PostgreSQL 8.2.20 Documentation
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# E.21. Release 8.2

> Release date: 2006-12-05

## E.21.1. Overview

This release adds many functionality and performance improvements that were requested by users, including:

- Query language enhancements including `INSERT/UPDATE/DELETE RETURNING`, multirow `VALUES` lists, and optional target-table alias in `UPDATE`/`DELETE`

- Index creation without blocking concurrent `INSERT`/`UPDATE`/`DELETE` operations

- Many query optimization improvements, including support for reordering outer joins

- Improved sorting performance with lower memory usage

- More efficient locking with better concurrency

- More efficient vacuuming

- Easier administration of warm standby servers

- New `FILLFACTOR` support for tables and indexes

- Monitoring, logging, and performance tuning additions

- More control over creating and dropping objects

- Table inheritance relationships can be defined for and removed from pre-existing tables

- `COPY TO` can copy the output of an arbitrary `SELECT` statement

- Array improvements, including nulls in arrays

- Aggregate-function improvements, including multiple-input aggregates and SQL:2003 statistical functions

- Many `contrib/` improvements

## E.21.2. Migration to Version 8.2

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

Observe the following incompatibilities:

- Set `escape_string_warning` to `on` by default (Bruce)

  This issues a warning if backslash escapes are used in non-escape (non-`E''`) strings.

- Change the row constructor syntax (`ROW(...)`) so that list elements `foo.*` will be expanded to a list of their member fields, rather than creating a nested row type field as formerly (Tom)

  The new behavior is substantially more useful since it allows, for example, triggers to check for data changes with `IF row(new.*) IS DISTINCT FROM row(old.*)`. The old behavior is still available by omitting `.*`.

- Make row comparisons follow SQL standard semantics and allow them to be used in index scans (Tom)

  Previously, row = and <> comparisons followed the standard but < <= > >= did not. A row comparison can now be used as an index constraint for a multicolumn index matching the row value.

- Make row `IS [NOT] NULL` tests follow SQL standard semantics (Tom)

  The former behavior conformed to the standard for simple cases with `IS NULL`, but `IS NOT NULL` would return true if any row field was non-null, whereas the standard says it should return true only when all fields are non-null.

- Make `SET CONSTRAINT` affect only one constraint (Kris Jurka)

  In previous releases, `SET CONSTRAINT` modified all constraints with a matching name. In this release, the schema search path is used to modify only the first matching constraint. A schema specification is also supported. This more nearly conforms to the SQL standard.

- Remove `RULE` permission for tables, for security reasons (Tom)

  As of this release, only a table's owner can create or modify rules for the table. For backwards compatibility, `GRANT`/`REVOKE RULE` is still accepted, but it does nothing.

- Array comparison improvements (Tom)

  Now array dimensions are also compared.

- Change array concatenation to match documented behavior (Tom)

  This changes the previous behavior where concatenation would modify the array lower bound.

- Make command-line options of postmaster and postgres identical (Peter)

  This allows the postmaster to pass arguments to each backend without using `-o`. Note that some options are now only available as long-form options, because there were conflicting single-letter options.

- Deprecate use of postmaster symbolic link (Peter)

  postmaster and postgres commands now act identically, with the behavior determined by command-line options. The postmaster symbolic link is kept for compatibility, but is not really needed.

- Change `log_duration` to output even if the query is not output (Tom)

  In prior releases, `log_duration` only printed if the query appeared earlier in the log.

- Make `to_char(time)` and `to_char(interval)` treat `HH` and `HH12` as 12-hour intervals

  Most applications should use `HH24` unless they want a 12-hour display.

- Zero unmasked bits in conversion from `INET` to `CIDR` (Tom)

  This ensures that the converted value is actually valid for `CIDR`.

- Remove `australian_timezones` configuration variable (Joachim Wieland)

  This variable has been superseded by a more general facility for configuring timezone abbreviations.

- Improve cost estimation for nested-loop index scans (Tom)

  This might eliminate the need to set unrealistically small values of `random_page_cost`. If you have been using a very small `random_page_cost`, please recheck your test cases.

