PostgreSQL 8.2.6 Documentation
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# E.55. Release 7.4

> Release date: 2003-11-17

## E.55.1. Overview

Major changes in this release:

`IN` / `NOT IN` subqueries are now much more efficient

  In previous releases, `IN`/`NOT IN` subqueries were joined to the upper query by sequentially scanning the subquery looking for a match. The 7.4 code uses the same sophisticated techniques used by ordinary joins and so is much faster. An `IN` will now usually be as fast as or faster than an equivalent `EXISTS` subquery; this reverses the conventional wisdom that applied to previous releases.

Improved `GROUP BY` processing by using hash buckets

  In previous releases, rows to be grouped had to be sorted first. The 7.4 code can do `GROUP BY` without sorting, by accumulating results into a hash table with one entry per group. It will still use the sort technique, however, if the hash table is estimated to be too large to fit in `sort_mem`.

New multikey hash join capability

  In previous releases, hash joins could only occur on single keys. This release allows multicolumn hash joins.

Queries using the explicit `JOIN` syntax are now better optimized

  Prior releases evaluated queries using the explicit `JOIN` syntax only in the order implied by the syntax. 7.4 allows full optimization of these queries, meaning the optimizer considers all possible join orderings and chooses the most efficient. Outer joins, however, must still follow the declared ordering.

Faster and more powerful regular expression code

  The entire regular expression module has been replaced with a new version by Henry Spencer, originally written for Tcl. The code greatly improves performance and supports several flavors of regular expressions.

Function-inlining for simple SQL functions

  Simple SQL functions can now be inlined by including their SQL in the main query. This improves performance by eliminating per-call overhead. That means simple SQL functions now behave like macros.

Full support for IPv6 connections and IPv6 address data types

  Previous releases allowed only IPv4 connections, and the IP data types only supported IPv4 addresses. This release adds full IPv6 support in both of these areas.

Major improvements in SSL performance and reliability

  Several people very familiar with the SSL API have overhauled our SSL code to improve SSL key negotiation and error recovery.

Make free space map efficiently reuse empty index pages, and other free space management improvements

  In previous releases, B-tree index pages that were left empty because of deleted rows could only be reused by rows with index values similar to the rows originally indexed on that page. In 7.4, `VACUUM` records empty index pages and allows them to be reused for any future index rows.

SQL-standard information schema

  The information schema provides a standardized and stable way to access information about the schema objects defined in a database.

Cursors conform more closely to the SQL standard

  The commands `FETCH` and `MOVE` have been overhauled to conform more closely to the SQL standard.

Cursors can exist outside transactions

  These cursors are also called holdable cursors.

New client-to-server protocol

  The new protocol adds error codes, more status information, faster startup, better support for binary data transmission, parameter values separated from SQL commands, prepared statements available at the protocol level, and cleaner recovery from `COPY` failures. The older protocol is still supported by both server and clients.

libpq and ECPG applications are now fully thread-safe

  While previous libpq releases already supported threads, this release improves thread safety by fixing some non-thread-safe code that was used during database connection startup. The `configure` option `--enable-thread-safety` must be used to enable this feature.

New version of full-text indexing

  A new full-text indexing suite is available in `contrib/tsearch2`.

New autovacuum tool

  The new autovacuum tool in `contrib/autovacuum` monitors the database statistics tables for `INSERT`/`UPDATE`/`DELETE` activity and automatically vacuums tables when needed.

Array handling has been improved and moved into the server core

  Many array limitations have been removed, and arrays behave more like fully-supported data types.

## E.55.2. Migration to Version 7.4

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

Observe the following incompatibilities:

- The server-side autocommit setting was removed and reimplemented in client applications and languages. Server-side autocommit was causing too many problems with languages and applications that wanted to control their own autocommit behavior, so autocommit was removed from the server and added to individual client APIs as appropriate.

- Error message wording has changed substantially in this release. Significant effort was invested to make the messages more consistent and user-oriented. If your applications try to detect different error conditions by parsing the error message, you are strongly encouraged to use the new error code facility instead.

- Inner joins using the explicit `JOIN` syntax might behave differently because they are now better optimized.

