Release date: 2016-01-07
Major enhancements in PostgreSQL 9.5 include:
      Allow INSERTs
      that would generate constraint conflicts to be turned into
      UPDATEs or ignored
     
      Add GROUP BY analysis features GROUPING SETS,
      CUBE and
      ROLLUP
     
Create mechanisms for tracking the progress of replication, including methods for identifying the origin of individual changes during logical replication
Add Block Range Indexes (BRIN)
Substantial performance improvements for sorting
Substantial performance improvements for multi-CPU machines
The above items are explained in more detail in the sections below.
A dump/restore using pg_dumpall, or use of pg_upgrade, is required for those wishing to migrate data from any previous release.
Version 9.5 contains a number of changes that may affect compatibility with previous releases. Observe the following incompatibilities:
Adjust operator precedence to match the SQL standard (Tom Lane)
      The precedence of <=, >=
      and <> has been reduced to match that of
      <, >
      and =.  The precedence of IS tests
      (e.g., x IS NULL) has been reduced to be
      just below these six comparison operators.
      Also, multi-keyword operators beginning with NOT now have
      the precedence of their base operator (for example, NOT
      BETWEEN now has the same precedence as BETWEEN) whereas
      before they had inconsistent precedence, behaving like NOT
      with respect to their left operand but like their base operator with
      respect to their right operand.  The new configuration
      parameter operator_precedence_warning can be
      enabled to warn about queries in which these precedence changes result
      in different parsing choices.
     
      Change pg_ctl's default shutdown mode from
      smart to fast (Bruce Momjian)
     
This means the default behavior will be to forcibly cancel existing database sessions, not simply wait for them to exit.
Use assignment cast behavior for data type conversions in PL/pgSQL assignments, rather than converting to and from text (Tom Lane)
      This change causes conversions of Booleans to strings to
      produce true or false, not t
      or f.  Other type conversions may succeed in more cases
      than before; for example, assigning a numeric value 3.9 to
      an integer variable will now assign 4 rather than failing.  If no
      assignment-grade cast is defined for the particular source and
      destination types, PL/pgSQL will fall back to its old
      I/O conversion behavior.
     
Allow characters in server command-line options to be escaped with a backslash (Andres Freund)
      Formerly, spaces in the options string always separated options, so
      there was no way to include a space in an option value.  Including
      a backslash in an option value now requires writing \\.
     
      Change the default value of the GSSAPI include_realm parameter to 1, so
      that by default the realm is not removed from a GSS
      or SSPI principal name (Stephen Frost)
     
      Replace configuration parameter checkpoint_segments
      with min_wal_size
      and max_wal_size (Heikki Linnakangas)
     
      If you previously adjusted checkpoint_segments, the
      following formula will give you an approximately equivalent setting:
max_wal_size = (3 * checkpoint_segments) * 16MB
      Note that the default setting for max_wal_size is
      much higher than the default checkpoint_segments used
      to be, so adjusting it might no longer be necessary.
     
        Control the Linux OOM killer via new environment
        variables PG_OOM_ADJUST_FILE
        and PG_OOM_ADJUST_VALUE,
        instead of compile-time options LINUX_OOM_SCORE_ADJ and
        LINUX_OOM_ADJ
        (Gurjeet Singh)
       
      Decommission server configuration
      parameter ssl_renegotiation_limit, which was deprecated
      in earlier releases (Andres Freund)
     
      While SSL renegotiation is a good idea in theory, it has caused enough
      bugs to be considered a net negative in practice, and it is due to be
      removed from future versions of the relevant standards.  We have
      therefore removed support for it from PostgreSQL.
      The ssl_renegotiation_limit parameter still exists, but
      cannot be set to anything but zero (disabled).  It's not documented
      anymore, either.
     
