ORM: relation where re-resolves a non-_id relation target once per drain #446

Summary

PR #420 fixed the main case — this is a narrower follow-up, not a duplicate.

#420 added a per-execution _documentByNormalizedId memo inside _getById, so relation targets resolved by db.get are now read once per query execution instead of once per (parent, drain). Verified: the original shape issued 200 db.get calls at the audit commit and issues 2 on current main.

What survives: a relation where referencing a one relation joined on anything other than _id still re-resolves its target once per drain.

Root cause

packages/kitcn/src/orm/query.ts:8362 — _loadOneRelation sets useGetById only when the join is on the primary id (:8409):

targetFields.length === 1 && targetFields[0] === '_id'

The else branch at :8429-8435 issues:

this._queryByFields(this.db.query(edge.targetTable), targetFields, values, indexName).first()

with no cross-drain memo. The chunk drain at :9221 re-enters it for every 32-row batch, so the same target is re-read once per batch.

So r.one.x({ to: x.id }) — the common shape — is covered by #420's memo; r.one.x({ to: x.someOtherColumn }) is not.

Not affected by the other merges

#425, #426 and #427 do not touch this path. #427 explicitly excludes one relations from its existence-probe lowering — its own note: "A one relation is a single row either way, so there is nothing to stop early at."

Suggested fix

Give _loadOneRelation's non-id branch the same execution-scoped memo, keyed on (targetTable, targetFields, values) rather than on a normalized id.

The staleness argument #420 already wrote for _documentByNormalizedId applies verbatim — same execution scope, same invalidation reasoning.

Small.

Existing tests

packages/kitcn/src/orm/query.relation-where-reads.vitest.ts:110 and :132 (added by #420) assert counts.get <= 2 over a 50-row scan with 2 distinct targets — those pin the _getById memo. The non-_id branch has no equivalent; extend that file rather than starting a new one.

Environment

• kitcn 0.32.1
• convex 1.44.0
• verified and measured against origin/main at 14bab503