arcadic usage rules

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A framework-agnostic Elixir client for ArcadeDB over the HTTP Cypher command API.

What arcadic is (and is not)

  • Is: a thin transport. Sends Cypher/SQL to ArcadeDB's HTTP command API, manages connections and session transactions, normalizes responses.
  • Is not: Ash-aware, tenant-aware, or classification-aware. Never put multitenancy or sensitive-data logic here — that is ash_arcadic's job.

Public surface

  • Arcadic — connect/3, with_database/2; query/4 + query!/4 (idempotent read endpoint), command/4 + command!/4 (write endpoint), command_async/4 (fire-and-forget, returns :ok on 202); transaction/3 and rollback/2 for session transactions. Non-bang calls return {:ok, rows} or {:error, %Arcadic.Error{} | %Arcadic.TransportError{}}. Default language is "cypher"; opt into sql/gremlin/graphql/mongo/sqlscript per call.
  • Arcadic.Conn — a pure-data connection handle (no process). Its Inspect redacts auth and session id.
  • Arcadic.Server — server admin: create_database/2 (+ !), drop_database/2 (+ !), database_exists?/2, list_databases/1, ready?/1.
  • Migrations — Arcadic.Migration (behaviour: version/0, up/1, down/1), Arcadic.MigrationRegistry (use + migrations [...]), Arcadic.Migrator (migrate/2, status/2, rollback/3, reset/2, pending_migrations/2), tracking applied versions in _arcadic_migrations.
  • Arcadic.Transport — the transport behaviour seam; Arcadic.Transport.HTTP (Req/Finch) is the default, Arcadic.Transport.Bolt is the optional Bolt one.
  • Arcadic.Error / Arcadic.TransportError — the typed error taxonomy.
  • Arcadic.Telemetry — value-free :telemetry.span/3 spans.
  • Arcadic.Identifier — allowlist identifier validation.

Non-negotiable rules

  • Parameters only. Every dynamic value goes into the request params map and is referenced as $name in the statement. Never interpolate a value into a Cypher/SQL string — that is a query-injection defect. This holds for query/4, command/4, command_async/4, and inside transaction/3.
  • Redact at the boundary. Errors and logs carry structure only. Arcadic.Error exposes a typed reason, http_status, and exception class; its detail field is quarantined (absent from message/1 and inspect/1). Arcadic.TransportError carries only the value-free reason atom. Never surface raw parameter values or response rows.
  • Validate identifiers. Database names and other identifiers reaching a URL path or statement go through Arcadic.Identifier.validate/1 first (a failure carries the invalid-shape fact only, never the offending string). Values are never identifiers — they ride params.

Bolt transport (optional)

The Arcadic.Transport.Bolt adapter (optional boltx dependency) runs the query hot path over Bolt. Start it with Arcadic.Transport.Bolt.start_link/1, which pins Bolt to v4 (versions: [4.4, 4.3, 4.2, 4.1] — ArcadeDB speaks v4; boltx defaults to v5), uses the non-TLS bolt scheme (ArcadeDB Bolt is TLS-disabled by default), and takes username/password. Pass the connection reference as transport: Arcadic.Transport.Bolt, transport_options: [bolt: ref]. Server admin (create/drop/list database) is HTTP-only — use an HTTP conn for admin even when queries run over Bolt.

See AGENTS.md for the full working rules and the verified ArcadeDB HTTP contract.