Provisioning and transactions

Explicit provisioning

await db.ensureCollections();
await db.ensureIndexes({ waitForIndexes: true });

These require appropriate Manage Scopes/query-index privileges. Collection provisioning creates only missing resources; it never updates, renames, or drops. _default is not created. Conflicting settings for the same target fail. Index ensure is create-only. Singleton models also support indexStatements(), ensureIndexes(), and top-level/static ensureIndexes.

const plan = await db.planIndexes(); // create | matching | replace
await db.applyIndexPlan(plan);
await db.applyIndexPlan(plan, { dropReplaced: true });

Drift creates a versioned replacement and waits for online before optional old-index removal. Dropping is affirmative. Runtime definitions can use db.registerModel(definition, {provision:{collections:true,indexes:true,waitForIndexes:true}}).

Transactions

await db.transaction(async (tx) => {
  const sessions = tx.model(sessionDefinition);
  const session = await sessions.getById(id);
  if (session) await sessions.remove(session);
});

Transaction models expose attempt-bound get/insert/replace/remove; insert needs an explicit ID. Couchbase may retry the callback. Do not perform irreversible external effects inside it. Hooks and validation can also repeat. Commit-ambiguous errors surface to the caller.

CAS

const current = await model.getWithCas(id);
await model.replaceIfCas(id, nextValue, current.cas);
const result = await model.consumeOnce(id, current.cas);
// consumed | missing | conflict

consumeOnce makes one conditional remove without rereading/retrying. createCouchsetTestFixture() provisions an isolated model and returns explicit cleanup(); always run it in teardown.