- Change behavior of `pg_dump` `-n` and `-t` options. (Greg Sabino Mullane)

  See the `pg_dump` manual page for details.

- Change libpq `PQdsplen()` to return a useful value (Martijn van Oosterhout)

- Declare libpq `PQgetssl()` as returning `void *`, rather than `SSL *` (Martijn van Oosterhout)

  This allows applications to use the function without including the OpenSSL headers.

- C-language loadable modules must now include a `PG_MODULE_MAGIC` macro call for version compatibility checking (Martijn van Oosterhout)

- For security's sake, modules used by a PL/PerlU function are no longer available to PL/Perl functions (Andrew)

  > Note: This also implies that data can no longer be shared between a PL/Perl function and a PL/PerlU function. Some Perl installations have not been compiled with the correct flags to allow multiple interpreters to exist within a single process. In this situation PL/Perl and PL/PerlU cannot both be used in a single backend. The solution is to get a Perl installation which supports multiple interpreters.

- In `contrib/xml2/`, rename `xml_valid()` to `xml_is_well_formed()` (Tom)

  `xml_valid()` will remain for backward compatibility, but its behavior will change to do schema checking in a future release.

- Remove `contrib/ora2pg/`, now at http://www.samse.fr/GPL/ora2pg

- Remove contrib modules that have been migrated to PgFoundry: `adddepend`, `dbase`, `dbmirror`, `fulltextindex`, `mac`, `userlock`

- Remove abandoned contrib modules: `mSQL-interface`, `tips`

- Remove QNX and BEOS ports (Bruce)

  These ports no longer had active maintainers.

## E.21.3. Changes

Below you will find a detailed account of the changes between PostgreSQL 8.2 and the previous major release.

### E.21.3.1. Performance Improvements

- Allow the planner to reorder outer joins in some circumstances (Tom)

  In previous releases, outer joins would always be evaluated in the order written in the query. This change allows the query optimizer to consider reordering outer joins, in cases where it can determine that the join order can be changed without altering the meaning of the query. This can make a considerable performance difference for queries involving multiple outer joins or mixed inner and outer joins.

- Improve efficiency of `IN` (list-of-expressions) clauses (Tom)

- Improve sorting speed and reduce memory usage (Simon, Tom)

- Improve subtransaction performance (Alvaro, Itagaki Takahiro, Tom)

- Add `FILLFACTOR` to table and index creation (ITAGAKI Takahiro)

  This leaves extra free space in each table or index page, allowing improved performance as the database grows. This is particularly valuable to maintain clustering.

- Increase default values for `shared_buffers` and `max_fsm_pages` (Andrew)

- Improve locking performance by breaking the lock manager tables into sections (Tom)

  This allows locking to be more fine-grained, reducing contention.

- Reduce locking requirements of sequential scans (Qingqing Zhou)

- Reduce locking required for database creation and destruction (Tom)

- Improve the optimizer's selectivity estimates for `LIKE`, `ILIKE`, and regular expression operations (Tom)

- Improve planning of joins to inherited tables and `UNION ALL` views (Tom)

- Allow constraint exclusion to be applied to inherited `UPDATE` and `DELETE` queries (Tom)

  `SELECT` already honored constraint exclusion.

- Improve planning of constant `WHERE` clauses, such as a condition that depends only on variables inherited from an outer query level (Tom)

- Protocol-level unnamed prepared statements are re-planned for each set of `BIND` values (Tom)

  This improves performance because the exact parameter values can be used in the plan.

- Speed up vacuuming of B-Tree indexes (Heikki Linnakangas, Tom)

- Avoid extra scan of tables without indexes during `VACUUM` (Greg Stark)

- Improve multicolumn GiST indexing (Oleg, Teodor)

- Remove dead index entries before B-Tree page split (Junji Teramoto)

### E.21.3.2. Server Changes

- Allow a forced switch to a new transaction log file (Simon, Tom)

  This is valuable for keeping warm standby slave servers in sync with the master. Transaction log file switching now also happens automatically during `pg_stop_backup()`. This ensures that all transaction log files needed for recovery can be archived immediately.