- A number of server configuration parameters have been renamed for clarity, primarily those related to logging.

- `FETCH 0` or `MOVE 0` now does nothing. In prior releases, `FETCH 0` would fetch all remaining rows, and `MOVE 0` would move to the end of the cursor.

- `FETCH` and `MOVE` now return the actual number of rows fetched/moved, or zero if at the beginning/end of the cursor. Prior releases would return the row count passed to the command, not the number of rows actually fetched or moved.

- `COPY` now can process files that use carriage-return or carriage-return/line-feed end-of-line sequences. Literal carriage-returns and line-feeds are no longer accepted in data values; use `\r` and `\n` instead.

- Trailing spaces are now trimmed when converting from type `char(`n`)` to `varchar(`n`)` or `text`. This is what most people always expected to happen anyway.

- The data type `float(`p`)` now measures `p` in binary digits, not decimal digits. The new behavior follows the SQL standard.

- Ambiguous date values now must match the ordering specified by the `datestyle` setting. In prior releases, a date specification of `10/20/03` was interpreted as a date in October even if `datestyle` specified that the day should be first. 7.4 will throw an error if a date specification is invalid for the current setting of `datestyle`.

- The functions `oidrand`, `oidsrand`, and `userfntest` have been removed. These functions were determined to be no longer useful.

- String literals specifying time-varying date/time values, such as `'now'` or `'today'` will no longer work as expected in column default expressions; they now cause the time of the table creation to be the default, not the time of the insertion. Functions such as `now()`, `current_timestamp`, or `current_date` should be used instead.

  In previous releases, there was special code so that strings such as `'now'` were interpreted at `INSERT` time and not at table creation time, but this work around didn't cover all cases. Release 7.4 now requires that defaults be defined properly using functions such as `now()` or `current_timestamp`. These will work in all situations.

- The dollar sign (`$`) is no longer allowed in operator names. It can instead be a non-first character in identifiers. This was done to improve compatibility with other database systems, and to avoid syntax problems when parameter placeholders (`$`n``) are written adjacent to operators.

## E.55.3. Changes

Below you will find a detailed account of the changes between release 7.4 and the previous major release.

### E.55.3.1. Server Operation Changes

- Allow IPv6 server connections (Nigel Kukard, Johan Jordaan, Bruce, Tom, Kurt Roeckx, Andrew Dunstan)

- Fix SSL to handle errors cleanly (Nathan Mueller)

  In prior releases, certain SSL API error reports were not handled correctly. This release fixes those problems.

- SSL protocol security and performance improvements (Sean Chittenden)

  SSL key renegotiation was happening too frequently, causing poor SSL performance. Also, initial key handling was improved.

- Print lock information when a deadlock is detected (Tom)

  This allows easier debugging of deadlock situations.

- Update `/tmp` socket modification times regularly to avoid their removal (Tom)

  This should help prevent `/tmp` directory cleaner administration scripts from removing server socket files.

- Enable PAM for Mac OS X (Aaron Hillegass)

- Make B-tree indexes fully WAL-safe (Tom)

  In prior releases, under certain rare cases, a server crash could cause B-tree indexes to become corrupt. This release removes those last few rare cases.

- Allow B-tree index compaction and empty page reuse (Tom)

- Fix inconsistent index lookups during split of first root page (Tom)

  In prior releases, when a single-page index split into two pages, there was a brief period when another database session could miss seeing an index entry. This release fixes that rare failure case.

- Improve free space map allocation logic (Tom)

- Preserve free space information between server restarts (Tom)

  In prior releases, the free space map was not saved when the postmaster was stopped, so newly started servers had no free space information. This release saves the free space map, and reloads it when the server is restarted.

- Add start time to `pg_stat_activity` (Neil)

- New code to detect corrupt disk pages; erase with `zero_damaged_pages` (Tom)

- New client/server protocol: faster, no username length limit, allow clean exit from `COPY` (Tom)

- Add transaction status, table ID, column ID to client/server protocol (Tom)

- Add binary I/O to client/server protocol (Tom)

- Remove autocommit server setting; move to client applications (Tom)

- New error message wording, error codes, and three levels of error detail (Tom, Joe, Peter)

### E.55.3.2. Performance Improvements

- Add hashing for `GROUP BY` aggregates (Tom)

- Make nested-loop joins be smarter about multicolumn indexes (Tom)

- Allow multikey hash joins (Tom)

- Improve constant folding (Tom)

- Add ability to inline simple SQL functions (Tom)

- Reduce memory usage for queries using complex functions (Tom)

  In prior releases, functions returning allocated memory would not free it until the query completed. This release allows the freeing of function-allocated memory when the function call completes, reducing the total memory used by functions.

