Is the duration of pruning roughly proportional to the size of the data.mdb file?

Question

I have the blockchain already downloaded. I stopped monerod and restarted it with a configuration file with prune-blockchain=true in it. I started monerod again and the last bit of output was:

2022-10-22 00:48:51.697 I Monero 'Fluorine Fermi' (v0.18.1.2-release)
2022-10-22 00:48:51.698 I Initializing cryptonote protocol...
2022-10-22 00:48:51.698 I Cryptonote protocol initialized OK
2022-10-22 00:48:51.698 I Initializing core...
2022-10-22 00:48:51.698 I Loading blockchain from folder [REDACTED]
2022-10-22 00:50:24.372 I Loading checkpoints
2022-10-22 00:50:24.726 I Pruning blockchain...

The data.mdb file in my lmdb folder is 152285372416 (about 152 GB). Can I translate that size into an expected duration for the pruning process? If it isn't roughly proportional to the size of the data.mdb file, is there another metric that can be used to estimate how long it will take?

Answer 1

Is the duration of pruning roughly proportional to the size of the data.mdb file?

Yes. The bigger blockchain you have the longer it will take.

Can I translate that size into an expected duration for the pruning process?

How fast your computer is (RAM, CPU and disk) will determine how long it will take. It will certainly be a lot quicker than starting over, but remember, pruning an already downloaded blockchain wont shrink the database size on disk, it will just mark space as free to use in future, thus slowing growth rate (ref this answer).