Hey,
as asked again let me elaborate the state of the PostgreSQL content graph adapter for Neos 9 as how I perceive it.
We are sorely focussing on the content graph here. All other Neos and Flow parts have been historically PostgreSQL compatible and lately have been bug-fixed for 9.x to be that again.
Separate repository for development
While the Neos development collection contains the Neos.ContentGraph.PostgreSQLAdapter package, please do note that this is currently frozen and not subsplitted nor installable.
Instead development happens sorely in the separate repository: Neos.ContentGraph.PostgreSQLAdapter
Alpha phase
I denoted a few points I would hold important for the first alpha version(s)
see → Requirements.
Beta phase
Additionally on the steps for the first alpha I denoted a few points I would hold important for the first beta
see → Requirements.
Neos compatibility with the external Neos.ContentGraph.PostgreSQLAdapter
The Neos versions 9.1.6, 9.0.13 and its successors are fully PostgreSQL compatible aside from the content graph. This is also validated in our Neos CI by running the tests in CI on PostgreSQL and tricking around to use MariaDB just for the content graph.
The idea was to allow to install the PostgreSQLAdapter along Neos 9.0, 9.1 in a single version as the graph requirements rarey change…
…but they do a little for 9.2 where the Workspace has a $version field, that could be handled at runtime or via maintaining 2 versions or deciding just to maintain 9.2 compatibility.
How can 
YOU 
help?
People who speack Management 
(Schnatterenten)
- Organise a sprint for PostgreSQL
- bring developers together to work on this
- organise regular meetings
- build a guild on slack.
Developers with a long not live project - or hobby enthusiasts
- try out the development branch and the soon to be created alpha versions - expect trouble<3
Developers speaking Neos CR
- keep the PostgreSQL adapter up to date with bugfixes for the M*SQL graph
- adjust the PostgreSQL adapter to support newer Neos versions
- like 9.2 which implements workspace versions
Developers speaking PostgreSQL and Neos CR
- review the graph implementation and optimise the schema
- evaluate hierarchy layer concept of M*SQL
- data reduction?
- speed up publishing?
- which might eventually become an implicit requirement as new API methods like diffing changes cannot be satisfied else-how
You cannot help but you need PostgreSQL?
If you have a large project requiring a stable PostgreSQL support you should team up with others with similar interests in the Neos community. Maybe gather a little sponsoring and find other developers to work on this.
