E.27. Release 9.1

Support unlogged tables using the UNLOGGED option in CREATE TABLE (Robert Haas)

Such tables provide better update performance than regular tables, but are not crash-safe: their contents are automatically cleared in case of a server crash. Their contents do not propagate to replication slaves, either.

Allow FULL OUTER JOIN to be implemented as a hash join, and allow either side of a LEFT OUTER JOIN or RIGHT OUTER JOIN to be hashed (Tom Lane)

Previously FULL OUTER JOIN could only be implemented as a merge join, and LEFT OUTER JOIN and RIGHT OUTER JOIN could hash only the nullable side of the join. These changes provide additional query optimization possibilities.

Merge duplicate fsync requests (Robert Haas, Greg Smith)

This greatly improves performance under heavy write loads.

Improve performance of commit_siblings (Greg Smith)

This allows the use of commit_siblings with less overhead.

Reduce the memory requirement for large ispell dictionaries (Pavel Stehule, Tom Lane)

Avoid leaving data files open after "blind writes" (Alvaro Herrera)

This fixes scenarios in which backends might hold files open long after they were deleted, preventing the kernel from reclaiming disk space.

Allow inheritance table scans to return meaningfully-sorted results (Greg Stark, Hans-Jurgen Schonig, Robert Haas, Tom Lane)

This allows better optimization of queries that use ORDER BY, LIMIT, or MIN/MAX with inherited tables.

Improve GIN index scan cost estimation (Teodor Sigaev)

Improve cost estimation for aggregates and window functions (Tom Lane)

Support host names and host suffixes (e.g. .example.com) in pg_hba.conf (Peter Eisentraut)

Previously only host IP addresses and CIDR values were supported.

Support the key word all in the host column of pg_hba.conf (Peter Eisentraut)

Previously people used 0.0.0.0/0 or ::/0 for this.

Reject local lines in pg_hba.conf on platforms that don't support Unix-socket connections (Magnus Hagander)

Formerly, such lines were silently ignored, which could be surprising. This makes the behavior more like other unsupported cases.

Allow GSSAPI to be used to authenticate to servers via SSPI (Christian Ullrich)

Specifically this allows Unix-based GSSAPI clients to do SSPI authentication with Windows servers.

ident authentication over local sockets is now known as peer (Magnus Hagander)

The old term is still accepted for backward compatibility, but since the two methods are fundamentally different, it seemed better to adopt different names for them.

Rewrite peer authentication to avoid use of credential control messages (Tom Lane)

This change makes the peer authentication code simpler and better-performing. However, it requires the platform to provide the getpeereid function or an equivalent socket operation. So far as is known, the only platform for which peer authentication worked before and now will not is pre-5.0 NetBSD.

Add details to the logging of restartpoints and checkpoints, which is controlled by log_checkpoints (Fujii Masao, Greg Smith)

New details include WAL file and sync activity.

Add log_file_mode which controls the permissions on log files created by the logging collector (Martin Pihlak)

Reduce the default maximum line length for syslog logging to 900 bytes plus prefixes (Noah Misch)

This avoids truncation of long log lines on syslog implementations that have a 1KB length limit, rather than the more common 2KB.

Add client_hostname column to pg_stat_activity (Peter Eisentraut)

Previously only the client address was reported.

Add pg_stat_xact_* statistics functions and views (Joel Jacobson)

These are like the database-wide statistics counter views, but reflect counts for only the current transaction.

Add time of last reset in database-level and background writer statistics views (Tomas Vondra)

Add columns showing the number of vacuum and analyze operations in pg_stat_*_tables views (Magnus Hagander)

Add buffers_backend_fsync column to pg_stat_bgwriter (Greg Smith)

This new column counts the number of times a backend fsyncs a buffer.

Provide auto-tuning of wal_buffers (Greg Smith)

By default, the value of wal_buffers is now chosen automatically based on the value of shared_buffers.

Increase the maximum values for deadlock_timeout, log_min_duration_statement, and log_autovacuum_min_duration (Peter Eisentraut)

The maximum value for each of these parameters was previously only about 35 minutes. Much larger values are now allowed.

Allow synchronous replication (Simon Riggs, Fujii Masao)

This allows the primary server to wait for a standby to write a transaction's information to disk before acknowledging the commit. One standby at a time can take the role of the synchronous standby, as controlled by the synchronous_standby_names setting. Synchronous replication can be enabled or disabled on a per-transaction basis using the synchronous_commit setting.

Add protocol support for sending file system backups to standby servers using the streaming replication network connection (Magnus Hagander, Heikki Linnakangas)

This avoids the requirement of manually transferring a file system backup when setting up a standby server.

Add replication_timeout setting (Fujii Masao, Heikki Linnakangas)

Replication connections that are idle for more than the replication_timeout interval will be terminated automatically. Formerly, a failed connection was typically not detected until the TCP timeout elapsed, which is inconveniently long in many situations.