- Add WAL informational functions (Simon)

  Add functions for interrogating the current transaction log insertion point and determining WAL filenames from the hex WAL locations displayed by `pg_stop_backup()` and related functions.

- Improve recovery from a crash during WAL replay (Simon)

  The server now does periodic checkpoints during WAL recovery, so if there is a crash, future WAL recovery is shortened. This also eliminates the need for warm standby servers to replay the entire log since the base backup if they crash.

- Improve reliability of long-term WAL replay (Heikki, Simon, Tom)

  Formerly, trying to roll forward through more than 2 billion transactions would not work due to XID wraparound. This meant warm standby servers had to be reloaded from fresh base backups periodically.

- Add `archive_timeout` to force transaction log file switches at a given interval (Simon)

  This enforces a maximum replication delay for warm standby servers.

- Add native LDAP authentication (Magnus Hagander)

  This is particularly useful for platforms that do not support PAM, such as Windows.

- Add `GRANT CONNECT ON DATABASE` (Gevik Babakhani)

  This gives SQL-level control over database access. It works as an additional filter on top of the existing `pg_hba.conf` controls.

- Add support for SSL Certificate Revocation List (CRL) files (Libor Hohoš)

  The server and libpq both recognize CRL files now.

- GiST indexes are now clusterable (Teodor)

- Remove routine autovacuum server log entries (Bruce)

  `pg_stat_activity` now shows autovacuum activity.

- Track maximum XID age within individual tables, instead of whole databases (Alvaro)

  This reduces the overhead involved in preventing transaction ID wraparound, by avoiding unnecessary VACUUMs.

- Add last vacuum and analyze timestamp columns to the stats collector (Larry Rosenman)

  These values now appear in the `pg_stat_*_tables` system views.

- Improve performance of statistics monitoring, especially `stats_command_string` (Tom, Bruce)

  This release enables `stats_command_string` by default, now that its overhead is minimal. This means `pg_stat_activity` will now show all active queries by default.

- Add a `waiting` column to `pg_stat_activity` (Tom)

  This allows `pg_stat_activity` to show all the information included in the ps display.

- Add configuration parameter `update_process_title` to control whether the ps display is updated for every command (Bruce)

  On platforms where it is expensive to update the ps display, it might be worthwhile to turn this off and rely solely on `pg_stat_activity` for status information.

- Allow units to be specified in configuration settings (Peter)

  For example, you can now set `shared_buffers` to `32MB` rather than mentally converting sizes.

- Add support for include directives in `postgresql.conf` (Joachim Wieland)

- Improve logging of protocol-level prepare/bind/execute messages (Bruce, Tom)

  Such logging now shows statement names, bind parameter values, and the text of the query being executed. Also, the query text is properly included in logged error messages when enabled by `log_min_error_statement`.

- Prevent `max_stack_depth` from being set to unsafe values

  On platforms where we can determine the actual kernel stack depth limit (which is most), make sure that the initial default value of `max_stack_depth` is safe, and reject attempts to set it to unsafely large values.

- Enable highlighting of error location in query in more cases (Tom)

  The server is now able to report a specific error location for some semantic errors (such as unrecognized column name), rather than just for basic syntax errors as before.

- Fix "failed to re-find parent key" errors in `VACUUM` (Tom)

- Clean out `pg_internal.init` cache files during server restart (Simon)

  This avoids a hazard that the cache files might contain stale data after PITR recovery.

- Fix race condition for truncation of a large relation across a gigabyte boundary by `VACUUM` (Tom)

- Fix bug causing needless deadlock errors on row-level locks (Tom)

- Fix bugs affecting multi-gigabyte hash indexes (Tom)

- Each backend process is now its own process group leader (Tom)

  This allows query cancel to abort subprocesses invoked from a backend or archive/recovery process.

### E.21.3.3. Query Changes

- Add `INSERT`/`UPDATE`/`DELETE` `RETURNING` (Jonah Harris, Tom)

  This allows these commands to return values, such as the computed serial key for a new row. In the `UPDATE` case, values from the updated version of the row are returned.

