Release date: 2016-09-29
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
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.
Version 9.6 contains a number of changes that may affect compatibility with previous releases. Observe the following incompatibilities:
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
to_char(), do not count a minus sign (when
needed) as part of the field width for time-related fields (Bruce
'YY') now returns
extract() behave more reasonably with
infinite inputs (Vitaly Burovoy)
function just returned zero given an infinite timestamp, regardless
of the given field name. Make it return
as appropriate when the requested field is one that is
monotonically increasing (e.g,
NULL when it is not (e.g.,
throw the expected error for bad field names.
Remove PL/pgSQL's “feature” that suppressed the innermost line
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
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.
unaccent.rules file to handle all diacritics
known to Unicode, and to expand ligatures correctly (Thomas Munro,
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
tsvector columns and indexes
that depend on the result.
Remove the long-deprecated
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
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
routines view from
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
-c option no longer implies
--no-psqlrc (Pavel Stehule, Catalin Iacob)
--no-psqlrc (or its
-X) explicitly to obtain
the old behavior. Scripts so modified will still work with old
versions of psql.
-t 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,
Display epoch-and-transaction-ID values in the format
The previous format
was confusingly similar to that used for LSNs.
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
ALTER EXTENSION UPDATE to each
such extension (in each database of a cluster).
Below you will find a detailed account of the changes between PostgreSQL 9.6 and the previous major release.
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 max_parallel_workers_per_gather
to a value larger than zero. Additional control over use of
parallelism is available through other new configuration parameters
Provide infrastructure for marking the parallel-safety status of functions (Robert Haas, Amit Kapila)
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.
gin_clean_pending_list() function to allow
manual invocation of pending-list cleanup for a GIN index (Jeff
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
box (Alexander Lebedev)
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
Speed up text sorts where the same string occurs multiple times (Peter Geoghegan)
Speed up sorting of
by using “abbreviated” keys (Peter Geoghegan)
Support for abbreviated keys has also been added to the
non-default operator classes
bpchar_pattern_ops. Processing of ordered-set
aggregates can also now exploit abbreviated keys.
CREATE INDEX CONCURRENTLY
by treating TIDs as 64-bit
integers during sorting (Peter Geoghegan)
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
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.
ANALYZE's estimates for
columns with many nulls (Tomas Vondra, Alex Shulgin)
ANALYZE tended to
underestimate the number of non-
distinct values in a column with many
NULLs, and was also inaccurate in computing the
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
(a,b) REFERENCES r
(x,y), then a
t.a = r.x AND t.b = r.y cannot
select more than one
r row per
t row. The planner formerly considered
AND conditions to be independent
and would often drastically misestimate selectivity as a result.
Now it compares the
to applicable foreign key constraints and produces better
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
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.
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 old_snapshot_threshold, 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.
GROUP BY columns that are
functionally dependent on other columns (David Rowley)
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
Allow use of an index-only scan on a partial
index when the index's
references columns that are not indexed (Tomas Vondra, Kyotaro
For example, an index defined by
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
a is not listed as an index
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.
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
posix_fadvise(), but those interfaces have some
undesirable side-effects so the feature is disabled by default on
Improve aggregate-function performance by sharing calculations across multiple aggregates if they have the same arguments and transition functions (David Rowley)
SELECT AVG(x), VARIANCE(x)
FROM tab can use a single per-row computation for both
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
PREPARE TRANSACTION, and will be read back from
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
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
date data types (David Rowley, Andres
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
setting below its default on recent Windows versions (Chen
Disable update_process_title 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.
pg_stat_progress_vacuum system view to
provide progress reporting for
operations (Amit Langote, Robert Haas, Vinayak Pokale, Rahila
pg_control_init() functions to expose fields of
pg_control to SQL (Joe Conway, Michael Paquier)
pg_config system view (Joe Conway)
This view exposes the same information available from the pg_config command-line utility, namely assorted compile-time configuration information for PostgreSQL.
column to the
pg_replication_slots system view (Marko
pg_stat_wal_receiver system view to provide
information about the state of a hot-standby server's
WAL receiver process (Michael
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
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
pg_current_xlog_flush_location() to expose
the current transaction log flush location (Tomas Vondra)
pg_notification_queue_usage() to report how
NOTIFY queue is (Brendan
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.