- Improve GEQO optimizer performance (Tom)

  This release fixes several inefficiencies in the way the GEQO optimizer manages potential query paths.

- Allow `IN`/`NOT IN` to be handled via hash tables (Tom)

- Improve `NOT IN (`subquery`)` performance (Tom)

- Allow most `IN` subqueries to be processed as joins (Tom)

- Pattern matching operations can use indexes regardless of locale (Peter)

  There is no way for non-ASCII locales to use the standard indexes for `LIKE` comparisons. This release adds a way to create a special index for `LIKE`.

- Allow the postmaster to preload libraries using `preload_libraries` (Joe)

  For shared libraries that require a long time to load, this option is available so the library can be preloaded in the postmaster and inherited by all database sessions.

- Improve optimizer cost computations, particularly for subqueries (Tom)

- Avoid sort when subquery `ORDER BY` matches upper query (Tom)

- Deduce that `WHERE a.x = b.y AND b.y = 42` also means `a.x = 42` (Tom)

- Allow hash/merge joins on complex joins (Tom)

- Allow hash joins for more data types (Tom)

- Allow join optimization of explicit inner joins, disable with `join_collapse_limit` (Tom)

- Add parameter `from_collapse_limit` to control conversion of subqueries to joins (Tom)

- Use faster and more powerful regular expression code from Tcl (Henry Spencer, Tom)

- Use bit-mapped relation sets in the optimizer (Tom)

- Improve connection startup time (Tom)

  The new client/server protocol requires fewer network packets to start a database session.

- Improve trigger/constraint performance (Stephan)

- Improve speed of `col IN (const, const, const, ...)` (Tom)

- Fix hash indexes which were broken in rare cases (Tom)

- Improve hash index concurrency and speed (Tom)

  Prior releases suffered from poor hash index performance, particularly for high concurrency situations. This release fixes that, and the development group is interested in reports comparing B-tree and hash index performance.

- Align shared buffers on 32-byte boundary for copy speed improvement (Manfred Spraul)

  Certain CPU's perform faster data copies when addresses are 32-byte aligned.

- Data type `numeric` reimplemented for better performance (Tom)

  `numeric` used to be stored in base 100. The new code uses base 10000, for significantly better performance.

### E.55.3.3. Server Configuration Changes

- Rename server parameter `server_min_messages` to `log_min_messages` (Bruce)

  This was done so most parameters that control the server logs begin with `log_`.

- Rename `show_*_stats` to `log_*_stats` (Bruce)

- Rename `show_source_port` to `log_source_port` (Bruce)

- Rename `hostname_lookup` to `log_hostname` (Bruce)

- Add `checkpoint_warning` to warn of excessive checkpointing (Bruce)

  In prior releases, it was difficult to determine if checkpoint was happening too frequently. This feature adds a warning to the server logs when excessive checkpointing happens.

- New read-only server parameters for localization (Tom)

- Change debug server log messages to output as `DEBUG` rather than `LOG` (Bruce)

- Prevent server log variables from being turned off by non-superusers (Bruce)

  This is a security feature so non-superusers cannot disable logging that was enabled by the administrator.

- `log_min_messages`/`client_min_messages` now controls `debug_*` output (Bruce)

  This centralizes client debug information so all debug output can be sent to either the client or server logs.

- Add Mac OS X Rendezvous server support (Chris Campbell)

  This allows Mac OS X hosts to query the network for available PostgreSQL servers.

- Add ability to print only slow statements using `log_min_duration_statement` (Christopher)

  This is an often requested debugging feature that allows administrators to see only slow queries in their server logs.

