PostgreSQL alpha releases are snapshots of development code. They are intended to preview and test upcoming features and to provide the possibility for early feedback. They should not be used in production installations or active development projects. While the PostgreSQL code is continuously subject to a number of automated and manual tests, alpha releases might have serious bugs. Also features may be changed incompatibly or removed at any time during the development cycle. The development cycle of a PostgreSQL major release alternates between periods of development and periods of integration work, called commit fests, normally one month each. Alpha releases are planned to be produced at the end of every commit fest, thus every two months. Since the first commit fest starts within a month from the beginning of development altogether, early alpha releases are not indicative of the likely feature set of the final release. The primary reason we release alphas is to get users to test new features as early as possible. If you are interested in helping with organized testing, please see the testing information page. A dump/restore using pg_dump, or use of pg_upgrade, is required for those wishing to migrate data from any previous release. Version 9.1 contains a number of changes that may affect compatibility with previous releases. Observe the following incompatibilities: Change the default value of standard_conforming_strings to on (Robert Haas) This removes a long-standing incompatibility with the SQL standard; escape_string_warning has produced warnings about this usage for years. E'' strings the proper way to embed escapes in strings and is unaffected by this change. Disallow function-style and attribute-style data type casts for composite types (Tom Lane) For example, disallow composite_name.text and text(composite_name). CAST and :: are still available for casting. Tighten casting checks for domains based on arrays (Tom Lane) **Details? Change string_to_array() to return an empty array for a zero-length string (Pavel Stehule) Previously this returned NULL. Change string_to_array() so a NULL separator splits the string into characters (Pavel Stehule) Previously this returned NULL. Fix improper checks for before/after triggers (Tom Lane) **Tom, I need more details on the impact of this for existing installs. Require superuser or CREATEROLE permissions in order to set role comments (Tom Lane) Change pg_last_xlog_receive_location() so it never moves backwards (Fujii Masao) Previously pg_last_xlog_receive_location() could move backward when streaming replication is restarted. Have logging of replication connections honor log_connections (Magnus Hagander) Previously replication connections were always logged. Change PL/pgSQL's RAISE command without parameters to be catchable by the attached exception block (Piyush Newe) Previously RAISE in a code block always scoped to an attached exception block, so it was uncatchable at the same scope. Adjust PL/pgSQL's error line reporting code to be consistent with SQL error line reporting (Pavel Stehule) Previously error numbering was off by one. Have pg_stat_reset() reset all database-level statistics (Tom Lane) Some counters were not being reset. Fix some information_schema.triggers column names to match the new SQL-standard names (Dean Rasheed) Treat ECPG cursor names as case-insensitive (Zoltan Boszormenyi) Version 9.1 has ... Allow unlogged tables using UNLOGGED during CREATE TABLE (Robert Haas) These tables are optimized for performance but are cleared in case of a server crash. 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 has only the nullable side of the join. These changes provide additional query optimization possibilities. Merge duplicate fsync requests on busy systems (Robert Haas, Greg Smith) 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) Allow inheritance table queries to return meaningfully-sorted results (Greg Stark, Hans-Jurgen Schonig, Robert Haas, Tom Lane) This allows optimization of ORDER BY and LIMIT clauses in inheritance table queries. Allow optimizations of MIN/MAX for inheritance table queries (Tom Lane) Allow hash joins for array values (Tom Lane) This provides additional query optimization possibilities. Improve GIN index scan cost estimation (Teodor Sigaev) 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 keyword all in the host column of pg_hba.conf (Peter Eisentraut) Previously people used 0.0.0.0/0 or ::/0 for this. Allow GSSAPI to be used to authenticate to servers via SSPI (Christian Ullrich) Specifically this allows Unix-based GSSAPI clients to SSPI authenticate to Windows servers. Add details to the logging of restartpoints and checkpoints, which is controlled by log_checkpoints (Fujii Masao, Greg Smith) New details show WAL file and sync activity. Add log_file_mode which controls the permissions