fix race condition in loading joined collections into live query

[samwillis]

Fixes #438

The issue was that the subscription to the live changes could start emitting results before we had first done any join processing. The join called either loadKeys or loadInitialState depending on if there was an index it could use. These now set a flag to indicate that we now actually want to start tailing the live changes, until then they are filtered out. We still have to send an empty array of changes when there are any before then so that the query is notified of any collection status change.

Failed test run with repo before it's then fixed: https://github.com/TanStack/db/actions/runs/17233860827/job/48894002331?pr=451

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🦋 Changeset detected

Latest commit: 30f29e4

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

This PR includes changesets to release 8 packages

Name	Type
@tanstack/db	Patch
@tanstack/electric-db-collection	Patch
@tanstack/query-db-collection	Patch
@tanstack/react-db	Patch
@tanstack/solid-db	Patch
@tanstack/svelte-db	Patch
@tanstack/trailbase-db-collection	Patch
@tanstack/vue-db	Patch

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commit: 30f29e4

[samwillis]

We were only adding keys to the sentKeys when they were requested, not when they were send due to just watching the live changes.

[github-actions]

Size Change: +25 B (+0.04%)

Total Size: 64.3 kB

Filename	Size	Change
./packages/db/dist/esm/query/live/collection-subscriber.js	2.27 kB	+25 B (+1.11%)

ℹ️ View Unchanged

Filename	Size
./packages/db/dist/esm/change-events.js	1.13 kB
./packages/db/dist/esm/collection.js	10.6 kB
./packages/db/dist/esm/deferred.js	230 B
./packages/db/dist/esm/errors.js	3 kB
./packages/db/dist/esm/index.js	1.52 kB
./packages/db/dist/esm/indexes/auto-index.js	745 B
./packages/db/dist/esm/indexes/base-index.js	605 B
./packages/db/dist/esm/indexes/btree-index.js	1.74 kB
./packages/db/dist/esm/indexes/lazy-index.js	1.25 kB
./packages/db/dist/esm/local-only.js	827 B
./packages/db/dist/esm/local-storage.js	2.03 kB
./packages/db/dist/esm/optimistic-action.js	294 B
./packages/db/dist/esm/proxy.js	4.19 kB
./packages/db/dist/esm/query/builder/functions.js	575 B
./packages/db/dist/esm/query/builder/index.js	3.79 kB
./packages/db/dist/esm/query/builder/ref-proxy.js	890 B
./packages/db/dist/esm/query/compiler/evaluators.js	1.48 kB
./packages/db/dist/esm/query/compiler/expressions.js	631 B
./packages/db/dist/esm/query/compiler/group-by.js	2.06 kB
./packages/db/dist/esm/query/compiler/index.js	2.15 kB
./packages/db/dist/esm/query/compiler/joins.js	2.36 kB
./packages/db/dist/esm/query/compiler/order-by.js	1.17 kB
./packages/db/dist/esm/query/compiler/select.js	655 B
./packages/db/dist/esm/query/ir.js	466 B
./packages/db/dist/esm/query/live-query-collection.js	333 B
./packages/db/dist/esm/query/live/collection-config-builder.js	2.48 kB
./packages/db/dist/esm/query/optimizer.js	2.63 kB
./packages/db/dist/esm/SortedMap.js	1.24 kB
./packages/db/dist/esm/transactions.js	2.29 kB
./packages/db/dist/esm/utils.js	419 B
./packages/db/dist/esm/utils/btree.js	6.02 kB
./packages/db/dist/esm/utils/comparison.js	718 B
./packages/db/dist/esm/utils/index-optimization.js	1.62 kB

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

[github-actions]

Size Change: 0 B

Total Size: 1.16 kB

ℹ️ View Unchanged

Filename	Size
./packages/react-db/dist/esm/index.js	152 B
./packages/react-db/dist/esm/useLiveQuery.js	1.01 kB

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

[kevin-dp]

Great job, this was a really hard one to find!
I left two very minor comments.

[kevin-dp]

I would add some more comments explaining why the filtering is needed:

We filter out changes when sendChanges is false to ensure that we don't send any changes from the live subscription until the join operator requests either the initial state or its first key. This is needed otherwise it could receive changes which are then later subsumed by the initial state (and that would lead to weird bugs due to the data being received twice).

[kevin-dp]

The code for creating the collections and storing their callbacks is the same for Players and challenges. Could define a helper function that does this such that we don't have to duplicate the code. And then just call it once per collection.