[amitkapila]

Vacuum can't recover dead space in all cases. Consider if the dead rows are distributed throughout the table, it won't be able to reclaim it, only it can facilitate the future insertions into it. Also, the work it does to do that is many-a-times quite heavy for many workloads as it can slow down the system. I think you haven't fully looked at all the other benefits of this system which includes reducing write amplification by (a) by avoiding rewrites due to freezing, hint bits (b) making it possible to do an update that touches indexed columns without updating every index.

I think there are other benefits too in terms of just raw performance because it avoids a lot of work like HOT pruning. Yes, it instead needs to discard undo, but that is much cheaper.

In general, I think it is an overstatement to say that this is a wasted effort.

[garyclarke27]

Yes I didn’t mean completely wasted, just feels to me that this requires a huge effort and is a risk to Postgres’s legendary reliability - for a relatively small gain, especially considering that ssd storage capacity will continue to increase dramatically and plummet in price. Would be better I think to prepare for new paradigm of unified immutable memory coming v soon, (Optane already shipping) which will enable Postgres to compete with ‘in memory, databases like SAP Hanna