- Add support for multiple-row `VALUES` clauses, per SQL standard (Joe, Tom)

  This allows `INSERT` to insert multiple rows of constants, or queries to generate result sets using constants. For example, `INSERT ... VALUES (...), (...), ....`, and `SELECT * FROM (VALUES (...), (...), ....) AS alias(f1, ...)`.

- Allow `UPDATE` and `DELETE` to use an alias for the target table (Atsushi Ogawa)

  The SQL standard does not permit an alias in these commands, but many database systems allow one anyway for notational convenience.

- Allow `UPDATE` to set multiple columns with a list of values (Susanne Ebrecht)

  This is basically a short-hand for assigning the columns and values in pairs. The syntax is `UPDATE tab SET (`column`, ...) = (`val`, ...)`.

- Make row comparisons work per standard (Tom)

  The forms <, <=, >, >= now compare rows lexicographically, that is, compare the first elements, if equal compare the second elements, and so on. Formerly they expanded to an AND condition across all the elements, which was neither standard nor very useful.

- Add `CASCADE` option to `TRUNCATE` (Joachim Wieland)

  This causes `TRUNCATE` to automatically include all tables that reference the specified table(s) via foreign keys. While convenient, this is a dangerous tool — use with caution!

- Support `FOR UPDATE` and `FOR SHARE` in the same `SELECT` command (Tom)

- Add `IS NOT DISTINCT FROM` (Pavel Stehule)

  This operator is similar to equality (`=`), but evaluates to true when both left and right operands are `NULL`, and to false when just one is, rather than yielding `NULL` in these cases.

- Improve the length output used by `UNION`/`INTERSECT`/`EXCEPT` (Tom)

  When all corresponding columns are of the same defined length, that length is used for the result, rather than a generic length.

- Allow `ILIKE` to work for multi-byte encodings (Tom)

  Internally, `ILIKE` now calls `lower()` and then uses `LIKE`. Locale-specific regular expression patterns still do not work in these encodings.

- Enable `standard_conforming_strings` to be turned `on` (Kevin Grittner)

  This allows backslash escaping in strings to be disabled, making PostgreSQL more standards-compliant. The default is `off` for backwards compatibility, but future releases will default this to `on`.

- Do not flatten subqueries that contain `volatile` functions in their target lists (Jaime Casanova)

  This prevents surprising behavior due to multiple evaluation of a `volatile` function (such as `random()` or `nextval()`). It might cause performance degradation in the presence of functions that are unnecessarily marked as `volatile`.

- Add system views `pg_prepared_statements` and `pg_cursors` to show prepared statements and open cursors (Joachim Wieland, Neil)

  These are very useful in pooled connection setups.

- Support portal parameters in `EXPLAIN` and `EXECUTE` (Tom)

  This allows, for example, JDBC `?` parameters to work in these commands.

- If SQL-level `PREPARE` parameters are unspecified, infer their types from the content of the query (Neil)

  Protocol-level `PREPARE` already did this.

- Allow `LIMIT` and `OFFSET` to exceed two billion (Dhanaraj M)

### E.21.3.4. Object Manipulation Changes

- Add `TABLESPACE` clause to `CREATE TABLE AS` (Neil)

  This allows a tablespace to be specified for the new table.

- Add `ON COMMIT` clause to `CREATE TABLE AS` (Neil)

  This allows temporary tables to be truncated or dropped on transaction commit. The default behavior is for the table to remain until the session ends.

- Add `INCLUDING CONSTRAINTS` to `CREATE TABLE LIKE` (Greg Stark)

  This allows easy copying of `CHECK` constraints to a new table.

- Allow the creation of placeholder (shell) types (Martijn van Oosterhout)

  A shell type declaration creates a type name, without specifying any of the details of the type. Making a shell type is useful because it allows cleaner declaration of the type's input/output functions, which must exist before the type can be defined "for real". The syntax is `CREATE TYPE `typename``.

- Aggregate functions now support multiple input parameters (Sergey Koposov, Tom)

- Add new aggregate creation syntax (Tom)

  The new syntax is `CREATE AGGREGATE `aggname` (`input_type`) (`parameter_list`)`. This more naturally supports the new multi-parameter aggregate functionality. The previous syntax is still supported.