on log files created by the logging_collector (Martin Pihlak) Add client_hostname field to pg_stat_activity (Peter Eisentraut) Previously only the client address was reported. Add pg_stat_xact_* statistic functions and views (Joel Jacobson) These are like the database-wide statistics counter views but reflect counts for only the current transaction. Add record of last reset in database and background writer-level 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 field to pg_stat_bgwriter (Greg Smith) This new field counts the number of times a backend fsyncs a buffer. Allow auto-tuning of wal_buffers (Greg Smith) wal_buffers is now auto-tuned by default based on the size of shared_buffers. Increase the maximum values for deadlock_timeout, log_min_duration_statement, and log_autovacuum_min_duration. 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 to wait for a standby to write the transaction 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 standbys using the streaming replication network connection (Magnus Hagander, Heikki Linnakangas) This avoids the requirement of manually transferring a file system backup when creating a standby server. Add command-line tool pg_basebackup for creating a new standby server or database backup (Magnus Hagander) Add replication permission for roles (Magnus Hagander) This is a read-only permission used for streaming replication and allows non-superusers to initiate replication connections. Previously only superusers could initiate replication connections; superusers have this permission by default. ident authentication over local sockets is now known as peer (Magnus Hagander) The old term is still accepted for backward compatibility. 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 on the primary that generated the most recent commit or abort record applied on the standby. Add variable hot_standby_feedback to enable standbys to postpone cleanup of old row versions on the primary (Simon Riggs) This helps avoid cancelling 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) Cancelations 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 if 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 which disables server restart after a backend crash (Robert Haas) This allows external cluster management software to take control of whether servers restart or not. Allow recovery.conf to use the same quoting behavior as postgresql.conf (Dimitri Fontaine) Previously all values had to be quoted. Allow data-modification commands (INSERT/UPDATE/DELETE) in WITH clauses (Marko Tiikkaja, Hitoshi Harada) This allows INSERT/UPDATE/DELETE RETURNING in WITH clauses to pass rows to outer queries. Allow WITH clauses to be fed into INSERT, UPDATE, DELETE statements (Marko Tiikkaja, Hitoshi Harada) Allow non-GROUP BY columns in the query target list when the primary key is specified in the GROUP BY clause (Peter Eisentraut) Some other database system already allowed this behavior, and because of the primary key, the result is unambiguous. Allow the use of the keyword DISTINCT in UNION/INTERSECT/EXCEPT clauses (Tom Lane) DISTINCT is the default behavior so use of this keyword is redundant. Fix ordinary queries with rules to use the same snapshot behavior as EXPLAIN ANALYZE (Marko Tiikkaja) Previously EXPLAIN ANALYZE used a slightly different snapshot for queries involving rules. The EXPLAIN ANALYZE behavior was judged to be more logical. Add per-column collation support (Peter Eisentraut, Tom Lane) Previously collation could only be set at the database level. Collation can now be set per column, domain, index, or expression. Add support for foreign tables (Shigeru Hanada, Robert Haas, Jan Urbanski, Heikki Linnakangas) This allows data stored in foreign sources to be used like native PostgreSQL-stored data. Allow new values to be added to an existing enum type via ALTER TYPE (Andrew Dunstan) Add ALTER TYPE ... ADD/DROP/ALTER/RENAME ATTRIBUTE (Peter Eisentraut) This allows modification of composite types. Add RESTRICT/CASCADE to ALTER TYPE operations on typed tables (Peter Eisentraut) This controls ADD/DROP/ALTER/RENAME ATTRIBUTE cascading behavior. 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, and 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 added 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, which 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 server backends attempted to add an inheritance parent to the same table at the same time (Robert Haas) ALTER TABLE now takes a stronger lock on the parent table, so that both children do not try to update it simultaneously. Add a SECURITY LABEL command (KaiGai Kohei) This allows security labels to be assigned to objects. Add a true serializable isolation level (Kevin Grittner, Dan Ports) Previously asking for serializable isolation guaranteed only that a single MVCC snapshot would be used for the entire transaction, which allowed certain documented anomalies. The old snapshot isolation level is still accessible by requesting the REPEATABLE READ isolation level. Add transaction-level advisory locks (Marko Tiikkaja) This is similar to the existing session-level advisory locks, but are freed at transaction end. Make TRUNCATE ... RESTART IDENTITY restart sequences transactionally (Steve Singer) Previously the counter could have been left out of sync if a backend crashed between the on-commit truncation activity and commit completion. 