feat: subscribeChanges #30
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commit: |
| } else if (!prevDerivedState.has(key) && derivedState.has(key)) { | ||
| changes.push({ type: `insert`, key, value: derivedState.get(key)! }) | ||
| } else if (prevDerivedState.has(key) && derivedState.has(key)) { | ||
| // Check if the value has changed and only emit a change if it has |
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I'd say it's the collections job to figure out if something has changed. Deep equality is pretty fast but not that fast and it should be far more efficient for someone else to do it. So I'd remove all this checking code and just push out the updates.
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If we remove this check the tests fail, we get an insert and then two updates, when it should just be an insert.
When doing an inserting transaction we are somewhere triggering optimisticOperations to be derived three times. That causes derivedState and derivedChanges to then be run three times.
I would only expect this to be triggered once.
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Oh I was reacting to the code below:
// TODO: Better way to do this? deep equality?
const prevValue = JSON.stringify(prevDerivedState.get(key))
const newValue = JSON.stringify(derivedState.get(key))
if (prevValue !== newValue) {Is this check necessary?
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But sounds like this is a bug somewhere else?
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Yep, removing the JSON.stringify check that the two values have changed results in the test failing.
I'm suspicious something else is triggering excessive recomputations.
This adds a few public APIs:
collection.derivedChangesis a tanstack/storeDerivedstate, it is replaced with the latest changes (insert/update/delete) each time the derived state changes. This can be used inside anEffectalong with other collections to essentially subscribe to a set of charges across the collections. This will be the foundation of the IVM queries.collection.currentStateAsChangesreturns the current state as a set of inserts. It's needed to bootstrap the initial state of a query.collection.subscribeChangesis a thin wrapper of the above as a higher level public api