- Allow `pg_hba.conf` to accept netmasks in CIDR format (Andrew Dunstan)

  This allows administrators to merge the host IP address and netmask fields into a single CIDR field in `pg_hba.conf`.

- New read-only parameter `is_superuser` (Tom)

- New parameter `log_error_verbosity` to control error detail (Tom)

  This works with the new error reporting feature to supply additional error information like hints, file names and line numbers.

- `postgres --describe-config` now dumps server config variables (Aizaz Ahmed, Peter)

  This option is useful for administration tools that need to know the configuration variable names and their minimums, maximums, defaults, and descriptions.

- Add new columns in `pg_settings`: `context`, `type`, `source`, `min_val`, `max_val` (Joe)

- Make default `shared_buffers` 1000 and `max_connections` 100, if possible (Tom)

  Prior versions defaulted to 64 shared buffers so PostgreSQL would start on even very old systems. This release tests the amount of shared memory allowed by the platform and selects more reasonable default values if possible. Of course, users are still encouraged to evaluate their resource load and size `shared_buffers` accordingly.

- New `pg_hba.conf` record type `hostnossl` to prevent SSL connections (Jon Jensen)

  In prior releases, there was no way to prevent SSL connections if both the client and server supported SSL. This option allows that capability.

- Remove parameter `geqo_random_seed` (Tom)

- Add server parameter `regex_flavor` to control regular expression processing (Tom)

- Make `pg_ctl` better handle nonstandard ports (Greg)

### E.55.3.4. Query Changes

- New SQL-standard information schema (Peter)

- Add read-only transactions (Peter)

- Print key name and value in foreign-key violation messages (Dmitry Tkach)

- Allow users to see their own queries in `pg_stat_activity` (Kevin Brown)

  In prior releases, only the superuser could see query strings using `pg_stat_activity`. Now ordinary users can see their own query strings.

- Fix aggregates in subqueries to match SQL standard (Tom)

  The SQL standard says that an aggregate function appearing within a nested subquery belongs to the outer query if its argument contains only outer-query variables. Prior PostgreSQL releases did not handle this fine point correctly.

- Add option to prevent auto-addition of tables referenced in query (Nigel J. Andrews)

  By default, tables mentioned in the query are automatically added to the `FROM` clause if they are not already there. This is compatible with historic POSTGRES behavior but is contrary to the SQL standard. This option allows selecting standard-compatible behavior.

- Allow `UPDATE ... SET col = DEFAULT` (Rod)

  This allows `UPDATE` to set a column to its declared default value.

- Allow expressions to be used in `LIMIT`/`OFFSET` (Tom)

  In prior releases, `LIMIT`/`OFFSET` could only use constants, not expressions.

- Implement `CREATE TABLE AS EXECUTE` (Neil, Peter)

### E.55.3.5. Object Manipulation Changes

- Make `CREATE SEQUENCE` grammar more conforming to SQL:2003 (Neil)

- Add statement-level triggers (Neil)

  While this allows a trigger to fire at the end of a statement, it does not allow the trigger to access all rows modified by the statement. This capability is planned for a future release.

- Add check constraints for domains (Rod)

  This greatly increases the usefulness of domains by allowing them to use check constraints.

- Add `ALTER DOMAIN` (Rod)

  This allows manipulation of existing domains.

- Fix several zero-column table bugs (Tom)

  PostgreSQL supports zero-column tables. This fixes various bugs that occur when using such tables.

- Have `ALTER TABLE ... ADD PRIMARY KEY` add not-null constraint (Rod)

  In prior releases, `ALTER TABLE ... ADD PRIMARY` would add a unique index, but not a not-null constraint. That is fixed in this release.

- Add `ALTER TABLE ... WITHOUT OIDS` (Rod)

  This allows control over whether new and updated rows will have an OID column. This is most useful for saving storage space.

- Add `ALTER SEQUENCE` to modify minimum, maximum, increment, cache, cycle values (Rod)

- Add `ALTER TABLE ... CLUSTER ON` (Alvaro Herrera)

  This command is used by `pg_dump` to record the cluster column for each table previously clustered. This information is used by database-wide cluster to cluster all previously clustered tables.