      Remove server configuration parameter autocommit, which
      was already deprecated and non-operational (Tom Lane)
     
      Remove the pg_authid
      catalog's rolcatupdate field, as it had no usefulness
      (Adam Brightwell)
     
      The pg_stat_replication
      system view's sent field is now NULL, not zero, when
      it has no valid value (Magnus Hagander)
     
      Allow json and jsonb array extraction operators to
      accept negative subscripts, which count from the end of JSON arrays
      (Peter Geoghegan, Andrew Dunstan)
     
      Previously, these operators returned NULL for negative
      subscripts.
     
Below you will find a detailed account of the changes between PostgreSQL 9.5 and the previous major release.
Add Block Range Indexes (BRIN) (Álvaro Herrera)
BRIN indexes store only summary data (such as minimum and maximum values) for ranges of heap blocks. They are therefore very compact and cheap to update; but if the data is naturally clustered, they can still provide substantial speedup of searches.
Allow queries to perform accurate distance filtering of bounding-box-indexed objects (polygons, circles) using GiST indexes (Alexander Korotkov, Heikki Linnakangas)
Previously, to exploit such an index a subquery had to be used to select a large number of rows ordered by bounding-box distance, and the result then had to be filtered further with a more accurate distance calculation.
Allow GiST indexes to perform index-only scans (Anastasia Lubennikova, Heikki Linnakangas, Andreas Karlsson)
Add configuration parameter gin_pending_list_limit to control the size of GIN pending lists (Fujii Masao)
        This value can also be set on a per-index basis as an index storage
        parameter.  Previously the pending-list size was controlled
        by work_mem, which was awkward because
        appropriate values for work_mem are often much too large
        for this purpose.
       
Issue a warning during the creation of hash indexes because they are not crash-safe (Bruce Momjian)
        Improve the speed of sorting of varchar, text,
        and numeric fields via “abbreviated” keys
        (Peter Geoghegan, Andrew Gierth, Robert Haas)
       
        Extend the infrastructure that allows sorting to be performed by
        inlined, non-SQL-callable comparison functions to
        cover CREATE INDEX, REINDEX, and
        CLUSTER (Peter Geoghegan)
       
Improve performance of hash joins (Tomas Vondra, Robert Haas)
Improve concurrency of shared buffer replacement (Robert Haas, Amit Kapila, Andres Freund)
Reduce the number of page locks and pins during index scans (Kevin Grittner)
The primary benefit of this is to allow index vacuums to be blocked less often.
Make per-backend tracking of buffer pins more memory-efficient (Andres Freund)
Improve lock scalability (Andres Freund)
This particularly addresses scalability problems when running on systems with multiple CPU sockets.
Allow the optimizer to remove unnecessary references to left-joined subqueries (David Rowley)
Allow pushdown of query restrictions into subqueries with window functions, where appropriate (David Rowley)
Allow a non-leakproof function to be pushed down into a security barrier view if the function does not receive any view output columns (Dean Rasheed)
        Teach the planner to use statistics obtained from an expression
        index on a boolean-returning function, when a matching function call
        appears in WHERE (Tom Lane)
       
        Make ANALYZE compute basic statistics (null fraction and
        average column width) even for columns whose data type lacks an
        equality function (Oleksandr Shulgin)
       
Speed up CRC (cyclic redundancy check) computations and switch to CRC-32C (Abhijit Menon-Sen, Heikki Linnakangas)
Improve bitmap index scan performance (Teodor Sigaev, Tom Lane)
        Speed up CREATE INDEX by avoiding unnecessary memory
        copies (Robert Haas)
       
Increase the number of buffer mapping partitions (Amit Kapila, Andres Freund, Robert Haas)
This improves performance for highly concurrent workloads.
        Add per-table autovacuum logging control via new
        log_autovacuum_min_duration storage parameter
        (Michael Paquier)
       
Add new configuration parameter cluster_name (Thomas Munro)
        This string, typically set in postgresql.conf,
        allows clients to identify the cluster.  This name also appears
        in the process title of all server processes, allowing for easier
        identification of processes belonging to the same cluster.
       
