTC> time, not local time, so as to
be independent of timezone>.
Also, PostgreSQL> is now more careful to detect
overflow in operations that compute new date or timestamp values,
such as date> +> integer>.
For geometric data types, make sure infinity> and
NaN> component values are treated consistently during
input and output (Tom Lane)
Such values will now always print the same as they would in
a simple float8> column, and be accepted the same way
on input. Previously the behavior was platform-dependent.
Upgrade
the ispell>>
dictionary type to handle modern Hunspell> files and
support more languages (Artur Zakirov)
Implement look-behind constraints
in regular expressions>
(Tom Lane)
A look-behind constraint is like a lookahead constraint in that it
consumes no text; but it checks for existence (or nonexistence)
of a match ending at the current point in the string, rather
than one starting at the current point. Similar features exist
in many other regular-expression engines.
In regular expressions, if an apparent three-digit octal escape
\>nnn> would exceed 377 (255 decimal),
assume it is a two-digit octal escape instead (Tom Lane)
This makes the behavior match current Tcl> releases.
Add transaction ID operators xid> <>>
xid> and xid> <>> int4>,
for consistency with the corresponding equality operators
(Michael Paquier)
Functions
Add jsonb_insert()>>
function to insert a new element into a jsonb> array,
or a not-previously-existing key into a jsonb> object
(Dmitry Dolgov)
Improve the accuracy of the ln()>, log()>,
exp()>, and pow()> functions for type
numeric> (Dean Rasheed)
Add a scale(numeric)>>
function to extract the display scale of a numeric> value
(Marko Tiikkaja)
Add trigonometric functions that work in degrees (Dean Rasheed)
For example, sind()>>
measures its argument in degrees, whereas sin()>
measures in radians. These functions go to some lengths to
deliver exact results for values where an exact result can be
expected, for instance sind(30) = 0.5.
Ensure that trigonometric functions handle infinity>
and NaN> inputs per the POSIX> standard
(Dean Rasheed)
The POSIX> standard says that these functions should
return NaN> for NaN> input, and should throw
an error for out-of-range inputs including infinity>.
Previously our behavior varied across platforms.
Make to_timestamp(float8)>>
convert float infinity> to
timestamp infinity> (Vitaly Burovoy)
Formerly it just failed on an infinite input.
Add new functions for tsvector> data (Stas Kelvich)
The new functions are ts_delete()>>,
ts_filter()>, unnest()>,
tsvector_to_array()>, array_to_tsvector()>,
and a variant of setweight()> that sets the weight
only for specified lexeme(s).
Allow ts_stat()>>
and tsvector_update_trigger()>>
to operate on values that are of types binary-compatible with the
expected argument type, not just exactly that type; for example
allow citext> where text> is expected (Teodor
Sigaev)
Add variadic functions num_nulls()>>
and num_nonnulls()> that count the number of their
arguments that are null or non-null (Marko Tiikkaja)
An example usage is CHECK(num_nonnulls(a,b,c) = 1)>
which asserts that exactly one of a,b,c is not NULL>.
These functions can also be used to count the number of null or
nonnull elements in an array.
Add function parse_ident()>>
to split a qualified, possibly quoted SQL> identifier
into its parts (Pavel Stehule)
In to_number()>>,
interpret a V> format code as dividing by 10 to the
power of the number of digits following V> (Bruce
Momjian)
This makes it operate in an inverse fashion to
to_char()>.
Make the to_reg*()>>
functions accept type text> not cstring>
(Petr Korobeinikov)
This avoids the need to write an explicit cast in most cases
where the argument is not a simple literal constant.
Add pg_size_bytes()>>
function to convert human-readable size strings to numbers (Pavel
Stehule, Vitaly Burovoy, Dean Rasheed)
This function converts strings like those produced by
pg_size_pretty()> into bytes. An example
usage is SELECT oid::regclass FROM pg_class WHERE
pg_total_relation_size(oid) > pg_size_bytes('10 GB')>.
In pg_size_pretty()>>,
format negative numbers similarly to positive ones (Adrian
Vondendriesch)
Previously, negative numbers were never abbreviated, just printed
in bytes.
Add an optional missing_ok> argument to the current_setting()>>
function (David Christensen)
This allows avoiding an error for an unrecognized parameter
name, instead returning a NULL>.