- Add `ALTER ROLE PASSWORD NULL` to remove a previously set role password (Peter)

- Add `DROP` object `IF EXISTS` for many object types (Andrew)

  This allows `DROP` operations on non-existent objects without generating an error.

- Add `DROP OWNED` to drop all objects owned by a role (Alvaro)

- Add `REASSIGN OWNED` to reassign ownership of all objects owned by a role (Alvaro)

  This, and `DROP OWNED` above, facilitate dropping roles.

- Add `GRANT ON SEQUENCE` syntax (Bruce)

  This was added for setting sequence-specific permissions. `GRANT ON TABLE` for sequences is still supported for backward compatibility.

- Add `USAGE` permission for sequences that allows only `currval()` and `nextval()`, not `setval()` (Bruce)

  `USAGE` permission allows more fine-grained control over sequence access. Granting `USAGE` allows users to increment a sequence, but prevents them from setting the sequence to an arbitrary value using `setval()`.

- Add `ALTER TABLE [ NO ] INHERIT` (Greg Stark)

  This allows inheritance to be adjusted dynamically, rather than just at table creation and destruction. This is very valuable when using inheritance to implement table partitioning.

- Allow comments on global objects to be stored globally (Kris Jurka)

  Previously, comments attached to databases were stored in individual databases, making them ineffective, and there was no provision at all for comments on roles or tablespaces. This change adds a new shared catalog `pg_shdescription` and stores comments on databases, roles, and tablespaces therein.

### E.21.3.5. Utility Command Changes

- Add option to allow indexes to be created without blocking concurrent writes to the table (Greg Stark, Tom)

  The new syntax is `CREATE INDEX CONCURRENTLY`. The default behavior is still to block table modification while a index is being created.

- Provide advisory locking functionality (Abhijit Menon-Sen, Tom)

  This is a new locking API designed to replace what used to be in /contrib/userlock. The userlock code is now on pgfoundry.

- Allow `COPY` to dump a `SELECT` query (Zoltan Boszormenyi, Karel Zak)

  This allows `COPY` to dump arbitrary SQL queries. The syntax is `COPY (SELECT ...) TO`.

- Make the `COPY` command return a command tag that includes the number of rows copied (Volkan YAZICI)

- Allow `VACUUM` to expire rows without being affected by other concurrent `VACUUM` operations (Hannu Krossing, Alvaro, Tom)

- Make initdb detect the operating system locale and set the default `DateStyle` accordingly (Peter)

  This makes it more likely that the installed `postgresql.conf` `DateStyle` value will be as desired.

- Reduce number of progress messages displayed by initdb (Tom)

### E.21.3.6. Date/Time Changes

- Allow full timezone names in `timestamp` input values (Joachim Wieland)

  For example, `'2006-05-24 21:11 America/New_York'::timestamptz`.

- Support configurable timezone abbreviations (Joachim Wieland)

  A desired set of timezone abbreviations can be chosen via the configuration parameter `timezone_abbreviations`.

- Add `pg_timezone_abbrevs` and `pg_timezone_names` views to show supported timezones (Magnus Hagander)

- Add `clock_timestamp()`, `statement_timestamp()`, and `transaction_timestamp()` (Bruce)

  `clock_timestamp()` is the current wall-clock time, `statement_timestamp()` is the time the current statement arrived at the server, and `transaction_timestamp()` is an alias for `now()`.

- Allow `to_char()` to print localized month and day names (Euler Taveira de Oliveira)

- Allow `to_char(time)` and `to_char(interval)` to output AM/PM specifications (Bruce)

  Intervals and times are treated as 24-hour periods, e.g. `25 hours` is considered AM.

- Add new function `justify_interval()` to adjust interval units (Mark Dilger)

- Allow timezone offsets up to 14:59 away from GMT

  Kiribati uses GMT+14, so we'd better accept that.