Prevent non-superusers from changing log_disconnections on connection startup (Fujii Masao)
Check “Subject Alternative Names” in SSL server certificates, if present (Alexey Klyukin)
When they are present, this replaces checks against the certificate's “Common Name”.
        Add system view pg_stat_ssl to report
        SSL connection information (Magnus Hagander)
       
Add libpq functions to return SSL information in an implementation-independent way (Heikki Linnakangas)
        While PQgetssl() can
        still be used to call OpenSSL functions, it is now
        considered deprecated because future versions
        of libpq might support other SSL
        implementations.  When possible, use the new
        functions PQsslAttribute(), PQsslAttributeNames(),
        and PQsslInUse()
        to obtain SSL information in
        an SSL-implementation-independent way.
       
Make libpq honor any OpenSSL thread callbacks (Jan Urbanski)
Previously they were overwritten.
        Replace configuration parameter checkpoint_segments
        with min_wal_size
        and max_wal_size (Heikki Linnakangas)
       
        This change allows the allocation of a large number of WAL
        files without keeping them after they are no longer needed.
        Therefore the default for max_wal_size has been set
        to 1GB, much larger than the old default
        for checkpoint_segments.
        Also note that standby servers perform restartpoints to try to limit
        their WAL space consumption to max_wal_size; previously
        they did not pay any attention to checkpoint_segments.
       
        Control the Linux OOM killer via new environment
        variables PG_OOM_ADJUST_FILE
        and PG_OOM_ADJUST_VALUE
        (Gurjeet Singh)
       
        The previous OOM control infrastructure involved
        compile-time options LINUX_OOM_SCORE_ADJ and
        LINUX_OOM_ADJ, which are no longer supported.
        The new behavior is available in all builds.
       
Allow recording of transaction commit time stamps when configuration parameter track_commit_timestamp is enabled (Álvaro Herrera, Petr Jelínek)
        Time stamp information can be accessed using functions pg_xact_commit_timestamp()
        and pg_last_committed_xact().
       
        Allow local_preload_libraries to be set
        by ALTER ROLE SET (Peter Eisentraut, Kyotaro Horiguchi)
       
Allow autovacuum workers to respond to configuration parameter changes during a run (Michael Paquier)
Make configuration parameter debug_assertions read-only (Andres Freund)
        This means that assertions can no longer be turned
        off if they were enabled at compile time, allowing for more
        efficient code optimization.  This change also removes the postgres -A option.
       
Allow setting effective_io_concurrency on systems where it has no effect (Peter Eisentraut)
        Add system view pg_file_settings
        to show the contents of the server's configuration files
        (Sawada Masahiko)
       
        Add pending_restart to the system view pg_settings to
        indicate a change has been made but will not take effect until a
        database restart (Peter Eisentraut)
       
        Allow ALTER SYSTEM
        values to be reset with ALTER SYSTEM RESET (Vik
        Fearing)
       
        This command removes the specified setting
        from postgresql.auto.conf.
       
Create mechanisms for tracking the progress of replication, including methods for identifying the origin of individual changes during logical replication (Andres Freund)
This is helpful when implementing replication solutions.
Rework truncation of the multixact commit log to be properly WAL-logged (Andres Freund)
This makes things substantially simpler and more robust.
        Add recovery.conf
        parameter recovery_target_action
        to control post-recovery activity (Petr Jelínek)
       
        This replaces the old parameter pause_at_recovery_target.
       
        Add new archive_mode value
        always to allow standbys to always archive received
        WAL files (Fujii Masao)
       
Add configuration parameter wal_retrieve_retry_interval to control WAL read retry after failure (Alexey Vasiliev, Michael Paquier)
This is particularly helpful for warm standbys.
Allow compression of full-page images stored in WAL (Rahila Syed, Michael Paquier)
This feature reduces WAL volume, at the cost of more CPU time spent on WAL logging and WAL replay. It is controlled by a new configuration parameter wal_compression, which currently is off by default.
        Archive WAL files with suffix .partial
        during standby promotion (Heikki Linnakangas)
       
Add configuration parameter log_replication_commands to log replication commands (Fujii Masao)
        By default, replication commands, e.g. IDENTIFY_SYSTEM,
        are not logged, even when log_statement is set
        to all.
       
