Release date: 2008-02-04
With significant new functionality and performance enhancements, this release represents a major leap forward for PostgreSQL. This was made possible by a growing community that has dramatically accelerated the pace of development. This release adds the following major features:
Full text search is integrated into the core database system
      Support for the SQL/XML standard, including new operators and an
      XML data type
     
      Enumerated data types (ENUM)
     
Arrays of composite types
      Universally Unique Identifier (UUID) data type
     
      Add control over whether NULLs sort first or last
     
Updatable cursors
Server configuration parameters can now be set on a per-function basis
User-defined types can now have type modifiers
Automatically re-plan cached queries when table definitions change or statistics are updated
Numerous improvements in logging and statistics collection
Support Security Service Provider Interface (SSPI) for authentication on Windows
Support multiple concurrent autovacuum processes, and other autovacuum improvements
Allow the whole PostgreSQL distribution to be compiled with Microsoft Visual C++
Major performance improvements are listed below. Most of these enhancements are automatic and do not require user changes or tuning:
Asynchronous commit delays writes to WAL during transaction commit
Checkpoint writes can be spread over a longer time period to smooth the I/O spike during each checkpoint
      Heap-Only Tuples (HOT) accelerate space reuse for
      most UPDATEs and DELETEs
     
Just-in-time background writer strategy improves disk write efficiency
      Using non-persistent transaction IDs for read-only transactions
      reduces overhead and VACUUM requirements
     
Per-field and per-row storage overhead has been reduced
Large sequential scans no longer force out frequently used cached pages
Concurrent large sequential scans can now share disk reads
      ORDER BY ... LIMIT can be done without sorting
     
The above items are explained in more detail in the sections below.
A dump/restore using pg_dump is required for those wishing to migrate data from any previous release.
Observe the following incompatibilities:
       Non-character data types are no longer automatically cast to
       TEXT (Peter, Tom)
      
       Previously, if a non-character value was supplied to an operator or
       function that requires text input, it was automatically
       cast to text, for most (though not all) built-in data types.
       This no longer happens: an explicit cast to text is now
       required for all non-character-string types.  For example, these
       expressions formerly worked:
substr(current_date, 1, 4) 23 LIKE '2%'
but will now draw “function does not exist” and “operator does not exist” errors respectively. Use an explicit cast instead:
substr(current_date::text, 1, 4) 23::text LIKE '2%'
       (Of course, you can use the more verbose CAST() syntax too.)
       The reason for the change is that these automatic casts too often caused
       surprising behavior.  An example is that in previous releases, this
       expression was accepted but did not do what was expected:
current_date < 2017-11-17
       This is actually comparing a date to an integer, which should be
       (and now is) rejected — but in the presence of automatic
       casts both sides were cast to text and a textual comparison
       was done, because the text < text operator was able
       to match the expression when no other < operator could.
      
       Types char( and
       n)varchar( still cast to n)text
       automatically.  Also, automatic casting to text still works for
       inputs to the concatenation (||) operator, so long as least
       one input is a character-string type.
      
        Full text search features from contrib/tsearch2 have
        been moved into the core server, with some minor syntax changes
      
       contrib/tsearch2 now contains a compatibility
       interface.
      
       ARRAY(SELECT ...), where the SELECT
       returns no rows, now returns an empty array, rather than NULL
       (Tom)
      
The array type name for a base data type is no longer always the base type's name with an underscore prefix
       The old naming convention is still honored when possible, but
       application code should no longer depend on it. Instead
       use the new pg_type.typarray column to
       identify the array data type associated with a given type.
      
       ORDER BY ... USING operator must now
       use a less-than or greater-than operator that is
       defined in a btree operator class
      
This restriction was added to prevent inconsistent results.
       SET LOCAL changes now persist until
       the end of the outermost transaction, unless rolled back (Tom)
      
       Previously SET LOCAL's effects were lost
       after subtransaction commit (RELEASE SAVEPOINT
       or exit from a PL/pgSQL exception block).
      
Commands rejected in transaction blocks are now also rejected in multiple-statement query strings (Tom)
       For example, "BEGIN; DROP DATABASE; COMMIT" will now be
       rejected even if submitted as a single query message.
      
       ROLLBACK outside a transaction block now
       issues NOTICE instead of WARNING (Bruce)
      
       Prevent NOTIFY/LISTEN/UNLISTEN
       from accepting schema-qualified names (Bruce)
      
       Formerly, these commands accepted schema.relation but
       ignored the schema part, which was confusing.
      
