Implement Backup

[alexanderkiel]

The idea doesn't work, because referential integrity will most likely violated on restore. But I'll leave this here for possible improvements.

The idea is to implement a simple backup using the system history interaction.

Full Backup

A full backup can be obtained by paging through the whole output of the system history interaction. Such paging should be stable on a FHIR server. So no versions should be missing or duplicate.

Incremental Backups

After the first download of all versions, incremental backups are possible using the _since query parameter. The last seen versions timestamp can be obtained through response.lastModified.

Full Restore without History

The history bundles can be processed from the most recent to the least recent. For each entry:

• the combination of resourceType and id will be looked up in a table
• if the resource was already processed or the request is a DELETE, the entry will be skipped
• if the request is a POST or PUT, the entry will be appended to a transaction bundle

Transaction bundles are then POST'ed to the server to restore. The result would be that all resources are restored but without any history.