Change various catalog-inspection functions to return
NULL> for invalid input (Michael Paquier)
pg_get_viewdef()>>
now returns NULL> if given an invalid view OID>,
and several similar functions likewise return NULL> for
bad input. Previously, such cases usually led to cache
lookup failed> errors, which are not meant to occur in
user-facing cases.
Fix pg_replication_origin_xact_reset()>>
to not have any arguments (Fujii Masao)
The documentation said that it has no arguments, and the C code did
not expect any arguments, but the entry in pg_proc>
mistakenly specified two arguments.
Server-Side Languages
In PL/pgSQL, detect mismatched
CONTINUE> and EXIT> statements while
compiling a function, rather than at execution time
(Jim Nasby)
Extend PL/Python>'s error-reporting and
message-reporting functions to allow specifying additional message
fields besides the primary error message (Pavel Stehule)
Allow PL/Python functions to call themselves recursively
via SPI>, and fix the behavior when multiple
set-returning PL/Python functions are called within one query
(Alexey Grishchenko, Tom Lane)
Fix session-lifespan memory leaks in PL/Python (Heikki Linnakangas,
Haribabu Kommi, Tom Lane)
Modernize PL/Tcl> to use Tcl's object>
API>s instead of simple strings (Jim Nasby, Karl
Lehenbauer)
This can improve performance substantially in some cases.
Note that PL/Tcl> now requires Tcl 8.4 or later.
In PL/Tcl>, make database-reported errors return
additional information in Tcl's errorCode> global
variable (Jim Nasby, Tom Lane)
This feature follows the Tcl convention for returning auxiliary
data about an error.
Fix PL/Tcl> to perform encoding conversion between
the database encoding and UTF-8>, which is what Tcl
expects (Tom Lane)
Previously, strings were passed through without conversion,
leading to misbehavior with non-ASCII> characters when
the database encoding was not UTF-8>.
Client Interfaces
Add a nonlocalized version of
the severity field> in
error and notice messages (Tom Lane)
This change allows client code to determine severity of an error or
notice without having to worry about localized variants of the
severity strings.
Introduce a feature in libpq> whereby the
CONTEXT> field of messages can be suppressed, either
always or only for non-error messages (Pavel Stehule)
The default behavior of PQerrorMessage()>>
is now to print CONTEXT>
only for errors. The new function PQsetErrorContextVisibility()>>
can be used to adjust this.
Add support in libpq> for regenerating an error
message with a different verbosity level (Alex Shulgin)
This is done with the new function PQresultVerboseErrorMessage()>>.
This supports psql>'s new \errverbose>
feature, and may be useful for other clients as well.
Improve libpq>'s PQhost()>> function to return
useful data for default Unix-socket connections (Tom Lane)
Previously it would return NULL> if no explicit host
specification had been given; now it returns the default socket
directory path.
Fix ecpg>'s lexer to handle line breaks within
comments starting on preprocessor directive lines (Michael Meskes)
Client Applications
Add a
This option causes the program to complain if there is no match
for a or option, rather
than silently doing nothing.
In pg_dump>, dump locally-made changes of privilege
assignments for system objects (Stephen Frost)
While it has always been possible for a superuser to change
the privilege assignments for built-in or extension-created
objects, such changes were formerly lost in a dump and reload.
Now, pg_dump> recognizes and dumps such changes.
(This works only when dumping from a 9.6 or later server, however.)
Allow pg_dump> to dump non-extension-owned objects
that are within an extension-owned schema
(Martín Marqués)
Previously such objects were ignored because they were mistakenly
assumed to belong to the extension owning their schema.
In pg_dump> output, include the table name in object
tags for object types that are only uniquely named per-table
(for example, triggers) (Peter Eisentraut)
Support multiple and
command-line options (Pavel Stehule, Catalin Iacob)
The specified operations are carried out in the order in which the
options are given, and then psql> terminates.
Add a \crosstabview> command that prints the results of
a query in a cross-tabulated display (Daniel Vérité)
In the crosstab display, data values from one query result column
are placed in a grid whose column and row headers come from other
query result columns.
Add an \errverbose> command that shows the last server
error at full verbosity (Alex Shulgin)
This is useful after getting an unexpected error — you
no longer need to adjust the VERBOSITY> variable and
recreate the failure in order to see error fields that are not
shown by default.