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
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
fields in the log.
Support RADIUS passwords up to 128 characters long (Marko Tiikkaja)
Add new SSPI authentication parameters
upn_username to control whether NetBIOS or Kerberos realm names and user names are used
during SSPI authentication
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 idle_in_transaction_session_timeout. It can be useful to prevent forgotten transactions from holding locks or preventing vacuum cleanup for too long.
Raise the maximum allowed value of checkpoint_timeout to 24 hours (Simon Riggs)
be set per-tablespace to support cases where different tablespaces
have different I/O characteristics (Julien Rouhaud)
%n to print the current time in
Unix epoch form, with milliseconds (Tomas Vondra, Jeff Davis)
hot_standby values of the wal_level 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
Add configure option
to enable calling
server start and stop (Peter Eisentraut)
This allows the use of systemd
service units of type
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.
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.
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 synchronous_standby_names parameter.
Add new setting
configuration parameter synchronous_commit
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
allow reserving WAL immediately
when creating a replication slot (Gurjeet Singh, Michael
This allows the creation of a replication slot to guarantee that all the WAL needed for a base backup will be available.
--slot option to pg_basebackup
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.
pg_stop_backup() to support non-exclusive backups
Allow functions that return sets of tuples to return simple
NULLs (Andrew Gierth, Tom Lane)
In the context of
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
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
VALUES rows (Tom Lane)
Previously, such cases failed if the same target column was
mentioned more than once, e.g.,
tab (x, x) VALUES (...).
When appropriate, postpone evaluation of
SELECT output expressions until after an
ORDER BY sort (Konstantin
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
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.
COPY to copy the output of an
RETURNING query (Marko Tiikkaja)
Previously, an intermediate CTE had to be written to get this result.
object DEPENDS ON EXTENSION
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.
ALTER do nothing
when the object is already in the requested schema, rather than
throwing an error as it historically has for most object types
object SET SCHEMA
Add options to
ALTER OPERATOR to
allow changing the selectivity functions associated with an
existing operator (Yury Zhuravlev)
IF NOT EXISTS option to
ALTER TABLE ADD COLUMN (Fabrízio de
Reduce the lock strength needed by
TABLE when setting fillfactor and autovacuum-related
relation options (Fabrízio de Royes Mello, Simon Riggs)
METHOD to allow extensions to create index access
methods (Alexander Korotkov, Petr Jelínek)
CASCADE option to
CREATE EXTENSION to automatically
create any extensions the requested one depends on (Petr
CREATE TABLE ... LIKE include
OID column if any source table has one
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
DROP OPERATOR to clear
oprnegate links to the dropped operator (Roma
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
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.
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
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.
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
<. 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
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
Also, PostgreSQL is now more
careful to detect overflow in operations that compute new date or
timestamp values, such as
For geometric data types, make sure
component values are treated consistently during input and output
Such values will now always print the same as they would in a
float8 column, and be accepted the
same way on input. Previously the behavior was
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
consistency with the corresponding equality operators (Michael
jsonb_insert() function to insert a new
element into a
jsonb array, or a
not-previously-existing key into a
object (Dmitry Dolgov)
Improve the accuracy of the
functions for type
scale(numeric) function to extract the
display scale of a
numeric value (Marko
Add trigonometric functions that work in degrees (Dean Rasheed)
sind() measures its argument in degrees,
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
inputs per the POSIX standard
The POSIX standard says that
these functions should return
NaN input, and should throw an error
for out-of-range inputs including
infinity. Previously our behavior varied across
to_timestamp(float8) convert float
infinity to timestamp
infinity (Vitaly Burovoy)
Formerly it just failed on an infinite input.
Add new functions for
The new functions are
array_to_tsvector(), and a variant of
setweight() that sets the weight only
for specified lexeme(s).