        Report the processes holding replication slots in pg_replication_slots
        (Craig Ringer)
       
        The new output column is active_pid.
       
        Allow recovery.conf's primary_conninfo setting to
        use connection URIs, e.g. postgres://
        (Alexander Shulgin)
       
        Allow INSERTs
        that would generate constraint conflicts to be turned into
        UPDATEs or ignored (Peter Geoghegan, Heikki
        Linnakangas, Andres Freund)
       
        The syntax is INSERT ... ON CONFLICT DO NOTHING/UPDATE.
        This is the Postgres implementation of the popular
        UPSERT command.
       
        Add GROUP BY analysis features GROUPING SETS,
        CUBE and
        ROLLUP
        (Andrew Gierth, Atri Sharma)
       
        Allow setting multiple target columns in
        an UPDATE from the result of
        a single sub-SELECT (Tom Lane)
       
        This is accomplished using the syntax UPDATE tab SET
        (col1, col2, ...) = (SELECT ...).
       
        Add SELECT option
        SKIP LOCKED to skip locked rows (Thomas Munro)
       
        This does not throw an error for locked rows like
        NOWAIT does.
       
        Add SELECT option
        TABLESAMPLE to return a subset of a table (Petr
        Jelínek)
       
This feature supports the SQL-standard table sampling methods. In addition, there are provisions for user-defined table sampling methods.
Suggest possible matches for mistyped column names (Peter Geoghegan, Robert Haas)
        Add more details about sort ordering in EXPLAIN output (Marius Timmer,
        Lukas Kreft, Arne Scheffer)
       
        Details include COLLATE, DESC,
        USING, and NULLS FIRST/LAST.
       
        Make VACUUM log the
        number of pages skipped due to pins (Jim Nasby)
       
        Make TRUNCATE properly
        update the pg_stat* tuple counters (Alexander Shulgin)
       
        Allow REINDEX to reindex an entire schema using the
        SCHEMA option (Sawada Masahiko)
       
        Add VERBOSE option to REINDEX (Sawada
        Masahiko)
       
        Prevent REINDEX DATABASE and SCHEMA
        from outputting object names, unless VERBOSE is used
        (Simon Riggs)
       
        Remove obsolete FORCE option from REINDEX
        (Fujii Masao)
       
Add row-level security control (Craig Ringer, KaiGai Kohei, Adam Brightwell, Dean Rasheed, Stephen Frost)
        This feature allows row-by-row control over which users can add,
        modify, or even see rows in a table.  This is controlled by new
        commands CREATE/ALTER/DROP POLICY and ALTER TABLE ... ENABLE/DISABLE
        ROW SECURITY.
       
        Allow changing of the WAL
        logging status of a table after creation with ALTER TABLE ... SET LOGGED /
        UNLOGGED (Fabrízio de Royes Mello)
       
        Add IF NOT EXISTS clause to CREATE TABLE AS,
        CREATE INDEX,
        CREATE SEQUENCE,
        and CREATE
        MATERIALIZED VIEW (Fabrízio de Royes Mello)
       
        Add support for IF EXISTS to ALTER TABLE ... RENAME
        CONSTRAINT (Bruce Momjian)
       
        Allow some DDL commands to accept CURRENT_USER
        or SESSION_USER, meaning the current user or session
        user, in place of a specific user name (Kyotaro Horiguchi,
        Álvaro Herrera)
       
        This feature is now supported in
        ALTER USER, ALTER GROUP,
        ALTER ROLE, GRANT,
        and ALTER  commands.
       object OWNER TO
Support comments on domain constraints (Álvaro Herrera)
Reduce lock levels of some create and alter trigger and foreign key commands (Simon Riggs, Andreas Karlsson)
        Allow LOCK TABLE ... ROW EXCLUSIVE
        MODE for those with INSERT privileges on the
        target table (Stephen Frost)
       
        Previously this command required UPDATE, DELETE,
        or TRUNCATE privileges.
       
