Have you gotten any feedback from the core Postgres team about whether any of the improvements might make it into the mainline, or do you think it will remain an extension for ever?

I haven't studied the design super closely, so there might be shortcomings or design compromises that aren't immediately obvious. But from where I'm sitting the performance improvements seem so extreme that it's hard to see why anyone would not want to replace the current MVCC heap with this.

An undo log-based system is essentially the way Oracle structures its core row storage, with each row mutated in place and containing a header listing the chain of transactions currently holding different versions of it. This means you avoid the bloat that comes with Postgres-style MVCC, by sacrificing some read performance whenever someone needs to read a row that has been mutated but not committed, as the reader has to follow the chain to find the old committed version in the undo log. That's always seemed to me to be a better design. Moving the dead tuple bloat away from the main heap and into a separate undo log makes a lot of sense.

But I wonder if the core team, which is famously quite conservative about introducing big changes, sees this as too different to adopt as a replacement for what's been the state of the art since forever.