PostgreSQL alpha releases are snapshots of development code. They are intended to preview and test upcoming features and to provide the possibility for early feedback. They should not be used in production installations or active development projects. While the PostgreSQL code is continuously subject to a number of automated and manual tests, alpha releases might have serious bugs. Also features may be changed incompatibly or removed at any time during the development cycle.
The development cycle of a PostgreSQL major release alternates between periods of development and periods of integration work, called commit fests, normally one month each. Alpha releases are planned to be produced at the end of every commit fest, thus every two months. Since the first commit fest starts within a month from the beginning of development altogether, early alpha releases are not indicative of the likely feature set of the final release.
The current alpha is 9.0alpha4, the fourth alpha for version 9.0. The first three alphas were named "8.5"; the change to 9.0 is due to a project decision to rename the release, but it is still the same actual version.
As alpha releases are intended for developers, it is available in source code form. Binary releases for some platforms may be available later.
We depend on our large community of users to test the features in alpha releases and report issues. If you are able to contribute to PostgreSQL by doing alpha testing, please see our Alpha/Beta Testing Page.