corium-db

The immutable Db value: time views, covering-index access, naming, per-attribute statistics, and bootstrap metadata.

What it does

Defines the central database value that queries run against. A Db is a value — cheap to clone, never mutated in place. It provides:

• Time views — Db::as_of, Db::since, and Db::history (via DbView), each wrapping the same recorded datoms with a different fold policy; no facts are copied.
• Covering-index access — the four indexes for a view, materialized lazily on first read and shared by every clone.
• Naming — the Idents registry mapping :db/ident keywords to entity ids.
• Statistics — per-attribute counts used by the query planner.
• Bootstrap — the reserved-id layout (FIRST_USER_ID) and the initial schema every database starts with.

Dependencies

• corium-core — value/datom/schema types and encoding.
• corium-index (transitively, via the transactor/peer that build the index data a Db merges).

Pure, synchronous library code — no async, network, or storage dependencies. It is consumed by corium-tx (validation), corium-query and corium-sql (reads), and produced by corium-transactor/corium-peer.

Architecture

Db is the immutability boundary of the whole system. A view merges persistent index segments with the in-memory log tail up to a basis-t; because that merge is pure and the value is shared by Arc, obtaining a database value never blocks on the transactor and never takes a lock. Time views are just a different fold over the same datoms, so as-of/since/history cost nothing to construct. The four covering indexes for a view are built lazily and cached in the value, so the first read pays for materialization and every clone reuses it. See docs/design/time-model.md.