How are documents deleted by sync gateway?

I am trying to debug an issue with my app trying to retrieve deleted documents. I want to know what the original doc it was trying to retrieve was, but all I can find is the current version which just has sync gateway metadata. On our dev server when I delete a doc I am still able to retrieve previous versions by using the admin url. E.g if I delete doc with id=xxx and it has rev 1-a and rev 1-b, where 1-b is just the metadata with the _deleted flag, I can retrieve 1-a by using:
localhost:4985//xxx?rev=1-a

When I try this on our production server with the actual docs I get:
{“error”:“not found”,“reason”:“deleted”}

Does sync gateway clean up old docs and remove them if they were deleted? Is there any way I can retrieve the document data of deleted documents, or was it removed from couchbase forever?

It sounds like there might be a difference in your dev and production configs. You can set the revs_limit in the database config. Do they appear to be different?

To answer the question above, once a compaction happens, the documents are deleted forever (other than doing some forensic work on the filesystem, perhaps).

Thanks for letting me know. Makes sense that they would be removed during compaction.