       ALTER SEQUENCE no longer affects the sequence's
       currval() state (Tom)
      
Foreign keys now must match indexable conditions for cross-data-type references (Tom)
This improves semantic consistency and helps avoid performance problems.
Restrict object size functions to users who have reasonable permissions to view such information (Tom)
       For example, pg_database_size() now requires
       CONNECT permission, which is granted to everyone by
       default. pg_tablespace_size() requires
       CREATE permission in the tablespace, or is allowed if
       the tablespace is the default tablespace for the database.
      
       Remove the undocumented !!= (not in) operator (Tom)
      
       NOT IN (SELECT ...) is the proper way to
       perform this operation.
      
Internal hashing functions are now more uniformly-distributed (Tom)
If application code was computing and storing hash values using internal PostgreSQL hashing functions, the hash values must be regenerated.
C-code conventions for handling variable-length data values have changed (Greg Stark, Tom)
       The new SET_VARSIZE() macro must be used
       to set the length of generated varlena values. Also, it
       might be necessary to expand (“de-TOAST”) input values
       in more cases.
      
       Continuous archiving no longer reports each successful archive
       operation to the server logs unless DEBUG level is used
       (Simon)
      
Numerous changes in administrative server parameters
       bgwriter_lru_percent,
       bgwriter_all_percent,
       bgwriter_all_maxpages,
       stats_start_collector, and
       stats_reset_on_server_start are removed.
       redirect_stderr is renamed to
       logging_collector.
       stats_command_string is renamed to
       track_activities.
       stats_block_level and stats_row_level
       are merged into track_counts.
       A new boolean configuration parameter, archive_mode,
       controls archiving. Autovacuum's default settings have changed.
      
       Remove stats_start_collector parameter (Tom)
      
We now always start the collector process, unless UDP socket creation fails.
       Remove stats_reset_on_server_start parameter (Tom)
      
       This was removed because pg_stat_reset()
       can be used for this purpose.
      
       Commenting out a parameter in postgresql.conf now
       causes it to revert to its default value (Joachim Wieland)
      
Previously, commenting out an entry left the parameter's value unchanged until the next server restart.
Add more checks for invalidly-encoded data (Andrew)
       This change plugs some holes that existed in literal backslash
       escape string processing and COPY escape
       processing. Now the de-escaped string is rechecked to see if the
       result created an invalid multi-byte character.
      
Disallow database encodings that are inconsistent with the server's locale setting (Tom)
       On most platforms, C locale is the only locale that
       will work with any database encoding.  Other locale settings imply
       a specific encoding and will misbehave if the database encoding
       is something different.  (Typical symptoms include bogus textual
       sort order and wrong results from upper() or
       lower().)  The server now rejects attempts to create
       databases that have an incompatible encoding.
      
       Ensure that chr() cannot create
       invalidly-encoded values (Andrew)
      
       In UTF8-encoded databases the argument of chr() is
       now treated as a Unicode code point. In other multi-byte encodings
       chr()'s argument must designate a 7-bit ASCII
       character.  Zero is no longer accepted.
       ascii() has been adjusted to match.
      
       Adjust convert() behavior to ensure encoding
       validity (Andrew)
      
       The two argument form of convert() has been
       removed. The three argument form now takes a bytea
       first argument and returns a bytea. To cover the
       loss of functionality, three new functions have been added:
      
         convert_from(bytea, name) returns
         text — converts the first argument from the named
         encoding to the database encoding
        
         convert_to(text, name) returns
         bytea — converts the first argument from the
         database encoding to the named encoding
        
         length(bytea, name) returns
         integer — gives the length of the first
         argument in characters in the named encoding
        
       Remove convert(argument USING conversion_name)
       (Andrew)
      
Its behavior did not match the SQL standard.
Make JOHAB encoding client-only (Tatsuo)
JOHAB is not safe as a server-side encoding.
Below you will find a detailed account of the changes between PostgreSQL 8.3 and the previous major release.
Asynchronous commit delays writes to WAL during transaction commit (Simon)
       This feature dramatically increases performance for short data-modifying
       transactions.  The disadvantage is that because disk writes are delayed,
       if the database or operating system crashes before data is written to
       the disk, committed data will be lost.  This feature is useful for
       applications that can accept some data loss.  Unlike turning off
       fsync, using asynchronous commit does not put
       database consistency at risk; the worst case is that after a crash the
       last few reportedly-committed transactions might not be committed after
       all.
       This feature is enabled by turning off synchronous_commit
       (which can be done per-session or per-transaction, if some transactions
       are critical and others are not).
       wal_writer_delay can be adjusted to control the maximum
       delay before transactions actually reach disk.
      
