@memberjunction/record-comparison

Framework-agnostic record comparison primitive for MemberJunction.

RecordComparisonEngine loads a set of records for a single entity and computes a structured, field-level delta between them — a survivor candidate plus its potential matches diffed column-by-column. It performs a read-only load (RunView with ResultType: 'simple' and a targeted field list) and never mutates records.

Why this package exists

The comparison logic is needed by two callers that sit on opposite sides of the dependency graph:

• The LLM duplicate-detection reasoning path (@memberjunction/ai-vector-dupe), which feeds the differing-field deltas to the reasoning provider as context.
• The server/UI side-by-side comparison panel (@memberjunction/core-entities-server → MJServer resolver → GraphQL client → Angular record-merge).

@memberjunction/core-entities-server depends on @memberjunction/ai-vector-dupe, so the dupe package sits lower in the graph and cannot reach an engine that lives in the server package without creating a build cycle. Hoisting the engine into this low-level package (its only dependency is @memberjunction/core) gives both sides a single implementation with no cycle and no duplicated delta logic.

Usage

import { RecordComparisonEngine } from '@memberjunction/record-comparison';
import { CompositeKey } from '@memberjunction/core';

const engine = new RecordComparisonEngine();

// By entity name (resolver / UI path) — resolves the entity from metadata.
const result = await engine.CompareRecords(
  { EntityName: 'Accounts', Keys: [survivorKey, candidateKey] },
  contextUser,
  provider // request-scoped IMetadataProvider (multi-provider safety)
);

// With an already-resolved EntityInfo + an injected RunView (dupe path) — skips the
// by-name lookup and reuses the caller's request-scoped RunView.
const result2 = await engine.CompareRecordsForEntity(
  entityInfo,
  [sourceKey, ...candidateKeys],
  contextUser,
  { runView }
);

result.Fields is a plain-data delta matrix (no BaseEntity instances), so it serializes cleanly across GraphQL and into a reasoning prompt.