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. Have EXPLAIN VERBOSE show the function call expression (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 lock (Robert Haas) It will try to vacuum 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 LIMIT-specified closest values. Allow GIN indexes to index null and empty values (Tom Lane) This allows full GIN index scans. 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). Allow numeric to use a more compact, two-byte header in many cases (Robert Haas) Previously all numeric values had four-byte headers; this saves on disk storage. Add support for dividing money by money (Andy Balholm) Allow binary I/O on type void (Radoslaw Smogura) Improve hypotenuse calculations for geometric operators (Paul Matthews) This avoids unnecessary overflows, and may also be more accurate. Add support for casting between money and numeric (Andy Balholm) 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 supersede functionality that was previously available only using contrib/xml2. Add SQL function format(text), which behaves like C's printf() (Pavel Stehule, Robert Haas) It currently supports formats for strings, SQL literals, and SQL identifiers. Add string functions concat(), concat_ws(), left(), right(), and reverse() (Pavel Stehule) These improve compatibility with other database products. Add function pg_read_binary_file() to read binary files (Dimitri Fontaine, Itagaki Takahiro) Add a single-parameter version of function pg_read_file() to read an entire file (Dimitri Fontaine, Itagaki Takahiro) Add three-parameter forms of array_to_string() and string_to_array() for NULL processing control (Pavel Stehule) 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 OID. It can be used to help interpret the contents of pg_depend. Update comments for built-in operators and their underlying functions (Tom Lane) 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 fields to the information_schema.sequences system view (Peter Eisentraut) Previously, though the view existed, all of these view fields were unimplemented. Allow public as a pseudo-role name in has_table_privilege() and related functions (Alvaro Herrera) This allows checking for public permissions. Allow INSTEAD OF triggers on views (Dean Rasheed) This feature can be used to implement fully updatable views. Minimise lock levels for CREATE TRIGGER and many ALTER TABLE and CREATE RULE operations (Simon Riggs) This improves database availability when altering active databases. Add FOREACH IN ARRAY to PL/pgSQL to allow array iteration (Pavel Stehule) This is more efficient than previous methods. Add FOREACH IN ARRAY to PL/pgSQL to allow array iteration (Pavel Stehule) This is more efficient than previous methods. Allow RAISE without parameters to be caught in the same places that could catch a RAISE ERROR from the same location. The new behavior is more consistent. Allow generic record arguments to PL/Perl functions (Andrew Dunstan) **Andrew, I need details on this. Convert PL/Perl input arguments to Perl arrays (Alexey Klyukin, Alex Hunsaker) String representations are still available. Convert PL/Perl row and 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 now can return multiple OUT parameters and record sets. Add validator to PL/Python (Jan Urbanski) This allows PL/Python functions to be validated 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. Allow PL/Python to access SQLSTATE exception values (Jan Urbanski) **Is this the same as the item above? Add PL/Python explicit subtransactions (Jan Urbanski) Add PL/Python functions for quoting strings (Jan Urbanski) The functions are plpy.quote_ident, plpy.quote_literal, and plpy.quote_nullable. Report PL/Python errors from iterators with PLy_elog (Jan Urbanski) plpy.Fatal now raises FATAL, rather than ERROR (Jan Urbanski) The old behavior was incorrect. Overhaul of PL/Python (Jan Urbanski) This includes exception support for Python 3. **More? Mark createlang and droplang as deprecated now that they use the extension framework (Tom Lane) Add the \conninfo command to psql, 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 system table S option to psql \dn (schemas) (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 using the EDITOR_LINENUMBER_SWITCH 