non-Datomic persisted backend about datascript HOT 2 CLOSED

Converting data is a performance hit, of course. But DS does not require namespaced attributes, :name or :title would work fine. It’s convenient to use namespaced attrs so you can differentiate entity types by attribute name (e.g. :person/name is certainly a person, but :name could be person, car, dog, anything). If you don’t have this ambiguity, you’ll do fine without namespace. Another option is to have special “:type” attribute.

Biggest penalty comes not from attributes, but from managing cross-entities references. In DS, entities should reference each other by :db/id attribute, it should be a number and it should be unique among all entities. So you cannot directly assign entities ids = PK from SQL database, as in different tables there may be overlapping PKs.

There’re two solution to this. First is to let DS assign ids and store PKs in external id attribute. This is how we convert to DS format in acha-acha: https://github.com/clojurecup2014/acha/blob/clojurecup/src-cljs/acha.cljs#L418

Second is to tune your DB so that different tables have non-overlapping id ranges. It allows for PK to be used directly as :db/id in DataScript. We moved to this solution in Acha-acha, as it eliminates lookup by external id at conversion step and makes server pushes much easier to handle. Here’s an example for SQLite https://github.com/clojurecup2014/acha/blob/0.2.0/src-clj/acha/db.clj#L67

from datascript.

Thanks for the informative answer @tonsky.

from datascript.