- Improve automatic type casting for domains (Rod, Tom)

- Allow dollar signs in identifiers, except as first character (Tom)

- Disallow dollar signs in operator names, so `x=$1` works (Tom)

- Allow copying table schema using `LIKE `subtable``, also SQL:2003 feature `INCLUDING DEFAULTS` (Rod)

- Add `WITH GRANT OPTION` clause to `GRANT` (Peter)

  This enabled `GRANT` to give other users the ability to grant privileges on a object.

### E.55.3.6. Utility Command Changes

- Add `ON COMMIT` clause to `CREATE TABLE` for temporary tables (Gavin)

  This adds the ability for a table to be dropped or all rows deleted on transaction commit.

- Allow cursors outside transactions using `WITH HOLD` (Neil)

  In previous releases, cursors were removed at the end of the transaction that created them. Cursors can now be created with the `WITH HOLD` option, which allows them to continue to be accessed after the creating transaction has committed.

- `FETCH 0` and `MOVE 0` now do nothing (Bruce)

  In previous releases, `FETCH 0` fetched all remaining rows, and `MOVE 0` moved to the end of the cursor.

- Cause `FETCH` and `MOVE` to return the number of rows fetched/moved, or zero if at the beginning/end of cursor, per SQL standard (Bruce)

  In prior releases, the row count returned by `FETCH` and `MOVE` did not accurately reflect the number of rows processed.

- Properly handle `SCROLL` with cursors, or report an error (Neil)

  Allowing random access (both forward and backward scrolling) to some kinds of queries cannot be done without some additional work. If `SCROLL` is specified when the cursor is created, this additional work will be performed. Furthermore, if the cursor has been created with `NO SCROLL`, no random access is allowed.

- Implement SQL-compatible options `FIRST`, `LAST`, `ABSOLUTE `n``, `RELATIVE `n`` for `FETCH` and `MOVE` (Tom)

- Allow `EXPLAIN` on `DECLARE CURSOR` (Tom)

- Allow `CLUSTER` to use index marked as pre-clustered by default (Alvaro Herrera)

- Allow `CLUSTER` to cluster all tables (Alvaro Herrera)

  This allows all previously clustered tables in a database to be reclustered with a single command.

- Prevent `CLUSTER` on partial indexes (Tom)

- Allow DOS and Mac line-endings in `COPY` files (Bruce)

- Disallow literal carriage return as a data value, backslash-carriage-return and `\r` are still allowed (Bruce)

- `COPY` changes (binary, `\.`) (Tom)

- Recover from `COPY` failure cleanly (Tom)

- Prevent possible memory leaks in `COPY` (Tom)

- Make `TRUNCATE` transaction-safe (Rod)

  `TRUNCATE` can now be used inside a transaction. If the transaction aborts, the changes made by the `TRUNCATE` are automatically rolled back.

- Allow prepare/bind of utility commands like `FETCH` and `EXPLAIN` (Tom)

- Add `EXPLAIN EXECUTE` (Neil)

- Improve `VACUUM` performance on indexes by reducing WAL traffic (Tom)

- Functional indexes have been generalized into indexes on expressions (Tom)

  In prior releases, functional indexes only supported a simple function applied to one or more column names. This release allows any type of scalar expression.

- Have `SHOW TRANSACTION ISOLATION` match input to `SET TRANSACTION ISOLATION` (Tom)

- Have `COMMENT ON DATABASE` on nonlocal database generate a warning, rather than an error (Rod)

  Database comments are stored in database-local tables so comments on a database have to be stored in each database.

- Improve reliability of `LISTEN`/`NOTIFY` (Tom)

- Allow `REINDEX` to reliably reindex nonshared system catalog indexes (Tom)

  This allows system tables to be reindexed without the requirement of a standalone session, which was necessary in previous releases. The only tables that now require a standalone session for reindexing are the global system tables `pg_database`, `pg_shadow`, and `pg_group`.

### E.55.3.7. Data Type and Function Changes

- New server parameter `extra_float_digits` to control precision display of floating-point numbers (Pedro Ferreira, Tom)

  This controls output precision which was causing regression testing problems.