Add command-line tool pg_basebackup for creating a new standby server or database backup (Magnus Hagander)

Add a replication permission for roles (Magnus Hagander)

This is a read-only permission used for streaming replication. It allows a non-superuser role to be used for replication connections. Previously only superusers could initiate replication connections; superusers still have this permission by default.

Add system view pg_stat_replication which displays activity of WAL sender processes (Itagaki Takahiro, Simon Riggs)

This reports the status of all connected standby servers.

Add monitoring function pg_last_xact_replay_timestamp() (Fujii Masao)

This returns the time at which the primary generated the most recent commit or abort record applied on the standby.

Add configuration parameter hot_standby_feedback to enable standbys to postpone cleanup of old row versions on the primary (Simon Riggs)

This helps avoid canceling long-running queries on the standby.

Add the pg_stat_database_conflicts system view to show queries that have been canceled and the reason (Magnus Hagander)

Cancellations can occur because of dropped tablespaces, lock timeouts, old snapshots, pinned buffers, and deadlocks.

Add a conflicts count to pg_stat_database (Magnus Hagander)

This is the number of conflicts that occurred in the database.

Increase the maximum values for max_standby_archive_delay and max_standby_streaming_delay

The maximum value for each of these parameters was previously only about 35 minutes. Much larger values are now allowed.

Add ERRCODE_T_R_DATABASE_DROPPED error code to report recovery conflicts due to dropped databases (Tatsuo Ishii)

This is useful for connection pooling software.

Add functions to control streaming replication replay (Simon Riggs)

The new functions are pg_xlog_replay_pause(), pg_xlog_replay_resume(), and the status function pg_is_xlog_replay_paused().

Add recovery.conf setting pause_at_recovery_target to pause recovery at target (Simon Riggs)

This allows a recovery server to be queried to check whether the recovery point is the one desired.

Add the ability to create named restore points using pg_create_restore_point() (Jaime Casanova)

These named restore points can be specified as recovery targets using the new recovery.conf setting recovery_target_name.

Allow standby recovery to switch to a new timeline automatically (Heikki Linnakangas)

Now standby servers scan the archive directory for new timelines periodically.

Add restart_after_crash setting which disables automatic server restart after a backend crash (Robert Haas)

This allows external cluster management software to control whether the database server restarts or not.

Allow recovery.conf to use the same quoting behavior as postgresql.conf (Dimitri Fontaine)

Previously all values had to be quoted.

Add per-column collation support (Peter Eisentraut, Tom Lane)

Previously collation (the sort ordering of text strings) could only be chosen at database creation. Collation can now be set per column, domain, index, or expression, via the SQL-standard COLLATE clause.

Add RESTRICT/CASCADE to ALTER TYPE operations on typed tables (Peter Eisentraut)

This controls ADD/DROP/ALTER/RENAME ATTRIBUTE cascading behavior.

Support ALTER TABLE name {OF | NOT OF} type (Noah Misch)

This syntax allows a standalone table to be made into a typed table, or a typed table to be made standalone.

Add support for more object types in ALTER ... SET SCHEMA commands (Dimitri Fontaine)

This command is now supported for conversions, operators, operator classes, operator families, text search configurations, text search dictionaries, text search parsers, and text search templates.

Add ALTER TABLE ... ADD UNIQUE/PRIMARY KEY USING INDEX (Gurjeet Singh)

This allows a primary key or unique constraint to be defined using an existing unique index, including a concurrently created unique index.

Allow ALTER TABLE to add foreign keys without validation (Simon Riggs)

The new option is called NOT VALID. The constraint's state can later be modified to VALIDATED and validation checks performed. Together these allow you to add a foreign key with minimal impact on read and write operations.

Allow ALTER TABLE ... SET DATA TYPE to avoid table rewrites in appropriate cases (Noah Misch, Robert Haas)

For example, converting a varchar column to text no longer requires a rewrite of the table. However, increasing the length constraint on a varchar column still requires a table rewrite.

Add CREATE TABLE IF NOT EXISTS syntax (Robert Haas)

This allows table creation without causing an error if the table already exists.

Fix possible "tuple concurrently updated" error when two backends attempt to add an inheritance child to the same table at the same time (Robert Haas)

ALTER TABLE now takes a stronger lock on the parent table, so that the sessions cannot try to update it simultaneously.

Add a SECURITY LABEL command (KaiGai Kohei)

This allows security labels to be assigned to objects.

Add ENCODING option to COPY TO/FROM (Hitoshi Harada, Itagaki Takahiro)

This allows the encoding of the COPY file to be specified separately from client encoding.

Add bidirectional COPY protocol support (Fujii Masao)

This is currently only used by streaming replication.

