-<!-- $PostgreSQL: pgsql/doc/src/sgml/release-9.0.sgml,v 2.35 2010/06/24 18:33:05 rhaas Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/release-9.0.sgml,v 2.36 2010/06/29 21:20:19 tgl Exp $ -->
<sect1 id="release-9-0">
<title>Release 9.0</title>
<listitem>
<para>
- Built-in, binary, log-based replication. This advance consists of two features:
- Hot Standby allows continuous archive standby database servers to accept read-only
- queries, and Streaming Replication allows continuous archive (<acronym>WAL</>) files
- to be streamed over a network port to a standby database server.
+ Built-in, binary, log-based replication. This advance consists of two
+ features: Hot Standby allows continuous archive standby database servers
+ to accept read-only queries, and Streaming Replication allows continuous
+ archive (<acronym>WAL</>) files to be streamed over a network port to a
+ standby database server.
</para>
</listitem>
Broadly enhanced stored procedure support.
The <link linkend="SQL-DO"><command>DO</></link> statement permits
ad-hoc or anonymous code blocks. Functions can now be called using named
- parameters. PL/pgSQL is now installed by default, and PL/Perl and PL/Python
- have been enhanced in several ways, including support for Python3.
+ parameters. PL/pgSQL is now installed by default, and PL/Perl and
+ PL/Python have been enhanced in several ways, including support for
+ Python3.
</para>
</listitem>
<para>
Triggers now support two new features,
SQL-compliant <link
- linkend="SQL-CREATETRIGGER">per-column triggers</link>, and
+ linkend="SQL-CREATETRIGGER">per-column triggers</link>, and
conditional trigger execution.
</para>
</listitem>
<listitem>
<para>
The <link linkend="SQL-LISTEN"><command>LISTEN</></link>/<link
- linkend="SQL-NOTIFY"><command>NOTIFY</></link>
+ linkend="SQL-NOTIFY"><command>NOTIFY</></link>
feature has been overhauled to make it into
a high-performance event queuing system. It now stores
events in a memory-based queue, and it now allows delivery
<para>
A dump/restore using <application>pg_dump</application>
- or use of <application>pg_upgrade</application> is required
+ or use of <application>pg_upgrade</application> is required
for those wishing to migrate data from any previous
release.
</para>
<para>
- Version 9.0 contains a number of changes which selectively break backwards compatibility
- in order to support new features and code quality improvements. Particularly, users
- who make extensive use of PL/pgSQL and/or PITR and Warm Standby should test their
- solutions for breakage. Observe the following incompatibilities:
+ Version 9.0 contains a number of changes which selectively break backwards
+ compatibility in order to support new features and code quality
+ improvements. Particularly, users who make extensive use of PL/pgSQL
+ and/or PITR and Warm Standby should test their solutions for breakage.
+ Observe the following incompatibilities:
</para>
<sect3>
<listitem>
<para>
- No longer change function input variable names via
- <command>REPLACE FUNCTION</command>(Pavel Stehule).
+ <command>CREATE OR REPLACE FUNCTION</command> can no longer change
+ the declared names of function parameters (Pavel Stehule)
</para>
<para>
- In order to support names parameter calls, it is
- no longer possible to change the aliases for input variables
- in the function declaration in place. You now have to <command>DROP
- </command> and recreate the function.
+ In order to support named-parameter calls, it is
+ no longer allowed to change the aliases for input variables
+ in the declaration of an existing function. You now have to
+ <command>DROP</command> and recreate the function.
</para>
</listitem>
</sect3>
<sect3>
- <title>PL/pgSQL Variables</title>
+ <title>PL/pgSQL</title>
<itemizedlist>
<listitem>
<para>
- Have PL/pgSQL throw an error if a variable name conflicts with a
+ PL/pgSQL now throws an error if a variable name conflicts with a
column name used in a query (Tom Lane)
</para>
<para>
- This behavior can be changed via the server variable <link
+ The former behavior was to bind to variable names in preference to
+ query column names, which often resulted in surprising misbehavior.
+ Throwing an error allows easy detection of ambiguous situations.