Add \ev> and \sv> commands for editing and
showing view definitions (Petr Korobeinikov)
These are parallel to the existing \ef> and
\sf> commands for functions.
Add a \gexec> command that executes a query and
re-submits the result(s) as new queries (Corey Huinker)
Allow \pset C string>
to set the table title, for consistency with \C
string> (Bruce Momjian)
In \pset expanded auto> mode, do not use expanded
format for query results with only one column (Andreas Karlsson,
Robert Haas)
Improve the headers output by the \watch> command
(Michael Paquier, Tom Lane)
Include the \pset title> string if one has
been set, and shorten the prefabricated part of the
header to be timestamp> (every
N>s). Also, the timestamp format now
obeys psql>'s locale environment.
Improve tab-completion logic to consider the entire input query,
not only the current line (Tom Lane)
Previously, breaking a command into multiple lines defeated any
tab completion rules that needed to see words on earlier lines.
Numerous minor improvements in tab-completion behavior (Peter
Eisentraut, Vik Fearing, Kevin Grittner, Kyotaro Horiguchi, Jeff
Janes, Andreas Karlsson, Fujii Masao, Thomas Munro, Masahiko
Sawada, Pavel Stehule)
Add a PROMPT> option %p> to insert the
process ID of the connected backend (Julien Rouhaud)
Introduce a feature whereby the CONTEXT> field of
messages can be suppressed, either always or only for non-error
messages (Pavel Stehule)
Printing CONTEXT> only for errors is now the default
behavior. This can be changed by setting the special variable
SHOW_CONTEXT.
Make \df+> show function access privileges and
parallel-safety attributes (Michael Paquier)
SQL commands in pgbench> scripts are now ended by
semicolons, not newlines (Kyotaro Horiguchi, Tom Lane)
This change allows SQL commands in scripts to span multiple lines.
Existing custom scripts will need to be modified to add a semicolon
at the end of each line that does not have one already. (Doing so
does not break the script for use with older versions
of pgbench>.)
Support floating-point arithmetic, as well as some built-in functions>, in
expressions in backslash commands (Fabien Coelho)
Replace \setrandom> with built-in functions (Fabien
Coelho)
The new built-in functions include random()>>,
random_exponential()>, and
random_gaussian()>, which perform the same work as
\setrandom>, but are easier to use since they can be
embedded in larger expressions. Since these additions have made
\setrandom> obsolete, remove it.
Allow invocation of multiple copies of the built-in scripts,
not only custom scripts (Fabien Coelho)
This is done with the new
Allow changing the selection probabilities (weights) for scripts
(Fabien Coelho)
When multiple scripts are specified, each pgbench>
transaction randomly chooses one to execute. Formerly this was
always done with uniform probability, but now different selection
probabilities can be specified for different scripts.
Collect statistics for each script in a multi-script run (Fabien
Coelho)
This feature adds an intermediate level of detail to existing
global and per-command statistics printouts.
Add a
Allow the number of client connections (
When the
Previously, specifying a low transaction rate could cause
pgbench> to wait significantly longer than
specified.
Server Applications
Improve error reporting during initdb>'s
post-bootstrap phase (Tom Lane)
Previously, an error here led to reporting the entire input
file as the failing query>; now just the current
query is reported. To get the desired behavior, queries in
initdb>'s input files must be separated by blank
lines.
Speed up initdb> by using just one
standalone-backend session for all the post-bootstrap steps
(Tom Lane)
Improve pg_rewind>>
so that it can work when the target timeline changes (Alexander
Korotkov)
This allows, for example, rewinding a promoted standby back to
some state of the old master's timeline.
Source Code
Remove obsolete
heap_formtuple>/heap_modifytuple>/heap_deformtuple>
functions (Peter Geoghegan)
Add macros to make AllocSetContextCreate()> calls simpler
and safer (Tom Lane)
Writing out the individual sizing parameters for a memory context
is now deprecated in favor of using one of the new
macros ALLOCSET_DEFAULT_SIZES>,
ALLOCSET_SMALL_SIZES>,
or ALLOCSET_START_SMALL_SIZES>.
Existing code continues to work, however.