        Apply table and domain CHECK constraints in order by name
        (Tom Lane)
       
The previous ordering was indeterminate.
        Allow CREATE/ALTER DATABASE
        to manipulate datistemplate and
        datallowconn (Vik Fearing)
       
        This allows these per-database settings to be
        changed without manually modifying the pg_database
        system catalog.
       
Add support for IMPORT FOREIGN SCHEMA (Ronan Dunklau, Michael Paquier, Tom Lane)
This command allows automatic creation of local foreign tables that match the structure of existing tables on a remote server.
        Allow CHECK constraints to be placed on foreign tables
        (Shigeru Hanada, Etsuro Fujita)
       
Such constraints are assumed to be enforced on the remote server, and are not enforced locally. However, they are assumed to hold for purposes of query optimization, such as constraint exclusion.
Allow foreign tables to participate in inheritance (Shigeru Hanada, Etsuro Fujita)
        To let this work naturally, foreign tables are now allowed to have
        check constraints marked as not valid, and to set storage
        and OID characteristics, even though these operations are
        effectively no-ops for a foreign table.
       
Allow foreign data wrappers and custom scans to implement join pushdown (KaiGai Kohei)
         Whenever a ddl_command_end event trigger is installed,
         capture details of DDL activity for it to inspect
         (Álvaro Herrera)
        
         This information is available through a set-returning function pg_event_trigger_ddl_commands(),
         or by inspection of C data structures if that function doesn't
         provide enough detail.
        
         Allow event triggers on table rewrites caused by ALTER TABLE (Dimitri
         Fontaine)
        
         Add event trigger support for database-level COMMENT, SECURITY LABEL,
         and GRANT/REVOKE (Álvaro Herrera)
        
         Add columns to the output of pg_event_trigger_dropped_objects
         (Álvaro Herrera)
        
This allows simpler processing of delete operations.
       Allow the xml data type
       to accept empty or all-whitespace content values (Peter Eisentraut)
      
This is required by the SQL/XML specification.
       Allow macaddr input
       using the format xxxx-xxxx-xxxx (Herwin Weststrate)
      
       Disallow non-SQL-standard syntax for interval with
       both precision and field specifications (Bruce Momjian)
      
       Per the standard, such type specifications should be written as,
       for example, INTERVAL MINUTE TO SECOND(2).
       PostgreSQL formerly allowed this to be written as
       INTERVAL(2) MINUTE TO SECOND, but it must now be
       written in the standard way.
      
       Add selectivity estimators for inet/cidr operators and improve
       estimators for text search functions (Emre Hasegeli, Tom Lane)
      
       Add data
       types regrole
       and regnamespace
       to simplify entering and pretty-printing the OID of a role
       or namespace (Kyotaro Horiguchi)
      
        Add jsonb functions jsonb_set()
        and jsonb_pretty()
        (Dmitry Dolgov, Andrew Dunstan, Petr Jelínek)
       
        Add jsonb generator functions to_jsonb(),
        jsonb_object(),
        jsonb_build_object(),
        jsonb_build_array(),
        jsonb_agg(),
        and jsonb_object_agg()
        (Andrew Dunstan)
       
        Equivalent functions already existed for type json.
       
        Reduce casting requirements to/from json and jsonb (Tom Lane)
       
        Allow text, text array, and integer
        values to be subtracted
        from jsonb documents (Dmitry Dolgov, Andrew Dunstan)
       
        Add jsonb || operator
        (Dmitry Dolgov, Andrew Dunstan)
       
        Add json_strip_nulls()
        and jsonb_strip_nulls()
        functions to remove JSON null values from documents
        (Andrew Dunstan)
       
        Add generate_series()
        for numeric values (Plato Malugin)
       
        Allow array_agg() and
        ARRAY() to take arrays as inputs (Ali Akbar, Tom Lane)
       