Make EXPLAIN VERBOSE show the function call expression in a FunctionScan node (Tom Lane)

Add additional details to the output of VACUUM FULL VERBOSE and CLUSTER VERBOSE (Itagaki Takahiro)

New information includes the live and dead tuple count and whether CLUSTER is using an index to rebuild.

Prevent autovacuum from waiting if it cannot acquire a table lock (Robert Haas)

It will try to vacuum that table later.

Allow CLUSTER to sort the table rather than scanning the index when it seems likely to be cheaper (Leonardo Francalanci)

Add nearest-neighbor (order-by-operator) searching to GiST indexes (Teodor Sigaev, Tom Lane)

This allows GiST indexes to quickly return the N closest values in a query with LIMIT. For example

SELECT * FROM places ORDER BY location <-> point '(101,456)' LIMIT 10;

finds the ten places closest to a given target point.

Allow GIN indexes to index null and empty values (Tom Lane)

This allows full GIN index scans, and fixes various corner cases in which GIN scans would fail.

Allow GIN indexes to better recognize duplicate search entries (Tom Lane)

This reduces the cost of index scans, especially in cases where it avoids unnecessary full index scans.

Fix GiST indexes to be fully crash-safe (Heikki Linnakangas)

Previously there were rare cases where a REINDEX would be required (you would be informed).

Add support for casting between money and numeric (Andy Balholm)

Add support for casting from int4 and int8 to money (Joey Adams)

Allow casting a table's row type to the table's supertype if it's a typed table (Peter Eisentraut)

This is analogous to the existing facility that allows casting a row type to a supertable's row type.

Add XML function XMLEXISTS and xpath_exists() functions (Mike Fowler)

These are used for XPath matching.

Add XML functions xml_is_well_formed(), xml_is_well_formed_document(), xml_is_well_formed_content() (Mike Fowler)

These check whether the input is properly-formed XML. They provide functionality that was previously available only in the deprecated contrib/xml2 module.

Add the pg_describe_object() function (Alvaro Herrera)

This function is used to obtain a human-readable string describing an object, based on the pg_class OID, object OID, and sub-object ID. It can be used to help interpret the contents of pg_depend.

Update comments for built-in operators and their underlying functions (Tom Lane)

Functions that are meant to be used via an associated operator are now commented as such.

Add variable quote_all_identifiers to force the quoting of all identifiers in EXPLAIN and in system catalog functions like pg_get_viewdef() (Robert Haas)

This makes exporting schemas to tools and other databases with different quoting rules easier.

Add columns to the information_schema.sequences system view (Peter Eisentraut)

Previously, though the view existed, the columns about the sequence parameters were unimplemented.

Allow public as a pseudo-role name in has_table_privilege() and related functions (Alvaro Herrera)

This allows checking for public permissions.

Support INSTEAD OF triggers on views (Dean Rasheed)

This feature can be used to implement fully updatable views.

Add FOREACH IN ARRAY to PL/pgSQL (Pavel Stehule)

This is more efficient and readable than previous methods of iterating through the elements of an array value.

Allow RAISE without parameters to be caught in the same places that could catch a RAISE ERROR from the same location (Piyush Newe)

The previous coding threw the error from the block containing the active exception handler. The new behavior is more consistent with other DBMS products.

Allow generic record arguments to PL/Perl functions (Andrew Dunstan)

PL/Perl functions can now be declared to accept type record. The behavior is the same as for any named composite type.

Convert PL/Perl array arguments to Perl arrays (Alexey Klyukin, Alex Hunsaker)

String representations are still available.

Convert PL/Perl composite-type arguments to Perl hashes (Alexey Klyukin, Alex Hunsaker)

String representations are still available.

Add table function support for PL/Python (Jan Urbanski)

PL/Python can now return multiple OUT parameters and record sets.

Add a validator to PL/Python (Jan Urbanski)

This allows PL/Python functions to be syntax-checked at function creation time.

Allow exceptions for SQL queries in PL/Python (Jan Urbanski)

This allows access to SQL-generated exception error codes from PL/Python exception blocks.

Add explicit subtransactions to PL/Python (Jan Urbanski)

Add PL/Python functions for quoting strings (Jan Urbanski)

These functions are plpy.quote_ident, plpy.quote_literal, and plpy.quote_nullable.

Add traceback information to PL/Python errors (Jan Urbanski)

Report PL/Python errors from iterators with PLy_elog (Jan Urbanski)

Fix exception handling with Python 3 (Jan Urbanski)

Exception classes were previously not available in plpy under Python 3.

Add psql command \conninfo to show current connection information (David Christensen)

Add psql command \sf to show a function's definition (Pavel Stehule)

Add psql command \dL to list languages (Fernando Ike)

Add the S ("system") option to psql's \dn (list schemas) command (Tom Lane)

\dn without S now suppresses system schemas.