- Interval computation improvements (Michael Glaesemann, Bruce)

### E.21.3.7. Other Data Type and Function Changes

- Allow arrays to contain `NULL` elements (Tom)

- Allow assignment to array elements not contiguous with the existing entries (Tom)

  The intervening array positions will be filled with nulls. This is per SQL standard.

- New built-in operators for array-subset comparisons (`@>`, `<@`, `&&`) (Teodor, Tom)

  These operators can be indexed for many data types using GiST or GIN indexes.

- Add convenient arithmetic operations on `INET`/`CIDR` values (Stephen R. van den Berg)

  The new operators are `&` (and), `|` (or), `~` (not), `inet` `+` `int8`, `inet` `-` `int8`, and `inet` `-` `inet`.

- Add new aggregate functions from SQL:2003 (Neil)

  The new functions are `var_pop()`, `var_samp()`, `stddev_pop()`, and `stddev_samp()`. `var_samp()` and `stddev_samp()` are merely renamings of the existing aggregates `variance()` and `stddev()`. The latter names remain available for backward compatibility.

- Add SQL:2003 statistical aggregates (Sergey Koposov)

  New functions: `regr_intercept()`, `regr_slope()`, `regr_r2()`, `corr()`, `covar_samp()`, `covar_pop()`, `regr_avgx()`, `regr_avgy()`, `regr_sxy()`, `regr_sxx()`, `regr_syy()`, `regr_count()`.

- Allow domains to be based on other domains (Tom)

- Properly enforce domain `CHECK` constraints everywhere (Neil, Tom)

  For example, the result of a user-defined function that is declared to return a domain type is now checked against the domain's constraints. This closes a significant hole in the domain implementation.

- Fix problems with dumping renamed `SERIAL` columns (Tom)

  The fix is to dump a `SERIAL` column by explicitly specifying its `DEFAULT` and sequence elements, and reconstructing the `SERIAL` column on reload using a new `ALTER SEQUENCE OWNED BY` command. This also allows dropping a `SERIAL` column specification.

- Add a server-side sleep function `pg_sleep()` (Joachim Wieland)

- Add all comparison operators for the `tid` (tuple id) data type (Mark Kirkwood, Greg Stark, Tom)

### E.21.3.8. PL/pgSQL Server-Side Language Changes

- Add `TG_table_name` and `TG_table_schema` to trigger parameters (Andrew)

  `TG_relname` is now deprecated. Comparable changes have been made in the trigger parameters for the other PLs as well.

- Allow `FOR` statements to return values to scalars as well as records and row types (Pavel Stehule)

- Add a `BY` clause to the `FOR` loop, to control the iteration increment (Jaime Casanova)

- Add `STRICT` to `SELECT INTO` (Matt Miller)

  `STRICT` mode throws an exception if more or less than one row is returned by the `SELECT`, for Oracle PL/SQL compatibility.

### E.21.3.9. PL/Perl Server-Side Language Changes

- Add `table_name` and `table_schema` to trigger parameters (Adam Sjøgren)

- Add prepared queries (Dmitry Karasik)

- Make `$_TD` trigger data a global variable (Andrew)

  Previously, it was lexical, which caused unexpected sharing violations.

- Run PL/Perl and PL/PerlU in separate interpreters, for security reasons (Andrew)

  In consequence, they can no longer share data nor loaded modules. Also, if Perl has not been compiled with the requisite flags to allow multiple interpreters, only one of these languages can be used in any given backend process.

### E.21.3.10. PL/Python Server-Side Language Changes

- Named parameters are passed as ordinary variables, as well as in the `args[]` array (Sven Suursoho)

- Add `table_name` and `table_schema` to trigger parameters (Andrew)

- Allow returning of composite types and result sets (Sven Suursoho)

- Return result-set as `list`, `iterator`, or `generator` (Sven Suursoho)

- Allow functions to return `void` (Neil)

- Python 2.5 is now supported (Tom)

### E.21.3.11. psql Changes

- Add new command `\password` for changing role password with client-side password encryption (Peter)

- Allow `\c` to connect to a new host and port number (David, Volkan YAZICI)

- Add tablespace display to `\l+` (Philip Yarra)

- Improve `\df` slash command to include the argument names and modes (`OUT` or `INOUT`) of the function (David Fetter)

- Support binary `COPY` (Andreas Pflug)

- Add option to run the entire session in a single transaction (Simon)

  Use option `-1` or `--single-transaction`.

