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$PostgreSQL: pgsql/doc/src/sgml/release.sgml,v 1.253 2004/02/10 20:51:39 neilc Exp $

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<appendix id="release">

<para>Add Mac OS X Rendezvous server support (Chris Campbell)</para>

<para>

This allows Mac OS X hosts to query the network for available

PostgreSQL servers.

<productname>PostgreSQL</productname> servers.

</para>

</listitem>

<varname>max_connections</> 100, if possible (Tom)

</para>

<para>

Prior versions defaulted to 64 shared buffers so PostgreSQL

Prior versions defaulted to 64 shared buffers so<productname>PostgreSQL</productname>

would start on even very old systems. This release tests the

amount of shared memory allowed by the platform and selects more

reasonable default values if possible. Of course, users are

<para>

The SQL standard says that an aggregate function appearing

within a nested subquery belongs to the outer query if its

argument contains only outer-query variables. Prior PostgreSQL

releases did not handle this fine point correctly.

argument contains only outer-query variables. Prior

<productname>PostgreSQL</productname> releases did not handle

this fine point correctly.

</para>

</listitem>

<para>

By default, tables mentioned in the query are automatically

added to the <literal>FROM</> clause if they are not already

there. This is compatible with historic POSTGRES behavior but

is contrary to the SQL standard. This option allows selecting

there. This is compatible with historic

<productname>POSTGRES</productname> behavior but is contrary to

the SQL standard. This option allows selecting

standard-compatible behavior.

</para>

</listitem>

<listitem>

<para>Fix several zero-column table bugs (Tom)</para>

<para>

PostgreSQL supports zero-column tables. This fixes various bugs

<productname>PostgreSQL</productname> supports zero-column tables. This fixes various bugs

that occur when using such tables.

</para>

</listitem>

<listitem>

<para>Long options for <application>pg_dump</application> are now available on all platforms</para>

<para>

PostgreSQL now includes its own long-option processing routines.

<productname>PostgreSQL</productname> now includes its own

long-option processing routines.

</para>

</listitem>

</itemizedlist>

<listitem><para>Allow libpq to compile with Borland C++ compiler (Lester Godwin, Karl Waclawek)</para></listitem>

<listitem><para>Use our own version of <function>getopt_long()</function> if needed (Peter)</para></listitem>

<listitem><para>Convert administration scripts to C (Peter)</para></listitem>

<listitem><para>Bison >= 1.85 is now required to build the PostgreSQL grammar, if building from CVS</para></listitem>

<listitem><para>Bison >= 1.85 is now required to build the<productname>PostgreSQL</> grammar, if building from CVS</para></listitem>

<listitem><para>Merge documentation into one book (Peter)</para></listitem>

<listitem><para>Add Windows compatibility functions (Bruce)</para></listitem>

<listitem><para>Allow client interfaces to compile under MinGW (Bruce)</para></listitem>

<para>

A dump/restore is <emphasis>not</emphasis> required for those

running version 7.3. However, it should be noted that the main

PostgreSQL interface library, libpq, has a new major version

number for this release, which may require recompilation of client

code in certain cases.

<productname>PostgreSQL</productname> interface library, libpq,

has a new major versionnumber for this release, which may require

recompilation of clientcode in certain cases.

</para>

</sect2>

<term>Drop Column</term>

<listitem>

<para>

PostgreSQL now supports the <literal>ALTER TABLE ... DROP

COLUMN</literal> functionality.

<productname>PostgreSQL</productname> now supports the

<literal>ALTER TABLE ... DROPCOLUMN</literal> functionality.

</para>

</listitem>

</varlistentry>

<term>Prepared Queries</term>

<listitem>

<para>

PostgreSQL now supports prepared queries, for improved

performance.

<productname>PostgreSQL</productname> now supports prepared

queries, for improvedperformance.

</para>

</listitem>

</varlistentry>

<term>Dependency Tracking</term>

<listitem>

<para>

PostgreSQL now records object dependencies, which allows

improvements in many areas. <command>DROP</command>

statements now take either <literal>CASCADE</> or

<literal>RESTRICT</> to control whether dependent objects are

also dropped.

<productname>PostgreSQL</productname> now records object

dependencies, which allowsimprovements in many areas.

<command>DROP</command>statements now take either

<literal>CASCADE</> or <literal>RESTRICT</> to control whether

dependent objects arealso dropped.

</para>

</listitem>

</varlistentry>

<itemizedlist>

<listitem><para>Add pg_locks view to show locks (Neil)</para></listitem>

<listitem><para>Security fixes for password negotiation memory allocation (Neil)</para></listitem>

<listitem><para>Remove support for version 0 FE/BE protocol (PostgreSQL 6.2 and earlier) (Tom)</para></listitem>

<listitem><para>Remove support for version 0 FE/BE protocol (<productname>PostgreSQL</productname> 6.2 and earlier) (Tom)</para></listitem>

<listitem><para>Reserve the last few backend slots for superusers, add parameter superuser_reserved_connections to control this (Nigel J. Andrews)</para></listitem>

</itemizedlist>

</sect3>

<para>

This release focuses on removing limitations that have existed in the

PostgreSQL code for many years.

<productname>PostgreSQL</productname> code for many years.

</para>

<para>

</term>

<listitem>

<para>

To maintain database consistency in case

of an operating system crash,previous releases of PostgreSQL have

forcedall data modifications to disk before each transaction commit.

WithWAL, only one log file must be flushed to disk, greatly improving

performance. If you have been using -F in previous releases to disable

disk flushes, you may want to consider discontinuing its use.

To maintain database consistency in case of an operating system crash,

previous releases of<productname>PostgreSQL</productname> have forced

all data modifications to disk before each transaction commit. With

WAL, only one log file must be flushed to disk, greatly improving

performance. If you have been using -F in previous releases to

disabledisk flushes, you may want to consider discontinuing its use.

</para>

</listitem>

</varlistentry>

</term>

<listitem>

<para>

This removes our old

table-level locking, and replaces it with a locking system that is

superior to most commercial database systems. In a traditional system,

each row that is modified is locked until committed, preventing reads by

other users. MVCC uses the natural multiversion nature of PostgreSQL

to allow readers to continue reading consistent data during writer

activity. Writers continue to use the compact pg_log transaction

system. This is all performed without having to allocate a lock for

every row like traditional database systems. So, basically, we no

longer are restricted by simple table-level locking;

we have something better than row-level locking.

This removes our old table-level locking, and replaces it with

a locking system that is superior to most commercial database

systems. In a traditional system, each row that is modified

is locked until committed, preventing reads by other users.

MVCC uses the natural multiversion nature of

<productname>PostgreSQL</productname> to allow readers to

continue reading consistent data during writer activity.

Writers continue to use the compact pg_log transaction system.

This is all performed without having to allocate a lock for

every row like traditional database systems. So, basically,

we no longer are restricted by simple table-level locking; we

have something better than row-level locking.

</para>

</listitem>

</varlistentry>

</term>

<listitem>

<para>

We continue to speed up PostgreSQL, thanks to the variety of

talents within our team. We have sped up memory allocation,

optimization, table joins, and row transfer routines.

We continue to speed up <productname>PostgreSQL</productname>,

thanks to the variety of talents within our team. We have

sped up memory allocation, optimization, table joins, and row

transfer routines.

</para>

</listitem>

</varlistentry>