Checkpoint writes can be spread over a longer time period to smooth the I/O spike during each checkpoint (Itagaki Takahiro and Heikki Linnakangas)
Previously all modified buffers were forced to disk as quickly as possible during a checkpoint, causing an I/O spike that decreased server performance. This new approach spreads out disk writes during checkpoints, reducing peak I/O usage. (User-requested and shutdown checkpoints are still written as quickly as possible.)
       Heap-Only Tuples (HOT) accelerate space reuse for most
       UPDATEs and DELETEs (Pavan Deolasee, with
       ideas from many others)
      
       UPDATEs and DELETEs leave dead tuples
       behind, as do failed INSERTs.  Previously only
       VACUUM could reclaim space taken by dead tuples. With
       HOT dead tuple space can be automatically reclaimed at
       the time of INSERT or UPDATE if no changes
       are made to indexed columns.  This allows for more consistent
       performance.  Also, HOT avoids adding duplicate index
       entries.
      
Just-in-time background writer strategy improves disk write efficiency (Greg Smith, Itagaki Takahiro)
This greatly reduces the need for manual tuning of the background writer.
Per-field and per-row storage overhead have been reduced (Greg Stark, Heikki Linnakangas)
       Variable-length data types with data values less than 128 bytes long
       will see a storage decrease of 3 to 6 bytes. For example, two adjacent
       char(1) fields now use 4 bytes instead of 16. Row headers
       are also 4 bytes shorter than before.
      
       Using non-persistent transaction IDs for read-only transactions
       reduces overhead and VACUUM requirements (Florian Pflug)
      
       Non-persistent transaction IDs do not increment the global
       transaction counter. Therefore, they reduce the load on
       pg_clog and increase the time between forced
       vacuums to prevent transaction ID wraparound.
       Other performance
       improvements were also made that should improve concurrency.
      
Avoid incrementing the command counter after a read-only command (Tom)
There was formerly a hard limit of 232 (4 billion) commands per transaction. Now only commands that actually changed the database count, so while this limit still exists, it should be significantly less annoying.
Create a dedicated WAL writer process to off-load work from backends (Simon)
       Skip unnecessary WAL writes for CLUSTER and
       COPY (Simon)
      
       Unless WAL archiving is enabled, the system now avoids WAL writes
       for CLUSTER and just fsync()s the
       table at the end of the command.  It also does the same for
       COPY if the table was created in the same
       transaction.
      
Large sequential scans no longer force out frequently used cached pages (Simon, Heikki, Tom)
Concurrent large sequential scans can now share disk reads (Jeff Davis)
       This is accomplished by starting the new sequential scan in the
       middle of the table (where another sequential scan is already
       in-progress) and wrapping around to the beginning to finish.  This
       can affect the order of returned rows in a query that does not
       specify ORDER BY.  The synchronize_seqscans
       configuration parameter can be used to disable this if necessary.
      
       ORDER BY ... LIMIT can be done without sorting
       (Greg Stark)
      
       This is done by sequentially scanning the table and tracking just
       the “top N” candidate rows, rather than performing a
       full sort of the entire table.  This is useful when there is no
       matching index and the LIMIT is not large.
      
Put a rate limit on messages sent to the statistics collector by backends (Tom)
This reduces overhead for short transactions, but might sometimes increase the delay before statistics are tallied.
Improve hash join performance for cases with many NULLs (Tom)
Speed up operator lookup for cases with non-exact datatype matches (Tom)
Autovacuum is now enabled by default (Alvaro)
Several changes were made to eliminate disadvantages of having autovacuum enabled, thereby justifying the change in default. Several other autovacuum parameter defaults were also modified.
Support multiple concurrent autovacuum processes (Alvaro, Itagaki Takahiro)
This allows multiple vacuums to run concurrently. This prevents vacuuming of a large table from delaying vacuuming of smaller tables.
Automatically re-plan cached queries when table definitions change or statistics are updated (Tom)
       Previously PL/pgSQL functions that referenced temporary tables
       would fail if the temporary table was dropped and recreated
       between function invocations, unless EXECUTE was
       used.  This improvement fixes that problem and many related issues.
      
       Add a temp_tablespaces parameter to control
       the tablespaces for temporary tables and files (Jaime Casanova,
       Albert Cervera, Bernd Helmle)
      
       This parameter defines a list of tablespaces to be used.  This
       enables spreading the I/O load across multiple tablespaces. A random
       tablespace is chosen each time a temporary object is created.
       Temporary files are no longer stored in per-database
       pgsql_tmp/ directories but in per-tablespace
       directories.
      