- Allow `+1300` as a numeric time-zone specifier, for FJST (Tom)

- Remove rarely used functions `oidrand`, `oidsrand`, and `userfntest` functions (Neil)

- Add `md5()` function to main server, already in `contrib/pgcrypto` (Joe)

  An MD5 function was frequently requested. For more complex encryption capabilities, use `contrib/pgcrypto`.

- Increase date range of `timestamp` (John Cochran)

- Change `EXTRACT(EPOCH FROM timestamp)` so `timestamp without time zone` is assumed to be in local time, not GMT (Tom)

- Trap division by zero in case the operating system doesn't prevent it (Tom)

- Change the `numeric` data type internally to base 10000 (Tom)

- New `hostmask()` function (Greg Wickham)

- Fixes for `to_char()` and `to_timestamp()` (Karel)

- Allow functions that can take any argument data type and return any data type, using `anyelement` and `anyarray` (Joe)

  This allows the creation of functions that can work with any data type.

- Arrays can now be specified as `ARRAY[1,2,3]`, `ARRAY[['a','b'],['c','d']]`, or `ARRAY[ARRAY[ARRAY[2]]]` (Joe)

- Allow proper comparisons for arrays, including `ORDER BY` and `DISTINCT` support (Joe)

- Allow indexes on array columns (Joe)

- Allow array concatenation with `||` (Joe)

- Allow `WHERE` qualification ``expr` `op` ANY/SOME/ALL (`array_expr`)` (Joe)

  This allows arrays to behave like a list of values, for purposes like `SELECT * FROM tab WHERE col IN (array_val)`.

- New array functions `array_append`, `array_cat`, `array_lower`, `array_prepend`, `array_to_string`, `array_upper`, `string_to_array` (Joe)

- Allow user defined aggregates to use polymorphic functions (Joe)

- Allow assignments to empty arrays (Joe)

- Allow 60 in seconds fields of `time`, `timestamp`, and `interval` input values (Tom)

  Sixty-second values are needed for leap seconds.

- Allow `cidr` data type to be cast to `text` (Tom)

- Disallow invalid time zone names in SET TIMEZONE

- Trim trailing spaces when `char` is cast to `varchar` or `text` (Tom)

- Make `float(`p`)` measure the precision `p` in binary digits, not decimal digits (Tom)

- Add IPv6 support to the `inet` and `cidr` data types (Michael Graff)

- Add `family()` function to report whether address is IPv4 or IPv6 (Michael Graff)

- Have `SHOW datestyle` generate output similar to that used by `SET datestyle` (Tom)

- Make `EXTRACT(TIMEZONE)` and `SET/SHOW TIME ZONE` follow the SQL convention for the sign of time zone offsets, i.e., positive is east from UTC (Tom)

- Fix `date_trunc('quarter', ...)` (Böjthe Zoltán)

  Prior releases returned an incorrect value for this function call.

- Make `initcap()` more compatible with Oracle (Mike Nolan)

  `initcap()` now uppercases a letter appearing after any non-alphanumeric character, rather than only after whitespace.

- Allow only `datestyle` field order for date values not in ISO-8601 format (Greg)

- Add new `datestyle` values `MDY`, `DMY`, and `YMD` to set input field order; honor `US` and `European` for backward compatibility (Tom)

- String literals like `'now'` or `'today'` will no longer work as a column default. Use functions such as `now()`, `current_timestamp` instead. (change required for prepared statements) (Tom)

- Treat NaN as larger than any other value in `min()`/`max()` (Tom)

  NaN was already sorted after ordinary numeric values for most purposes, but `min()` and `max()` didn't get this right.

- Prevent interval from suppressing `:00` seconds display

- New functions `pg_get_triggerdef(prettyprint)` and `pg_conversion_is_visible()` (Christopher)

- Allow time to be specified as `040506` or `0405` (Tom)

- Input date order must now be `YYYY-MM-DD` (with 4-digit year) or match `datestyle`

- Make `pg_get_constraintdef` support unique, primary-key, and check constraints (Christopher)

### E.55.3.8. Server-Side Language Changes

- Prevent PL/pgSQL crash when `RETURN NEXT` is used on a zero-row record variable (Tom)

- Make PL/Python's `spi_execute` interface handle null values properly (Andrew Bosma)

- Allow PL/pgSQL to declare variables of composite types without `%ROWTYPE` (Tom)

- Fix PL/Python's `_quote()` function to handle big integers

- Make PL/Python an untrusted language, now called `plpythonu` (Kevin Jacobs, Tom)

  The Python language no longer supports a restricted execution environment, so the trusted version of PL/Python was removed. If this situation changes, a version of PL/Python that can be used by non-superusers will be readded.

