postgresql blocks update to 9.4beta3 with existing clusters

[joshiss]

while running apt-get update the postgresql failed to install

E: /var/cache/apt/archives/postgresql-9.4_9.4~beta3-1_i386.deb: subprocess new pre-installation script returned error exit status 1

(synaptic:10406): GLib-CRITICAL **: g_child_watch_add_full: assertion 'pid > 0' failed
(Reading database ... 827605 files and directories currently installed.)
Preparing to unpack .../postgresql-9.4_9.4~beta3-1_i386.deb ...
 * Stopping PostgreSQL 9.4 database server [ OK ]
ERROR: The database format changed between beta 2 and 3. Please dump your 9.4 clusters first and remove them before upgrading the package.
dpkg: error processing archive /var/cache/apt/archives/postgresql-9.4_9.4~beta3-1_i386.deb (--unpack):
 subprocess new pre-installation script returned error exit status 1
Errors were encountered while processing:
 /var/cache/apt/archives/postgresql-9.4_9.4~beta3-1_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
A package failed to install. Trying to recover:

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: postgresql 9.4+162
ProcVersionSignature: Ubuntu 3.16.0-22.29-generic 3.16.4
Uname: Linux 3.16.0-22-generic i686
NonfreeKernelModules: wl
ApportVersion: 2.14.7-0ubuntu5
Architecture: i386
CurrentDesktop: Unity
Date: Sun Oct 12 12:41:23 2014
InstallationDate: Installed on 2012-03-24 (931 days ago)
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Alpha i386 (20120324)
PackageArchitecture: all
SourcePackage: postgresql-common
UpgradeStatus: Upgraded to utopic on 2014-08-24 (49 days ago)

[Martin Pitt (pitti)]

> ERROR: The database format changed between beta 2 and 3. Please dump your 9.4 clusters first and remove them before upgrading the package.

Indeed. Sorry about that, 9.4 beta prematurely slipped into utopic. This is a safety measure so that you don't lose your existing databases after upgrading to beta 3. You need to make a dump of your existing clusters (using pg_dumpall), and then either remove the clusters using pg_dropcluster or purge the postgresql-9.4 package, and then install/upgrade the latest version.

Sorry for the inconvenience!