Unconditionally use static inline> functions in header
files (Andres Freund)
This may result in warnings and/or wasted code space with very
old compilers, but the notational improvement seems worth it.
Improve TAP> testing infrastructure (Michael
Paquier, Craig Ringer, Álvaro Herrera, Stephen Frost)
Notably, it is now possible to test recovery scenarios using
this infrastructure.
Make trace_lwlocks> identify individual locks by name
(Robert Haas)
Improve psql>'s tab-completion code infrastructure
(Thomas Munro, Michael Paquier)
Tab-completion rules are now considerably easier to write, and
more compact.
Nail the pg_shseclabel> system catalog into cache,
so that it is available for access during connection authentication
(Adam Brightwell)
The core code does not use this catalog for authentication,
but extensions might wish to consult it.
Restructure index access
method API>> to hide most of it at
the C> level (Alexander Korotkov, Andrew Gierth)
This change modernizes the index AM API> to look more
like the designs we have adopted for foreign data wrappers and
tablesample handlers. This simplifies the C> code
and makes it much more practical to define index access methods in
installable extensions. A consequence is that most of the columns
of the pg_am> system catalog have disappeared.
New inspection
functions have been added to allow SQL queries to determine
index AM properties that used to be discoverable
from pg_am>.
Add pg_init_privs>>
system catalog to hold original privileges
of initdb>-created and extension-created objects
(Stephen Frost)
This infrastructure allows pg_dump> to dump changes
that an installation may have made in privileges attached to
system objects. Formerly, such changes would be lost in a dump
and reload, but now they are preserved.
Change the way that extensions allocate custom LWLocks>
(Amit Kapila, Robert Haas)
The RequestAddinLWLocks()> function is removed,
and replaced by RequestNamedLWLockTranche()>.
This allows better identification of custom LWLocks>,
and is less error-prone.
Improve the isolation tester to allow multiple sessions to wait
concurrently, allowing testing of deadlock scenarios (Robert Haas)
Introduce extensible node types (KaiGai Kohei)
This change allows FDW>s or custom scan providers
to store data in a plan tree in a more convenient format than
was previously possible.
Make the planner deal with post-scan/join query steps by generating
and comparing Paths>, replacing a lot of ad-hoc logic
(Tom Lane)
This change provides only marginal user-visible improvements today,
but it enables future work on a lot of upper-planner improvements
that were impractical to tackle using the old code structure.
Support partial aggregation (David Rowley, Simon Riggs)
This change allows the computation of an aggregate function to be
split into separate parts, for example so that parallel worker
processes can cooperate on computing an aggregate. In future
it might allow aggregation across local and remote data to occur
partially on the remote end.
Add a generic command progress reporting facility (Vinayak Pokale,
Rahila Syed, Amit Langote, Robert Haas)
Separate out psql>'s flex> lexer to
make it usable by other client programs (Tom Lane, Kyotaro
Horiguchi)
This eliminates code duplication for programs that need to be able
to parse SQL commands well enough to identify command boundaries.
Doing that in full generality is more painful than one could
wish, and up to now only psql> has really gotten
it right among our supported client programs.
A new source-code subdirectory src/fe_utils/> has
been created to hold this and other code that is shared across
our client programs. Formerly such sharing was accomplished by
symbolic linking or copying source files at build time, which
was ugly and required duplicate compilation.
Introduce WaitEventSet> API> to allow
efficient waiting for event sets that usually do not change from
one wait to the next (Andres Freund, Amit Kapila)
Add a generic interface for writing WAL> records
(Alexander Korotkov, Petr Jelínek, Markus Nullmeier)
This change allows extensions to write WAL> records for
changes to pages using a standard layout. The problem of needing to
replay WAL> without access to the extension is solved by
having generic replay code. This allows extensions to implement,
for example, index access methods and have WAL>
support for them.
Support generic WAL> messages for logical decoding
(Petr Jelínek, Andres Freund)
This feature allows extensions to insert data into the
WAL> stream that can be read by logical-decoding
plugins, but is not connected to physical data restoration.
Allow SP-GiST operator classes to store an arbitrary
traversal value> while descending the index (Alexander
Lebedev, Teodor Sigaev)
This is somewhat like the reconstructed value>, but it
could be any arbitrary chunk of data, not necessarily of the same
data type as the indexed column.
