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<sect1 id="pgupgrade">

<title>pg_upgrade</title>

9.0.1 -> 9.0.4.

</para>

<para>

<application>pg_upgrade</> works because, though new features are

regularly added to Postgres major releases, the internal data storage

format rarely changes. <application>pg_upgrade</> does its best to

make sure the old and new clusters are binary-compatible, e.g. by

checking for compatible compile-time settings. It is important that

any external modules are also binary compatibile, though this cannot

be checked by <application>pg_upgrade</>.

</para>

<sect2>

<title>Supported Versions</title>

<sect2>

<title>Limitations in migrating <emphasis>from</> PostgreSQL 8.3</title>

<para>

Upgrading from PostgreSQL 8.3 has additional restrictions not present

when upgrading from later PostgreSQL releases. For example,

For Windows users, note that due to different integer datetimes settings

used by the one-click installer and the MSI installer, it is only

possible to upgrade from version 8.3 of the one-click distribution to

version 8.4 of the one-click distribution. It is not possible to upgrade

from the MSI installer to the one-click installer.

version 8.4or laterof the one-click distribution. It is not

possible to upgradefrom the MSI installer to the one-click installer.

</para>

<para>