- Support for automatically retrieving `SELECT` results in batches using a cursor (Chris Mair)

  This is enabled using `\set FETCH_COUNT `n``. This feature allows large result sets to be retrieved in psql without attempting to buffer the entire result set in memory.

- Make multi-line values align in the proper column (Martijn van Oosterhout)

  Field values containing newlines are now displayed in a more readable fashion.

- Save multi-line statements as a single entry, rather than one line at a time (Sergey E. Koposov)

  This makes up-arrow recall of queries easier. (This is not available on Windows, because that platform uses the native command-line editing present in the operating system.)

- Make the line counter 64-bit so it can handle files with more than two billion lines (David Fetter)

- Report both the returned data and the command status tag for `INSERT`/`UPDATE`/`DELETE RETURNING` (Tom)

### E.21.3.12. pg_dump Changes

- Allow complex selection of objects to be included or excluded by pg_dump (Greg Sabino Mullane)

  pg_dump now supports multiple `-n` (schema) and `-t` (table) options, and adds `-N` and `-T` options to exclude objects. Also, the arguments of these switches can now be wild-card expressions rather than single object names, for example `-t 'foo*'`, and a schema can be part of a `-t` or `-T` switch, for example `-t schema1.table1`.

- Add pg_restore `--no-data-for-failed-tables` option to suppress loading data if table creation failed (i.e., the table already exists) (Martin Pitt)

- Add pg_restore option to run the entire session in a single transaction (Simon)

  Use option `-1` or `--single-transaction`.

### E.21.3.13. libpq Changes

- Add `PQencryptPassword()` to encrypt passwords (Tom)

  This allows passwords to be sent pre-encrypted for commands like `ALTER ROLE ... PASSWORD`.

- Add function `PQisthreadsafe()` (Bruce)

  This allows applications to query the thread-safety status of the library.

- Add `PQdescribePrepared()`, `PQdescribePortal()`, and related functions to return information about previously prepared statements and open cursors (Volkan YAZICI)

- Allow LDAP lookups from `pg_service.conf` (Laurenz Albe)

- Allow a hostname in `~/.pgpass` to match the default socket directory (Bruce)

  A blank hostname continues to match any Unix-socket connection, but this addition allows entries that are specific to one of several postmasters on the machine.

### E.21.3.14. ecpg Changes

- Allow `SHOW` to put its result into a variable (Joachim Wieland)

- Add `COPY TO STDOUT` (Joachim Wieland)

- Add regression tests (Joachim Wieland, Michael)

- Major source code cleanups (Joachim Wieland, Michael)

### E.21.3.15. Windows Port

- Allow MSVC to compile the PostgreSQL server (Magnus, Hiroshi Saito)

- Add MSVC support for utility commands and pg_dump (Hiroshi Saito)

- Add support for Windows code pages `1253`, `1254`, `1255`, and `1257` (Kris Jurka)

- Drop privileges on startup, so that the server can be started from an administrative account (Magnus)

- Stability fixes (Qingqing Zhou, Magnus)

- Add native semaphore implementation (Qingqing Zhou)

  The previous code mimicked SysV semaphores.

### E.21.3.16. Source Code Changes

- Add GIN (Generalized Inverted iNdex) index access method (Teodor, Oleg)

- Remove R-tree indexing (Tom)

  Rtree has been re-implemented using GiST. Among other differences, this means that rtree indexes now have support for crash recovery via write-ahead logging (WAL).

- Reduce libraries needlessly linked into the backend (Martijn van Oosterhout, Tom)

- Add a configure flag to allow libedit to be preferred over GNU readline (Bruce)

  Use configure `--with-libedit-preferred`.

