feat(datastore): add per-model syncPageSize and maxRecordsToSync configuration

[danrivett]

Description of changes

Adds an optional third parameter to syncExpression() that allows configuring syncPageSize and maxRecordsToSync on a per-model basis. Models without per-model configuration continue to use the global defaults.

Problem: DataStore has a single global syncPageSize (default: 1000) that applies to all models during sync. When one model with large/denormalized records exceeds the AppSync 1MB response limit, users must lower syncPageSize globally, causing a significant performance penalty for all other (smaller) models.

Solution: Extend syncExpression() with an optional PerModelSyncConfig parameter:

DataStore.configure({
  syncPageSize: 1000,              // global default
  maxRecordsToSync: 10000,         // global default
  syncExpressions: [
    // Per-model config: use smaller page size for this model only
    syncExpression(LargeModel, () => Predicates.ALL, {
      syncPageSize: 100,
    }),
    // Existing usage unchanged (backward compatible)
    syncExpression(SmallModel, () => m => m.active.eq(true)),
  ]
});

Changes:

• packages/datastore/src/types.ts — Add PerModelSyncConfig interface, extend SyncExpression type and syncExpression() function with optional third parameter
• packages/datastore/src/datastore/datastore.ts — Extract per-model config in processSyncExpressions(), pass through amplifyConfig to SyncProcessor. Also replace non-null assertion on getModelDefinition() with an explicit null check and descriptive error
• packages/datastore/src/sync/processors/sync.ts — Look up per-model overrides when computing limit and done condition in the sync pagination loop, falling back to global defaults via nullish coalescing

This is fully backward compatible — the third parameter is optional and the existing two-parameter syncExpression() signature works unchanged.

Issue #, if available

Closes #7310

Description of how you validated changes

• Full DataStore test suite passes (yarn test in packages/datastore)
• ESLint passes with 0 errors
• TypeScript compilation passes
• Added unit tests for syncExpression() with per-model config (4 tests in syncExpression.test.ts)
• Added integration tests in connectivityHandling.test.ts verifying:
  • Per-model syncPageSize overrides the global default
  • Models without per-model config fall back to the global syncPageSize
  • Multiple models with different per-model syncPageSize values
  • Per-model maxRecordsToSync correctly caps the limit below syncPageSize
• Validated in a consumer application by configuring per-model syncPageSize: 50 for a model with large records while other models sync at the default of 1000

Checklist

• PR description included
• yarn test passes
• Unit Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

Checklist for repo maintainers

• Verify E2E tests for existing workflows are working as expected or add E2E tests for newly added workflows
• New source file paths included in this PR have been added to CODEOWNERS, if appropriate

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[changeset-bot]

🦋 Changeset detected

Latest commit: a192946

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@aws-amplify/datastore	Minor
aws-amplify	Patch

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