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<sect1 id="release-9-0">

<title>Release 9.0</title>

Add support for compiling on <link

linkend="install-win32-full">64-bit

<productname>Windows</></link> and running in 64-bit

mode

mode.

</para>

</listitem>

<para>CURRENT AS OF 2010-06-03</para>

<para>

A dump/restore using <application>pg_dump</application> is

required for those wishing to migrate data from any previous

A dump/restore using <application>pg_dump</application>

or use of <application>pg_upgrade</application> is required

for those wishing to migrate data from any previous

release.

</para>

<para>

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>

linkend="guc-geqo-seed">geqo_seed</link> to randomize

the starting value of the random plan generator.

</para>

<para>

This gives GEQO query response times and resource usage

repeatability and predictability.

</para>

</listitem>

<listitem>

name</link>, which is displayed in

<structname>pg_stat_activity</> (Dave Page)

</para>

<para>

This allows DBAs to characterize database traffic

and troubleshoot problems by source application.

</para>

</listitem>

<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

<link linkend="guc-search-path"><varname>search_path</varname></link>.

</para>

</listitem>

<listitem>

Log changed parameter values when <filename>postgresql.conf</> is

reloaded (Peter Eisentraut)

</para>

<para>

This lets DBAs and security staff to audit when database settings

were changed.

</para>

</listitem>

<listitem>

(Boszormenyi Zoltan)

</para>

<para>

For drivers which 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>

<para>

<application>psql</> does not display these counts.

</para>

<para>

Such operations either complete fully or are rolled back, so

<acronym>WAL</> archiving can be skipped, unless running in continuous

archiving mode.

archiving mode. This reduces I/O overhead and improves performance.

</para>

</listitem>

<function>PQescapeByteaConn()</> now uses the hex format

for <productname>PostgreSQL</> 9.0 servers.

</para>

<para>

The new hex format will be directly compatible with more applications

which use binary data, allowing them to store and retrieve

it without conversion.

</para>

</listitem>

<listitem>

<para>

For example, this is now supported, <literal>array_agg(a ORDER BY

b)</>. This is useful for aggregates where the order of values is

significant.

significant, and eliminates the need to have a subquery for

the ordering.

</para>

</listitem>