       Place temporary tables' TOAST tables in special schemas named
       pg_toast_temp_ (Tom)
      nnn
This allows low-level code to recognize these tables as temporary, which enables various optimizations such as not WAL-logging changes and using local rather than shared buffers for access. This also fixes a bug wherein backends unexpectedly held open file references to temporary TOAST tables.
Fix problem that a constant flow of new connection requests could indefinitely delay the postmaster from completing a shutdown or a crash restart (Tom)
Guard against a very-low-probability data loss scenario by preventing re-use of a deleted table's relfilenode until after the next checkpoint (Heikki)
       Fix CREATE CONSTRAINT TRIGGER
       to convert old-style foreign key trigger definitions into regular
       foreign key constraints (Tom)
      
       This will ease porting of foreign key constraints carried forward from
       pre-7.3 databases, if they were never converted using
       contrib/adddepend.
      
       Fix DEFAULT NULL to override inherited defaults (Tom)
      
       DEFAULT NULL was formerly considered a noise phrase, but it
       should (and now does) override non-null defaults that would otherwise
       be inherited from a parent table or domain.
      
Add new encodings EUC_JIS_2004 and SHIFT_JIS_2004 (Tatsuo)
These new encodings can be converted to and from UTF-8.
Change server startup log message from “database system is ready” to “database system is ready to accept connections”, and adjust its timing
The message now appears only when the postmaster is really ready to accept connections.
       Add log_autovacuum_min_duration parameter to
       support configurable logging of autovacuum activity (Simon, Alvaro)
      
       Add log_lock_waits parameter to log lock waiting
       (Simon)
      
       Add log_temp_files parameter to log temporary
       file usage (Bill Moran)
      
       Add log_checkpoints parameter to improve logging
       of checkpoints (Greg Smith, Heikki)
      
       log_line_prefix now supports
       %s and %c escapes in all
       processes (Andrew)
      
Previously these escapes worked only for user sessions, not for background database processes.
       Add log_restartpoints to control logging of
       point-in-time recovery restart points (Simon)
      
Last transaction end time is now logged at end of recovery and at each logged restart point (Simon)
       Autovacuum now reports its activity start time in
       pg_stat_activity (Tom)
      
Allow server log output in comma-separated value (CSV) format (Arul Shaji, Greg Smith, Andrew Dunstan)
CSV-format log files can easily be loaded into a database table for subsequent analysis.
Use PostgreSQL-supplied timezone support for formatting timestamps displayed in the server log (Tom)
       This avoids Windows-specific problems with localized time zone
       names that are in the wrong encoding. There is a new
       log_timezone parameter that controls the timezone
       used in log messages, independently of the client-visible
       timezone parameter.
      
       New system view pg_stat_bgwriter displays
       statistics about background writer activity (Magnus)
      
       Add new columns for database-wide tuple statistics to
       pg_stat_database (Magnus)
      
       Add an xact_start (transaction start time) column to
       pg_stat_activity (Neil)
      
This makes it easier to identify long-running transactions.
       Add n_live_tuples and n_dead_tuples columns
       to pg_stat_all_tables and related views (Glen
       Parker)
      
       Merge stats_block_level and stats_row_level
       parameters into a single parameter track_counts, which
       controls all messages sent to the statistics collector process
       (Tom)
      
       Rename stats_command_string parameter to
       track_activities (Tom)
      
Fix statistical counting of live and dead tuples to recognize that committed and aborted transactions have different effects (Tom)
Support Security Service Provider Interface (SSPI) for authentication on Windows (Magnus)
Support GSSAPI authentication (Henry Hotz, Magnus)
This should be preferred to native Kerberos authentication because GSSAPI is an industry standard.
Support a global SSL configuration file (Victor Wagner)
       Add ssl_ciphers parameter to control accepted SSL ciphers
       (Victor Wagner)
      
       Add a Kerberos realm parameter, krb_realm (Magnus)
      
Change the timestamps recorded in transaction WAL records from time_t to TimestampTz representation (Tom)
This provides sub-second resolution in WAL, which can be useful for point-in-time recovery.
Reduce WAL disk space needed by warm standby servers (Simon)
       This change allows a warm standby server to pass the name of the earliest
       still-needed WAL file to the recovery script, allowing automatic removal
       of no-longer-needed WAL files.  This is done using %r in
       the restore_command parameter of
       recovery.conf.
      
       New boolean configuration parameter, archive_mode,
       controls archiving (Simon)
      
       Previously setting archive_command to an empty string
       turned off archiving. Now archive_mode turns archiving
       on and off, independently of archive_command. This is
       useful for stopping archiving temporarily.
      
