Support an operation to compact the history without writing an archive

[haasn]

This would be semantically equivalent to createArchive, but instead of storing the archive on the disk, just delete it.

I have a pathological case where my working set is a few kB but my archive folder is several gigabytes. I could include my own removeDirectory (xapianDir </> "Archive") call but it feels hacky and arbitrary. Can't acid-state do this as well?

In fact, why doesn't acid-state do this out of the box? It feels like acid-state is designed to fail eventually by running the host out of disk space for history from years ago.

[dmjio]

Per the docs,

createArchive: Move all log files that are no longer necessary for state restoration into the Archive folder in the state directory. This folder can then be backed up or thrown out as you see fit. Reverting to a state before the last checkpoint will not be possible if the Archive folder has been thrown out.

Might be beneficial to have a separate thread monitoring that directory. I don't think acid-state does this out of the box since it probably doesn't want to be responsible for data loss. Since deleting old archives assures you won't be able to rollback to an earlier version.