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
text is expected (Teodor Sigaev)
Add variadic functions
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
These functions can also be used to count the number of null or
nonnull elements in an array.
parse_ident() to split a qualified, possibly
quoted SQL identifier into its
parts (Pavel Stehule)
to_number(), interpret a
V format code as dividing by 10 to the power of
the number of digits following
This makes it operate in an inverse fashion to
to_reg*() functions accept type
This avoids the need to write an explicit cast in most cases where the argument is not a simple literal constant.
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
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
Change various catalog-inspection functions to return
NULL for invalid input (Michael
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.
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.
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” APIs 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,
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-
characters when the database encoding was not
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
CONTEXT field of messages
can be suppressed, either always or only for non-error messages
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
\errverbose feature, and may be useful for other
clients as well.
PQhost() function to return useful data for
default Unix-socket connections (Tom Lane)
Previously it would return
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)
This option causes the program to complain if there is no match
-n 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)
-f command-line options (Pavel Stehule, Catalin
The specified operations are carried out in the order in which the options are given, and then psql terminates.
\crosstabview command that
prints the results of a query in a cross-tabulated display (Daniel
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.
\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
and recreate the failure in order to see error fields that are not
shown by default.
\sv commands for editing and showing view
definitions (Petr Korobeinikov)
These are parallel to the existing
\gexec command that executes
a query and re-submits the result(s) as new queries (Corey
\pset C to set the table
title, for consistency with
\C (Bruce Momjian)
\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)
\pset title string if
one has been set, and shorten the prefabricated part of the header
. Also, the timestamp
format now obeys psql's locale
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)
%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)
CONTEXT only for errors is
now the default behavior. This can be changed by setting the
\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)
\setrandom with built-in
functions (Fabien Coelho)
The new built-in functions include
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
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
which works similarly to
-f for custom
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.
--progress-timestamp option to
report progress with Unix epoch timestamps, instead of time since
the run started (Fabien Coelho)
Allow the number of client connections (
-c) to not be an exact multiple of the number of
-j) (Fabien Coelho)
-T option is used, stop
promptly at the end of the specified time (Fabien Coelho)
Previously, specifying a low transaction rate could cause pgbench to wait significantly longer than specified.
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.
heap_deformtuple functions (Peter Geoghegan)
Add macros to make
AllocSetContextCreate() calls simpler and safer
Writing out the individual sizing parameters for a memory
context is now deprecated in favor of using one of the new macros
ALLOCSET_START_SMALL_SIZES. Existing code continues
to work, however.
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.
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.
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
functions have been added to allow SQL queries to determine
index AM properties that used to be discoverable from
pg_init_privs system catalog to hold
original privileges of initdb-created and extension-created objects
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)
is removed, and replaced by
RequestNamedLWLockTranche(). This allows better
identification of custom
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 FDWs 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
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
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.
This level acts like
that the message is never sent to the client. It is meant for use
in auditing and similar applications.
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
Support OpenSSL 1.1.0 (Andreas Karlsson, Heikki Linnakangas)
Add configuration parameter
auto_explain.sample_rate to allow
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.
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.
introduce distance operators for cubes, and support kNN-style
searches in GiST indexes on cube columns (Stas Kelvich)
hstore_to_json_loose() functions agree on what is
a number (Tom Lane)
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
heap_page_items() function show the raw data in
each tuple, and add new functions
heap_page_item_attrs() for inspection of
individual tuple fields (Nikolay Shaplov)
Add an optional
S2K iteration count
pgp_sym_encrypt() function (Jeff Janes)
Add support for “word
contrib/pg_trgm (Alexander Korotkov, Artur
These functions and operators measure the similarity between one string and the most similar single word of another string.
Add configuration parameter
contrib/pg_trgm's similarity threshold (Artur
This threshold has always been configurable, but formerly it was
controlled by special-purpose functions
show_limit(). Those are now deprecated.
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
contrib/pg_visibility module to allow
examining table visibility maps (Robert Haas)
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)
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
DELETE entirely on the remote server
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)
fetched 100 rows at a time from remote queries; now that behavior
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, Etsuro Fujita)
Previously, a local query cancellation request did not cause an already-sent remote query to terminate early.
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