Enable auto-indexing for nested field paths

[KyleAMathews]

This fix allows auto-indexes to be created for nested field paths (e.g., profile.score, metadata.stats.views), not just top-level fields. This resolves performance issues where queries with eq(), gt(), etc. on nested fields were forced to do full table scans instead of using indexes.

Changes:

• Remove the fieldPath.length !== 1 restriction in extractIndexableExpressions()
• Update ensureIndexForField() to properly traverse nested paths when creating index accessors
• Add comprehensive tests for nested path auto-indexing with 1, 2, and 3-level nesting
• Verify that nested path indexes are properly used by the query optimizer

Fixes #727

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🎯 Changes

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🚀 Release Impact

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• This change is docs/CI/dev-only (no release).

[changeset-bot]

🦋 Changeset detected

Latest commit: f44b33a

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

This PR includes changesets to release 12 packages

Name	Type
@tanstack/db	Patch
@tanstack/angular-db	Patch
@tanstack/electric-db-collection	Patch
@tanstack/query-db-collection	Patch
@tanstack/react-db	Patch
@tanstack/rxdb-db-collection	Patch
@tanstack/solid-db	Patch
@tanstack/svelte-db	Patch
@tanstack/trailbase-db-collection	Patch
@tanstack/vue-db	Patch
todos	Patch
@tanstack/db-example-react-todo	Patch

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commit: f44b33a

[github-actions]

Size Change: +63 B (+0.07%)

Total Size: 84.5 kB

Filename	Size	Change
./packages/db/dist/esm/indexes/auto-index.js	857 B	+63 B (+7.93%)	🔍

ℹ️ View Unchanged

Filename	Size
./packages/db/dist/esm/collection/change-events.js	1.63 kB
./packages/db/dist/esm/collection/changes.js	1.01 kB
./packages/db/dist/esm/collection/events.js	413 B
./packages/db/dist/esm/collection/index.js	3.23 kB
./packages/db/dist/esm/collection/indexes.js	1.16 kB
./packages/db/dist/esm/collection/lifecycle.js	1.8 kB
./packages/db/dist/esm/collection/mutations.js	2.52 kB
./packages/db/dist/esm/collection/state.js	3.8 kB
./packages/db/dist/esm/collection/subscription.js	2.2 kB
./packages/db/dist/esm/collection/sync.js	2.2 kB
./packages/db/dist/esm/deferred.js	230 B
./packages/db/dist/esm/errors.js	3.48 kB
./packages/db/dist/esm/event-emitter.js	798 B
./packages/db/dist/esm/index.js	1.62 kB
./packages/db/dist/esm/indexes/base-index.js	835 B
./packages/db/dist/esm/indexes/btree-index.js	2 kB
./packages/db/dist/esm/indexes/lazy-index.js	1.21 kB
./packages/db/dist/esm/indexes/reverse-index.js	577 B
./packages/db/dist/esm/local-only.js	967 B
./packages/db/dist/esm/local-storage.js	2.42 kB
./packages/db/dist/esm/optimistic-action.js	294 B
./packages/db/dist/esm/proxy.js	3.86 kB
./packages/db/dist/esm/query/builder/functions.js	615 B
./packages/db/dist/esm/query/builder/index.js	4.04 kB
./packages/db/dist/esm/query/builder/ref-proxy.js	938 B
./packages/db/dist/esm/query/compiler/evaluators.js	1.55 kB
./packages/db/dist/esm/query/compiler/expressions.js	760 B
./packages/db/dist/esm/query/compiler/group-by.js	2.04 kB
./packages/db/dist/esm/query/compiler/index.js	2.21 kB
./packages/db/dist/esm/query/compiler/joins.js	2.65 kB
./packages/db/dist/esm/query/compiler/order-by.js	1.43 kB
./packages/db/dist/esm/query/compiler/select.js	1.28 kB
./packages/db/dist/esm/query/ir.js	785 B
./packages/db/dist/esm/query/live-query-collection.js	404 B
./packages/db/dist/esm/query/live/collection-config-builder.js	5.54 kB
./packages/db/dist/esm/query/live/collection-registry.js	233 B
./packages/db/dist/esm/query/live/collection-subscriber.js	2.11 kB
./packages/db/dist/esm/query/optimizer.js	3.33 kB
./packages/db/dist/esm/scheduler.js	1.29 kB
./packages/db/dist/esm/SortedMap.js	1.24 kB
./packages/db/dist/esm/transactions.js	3.05 kB
./packages/db/dist/esm/utils.js	1.01 kB
./packages/db/dist/esm/utils/browser-polyfills.js	365 B
./packages/db/dist/esm/utils/btree.js	6.01 kB
./packages/db/dist/esm/utils/comparison.js	754 B
./packages/db/dist/esm/utils/index-optimization.js	1.73 kB

_{compressed-size-action::db-package-size}

[github-actions]

Size Change: 0 B

Total Size: 2.89 kB

ℹ️ View Unchanged

Filename	Size
./packages/react-db/dist/esm/index.js	168 B
./packages/react-db/dist/esm/useLiveInfiniteQuery.js	1.41 kB
./packages/react-db/dist/esm/useLiveQuery.js	1.31 kB

_{compressed-size-action::react-db-package-size}

[samwillis]

Looks good except for the naming of the auto indexes - that plus a changeset and it will be good to merge.

[samwillis]

I'm not sure I like the naming of the index by replacing of the periods with underscores. It could product a conflict.

Maybe these automatic indexes should be named "auto:path.to.field" - no chance of a conflict.

[github-actions]

🎉 This PR has been released!

• @tanstack/db@0.4.16

Thank you for your contribution!