corium-tx

Pure transaction expansion, entity resolution, and validation.

What it does

Turns transaction data into a validated, ready-to-commit set of datoms. Given a list of operations against a database value, it:

• Expands map-form entities (EntityMap) into individual assertions.
• Resolves entity positions (EntityRef): concrete ids, transaction-local tempids, and unique-attribute lookup refs.
• Applies the built-in operations — Add, Retract, Cas (compare-and-swap), and RetractEntity (recursive component retraction).
• Validates against the schema: value types, cardinality, uniqueness, and component/ref rules.
• Produces a PreparedTx (resolved datoms plus the tempid → entity-id map).

Dependencies

• corium-core — value/datom/schema types.
• corium-db — reads the current Db value to resolve lookups and check uniqueness against existing facts.
• thiserror for errors.

Pure, synchronous library code — no async, network, or storage dependencies. The transactor drives it; database functions (:db/fn) that emit further ops are expanded on top of it by corium-cljrs.

Architecture

Transaction handling is a pure function of (current Db, tx ops) → PreparedTx, with no I/O. Keeping it side-effect-free means the transactor can run it, validate, and either commit or cleanly abort without touching storage, and the deterministic simulator can exercise every validation path. Native built-ins like :db/cas live here as Rust; sandboxed user-defined :db/fn code lives in corium-cljrs and feeds its emitted ops back through this expansion. See docs/design/log-and-transactor.md.