- Allow installation into directories containing spaces (Peter)

- Improve ability to relocate installation directories (Tom)

- Add support for Solaris x86_64 using the Solaris compiler (Pierre Girard, Theo Schlossnagle, Bruce)

- Add DTrace support (Robert Lor)

- Add `PG_VERSION_NUM` for use by third-party applications wanting to test the backend version in C using > and < comparisons (Bruce)

- Add `XLOG_BLCKSZ` as independent from `BLCKSZ` (Mark Wong)

- Add `LWLOCK_STATS` define to report locking activity (Tom)

- Emit warnings for unknown configure options (Martijn van Oosterhout)

- Add server support for "plugin" libraries that can be used for add-on tasks such as debugging and performance measurement (Korry Douglas)

  This consists of two features: a table of "rendezvous variables" that allows separately-loaded shared libraries to communicate, and a new configuration parameter `local_preload_libraries` that allows libraries to be loaded into specific sessions without explicit cooperation from the client application. This allows external add-ons to implement features such as a PL/pgSQL debugger.

- Rename existing configuration parameter `preload_libraries` to `shared_preload_libraries` (Tom)

  This was done for clarity in comparison to `local_preload_libraries`.

- Add new configuration parameter `server_version_num` (Greg Sabino Mullane)

  This is like `server_version`, but is an integer, e.g. `80200`. This allows applications to make version checks more easily.

- Add a configuration parameter `seq_page_cost` (Tom)

- Re-implement the regression test script as a C program (Magnus, Tom)

- Allow loadable modules to allocate shared memory and lightweight locks (Marc Munro)

- Add automatic initialization and finalization of dynamically loaded libraries (Ralf Engelschall, Tom)

  New functions `_PG_init()` and `_PG_fini()` are called if the library defines such symbols. Hence we no longer need to specify an initialization function in `shared_preload_libraries`; we can assume that the library used the `_PG_init()` convention instead.

- Add `PG_MODULE_MAGIC` header block to all shared object files (Martijn van Oosterhout)

  The magic block prevents version mismatches between loadable object files and servers.

- Add shared library support for AIX (Laurenz Albe)

- New XML documentation section (Bruce)

### E.21.3.17. Contrib Changes

- Major tsearch2 improvements (Oleg, Teodor)

  - multibyte encoding support, including UTF8

  - query rewriting support

  - improved ranking functions

  - thesaurus dictionary support

  - Ispell dictionaries now recognize MySpell format, used by OpenOffice

  - GIN support

- Add adminpack module containing Pgadmin administration functions (Dave)

  These functions provide additional file system access routines not present in the default PostgreSQL server.

- Add sslinfo module (Victor Wagner)

  Reports information about the current connection's SSL certificate.

- Add pgrowlocks module (Tatsuo)

  This shows row locking information for a specified table.

- Add hstore module (Oleg, Teodor)

- Add isn module, replacing isbn_issn (Jeremy Kronuz)

  This new implementation supports EAN13, UPC, ISBN (books), ISMN (music), and ISSN (serials).

- Add index information functions to pgstattuple (ITAGAKI Takahiro, Satoshi Nagayasu)

- Add pg_freespacemap module to display free space map information (Mark Kirkwood)

- pgcrypto now has all planned functionality (Marko Kreen)

  - Include iMath library in pgcrypto to have the public-key encryption functions always available.

  - Add SHA224 algorithm that was missing in OpenBSD code.

  - Activate builtin code for SHA224/256/384/512 hashes on older OpenSSL to have those algorithms always available.

  - New function gen_random_bytes() that returns cryptographically strong randomness. Useful for generating encryption keys.

  - Remove digest_exists(), hmac_exists() and cipher_exists() functions.

- Improvements to cube module (Joshua Reich)

  New functions are `cube(float[])`, `cube(float[], float[])`, and `cube_subset(cube, int4[])`.

- Add async query capability to dblink (Kai Londenberg, Joe Conway)

- New operators for array-subset comparisons (`@>`, `<@`, `&&`) (Tom)

  Various contrib packages already had these operators for their datatypes, but the naming wasn't consistent. We have now added consistently named array-subset comparison operators to the core code and all the contrib packages that have such functionality. (The old names remain available, but are deprecated.)

- Add uninstall scripts for all contrib packages that have install scripts (David, Josh Drake)

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