ADR-0009: Core Datomic schema scope for v1

Status: Accepted (2026-07-15)

Context

Datomic's attribute system has a well-understood core plus features that pull in significant machinery: :db/fulltext (a text index engine), tuple value types (composite uniqueness), entity specs/:db/ensure.

Decision

v1 implements the core: attributes as entities; :db/ident; value types bool, long, double, bigint, bigdec, instant, uuid, keyword, string, bytes, ref; cardinality one/many; :db/unique identity (upsert) and value; :db/isComponent; :db/index (AVET membership); :db/noHistory; :db/doc; partitions; tempids with upsert unification; lookup refs; Datomic's schema alteration rules. Deferred: fulltext (tantivy, post-v1), tuple types, :db/ensure entity specs, uri/symbol value types.

Consequences

• v1 schema expresses the overwhelming majority of real Datomic schemas; ports needing fulltext or composite uniqueness wait for the backlog items.
• Multi-attribute uniqueness has no v1 primitive; the documented workaround is a derived unique attribute maintained by a transaction function.
• The value-type enum and tag space reserve room for the deferred types so adding them is non-breaking to the storage format.