About

PostgreSQL is an object-relational database management system (ORDBMS) based on POSTGRES, Version 4.2, developed at the University of California at Berkeley Computer Science Department. POSTGRES pioneered many concepts that only became available in some commercial database systems much later.

PostgreSQL is an open-source descendant of this original Berkeley code. It supports SQL92 and SQL99 and offers many modern features:
complex queries
foreign keys
triggers
views
transactional integrity
multiversion concurrency control

Additionally, PostgreSQL can be extended by the user in many ways, for example by adding new
data types
functions
operators
aggregate functions
index methods
procedural languages

And because of the liberal license, PostgreSQL can be used, modified, and distributed by everyone free of charge for any purpose, be it private, commercial, or academic.

Prevent functions in indexes from executing with the privileges of the user running VACUUM, ANALYZE, etc (Tom)

Functions used in index expressions and partial-index predicates are evaluated whenever a new table entry is made. It has long been understood that this poses a risk of trojan-horse code execution if one modifies a table owned by an untrustworthy user. (Note that triggers, defaults, check constraints, etc. pose the same type of risk.) But functions in indexes pose extra danger because they will be executed by routine maintenance operations such as VACUUM FULL, which are commonly performed automatically under a superuser account. For example, a nefarious user can execute code with superuser privileges by setting up a trojan-horse index definition and waiting for the next routine vacuum. The fix arranges for standard maintenance operations (including VACUUM, ANALYZE, REINDEX, and CLUSTER) to execute as the table owner rather than the calling user, using the same privilege-switching mechanism already used for SECURITY DEFINER functions. To prevent bypassing this security measure, execution of SET SESSION AUTHORIZATION and SET ROLE is now forbidden within a SECURITY DEFINER context. (CVE-2007-6600)

Repair assorted bugs in the regular-expression package (Tom, Will Drewry)

Suitably crafted regular-expression patterns could cause crashes, infinite or near-infinite looping, and/or massive memory consumption, all of which pose denial-of-service hazards for applications that accept regex search patterns from untrustworthy sources. (CVE-2007-4769, CVE-2007-4772, CVE-2007-6067)

Require non-superusers who use /contrib/dblink to use only password authentication, as a security measure (Joe)

The fix that appeared for this in 8.2.5 was incomplete, as it plugged the hole for only some dblink functions. (CVE-2007-6601, CVE-2007-3278)

Fix bugs in WAL replay for GIN indexes (Teodor)

Fix GIN index build to work properly when maintenance_work_mem is 4GB or more (Tom)

Update time zone data files to tzdata release 2007k (in particular, recent Argentina changes) (Tom)

Improve planner's handling of LIKE/regex estimation in non-C locales (Tom)

Fix planning-speed problem for deep outer-join nests, as well as possible poor choice of join order (Tom)

Fix planner failure in some cases of WHERE false AND var IN (SELECT ...) (Tom)

Make CREATE TABLE ... SERIAL and ALTER SEQUENCE ... OWNED BY not change the currval() state of the sequence (Tom)

Preserve the tablespace and storage parameters of indexes that are rebuilt by ALTER TABLE ... ALTER COLUMN TYPE (Tom)

Make archive recovery always start a new WAL timeline, rather than only when a recovery stop time was used (Simon)

This avoids a corner-case risk of trying to overwrite an existing archived copy of the last WAL segment, and seems simpler and cleaner than the original definition.

Make VACUUM not use all of maintenance_work_mem when the table is too small for it to be useful (Alvaro)

Fix potential crash in translate() when using a multibyte database encoding (Tom)

Make corr() return the correct result for negative correlation values (Neil)

Fix overflow in extract(epoch from interval) for intervals exceeding 68 years (Tom)

Fix PL/Perl to not fail when a UTF-8 regular expression is used in a trusted function (Andrew)

Fix PL/Perl to cope when platform's Perl defines type bool as int rather than char (Tom)

While this could theoretically happen anywhere, no standard build of Perl did things this way ... until Mac OS X 10.5.

Fix PL/Python to work correctly with Python 2.5 on 64-bit machines (Marko Kreen)

Fix PL/Python to not crash on long exception messages (Alvaro)

Fix pg_dump to correctly handle inheritance child tables that have default expressions different from their parent's (Tom)

Fix libpq crash when PGPASSFILE refers to a file that is not a plain file (Martin Pitt)

ecpg parser fixes (Michael)

Make contrib/pgcrypto defend against OpenSSL libraries that fail on keys longer than 128 bits; which is the case at least on some Solaris versions (Marko Kreen)

Make contrib/tablefunc's crosstab() handle NULL rowid as a category in its own right, rather than crashing (Joe)

Fix tsvector and tsquery output routines to escape backslashes correctly (Teodor, Bruce)

Fix crash of to_tsvector() on huge input strings (Teodor)

Require a specific version of Autoconf to be used when re-generating the configure script (Peter)

This affects developers and packagers only. The change was made to prevent accidental use of untested combinations of Autoconf and PostgreSQL versions. You can remove the version check if you really want to use a different Autoconf version, but it's your responsibility whether the result works or not.

Update gettimeofday configuration check so that PostgreSQL can be built on newer versions of MinGW (Magnus)

E.1. Release 8.3

Release date: 2008-02-04
E.1.1. Overview

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.
E.1.2. Migration to Version 8.3

A dump/restore using pg_dump is required for those wishing to migrate data from any previous release.

Observe the following incompatibilities:
E.1.2.1. General


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(n) and varchar(n) still cast to 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)
E.1.2.2. Configuration Parameters


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.
E.1.2.3. Character Encodings


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.
E.1.3. Changes

Below you will find a detailed account of the changes between PostgreSQL 8.3 and the previous major release.
E.1.3.1. Performance


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 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, asynchronous commit does not put database consistency at risk; the worst case is that after a database or system crash the last few reportedly-committed transactions might be missing. 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 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)
E.1.3.2. Server


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_nnn (Tom)

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.
E.1.3.3. Monitoring


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)
E.1.3.4. Authentication


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)
E.1.3.5. Write-Ahead Log (WAL) and Continuous Archiving


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.
E.1.3.6. Queries


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)
E.1.3.7. Object Manipulation


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.
E.1.3.8. Utility Commands


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 table USING index (Holger Schurig)

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 ?columnN? for complicated cases.

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.
E.1.3.9. Data Types


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)
E.1.3.10. Functions


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.
E.1.3.11. PL/PgSQL Server-Side Language


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)
E.1.3.12. Other Server-Side Languages


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.
E.1.3.13. psql


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)
E.1.3.14. pg_dump


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)
E.1.3.15. Other Client Applications


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.
E.1.3.16. libpq


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.
E.1.3.17. ecpg


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)
E.1.3.18. Windows Port


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)
E.1.3.19. Server Programming Interface (SPI)


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.
E.1.3.20. Build Options


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.
E.1.3.21. Source Code


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., OS X 10.2 and up (Chris Marcellino)

Add acronym and NFS documentation sections (Bruce)

"Postgres" is now documented as an accepted alias for "PostgreSQL" (Peter)

Add documentation about preventing database server spoofing when the server is down (Bruce)
E.1.3.22. Contrib


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.