BUG #9422: PostgreSQL Zero downtime during deployement

The following bug has been logged on the website:

Bug reference:      9422
Logged by:          Muhammad Khalid
Email address:      muhammadk@chetu.com
PostgreSQL version: 9.2.1
Operating system:   CentOS
Description:

We need some idea about how can we deploy a financial application in
production environment using PostgreSQL DB with zero down time. I have two
servers in Master-Slave design. Currently we are giving downtime while
deploying applications and executing database script. For zero downtime, do
we need any configuration or any third party software or PostgreSQL utility
which will handle this scenario so that in production real time environment
we don't lose any transactions and I also can update database script
simultaneously?