Full text search is integrated into the core database system (Teodor, Oleg)
       Text search has been improved, moved into the core code, and is now
       installed by default.  contrib/tsearch2 now contains
       a compatibility interface.
      
       Add control over whether NULLs sort first or last (Teodor, Tom)
      
       The syntax is ORDER BY ... NULLS FIRST/LAST.
      
       Allow per-column ascending/descending (ASC/DESC)
       ordering options for indexes (Teodor, Tom)
      
       Previously a query using ORDER BY with mixed
       ASC/DESC specifiers could not fully use
       an index. Now an index can be fully used in such cases if the
       index was created with matching
       ASC/DESC specifications.
       NULL sort order within an index can be controlled, too.
      
       Allow col IS NULL to use an index (Teodor)
      
Updatable cursors (Arul Shaji, Tom)
       This eliminates the need to reference a primary key to
       UPDATE or DELETE rows returned by a cursor.
       The syntax is UPDATE/DELETE WHERE CURRENT OF.
      
       Allow FOR UPDATE in cursors (Arul Shaji, Tom)
      
       Create a general mechanism that supports casts to and from the
       standard string types (TEXT, VARCHAR,
       CHAR) for every datatype, by
       invoking the datatype's I/O functions (Tom)
      
Previously, such casts were available only for types that had specialized function(s) for the purpose. These new casts are assignment-only in the to-string direction, explicit-only in the other direction, and therefore should create no surprising behavior.
       Allow UNION and related constructs to return a domain
       type, when all inputs are of that domain type (Tom)
      
Formerly, the output would be considered to be of the domain's base type.
Allow limited hashing when using two different data types (Tom)
       This allows hash joins, hash indexes, hashed subplans, and hash
       aggregation to be used in situations involving cross-data-type
       comparisons, if the data types have compatible hash functions.
       Currently, cross-data-type hashing support exists for
       smallint/integer/bigint,
       and for float4/float8.
      
       Improve optimizer logic for detecting when variables are equal
       in a WHERE clause (Tom)
      
This allows mergejoins to work with descending sort orders, and improves recognition of redundant sort columns.
Improve performance when planning large inheritance trees in cases where most tables are excluded by constraints (Tom)
Arrays of composite types (David Fetter, Andrew, Tom)
In addition to arrays of explicitly-declared composite types, arrays of the rowtypes of regular tables and views are now supported, except for rowtypes of system catalogs, sequences, and TOAST tables.
Server configuration parameters can now be set on a per-function basis (Tom)
       For example, functions can now set their own
       search_path to prevent unexpected behavior if a
       different search_path exists at run-time.  Security
       definer functions should set search_path to
       avoid security loopholes.
      
       CREATE/ALTER FUNCTION now supports
       COST and ROWS options (Tom)
      
       COST allows specification of the cost of a
       function call.  ROWS allows specification of
       the average number or rows returned by a set-returning function.
       These values are used by the optimizer in choosing the best plan.
      
       Implement CREATE TABLE LIKE ...  INCLUDING
       INDEXES (Trevor Hardcastle, Nikhil Sontakke, Neil)
      
       Allow CREATE INDEX CONCURRENTLY to ignore
       transactions in other databases (Simon)
      
       Add ALTER VIEW ... RENAME TO and ALTER
       SEQUENCE ... RENAME TO (David Fetter, Neil)
      
       Previously this could only be done via ALTER TABLE ...
       RENAME TO.
      
       Make CREATE/DROP/RENAME DATABASE wait briefly for
       conflicting backends to exit before failing (Tom)
      
This increases the likelihood that these commands will succeed.
Allow triggers and rules to be deactivated in groups using a configuration parameter, for replication purposes (Jan)
       This allows replication systems to disable triggers and rewrite
       rules as a group without modifying the system catalogs directly.
       The behavior is controlled by ALTER TABLE and a new
       parameter session_replication_role.
      
User-defined types can now have type modifiers (Teodor, Tom)
       This allows a user-defined type to take a modifier, like
       ssnum(7).  Previously only built-in
       data types could have modifiers.
      
Non-superuser database owners now are able to add trusted procedural languages to their databases by default (Jeremy Drake)
       While this is reasonably safe, some administrators might wish to
       revoke the privilege. It is controlled by
       pg_pltemplate.tmpldbacreate.
      
Allow a session's current parameter setting to be used as the default for future sessions (Tom)
       This is done with SET ... FROM CURRENT in
       CREATE/ALTER FUNCTION, ALTER
       DATABASE, or ALTER ROLE.
      
