Rewriting history

A library to rewrite Datomic history.

This library can rewrite the history of top level entities. A top level entity is an entity that is not referred by any other external entities. That is to say: no other entities is dependent on its existence. This is important because the rewriting will cause the entity ID of the top level entity and its children to change.

Rationale

Regular Datomic excision does not remove retractions of non-existent entities that are part of the first transaction in the new history. This means that sensitive data can be left in the history database as retractions.

See rationale_test.clj for a demonstration of this problem.

This library aims to solve this problem, and leave the user free to rewrite the history as she/he likes.

Features

• Graph / loop structures is supported.

• Regular and component references is supported.

• :db/idents will not be excised during history rewriting and is thus considered permanent.

Limitations

Re-playing the transaction history must use several transactions. It's not possible to both excise and re-play the entire history in one go. Thus this is a potential source of bugs.