Introduce a LOG_SERVER_ONLY> message level for
ereport()> (David Steele)
This level acts like LOG> except that the message is
never sent to the client. It is meant for use in auditing and
similar applications.
Provide a Makefile> target to build all generated
headers (Michael Paquier, Tom Lane)
submake-generated-headers> can now be invoked to ensure
that generated backend header files are up-to-date. This is
useful in subdirectories that might be built standalone>.
Support OpenSSL 1.1.0 (Andreas Karlsson, Heikki Linnakangas)
Additional Modules
Add configuration parameter auto_explain.sample_rate> to
allow contrib/auto_explain>>
to capture just a configurable fraction of all queries (Craig
Ringer, Julien Rouhaud)
This allows reduction of overhead for heavy query traffic, while
still getting useful information on average.
Add contrib/bloom>> module that
implements an index access method based on Bloom filtering (Teodor
Sigaev, Alexander Korotkov)
This is primarily a proof-of-concept for non-core index access
methods, but it could be useful in its own right for queries that
search many columns.
In contrib/cube>>, introduce
distance operators for cubes, and support kNN-style searches in
GiST indexes on cube columns (Stas Kelvich)
Make contrib/hstore>'s hstore_to_jsonb_loose()>>
and hstore_to_json_loose()> functions agree on what
is a number (Tom Lane)
Previously, hstore_to_jsonb_loose()> would convert
numeric-looking strings to JSON> numbers, rather than
strings, even if they did not exactly match the JSON>
syntax specification for numbers. This was inconsistent with
hstore_to_json_loose()>, so tighten the test to match
the JSON> syntax.
Add selectivity estimation functions for
contrib/intarray>> operators
to improve plans for queries using those operators (Yury Zhuravlev,
Alexander Korotkov)
Make contrib/pageinspect>>'s
heap_page_items()> function show the raw data in each
tuple, and add new functions tuple_data_split()> and
heap_page_item_attrs()> for inspection of individual
tuple fields (Nikolay Shaplov)
Add an optional S2K> iteration count parameter to
contrib/pgcrypto>>'s
pgp_sym_encrypt()> function (Jeff Janes)
Add support for word similarity> to
contrib/pg_trgm>>
(Alexander Korotkov, Artur Zakirov)
These functions and operators measure the similarity between one
string and the most similar single word of another string.
Add configuration parameter
pg_trgm.similarity_threshold> for
contrib/pg_trgm>'s similarity threshold (Artur Zakirov)
This threshold has always been configurable, but formerly it was
controlled by special-purpose functions set_limit()>
and show_limit()>. Those are now deprecated.
Improve contrib/pg_trgm>'s GIN operator class to
speed up index searches in which both common and rare keys appear
(Jeff Janes)
Improve performance of similarity searches in
contrib/pg_trgm> GIN indexes (Christophe Fornaroli)
Add contrib/pg_visibility>> module
to allow examining table visibility maps (Robert Haas)
Add ssl_extension_info()>>
function to contrib/sslinfo>, to print information
about SSL> extensions present in the X509>
certificate used for the current connection (Dmitry Voronin)
postgres_fdw>>
Allow extension-provided operators and functions to be sent for
remote execution, if the extension is whitelisted in the foreign
server's options (Paul Ramsey)
Users can enable this feature when the extension is known to exist
in a compatible version in the remote database. It allows more
efficient execution of queries involving extension operators.
Consider performing sorts on the remote server (Ashutosh Bapat)
Consider performing joins on the remote server (Shigeru Hanada,
Ashutosh Bapat)
When feasible, perform UPDATE> or DELETE>
entirely on the remote server (Etsuro Fujita)
Formerly, remote updates involved sending a SELECT FOR UPDATE>
command and then updating or deleting the selected rows one-by-one.
While that is still necessary if the operation requires any local
processing, it can now be done remotely if all elements of the
query are safe to send to the remote server.
Allow the fetch size to be set as a server or table option
(Corey Huinker)
Formerly, postgres_fdw> always fetched 100 rows at
a time from remote queries; now that behavior is configurable.
Use a single foreign-server connection for local user IDs that
all map to the same remote user (Ashutosh Bapat)
Transmit query cancellation requests to the remote server
(Michael Paquier)
Previously, a local query cancellation request did not cause an
already-sent remote query to terminate early.