</para>

<para>

Version 9.1 contains a number of changes that...

Observe the following incompatibilities:

Version 9.1 contains a number of changes thatmay affect compatibility

with previous releases.Observe the following incompatibilities:

</para>

<sect3>

</para>

</listitem>

<listitem>

<para>

Increase the maximum values for <xref linkend="guc-deadlock-timeout">,

<xref linkend="guc-max-standby-archive-delay">,

<xref linkend="guc-max-standby-streaming-delay">,

<xref linkend="guc-log-min-duration-statement">, and

<xref linkend="guc-log-autovacuum-min-duration">.

</para>

<para>

The maximum value for each of these parameters was previously

only about 35 minutes. Much larger values are now allowed.

</para>

</listitem>

</itemizedlist>

</sect4>

</para>

</listitem>

<listitem>

<para>

<link linkend="auth-ident"><literal>ident</literal></link>

authentication over local sockets is now known as

<link linkend="auth-peer"><literal>peer</literal></link>

(Magnus Hagander)

</para>

<para>

The old term is still accepted for backward compatibility.

</para>

</listitem>

</itemizedlist>

<sect4>

</para>

</listitem>

<listitem>

<para>

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)

</para>

<para>

<xref linkend="sql-altertable"> now takes a stronger lock on the

parent table, so that both children do not try to update it

simultaneously.

</para>

</listitem>

</itemizedlist>

</sect4>

</para>

<para>

This function is used to obtain comments on objects.

This function is used to obtain a human-readable string describing an

object, based on the <link linkend="catalog-pg-class"><structname>pg_class</structname></link> OID, object OID, and sub-object OID. It can be used to

help interpret the contents of <link linkend="catalog-pg-depend"><structname>pg_depend</structname></link>.

</para>

</listitem>

<listitem>

<para>

Additional tab completion of <application>psql</> variables (Pavel

Stehule)

</para>

</listitem>

<listitem>

<para>

More <application>psql</> tab completion support (Itagaki

Takahiro)

Additional tab completion support (Itagaki Takahiro, Pavel Stehule,

Andrey Popp, Christoph Berg, David Fetter, Josh Kupershmidt)

</para>

</listitem>