- Allow polymorphic PL/pgSQL functions (Joe, Tom)

- Allow polymorphic SQL functions (Joe)

- Improved compiled function caching mechanism in PL/pgSQL with full support for polymorphism (Joe)

- Add new parameter `$0` in PL/pgSQL representing the function's actual return type (Joe)

- Allow PL/Tcl and PL/Python to use the same trigger on multiple tables (Tom)

- Fixed PL/Tcl's `spi_prepare` to accept fully qualified type names in the parameter type list (Jan)

### E.55.3.9. psql Changes

- Add `\pset pager always` to always use pager (Greg)

  This forces the pager to be used even if the number of rows is less than the screen height. This is valuable for rows that wrap across several screen rows.

- Improve tab completion (Rod, Ross Reedstrom, Ian Barwick)

- Reorder `\?` help into groupings (Harald Armin Massa, Bruce)

- Add backslash commands for listing schemas, casts, and conversions (Christopher)

- `\encoding` now changes based on the server parameter `client_encoding` (Tom)

  In previous versions, `\encoding` was not aware of encoding changes made using `SET client_encoding`.

- Save editor buffer into readline history (Ross)

  When `\e` is used to edit a query, the result is saved in the readline history for retrieval using the up arrow.

- Improve `\d` display (Christopher)

- Enhance HTML mode to be more standards-conforming (Greg)

- New `\set AUTOCOMMIT off` capability (Tom)

  This takes the place of the removed server parameter `autocommit`.

- New `\set VERBOSITY` to control error detail (Tom)

  This controls the new error reporting details.

- New prompt escape sequence `%x` to show transaction status (Tom)

- Long options for psql are now available on all platforms

### E.55.3.10. pg_dump Changes

- Multiple pg_dump fixes, including tar format and large objects

- Allow pg_dump to dump specific schemas (Neil)

- Make pg_dump preserve column storage characteristics (Christopher)

  This preserves `ALTER TABLE ... SET STORAGE` information.

- Make pg_dump preserve `CLUSTER` characteristics (Christopher)

- Have pg_dumpall use `GRANT`/`REVOKE` to dump database-level privileges (Tom)

- Allow pg_dumpall to support the options `-a`, `-s`, `-x` of pg_dump (Tom)

- Prevent pg_dump from lowercasing identifiers specified on the command line (Tom)

- pg_dump options `--use-set-session-authorization` and `--no-reconnect` now do nothing, all dumps use `SET SESSION AUTHORIZATION`

  pg_dump no longer reconnects to switch users, but instead always uses `SET SESSION AUTHORIZATION`. This will reduce password prompting during restores.

- Long options for pg_dump are now available on all platforms

  PostgreSQL now includes its own long-option processing routines.

### E.55.3.11. libpq Changes

- Add function `PQfreemem` for freeing memory on Windows, suggested for `NOTIFY` (Bruce)

  Windows requires that memory allocated in a library be freed by a function in the same library, hence `free()` doesn't work for freeing memory allocated by libpq. `PQfreemem` is the proper way to free libpq memory, especially on Windows, and is recommended for other platforms as well.

- Document service capability, and add sample file (Bruce)

  This allows clients to look up connection information in a central file on the client machine.

- Make `PQsetdbLogin` have the same defaults as `PQconnectdb` (Tom)

- Allow libpq to cleanly fail when result sets are too large (Tom)

- Improve performance of function `PQunescapeBytea` (Ben Lamb)

- Allow thread-safe libpq with `configure` option `--enable-thread-safety` (Lee Kindness, Philip Yarra)

- Allow function `pqInternalNotice` to accept a format string and arguments instead of just a preformatted message (Tom, Sean Chittenden)

- Control SSL negotiation with `sslmode` values `disable`, `allow`, `prefer`, and `require` (Jon Jensen)

- Allow new error codes and levels of text (Tom)

- Allow access to the underlying table and column of a query result (Tom)

  This is helpful for query-builder applications that want to know the underlying table and column names associated with a specific result set.