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 psql distinguish between unique indices and unique constraints (Josh Kupershmidt) 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) mode to handle non-standard port numbers, non-standard unix-domain socket locations, permission problems, and stale postmaster lock files (Bruce Momjian) 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 database clients to use Unix-domain sockets to check the user name of the server process using requirepeer (Peter Eisentraut) PostgreSQL already allowed servers to determine the client user name via Unix-domain sockets. Add PQping() and PQpingParams() to libpq (Bruce Momjian, Tom Lane) The allow detection of the server's status without creating a new session. Allow ecpg to accept dynamic cursor names even in WHERE CURRENT OF clauses Add extensions which simplify packaging of additions to PostgreSQL (Dimitri Fontaine, Tom Lane) This is controlled by the new CREATE/ALTER/DROP EXTENSION command; this replaces a more manual method of adding features to PostgreSQL. Require GNU make 3.80 or newer (Peter Eisentraut) Improved parallel make support (Peter Eisentraut) This allows for faster compiles. Also, make -k and make -q now work properly. **When was recursive make supported? 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 with cross-compiling. Add latches to the source code to wait for events (Heikki Linnakangas) Centralize data modification permissions-checking logic (KaiGai Kohei) Add missing get_{object}_oid() functions, for consistency (Robert Haas) Improve ability to use C++ compilers for backend compiles by removing conflicting keywords (Tom Lane) Add support for DragonFly BSD (Rumko) Expose quote_literal_cstr() for backend use (Robert Haas) Run regression tests in the default encoding (Peter Eisentraut) Regression tests were previously always run with SQL_ASCII encoding. Add src/tools/git_changelog to replace cvs2cl and pgcvslog (Robert Haas, Tom Lane) Add git-external-diff script to src/tools (Bruce Momjian) This is used to generate context diffs from git. 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) Modify /contrib modules and stored procedure languages to install via the new extension mechanism (Tom Lane, Dimitri Fontaine) This replaces a more manual method of installation. Add contrib/file_fdw foreign-data wrapper (Shigeru Hanada) Foreign tables using this foreign data wrapper will read flat files in a matter very similar to COPY. Add nearest-neighbor support to contrib/pg_trgm and contrib/btree_gist (Teodor Sigaev) Add contrib/btree_gist support for searching on not equals (Jeff Davis) Allow contrib/fuzzystrmatch's levenshtein() function handle multi-byte characters (Alexander Korotkov) Add ssl_cipher() and ssl_version() functions to contrib/sslinfo (Robert Haas) Fix contrib/intarray and contrib/hstore to give consistent results with indexed empty arrays (Tom Lane) Previously an empty-array query that used an index might return different results from one that used a sequential scan. Allow contrib/intarray to work properly on multi-dimensional arrays (Tom Lane) In contrib/intarray, avoid errors complaining about the presence nulls in cases where no nulls are actually present (Tom Lane) In contrib/intarray, fix behavior of containment operators with respect to empty arrays (Tom Lane) Empty arrays are now correctly considered to be contained in any other array. In contrib/xml2, remove arbitrary limit on the number of parameter=value pairs that can be handled by xslt_process() (Pavel Stehule) The previous limit was 20. In contrib/pageinspect, fix heap_page_item to return infomasks as 32-bit values (Alvaro Herrera) This avoids returning negative values, which was confusing. The underlying value is a 16-bit unsigned integer. Add contrib/sepgsql to interface permission checks with SE-Linux (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) **Confirm this does not affect pg_upgrade 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) Extensive ECPG documentation improvements (Satoshi Nagayasu) Extensive proofreading and documentation improvements (Thom Brown, Josh Kupershmidt, Susanne Ebrecht) Add documentation for exit_on_error (Robert Haas) This parameter causes sessions to exit on any error. Add documentation for pg_options_to_table() (Josh Berkus) This parameter shows table storage options. Document that it is possible to access all composite fields using (compositeval).* syntax (Peter Eisentraut) **Is this syntax new in 9.1? Document that translate() removes characters in from that don't have a corresponding to character (Josh Kupershmidt) Merge docs for CREATE CONSTRAINT TRIGGER and CREATE TRIGGER (Alvaro Herrera) Centralize permission and upgrade documentation (Bruce Momjian) Add kernel tuning documentation for Solaris 10 (Josh Berkus) Previously only Solaris 9 kernel tuning was documented.