+ Although it's recommended that functions encountering this type of
+ error be modified to remove the conflict, the old behavior can be
+ restored if necessary via the configuration parameter <link
linkend="plpgsql-var-subst"><varname>plpgsql.variable_conflict</></link>,
- or by the per-function option <literal>#variable_conflict</>.
- The former behavior was to bind to variable names over
- column names, but not consistently. Stored procedures
- with naming conflicts will probably need to be refactored.
+ or via the per-function option <literal>#variable_conflict</>.
</para>
</listitem>
<listitem>
<para>
- Remove PL/pgSQL's <literal>RENAME</> declaration option (Tom Lane)
+ PL/pgSQL no longer allows variable names that match SQL
+ reserved words (Tom Lane)
</para>
<para>
- Instead, use <link
- linkend="plpgsql-declaration-parameters"><literal>ALIAS</></link>,
- which can now alias any variable, not just dollar sign
- variables, e.g. <literal>$1</>.
+ This is a consequence of aligning the PL/pgSQL parser to match the
+ core SQL parser more closely. If necessary,
+ variable names can be double-quoted to avoid this restriction.
</para>
</listitem>
<listitem>
<para>
- PL/pgSQL no longer allows unquoted variables names that match SQL
- reserved words (Tom Lane)
+ PL/pgSQL now requires columns of composite results to match the
+ expected type modifier as well as base type (Pavel Stehule, Tom Lane)
+ </para>
+
+ <para>
+ For example, if a column of the result type is declared as
+ <literal>NUMERIC(30,2)</>, it is no longer acceptable to return a
+ <literal>NUMERIC</> of some other precision in that column. Previous
+ versions neglected to check the type modifier and would thus allow
+ result rows that didn't actually conform to the declared restrictions.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ Remove PL/pgSQL's <literal>RENAME</> declaration option (Tom Lane)
</para>
<para>
- Variables can be double-quoted to avoid this restriction.
+ Instead of <literal>RENAME</>, use <link
+ linkend="plpgsql-declaration-alias"><literal>ALIAS</></link>,
+ which can now alias any variable, not just dollar sign
+ parameter names (such as <literal>$1</>).
</para>
</listitem>
</itemizedlist>
<listitem>
<para>
Remove support for platforms that don't have a working 64-bit
- integer data types (Tom Lane)
+ integer data type (Tom Lane)
</para>
<para>
- It is believed all supported platforms have working 64-bit integer
- data types.
+ It is believed all still-supported platforms have working 64-bit
+ integer data types.
</para>
</listitem>
</itemizedlist>
<sect2>
<title>Changes</title>
<para>
- Version 9.0 has an unprecedented number of new major features,
+ Version 9.0 has an unprecedented number of new major features,
and over 200 enhancements, improvements, new commands,
new functions, and other changes.
</para>
<title>Performance</title>
<para>
- Version 9.0 also contains several performance and optimizer enhancements to
- improve specific uses of PostgreSQL and remedy certain poor-performing cases.
+ Version 9.0 also contains several performance and optimizer enhancements
+ to improve specific uses of PostgreSQL and remedy certain poor-performing
+ cases.
</para>
<itemizedlist>
<para>
Outer joins where the inner side is unique and not referenced in
- the query are unnecessary and are therefore now removed. This will
+ the query are unnecessary and are therefore now removed. This will
accelerate many automatically generated queries, such as those created
by object-relational mappers.
</para>
<sect4>
<title>Monitoring</title>
<para>
- With increased use of PostgreSQL in high-end production systems,
+ With increased use of PostgreSQL in high-end production systems,
users need increased monitoring. PostgresSQL 9.0 continues to add
more ways to monitor PostgreSQL applications.
</para>
</para>
<para>
- This allows DBAs to characterize database traffic
+ This allows DBAs to characterize database traffic
and troubleshoot problems by source application.
</para>
</listitem>
in the new <structname>pg_db_role_setting</> system table. A new
<application>psql</> <literal>\drds</> command shows these settings.
Backwards-compatible system views do not show this information.
- The primary use of this feature is setting schema
+ The primary use of this feature is setting schema
<link linkend="guc-search-path"><varname>search_path</varname></link>.