Allow psql's \e and \ef commands to accept a line number to be used to position the cursor in the editor (Pavel Stehule)

This is passed to the editor according to the PSQL_EDITOR_LINENUMBER_ARG environment variable.

Have psql set the client encoding from the operating system locale by default (Heikki Linnakangas)

This only happens if the PGCLIENTENCODING environment variable is not set.

Make \d distinguish between unique indexes and unique constraints (Josh Kupershmidt)

Make \dt+ report pg_table_size instead of pg_relation_size when talking to 9.0 or later servers (Bernd Helmle)

This is a more useful measure of table size, but note that it is not identical to what was previously reported in the same display.

Additional tab completion support (Itagaki Takahiro, Pavel Stehule, Andrey Popp, Christoph Berg, David Fetter, Josh Kupershmidt)

Add pg_dump and pg_dumpall option --quote-all-identifiers to force quoting of all identifiers (Robert Haas)

Add directory format to pg_dump (Joachim Wieland, Heikki Linnakangas)

This is internally similar to the tar pg_dump format.

Fix pg_ctl so it no longer incorrectly reports that the server is not running (Bruce Momjian)

Previously this could happen if the server was running but pg_ctl could not authenticate.

Improve pg_ctl start's "wait" (-w) option (Bruce Momjian, Tom Lane)

The wait mode is now significantly more robust. It will not get confused by non-default postmaster port numbers, non-default Unix-domain socket locations, permission problems, or stale postmaster lock files.

Add promote option to pg_ctl to switch a standby server to primary (Fujii Masao)

Add a libpq connection option client_encoding which behaves like the PGCLIENTENCODING environment variable (Heikki Linnakangas)

The value auto sets the client encoding based on the operating system locale.

Add PQlibVersion() function which returns the libpq library version (Magnus Hagander)

libpq already had PQserverVersion() which returns the server version.

Allow libpq-using clients to check the user name of the server process when connecting via Unix-domain sockets, with the new requirepeer connection option (Peter Eisentraut)

PostgreSQL already allowed servers to check the client user name when connecting via Unix-domain sockets.

Add PQping() and PQpingParams() to libpq (Bruce Momjian, Tom Lane)

These functions allow detection of the server's status without trying to open a new session.

Allow ECPG to accept dynamic cursor names even in WHERE CURRENT OF clauses (Zoltan Boszormenyi)

Make ecpglib write double values with a precision of 15 digits, not 14 as formerly (Akira Kurosawa)

Improved parallel make support (Peter Eisentraut)

This allows for faster compiles. Also, make -k now works more consistently.

Require GNU make 3.80 or newer (Peter Eisentraut)

This is necessary because of the parallel-make improvements.

Add make maintainer-check target (Peter Eisentraut)

This target performs various source code checks that are not appropriate for either the build or the regression tests. Currently: duplicate_oids, SGML syntax and tabs check, NLS syntax check.

Support make check in contrib (Peter Eisentraut)

Formerly only make installcheck worked, but now there is support for testing in a temporary installation. The top-level make check-world target now includes testing contrib this way.

On Windows, allow pg_ctl to register the service as auto-start or start-on-demand (Quan Zongliang)

Add support for collecting crash dumps on Windows (Craig Ringer, Magnus Hagander)

minidumps can now be generated by non-debug Windows binaries and analyzed by standard debugging tools.

Enable building with the MinGW64 compiler (Andrew Dunstan)

This allows building 64-bit Windows binaries even on non-Windows platforms via cross-compiling.

Add source code hooks to check permissions (Robert Haas, Stephen Frost)

Add post-object-creation function hooks for use by security frameworks (KaiGai Kohei)

Add a client authentication hook (KaiGai Kohei)

Add contrib/sepgsql to interface permission checks with SELinux (KaiGai Kohei)

This uses the new SECURITY LABEL facility.

Add contrib module auth_delay (KaiGai Kohei)

This causes the server to pause before returning authentication failure; it is designed to make brute force password attacks more difficult.

Add dummy_seclabel contrib module (KaiGai Kohei)

This is used for permission regression testing.

Add support for LIKE and ILIKE index searches to contrib/pg_trgm (Alexander Korotkov)

Add levenshtein_less_equal() function to contrib/fuzzystrmatch, which is optimized for small distances (Alexander Korotkov)

Improve performance of index lookups on contrib/seg columns (Alexander Korotkov)

Improve performance of pg_upgrade for databases with many relations (Bruce Momjian)

Add flag to contrib/pgbench to report per-statement latencies (Florian Pflug)

Move src/tools/test_fsync to contrib/pg_test_fsync (Bruce Momjian, Tom Lane)

Add O_DIRECT support to contrib/pg_test_fsync (Bruce Momjian)

This matches the use of O_DIRECT by wal_sync_method.

Add new tests to contrib/pg_test_fsync (Bruce Momjian)