We just found that our prod SGW 3.0.3 (Couchbase 6.6.3) installation flooded the log with these kind of warning messages:
2022-09-12T12:49:35.354+02:00 [WRN] c:#001 Error compacting key 349B70F0E729D83CC12588B80025991B (purge) - tombstone will not be compacted. SubdocGetBodyAndXattr 349B70F0E729D83CC12588B80025991B: Not Found – db.(*Database).Compact() at database.go:1195
We solved it by dropping the sg_tombstone_x1 indizies and re-creating them. As far as I understand the message tells me that the index contains data about deleted documents, but the corresponding xattr._sync.tombstoned_at data is not available anymore.
How can this happen?