</para>
</para>
<para>
- For drivers which support this feature, this saves an entire
+ For drivers that support this feature, this saves an entire
round-trip to the client, allowing result counts and pagination
to be calculated without a second <command>COUNT</command> query.
</para>
TABLE CONSTRAINT ... EXCLUDE</></link> clause. While
uniqueness checks could be specified using this syntax,
the real value of this feature is in using complex
- operators that do not have built-in constraints.
+ operators that do not have built-in constraints.
</para>
<para>
The primary use of exclusion constraints is to allow defining
non-overlapping uniqueness, such as for time periods, arrays
- or ranges of values. This supports data integrity at the
+ or ranges of values. This supports data integrity at the
table level for calendaring, time-management, and scientific
applications.
</para>
<para>
LISTEN/NOTIFY may now be used as a full-featured, high-performance
- event queue system for PostgreSQL, with transactional support
+ event queue system for PostgreSQL, with transactional support
and guaranteed delivery.
</para>
</listitem>
</para>
<para>
- The new output formats will support the development of new tools
+ The new output formats will support the development of new tools
for analysis of EXPLAIN output.
</para>
</listitem>
</para>
<para>
- The previous method was usually slower and caused index bloat.
+ The previous method was usually slower and caused index bloat.
Note that the new method may use more disk space during VACUUM
FULL.
</para>
</para>
<para>
- This feature supports GiST indexing of point operations on polygons,
+ This feature supports GiST indexing of point operations on polygons,
circles, and other points, such as "point is in polygon". Previously
- indexing only worked for bounding boxes. This should make many
+ indexing only worked for bounding boxes. This should make many
PostGIS queries faster.
</para>
</listitem>
<listitem>
<para>
- Install server-side language PL/pgSQL by default (Bruce Momjian)
+ Install PL/pgSQL by default (Bruce Momjian)
</para>
</listitem>
<listitem>
<para>
- Allow PL/pgSQL to handle row types with dropped columns (Pavel Stehule)
+ Improve PL/pgSQL's ability to handle row types with dropped columns
+ (Pavel Stehule)
</para>
</listitem>
<listitem>
<para>
- Allow <literal>IN</> parameters to be assigned values within
+ Allow input parameters to be assigned values within
PL/pgSQL functions (Steve Prentice)
</para>
+
+ <para>
+ Formerly, input parameters were treated as being declared
+ <literal>CONST</>. This restriction has been removed to simplify
+ porting of functions from other DBMSes that do not impose the
+ equivalent restriction. An input parameter now acts like a local
+ variable initialized to the passed-in value.
+ </para>
</listitem>
<listitem>
<listitem>
<para>
- Have PL/pgSQL use the main lexer, rather than a custom version (Tom Lane)
+ Make PL/pgSQL use the main lexer, rather than its own version
+ (Tom Lane)
</para>
- </listitem>
-
- </itemizedlist>
- </sect4>
-
- <sect4>
- <title><link linkend="plpgsql-cursors">PL/pgSQL Cursors</link></title>
- <itemizedlist>
+ <para>
+ This ensures accurate tracking of the main system's behavior for details
+ such as string escaping.
+ </para>
+ </listitem>
<listitem>
<para>
- Add count and <literal>ALL</> options to <command>MOVE
+ Add <replaceable>count</> and <literal>ALL</> options to <command>MOVE
FORWARD</>/<literal>BACKWARD</> in PL/pgSQL (Pavel Stehule)
</para>
</listitem>
<listitem>
<para>
- Add PL/pgSQL's <command>OPEN cursor FOR EXECUTE</> to use parameters
- (Pavel Stehule, Itagaki Takahiro)
+ Allow PL/pgSQL's <command>OPEN <replaceable>cursor</> FOR EXECUTE</> to
+ use parameters (Pavel Stehule, Itagaki Takahiro)
</para>
<para>
<listitem>
<para>
- Enable the server lexer to be reentrant (Tom Lane)
+ Enable the server's lexer to be reentrant (Tom Lane)
</para>
<para>
</para>
<para>
- This filter dictionary removes accents from tokens, and
- makes full-text searches over multiple languages much
- easier.
+ This filter dictionary removes accents from letters, which
+ makes full-text searches over multiple languages much easier.
</para>
</listitem>
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