DRAFT (this answer is to be reviewed)
Question
What are the consequences of having a high ratio of 'deleted' to 'active' documents?
Answer
Every document that is deleted is replaced with small amount of metadata called a tombstone which is used for conflict resolution during replication (a tombstone is also created for each document that is in a batch delete operation).
Although tombstone documents contain only a small amount of metadata, having lots of tombstone documents will have an impact on the size of used storage.
Tombstone documents still show up in _changes so require processing for replication and when building views.
- Compaction time is proportional to the ratio of deleted documents to the total document count.
See the FAQ entry "What are the options for purging deleted documents from my database?" for some workarounds.