E. Release Notes
The release notes contain the significant changes in each PostgreSQL™ release, with major features and migration issues listed at the top. The release notes do not contain changes that affect only a few users or changes that are internal and therefore not user-visible. For example, the optimizer is improved in almost every release, but the improvements are usually observed by users as simply faster queries.
A complete list of changes for each release can be obtained by viewing the CVS logs for each release. The pgsql-committers email list records all source code changes as well. There is also a web interface that shows changes to specific files.
The name appearing next to each item represents the major developer for that item. Of course all changes involve community discussion and patch review, so each item is truly a community effort.
E.1. Release 9.1alpha1
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 release notes below highlight user visible changes and new features. There are normally numerous bug fixes and performance improvements in every new snapshot of PostgreSQL, and it would be too bulky to attempt to list them all. Note that many bug fixes are also backported to stable releases of PostgreSQL, and you should be using those if you are looking for bug-fix-only upgrades for your current installations.
These notes are cumulative over all alpha releases of the current development cycle. Items that are new in the latest alpha release are emphasized.
To upgrade from any release to an alpha release or from an alpha release to any other release will most likely require a dump/restore upgrade procedure. It may happen that this is not necessary in particular cases, but that is not verified beforehand. (The server will warn you in any case when a dump/restore is necessary if you attempt to use it with an old data directory.) Note, however, that the dump/restore upgrade procedure is expected to work for alpha releases, and problems in this area should be reported.
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.
Recognize functional dependency on primary keys
This allows a table's other columns to be referenced without listing them in GROUP BY, so long as the primary key column(s) are listed in GROUP BY.
Add CREATE TABLE IF NOT EXISTS
Reduce lock levels of CREATE TRIGGER and some ALTER TABLE, CREATE RULE actions
Add some knowledge about prefix matches to tsmatchsel()
Replace the naive HYPOT() macro with a standards-conformant hypotenuse function
Change the default value of standard_conforming_strings to on
This is a significant incompatibility with previous releases, because it may break unwary applications in security-critical ways.
Add log_file_mode parameter
This allows control of the file permissions set on log files created by the syslogger process.
Add restart_after_crash parameter
Normally, we automatically restart after a backend crash, but in some cases when PostgreSQL is invoked by clusterware it may be desirable to suppress this behavior, so we now provide an option which does that.
Make EXPLAIN show the function call expression of a FunctionScan plan node, but only in VERBOSE mode
Make EXPLAIN print PARAM_EXEC Params as the referenced expressions, rather than just $N
Add vacuum and analyze counters to pg_stat_*_tables views
Add stats functions and views to provide access to a transaction's own statistics counts
Add server authentication over Unix-domain sockets
This adds a libpq connection parameter requirepeer that specifies the user name that the server process is expected to run under.
Add string functions: concat(), concat_ws(), left(), right(), and reverse()
Add three-parameter forms of array_to_string and string_to_array
Add XMLEXISTS function
Add xpath_exists() function
This is equivalent to XMLEXISTS except that it offers support for namespace mapping.
Add xml_is_well_formed, xml_is_well_formed_document, xml_is_well_formed_content functions to the core XML code
These supersede a version previously offered by contrib/xml2.
Allow numeric to use a more compact, 2-byte header in many cases
Add support for dividing money by money (yielding a float8 result) and for casting between money and numeric
Add options to force quoting of all identifiers
This includes a quote_all_identifiers parameter which affects the behavior of the backend, and a --quote-all-identifiers argument to pg_dump and pg_dumpall which sets the parameter and also affects the quoting done internally by those applications.
Add \conninfo command to psql, to show current connection info
Extend psql's \e and \ef commands so that a line number can be specified, and the editor's cursor will be initially placed on that line
To avoid assumptions about what switch the user's editor takes for this purpose, there is a new psql variable EDITOR_LINENUMBER_SWITCH with (at present) no default value.
Add a \sf (show function) command to psql, for those times when you need to look at a function but don't wish to fire up an editor
Make psql distinguish between unique indices and unique constraints in \d printout
Modify the handling of RAISE without parameters so that the error it throws can be caught in the same places that could catch an ordinary RAISE ERROR in the same location
The previous coding insisted on throwing the error from the block containing the active exception handler; which is arguably more surprising, and definitely unlike Oracle's behavior.
Remove ancient PL/pgSQL line numbering hack
PL/pgSQL used to count the second line of the function body as «line 1», if the first line was zero-length. While this hack arguably has some benefit in terms of making PL/pgsql's line numbering match the programmer's expectations, it also makes PL/pgsql inconsistent with the remaining PLs, making it difficult for clients to reliably determine where the error actually is. On balance, it seems better to be consistent.
Add the ability to compute per-statement latencies (ie, average execution times) to pgbench
Teach levenshtein() about multi-byte characters
Add btree_gist support for searching on «not equals»
Add ssl_cipher() and ssl_version() functions to contrib/sslinfo
Remove the arbitrary (and undocumented) limit on the number of parameter=value pairs that can be handled by xslt_process()
Include the backend ID in the relpath of temporary relations
This allows us to reliably remove all leftover temporary relation files on cluster startup without reference to system catalogs or WAL; therefore, we no longer include temporary relations in XLOG_XACT_COMMIT and XLOG_XACT_ABORT WAL records.
Rewrite COMMENT ON object code for better modularity, and add necessary locking
Add a hook in ExecCheckRTPerms() for eventual use by external security-checking modules
Standardize names and calling conventions of get_whatever_oid functions
Make NestLoop plan nodes pass outer-relation variables into their inner relation using the general PARAM_EXEC executor parameter mechanism, rather than the ad-hoc kluge of passing the outer tuple down through ExecReScan
Make details of the Numeric representation private to numeric.c
Suppress some compiler warnings from clang