       Implement new commands DISCARD ALL,
       DISCARD PLANS, DISCARD
       TEMPORARY, CLOSE ALL, and
       DEALLOCATE ALL (Marko Kreen, Neil)
      
These commands simplify resetting a database session to its initial state, and are particularly useful for connection-pooling software.
       Make CLUSTER MVCC-safe (Heikki Linnakangas)
      
       Formerly, CLUSTER would discard all tuples
       that were committed dead, even if there were still transactions
       that should be able to see them under MVCC visibility rules.
      
       Add new CLUSTER syntax: CLUSTER
       
       (Holger Schurig)
     table USING index
       The old CLUSTER syntax is still supported, but
       the new form is considered more logical.
      
       Fix EXPLAIN so it can show complex plans
       more accurately (Tom)
      
       References to subplan outputs are now always shown correctly,
       instead of using ?column
       for complicated cases.
      N?
Limit the amount of information reported when a user is dropped (Alvaro)
       Previously, dropping (or attempting to drop) a user who owned many
       objects could result in large NOTICE or
       ERROR messages listing all these objects; this
       caused problems for some client applications.  The length of the
       message is now limited, although a full list is still sent to the
       server log.
      
       Support for the SQL/XML standard, including new operators and an
       XML data type (Nikolay Samokhvalov, Pavel Stehule, Peter)
      
       Enumerated data types (ENUM) (Tom Dunstan)
      
       This feature provides convenient support for fields that have a
       small, fixed set of allowed values.  An example of creating an
       ENUM type is
       CREATE TYPE mood AS ENUM ('sad', 'ok', 'happy').
      
       Universally Unique Identifier (UUID) data type (Gevik
       Babakhani, Neil)
      
This closely matches RFC 4122.
       Widen the MONEY data type to 64 bits (D'Arcy Cain)
      
       This greatly increases the range of supported MONEY
       values.
      
       Fix float4/float8 to handle
       Infinity and NAN (Not A Number)
       consistently (Bruce)
      
       The code formerly was not consistent about distinguishing
       Infinity from overflow conditions.
      
       Allow leading and trailing whitespace during input of
       boolean values (Neil)
      
       Prevent COPY from using digits and lowercase letters as
       delimiters (Tom)
      
       Add new regular expression functions
       regexp_matches(),
       regexp_split_to_array(), and
       regexp_split_to_table() (Jeremy Drake, Neil)
      
These functions provide extraction of regular expression subexpressions and allow splitting a string using a POSIX regular expression.
       Add lo_truncate() for large object truncation
       (Kris Jurka)
      
       Implement width_bucket() for the float8
       data type (Neil)
      
       Add pg_stat_clear_snapshot() to discard
       statistics snapshots collected during the current transaction
       (Tom)
      
The first request for statistics in a transaction takes a statistics snapshot that does not change during the transaction. This function allows the snapshot to be discarded and a new snapshot loaded during the next statistics query. This is particularly useful for PL/pgSQL functions, which are confined to a single transaction.
       Add isodow option to EXTRACT() and
       date_part() (Bruce)
      
       This returns the day of the week, with Sunday as seven.
       (dow returns Sunday as zero.)
      
       Add ID (ISO day of week) and IDDD (ISO
       day of year) format codes for to_char(),
       to_date(), and to_timestamp() (Brendan
       Jurd)
      
       Make to_timestamp() and to_date()
       assume TM (trim) option for potentially
       variable-width fields (Bruce)
      
This matches Oracle's behavior.
       Fix off-by-one conversion error in
       to_date()/to_timestamp()
       D (non-ISO day of week) fields (Bruce)
      
       Make setseed() return void, rather than a
       useless integer value (Neil)
      
       Add a hash function for NUMERIC (Neil)
      
       This allows hash indexes and hash-based plans to be used with
       NUMERIC columns.
      
       Improve efficiency of
       LIKE/ILIKE, especially for
       multi-byte character sets like UTF-8 (Andrew, Itagaki Takahiro)
      
       Make currtid() functions require
       SELECT privileges on the target table (Tom)
      
       Add several txid_*() functions to query
       active transaction IDs (Jan)
      
This is useful for various replication solutions.
       Add scrollable cursor support, including directional control in
       FETCH (Pavel Stehule)
      
       Allow IN as an alternative to
       FROM in PL/pgSQL's FETCH
       statement, for consistency with the backend's
       FETCH command (Pavel Stehule)
      
       Add MOVE to PL/pgSQL (Magnus, Pavel Stehule,
       Neil)
      
       Implement RETURN QUERY (Pavel Stehule, Neil)
      
       This adds convenient syntax for PL/pgSQL set-returning functions
       that want to return the result of a query.  RETURN QUERY
       is easier and more efficient than a loop
       around RETURN NEXT.
      