        Add functions array_position()
        and array_positions()
        to return subscripts of array values (Pavel Stehule)
       
        Add a point-to-polygon distance operator
        <->
        (Alexander Korotkov)
       
        Allow multibyte characters as escapes in SIMILAR TO
        and SUBSTRING
        (Jeff Davis)
       
Previously, only a single-byte character was allowed as an escape.
        Add a width_bucket()
        variant that supports any sortable data type and non-uniform bucket
        widths (Petr Jelínek)
       
        Add an optional missing_ok argument to pg_read_file()
        and related functions (Michael Paquier, Heikki Linnakangas)
       
        Allow =>
        to specify named parameters in function calls (Pavel Stehule)
       
        Previously only := could be used.  This requires removing
        the possibility for => to be a user-defined operator.
        Creation of user-defined => operators has been issuing
        warnings since PostgreSQL 9.0.
       
Add POSIX-compliant rounding for platforms that use PostgreSQL-supplied rounding functions (Pedro Gimeno Fortea)
        Add function pg_get_object_address()
        to return OIDs that uniquely
        identify an object, and function pg_identify_object_as_address()
        to return object information based on OIDs (Álvaro
        Herrera)
       
        Loosen security checks for viewing queries in pg_stat_activity,
        executing pg_cancel_backend(),
        and executing pg_terminate_backend()
        (Stephen Frost)
       
Previously, only the specific role owning the target session could perform these operations; now membership in that role is sufficient.
        Add pg_stat_get_snapshot_timestamp()
        to output the time stamp of the statistics snapshot (Matt Kelly)
       
This represents the last time the snapshot file was written to the file system.
        Add mxid_age()
        to compute multi-xid age (Bruce Momjian)
       
Improve support for composite types in PL/Python (Ed Behn, Ronan Dunklau)
This allows PL/Python functions to return arrays of composite types.
Reduce lossiness of PL/Python floating-point value conversions (Marko Kreen)
Allow specification of conversion routines between SQL data types and data types of procedural languages (Peter Eisentraut)
       This change adds new commands CREATE/DROP TRANSFORM.
       This also adds optional transformations between the hstore and ltree types to/from PL/Perl and PL/Python.
      
       Move pg_archivecleanup,
       pg_test_fsync,
       pg_test_timing,
       and pg_xlogdump
       from contrib to src/bin (Peter Eisentraut)
      
This should result in these programs being installed by default in most installations.
Add pg_rewind, which allows re-synchronizing a master server after failback (Heikki Linnakangas)
Allow pg_receivexlog to manage physical replication slots (Michael Paquier)
       This is controlled via new --create-slot and
       --drop-slot options.
      
       Allow pg_receivexlog
       to synchronously flush WAL to storage using new
       --synchronous option (Furuya Osamu, Fujii Masao)
      
Without this, WAL files are fsync'ed only on close.
       Allow vacuumdb to
       vacuum in parallel using new --jobs option (Dilip Kumar)
      
In vacuumdb, do not prompt for the same password repeatedly when multiple connections are necessary (Haribabu Kommi, Michael Paquier)
       Add --verbose option to reindexdb (Sawada
       Masahiko)
      
Make pg_basebackup use a tablespace mapping file when using tar format, to support symbolic links and file paths of 100+ characters in length on MS Windows (Amit Kapila)
       Add pg_xlogdump option
       --stats to display summary statistics (Abhijit Menon-Sen)
      
Allow psql to produce AsciiDoc output (Szymon Guz)
         Add an errors mode that displays only failed commands
         to psql's ECHO variable
         (Pavel Stehule)
        
         This behavior can also be selected with psql's
         -b option.
        
Provide separate column, header, and border linestyle control in psql's unicode linestyle (Pavel Stehule)
         Single or double lines are supported; the default is
         single.
        
