A Document Runner would provide functionality to run a transform function across all documents in the database. This way you could do maintenance and migrations, with incurring a bunch of http overhead.
The idea was originally floated on the couchdb-user mailing list.
Requirements
Ability to specify a job in a view-server like context (Javascript other language function) and have it run across all docs (like a view is), but with the additional ability to write back to the document (through the http api, so we don't have to add a socket-based update interface).
Caveat:
We may not be able to guarantee that runner functions see each document only once, so functions need to be aware only to modify documents that require modification.
Uses
- Changing the format of a timestamp across all docs
- Removing sensitive fields before replicating to another jurisdiction
- (View runner... slightly different) Materializing the results of group=true reduce queries into a dataset for further map/reduce processing (a common pattern in Hadoop)