Allow function parameter names to be qualified with the function's name (Tom)
       For example, myfunc.myvar. This is particularly
       useful for specifying variables in a query where the variable
       name might match a column name.
      
Make qualification of variables with block labels work properly (Tom)
Formerly, outer-level block labels could unexpectedly interfere with recognition of inner-level record or row references.
       Tighten requirements for FOR loop
       STEP values (Tom)
      
       Prevent non-positive STEP values, and handle
       loop overflows.
      
Improve accuracy when reporting syntax error locations (Tom)
       Allow type-name arguments to PL/Perl
       spi_prepare() to be data type aliases in
       addition to names found in pg_type (Andrew)
      
       Allow type-name arguments to PL/Python
       plpy.prepare() to be data type aliases in
       addition to names found in pg_type (Andrew)
      
       Allow type-name arguments to PL/Tcl spi_prepare to
       be data type aliases in addition to names found in
       pg_type (Andrew)
      
Enable PL/PythonU to compile on Python 2.5 (Marko Kreen)
Support a true PL/Python boolean type in compatible Python versions (Python 2.3 and later) (Marko Kreen)
       Fix PL/Tcl problems with thread-enabled libtcl spawning
       multiple threads within the backend (Steve Marshall, Paul Bayer,
       Doug Knight)
      
This caused all sorts of unpleasantness.
       List disabled triggers separately in \d output
       (Brendan Jurd)
      
       In \d patterns, always match $
       literally (Tom)
      
       Show aggregate return types in \da output
       (Greg Sabino Mullane)
      
       Add the function's volatility status to the output of
       \df+ (Neil)
      
       Add \prompt capability (Chad Wagner)
      
       Allow \pset, \t, and
       \x to specify on or off,
       rather than just toggling (Chad Wagner)
      
       Add \sleep capability (Jan)
      
       Enable \timing output for \copy (Andrew)
      
       Improve \timing resolution on Windows
       (Itagaki Takahiro)
      
       Flush \o output after each backslash command (Tom)
      
       Correctly detect and report errors while reading a -f
       input file (Peter)
      
       Remove -u option (this option has long been deprecated)
       (Tom)
      
       Add --tablespaces-only and --roles-only
       options to pg_dumpall (Dave Page)
      
Add an output file option to pg_dumpall (Dave Page)
This is primarily useful on Windows, where output redirection of child pg_dump processes does not work.
       Allow pg_dumpall to accept an initial-connection
       database name rather than the default
       template1 (Dave Page)
      
       In -n and -t switches, always match
       $ literally (Tom)
      
Improve performance when a database has thousands of objects (Tom)
       Remove -u option (this option has long been deprecated)
       (Tom)
      
       In initdb, allow the location of the
       pg_xlog directory to be specified
       (Euler Taveira de Oliveira)
      
Enable server core dump generation in pg_regress on supported operating systems (Andrew)
       Add a -t (timeout) parameter to pg_ctl
       (Bruce)
      
This controls how long pg_ctl will wait when waiting for server startup or shutdown. Formerly the timeout was hard-wired as 60 seconds.
Add a pg_ctl option to control generation of server core dumps (Andrew)
Allow Control-C to cancel clusterdb, reindexdb, and vacuumdb (Itagaki Takahiro, Magnus)
Suppress command tag output for createdb, createuser, dropdb, and dropuser (Peter)
       The --quiet option is ignored and will be removed in 8.4.
       Progress messages when acting on all databases now go to stdout
       instead of stderr because they are not actually errors.
      
       Interpret the dbName parameter of
       PQsetdbLogin() as a conninfo string if
       it contains an equals sign (Andrew)
      
       This allows use of conninfo strings in client
       programs that still use PQsetdbLogin().
      
Support a global SSL configuration file (Victor Wagner)
       Add environment variable PGSSLKEY to control
       SSL hardware keys (Victor Wagner)
      
       Add lo_truncate() for large object
       truncation (Kris Jurka)
      
       Add PQconnectionNeedsPassword() that returns
       true if the server required a password but none was supplied
       (Joe Conway, Tom)
      
If this returns true after a failed connection attempt, a client application should prompt the user for a password. In the past applications have had to check for a specific error message string to decide whether a password is needed; that approach is now deprecated.
       Add PQconnectionUsedPassword() that returns
       true if the supplied password was actually used
       (Joe Conway, Tom)
      