         Add new option %l in psql's PROMPT variables
         to display the current multiline statement line number
         (Sawada Masahiko)
        
         Add \pset option pager_min_lines
         to control pager invocation (Andrew Dunstan)
        
Improve psql line counting used when deciding to invoke the pager (Andrew Dunstan)
         psql now fails if the file specified by
         an --output or --log-file switch cannot be
         written (Tom Lane, Daniel Vérité)
        
Previously, it effectively ignored the switch in such cases.
Add psql tab completion when setting the search_path variable (Jeff Janes)
Currently only the first schema can be tab-completed.
Improve psql's tab completion for triggers and rules (Andreas Karlsson)
         Add psql \? help sections
         variables and options (Pavel Stehule)
        
         \? variables shows psql's special
         variables and \? options shows the command-line options.
         \? commands shows the meta-commands, which is the
         traditional output and remains the default.  These help displays
         can also be obtained with the command-line
         option --help=.
        section
         Show tablespace size in psql's \db+
         (Fabrízio de Royes Mello)
        
         Show data type owners in psql's \dT+
         (Magnus Hagander)
        
         Allow psql's \watch to output
         \timing information (Fujii Masao)
        
         Also prevent --echo-hidden from echoing
         \watch queries, since that is generally unwanted.
        
         Make psql's \sf and \ef
         commands honor ECHO_HIDDEN (Andrew Dunstan)
        
         Improve psql tab completion for \set,
         \unset, and :variable names (Pavel
         Stehule)
        
         Allow tab completion of role names
         in psql \c commands (Ian Barwick)
        
        Allow pg_dump to share a snapshot taken by another
        session using --snapshot (Simon Riggs, Michael Paquier)
       
        The remote snapshot must have been exported by
        pg_export_snapshot() or logical replication slot
        creation.  This can be used to share a consistent snapshot
        across multiple pg_dump processes.
       
Support table sizes exceeding 8GB in tar archive format (Tom Lane)
The POSIX standard for tar format does not allow elements of a tar archive to exceed 8GB, but most modern implementations of tar support an extension that does allow it. Use the extension format when necessary, rather than failing.
Make pg_dump always print the server and pg_dump versions (Jing Wang)
        Previously, version information was only printed in
        --verbose mode.
       
        Remove the long-ignored -i/--ignore-version
        option from pg_dump, pg_dumpall,
        and pg_restore (Fujii Masao)
       
        Support multiple pg_ctl -o options,
        concatenating their values (Bruce Momjian)
       
Allow control of pg_ctl's event source logging on MS Windows (MauMau)
        This only controls pg_ctl, not the server, which
        has separate settings in postgresql.conf.
       
        If the server's listen address is set to a wildcard value
        (0.0.0.0 in IPv4 or :: in IPv6), connect via
        the loopback address rather than trying to use the wildcard address
        literally (Kondo Yuta)
       
This fix primarily affects Windows, since on other platforms pg_ctl will prefer to use a Unix-domain socket.
        Move pg_upgrade from contrib to
        src/bin (Peter Eisentraut)
       
In connection with this change, the functionality previously provided by the pg_upgrade_support module has been moved into the core server.
        Support multiple pg_upgrade
        -o/-O options,
        concatenating their values (Bruce Momjian)
       
Improve database collation comparisons in pg_upgrade (Heikki Linnakangas)
Remove support for upgrading from 8.3 clusters (Bruce Momjian)
        Move pgbench from contrib to src/bin
        (Peter Eisentraut)
       
Fix calculation of TPS number “excluding connections establishing” (Tatsuo Ishii, Fabien Coelho)
The overhead for connection establishment was miscalculated whenever the number of pgbench threads was less than the number of client connections. Although this is clearly a bug, we won't back-patch it into pre-9.5 branches since it makes TPS numbers not comparable to previous results.
Allow counting of pgbench transactions that take over a specified amount of time (Fabien Coelho)
        This is controlled by a new --latency-limit option.
       