- Allow access to the current transaction status (Tom)

- Add ability to pass binary data directly to the server (Tom)

- Add function `PQexecPrepared` and `PQsendQueryPrepared` functions which perform bind/execute of previously prepared statements (Tom)

### E.55.3.12. JDBC Changes

- Allow `setNull` on updateable result sets

- Allow `executeBatch` on a prepared statement (Barry)

- Support SSL connections (Barry)

- Handle schema names in result sets (Paul Sorenson)

- Add refcursor support (Nic Ferrier)

### E.55.3.13. Miscellaneous Interface Changes

- Prevent possible memory leak or core dump during libpgtcl shutdown (Tom)

- Add Informix compatibility to ECPG (Michael)

  This allows ECPG to process embedded C programs that were written using certain Informix extensions.

- Add type `decimal` to ECPG that is fixed length, for Informix (Michael)

- Allow thread-safe embedded SQL programs with `configure` option `--enable-thread-safety` (Lee Kindness, Bruce)

  This allows multiple threads to access the database at the same time.

- Moved Python client PyGreSQL to http://www.pygresql.org (Marc)

### E.55.3.14. Source Code Changes

- Prevent need for separate platform geometry regression result files (Tom)

- Improved PPC locking primitive (Reinhard Max)

- New function `palloc0` to allocate and clear memory (Bruce)

- Fix locking code for s390x CPU (64-bit) (Tom)

- Allow OpenBSD to use local ident credentials (William Ahern)

- Make query plan trees read-only to executor (Tom)

- Add Darwin startup scripts (David Wheeler)

- Allow libpq to compile with Borland C++ compiler (Lester Godwin, Karl Waclawek)

- Use our own version of `getopt_long()` if needed (Peter)

- Convert administration scripts to C (Peter)

- Bison >= 1.85 is now required to build the PostgreSQL grammar, if building from CVS

- Merge documentation into one book (Peter)

- Add Windows compatibility functions (Bruce)

- Allow client interfaces to compile under MinGW (Bruce)

- New `ereport()` function for error reporting (Tom)

- Support Intel compiler on Linux (Peter)

- Improve Linux startup scripts (Slawomir Sudnik, Darko Prenosil)

- Add support for AMD Opteron and Itanium (Jeffrey W. Baker, Bruce)

- Remove `--enable-recode` option from `configure`

  This was no longer needed now that we have `CREATE CONVERSION`.

- Generate a compile error if spinlock code is not found (Bruce)

  Platforms without spinlock code will now fail to compile, rather than silently using semaphores. This failure can be disabled with a new `configure` option.

### E.55.3.15. Contrib Changes

- Change dbmirror license to BSD

- Improve earthdistance (Bruno Wolff III)

- Portability improvements to pgcrypto (Marko Kreen)

- Prevent crash in xml (John Gray, Michael Richards)

- Update oracle

- Update mysql

- Update cube (Bruno Wolff III)

- Update earthdistance to use cube (Bruno Wolff III)

- Update btree_gist (Oleg)

- New tsearch2 full-text search module (Oleg, Teodor)

- Add hash-based crosstab function to tablefuncs (Joe)

- Add serial column to order `connectby()` siblings in tablefuncs (Nabil Sayegh,Joe)

- Add named persistent connections to dblink (Shridhar Daithanka)

- New pg_autovacuum allows automatic `VACUUM` (Matthew T. O'Connor)

- Make pgbench honor environment variables `PGHOST`, `PGPORT`, `PGUSER` (Tatsuo)

- Improve intarray (Teodor Sigaev)

- Improve pgstattuple (Rod)

- Fix bug in `metaphone()` in fuzzystrmatch

- Improve adddepend (Rod)

- Update spi/timetravel (Böjthe Zoltán)

- Fix dbase `-s` option and improve non-ASCII handling (Thomas Behr, Márcio Smiderle)

- Remove array module because features now included by default (Joe)

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