This is useful in some security contexts where it is important to know whether a user-supplied password is actually valid.
Use V3 frontend/backend protocol (Michael)
This adds support for server-side prepared statements.
Use native threads, instead of pthreads, on Windows (Magnus)
Improve thread-safety of ecpglib (Itagaki Takahiro)
Make the ecpg libraries export only necessary API symbols (Michael)
Allow the whole PostgreSQL distribution to be compiled with Microsoft Visual C++ (Magnus and others)
This allows Windows-based developers to use familiar development and debugging tools. Windows executables made with Visual C++ might also have better stability and performance than those made with other tool sets. The client-only Visual C++ build scripts have been removed.
Drastically reduce postmaster's memory usage when it has many child processes (Magnus)
Allow regression tests to be started by an administrative user (Magnus)
Add native shared memory implementation (Magnus)
Add cursor-related functionality in SPI (Pavel Stehule)
       Allow access to the cursor-related planning options, and add
       FETCH/MOVE routines.
      
       Allow execution of cursor commands through
       SPI_execute (Tom)
      
       The macro SPI_ERROR_CURSOR still exists but will
       never be returned.
      
       SPI plan pointers are now declared as SPIPlanPtr instead of
       void * (Tom)
      
This does not break application code, but switching is recommended to help catch simple programming mistakes.
       Add configure option --enable-profiling
       to enable code profiling (works only with gcc)
       (Korry Douglas and Nikhil Sontakke)
      
       Add configure option --with-system-tzdata
       to use the operating system's time zone database (Peter)
      
       Fix PGXS so extensions can be built against PostgreSQL
       installations whose pg_config program does not
       appear first in the PATH (Tom)
      
       Support gmake draft when building the
       SGML documentation (Bruce)
      
       Unless draft is used, the documentation build will
       now be repeated if necessary to ensure the index is up-to-date.
      
       Rename macro DLLIMPORT to PGDLLIMPORT to
       avoid conflicting with third party includes (like Tcl) that
       define DLLIMPORT (Magnus)
      
Create “operator families” to improve planning of queries involving cross-data-type comparisons (Tom)
       Update GIN extractQuery() API to allow signalling
       that nothing can satisfy the query (Teodor)
      
       Move NAMEDATALEN definition from
       postgres_ext.h to pg_config_manual.h
       (Peter)
      
       Provide strlcpy() and
       strlcat() on all platforms, and replace
       error-prone uses of strncpy(),
       strncat(), etc (Peter)
      
Create hooks to let an external plugin monitor (or even replace) the planner and create plans for hypothetical situations (Gurjeet Singh, Tom)
       Create a function variable join_search_hook to let plugins
       override the join search order portion of the planner (Julius
       Stroffek)
      
       Add tas() support for Renesas' M32R processor
       (Kazuhiro Inaoka)
      
       quote_identifier() and
       pg_dump no longer quote keywords that are
       unreserved according to the grammar (Tom)
      
       Change the on-disk representation of the NUMERIC
       data type so that the sign_dscale word comes
       before the weight (Tom)
      
Use SYSV semaphores rather than POSIX on Darwin >= 6.0, i.e., macOS 10.2 and up (Chris Marcellino)
"Postgres" is now documented as an accepted alias for "PostgreSQL" (Peter)
Add documentation about preventing database server spoofing when the server is down (Bruce)
       Move contrib README content into the
       main PostgreSQL documentation (Albert Cervera i
       Areny)
      
       Add contrib/pageinspect module for low-level
       page inspection (Simon, Heikki)
      
       Add contrib/pg_standby module for controlling
       warm standby operation (Simon)
      
       Add contrib/uuid-ossp module for generating
       UUID values using the OSSP UUID library (Peter)
      
       Use configure
       --with-ossp-uuid to activate. This takes
       advantage of the new UUID builtin type.
      
       Add contrib/dict_int,
       contrib/dict_xsyn, and
       contrib/test_parser modules to provide
       sample add-on text search dictionary templates and parsers
       (Sergey Karpov)
      
Allow contrib/pgbench to set the fillfactor (Pavan Deolasee)
       Add timestamps to contrib/pgbench -l
       (Greg Smith)
      
       Add usage count statistics to
       contrib/pgbuffercache (Greg Smith)
      
       Add GIN support for contrib/hstore (Teodor)
      
       Add GIN support for contrib/pg_trgm (Guillaume Smet, Teodor)
      
       Update OS/X startup scripts in
       contrib/start-scripts (Mark Cotner, David
       Fetter)
      
       Restrict pgrowlocks() and
       dblink_get_pkey() to users who have
       SELECT privilege on the target table (Tom)
      
       Restrict contrib/pgstattuple functions to
       superusers (Tom)
      
       contrib/xml2 is deprecated and planned for
       removal in 8.4 (Peter)
      
The new XML support in core PostgreSQL supersedes this module.