        Allow pgbench to generate Gaussian/exponential distributions
        using \setrandom (Kondo Mitsumasa, Fabien Coelho)
       
        Allow pgbench's \set command to handle
        arithmetic expressions containing more than one operator, and add
        % (modulo) to the set of operators it supports
        (Robert Haas, Fabien Coelho)
       
Simplify WAL record format (Heikki Linnakangas)
This allows external tools to more easily track what blocks are modified.
Improve the representation of transaction commit and abort WAL records (Andres Freund)
Add atomic memory operations API (Andres Freund)
Allow custom path and scan methods (KaiGai Kohei, Tom Lane)
This allows extensions greater control over the optimizer and executor.
Allow foreign data wrappers to do post-filter locking (Etsuro Fujita)
        Foreign tables can now take part in INSERT ... ON CONFLICT
        DO NOTHING queries (Peter Geoghegan, Heikki Linnakangas,
        Andres Freund)
       
        Foreign data wrappers must be modified to handle this.
        INSERT ... ON CONFLICT DO UPDATE is not supported on
        foreign tables.
       
        Improve hash_create()'s API for selecting
        simple-binary-key hash functions (Teodor Sigaev, Tom Lane)
       
Improve parallel execution infrastructure (Robert Haas, Amit Kapila, Noah Misch, Rushabh Lathia, Jeevan Chalke)
Remove Alpha (CPU) and Tru64 (OS) ports (Andres Freund)
Remove swap-byte-based spinlock implementation for ARMv5 and earlier CPUs (Robert Haas)
ARMv5's weak memory ordering made this locking implementation unsafe. Spinlock support is still possible on newer gcc implementations with atomics support.
Generate an error when excessively long (100+ character) file paths are written to tar files (Peter Eisentraut)
Tar does not support such overly-long paths.
        Change index operator class for columns pg_seclabel.provider
        and pg_shseclabel.provider
        to be text_pattern_ops (Tom Lane)
       
This avoids possible problems with these indexes when different databases of a cluster have different default collations.
Change the spinlock primitives to function as compiler barriers (Robert Haas)
Allow higher-precision time stamp resolution on Windows 8, Windows Server 2012, and later Windows systems (Craig Ringer)
        Install shared libraries to bin in MS Windows (Peter Eisentraut, Michael Paquier)
       
        Install src/test/modules together with
        contrib on MSVC builds (Michael
        Paquier)
       
        Allow configure's
        --with-extra-version option to be honored by the
        MSVC build (Michael Paquier)
       
        Pass PGFILEDESC into MSVC contrib builds
        (Michael Paquier)
       
Add icons to all MSVC-built binaries and version information to all MS Windows binaries (Noah Misch)
MinGW already had such icons.
        Add optional-argument support to the internal
        getopt_long() implementation (Michael Paquier,
        Andres Freund)
       
This is used by the MSVC build.
Add statistics for minimum, maximum, mean, and standard deviation times to pg_stat_statements (Mitsumasa Kondo, Andrew Dunstan)
       Add pgcrypto function
       pgp_armor_headers() to extract PGP
       armor headers (Marko Tiikkaja, Heikki Linnakangas)
      
Allow empty replacement strings in unaccent (Mohammad Alhashash)
This is useful in languages where diacritic signs are represented as separate characters.
Allow multicharacter source strings in unaccent (Tom Lane)
This could be useful in languages where diacritic signs are represented as separate characters. It also allows more complex unaccent dictionaries.
       Add contrib modules tsm_system_rows and
       tsm_system_time
       to allow additional table sampling methods (Petr Jelínek)
      
Add GIN index inspection functions to pageinspect (Heikki Linnakangas, Peter Geoghegan, Michael Paquier)
Add information about buffer pins to pg_buffercache display (Andres Freund)
       Allow pgstattuple
       to report approximate answers with less overhead using
       pgstattuple_approx() (Abhijit Menon-Sen)
      
       Move dummy_seclabel, test_shm_mq,
       test_parser, and worker_spi
       from contrib to src/test/modules
       (Álvaro Herrera)
      
These modules are only meant for server testing, so they do not need to be built or installed when packaging PostgreSQL.