Fix: (Nested) null values will never be applied to SQLite when batched in Onyx

[chrispader]

@tgolen

Details

When we batch queued changes in Onyx.merge and they contain (nested) null values, SQLite will never be able to apply the individual deltas. Therefore, when we pass null or a nested null in an object, SQLite will not delete the (nested) keys from storage.

Imagine having something like this:

const initialData = {
    a: 'a',
    b: 'b',
    c: {
        d: 'd',
        e: 'e',
    },
};
const change1 = {
    b: null
}
const change2 = null;
const change3 = {
    f: 'f',
    c: {
        g: 'g',
        h: 'h',
    },
};
const change4 = {
    c: {
        g: null,
    },
};
const changes = [change1, change2, change3, change4];

const batchedChanges = OnyxUtils.applyMerge(undefined, changes, false);

This will result in the following batchedChanges:

{
    f: 'f',
    c: {
        g: 'g',
    },
}

When we then apply these batched changes in the native storage layer (SQLite) with JSON_PATCH, the initial data will not be erased and keys "a", "b", "d" and "e" will not be removed either, because SQLite never applied the top-level and nested null's.

The expected value in storage after applying the batched changes should be:

{
    f: 'f',
    c: {
        h: 'h',
    },
}

Whereas the actual value will be:

{
    a: 'a',
    b: 'b',
    c: {
        d: 'd',
        e: 'e',
        h: 'h'
    },
    f: 'f'
};

Generally, when SQLite sees a top-level or nested null value, it will remove this (nested) key from the database. But since we already batched the changes beforehand and don't pass every delta from the queue individually.

Cases that will prevent SQLite from removing the key from storage:

• any top-level null will not affect SQLite, if there's a change after, because the batchedChanges will get merged with the last values
• any nested null before a top-level null will be cancelled out, since the top-level null just clears the batched changes

Notes multiple follow-up PRs

Creating a SQLite mock in react-native-quick-sqlite

I'm going to fix this issue in this PR. Additionally, i'm thinking about creating a in-memory or local SQLite mock and ship it with https://github.com/margelo/react-native-quick-sqlite. The mock could then either run in-memory directly - if possible - or we would need to spin up a local SQLite database.

Creating storage provider specific tests (with actual mocks)

With this mock we could add more native-specific tests in react-native-onyx and potentially improve other tests so that we test for all platforms.

Related Issues

GH_LINK

Automated Tests

Manual Tests

Author Checklist

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• I verified all code is DRY (the PR doesn't include any logic written more than once, with the exception of tests)
• I verified any variables that can be defined as constants (ie. in CONST.js or at the top of the file that uses the constant) are defined as such
• I verified that if a function's arguments changed that all usages have also been updated correctly
• If a new component is created I verified that:
  • A similar component doesn't exist in the codebase
  • All props are defined accurately and each prop has a /** comment above it */
  • The file is named correctly
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• I have checked off every checkbox in the PR author checklist, including those that don't apply to this PR.

Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

MacOS: Desktop

[tgolen]

Interesting issue! I'm not sure I fully understand it, even after reading it a couple of times, but as long as you have some tests that prove the bug and the fix, then I'm good with it.

As for the SQLite mock, I think it would be ideal to be able to spin up an actual SQLite database and run tests directly against it. That would give us extremely accurate and reliable tests. What would need to happen to have that?

[chrispader]

Interesting issue! I'm not sure I fully understand it, even after reading it a couple of times, but as long as you have some tests that prove the bug and the fix, then I'm good with it.

I'm gonna further enhance the description. The thing is, that we're batching the changes from the mergeQueue here before even passing it to Storage.mergeItem and therefore to SQLite.

As for the SQLite mock, I think it would be ideal to be able to spin up an actual SQLite database and run tests directly against it. That would give us extremely accurate and reliable tests. What would need to happen to have that?

The idea about an in-memory SQLite database is as in https://www.sqlite.org/inmemorydb.html. It's possible to temporarily store the database only in-memory and this seems more than sufficient for testing/mocking purposes. If this is possible, i think we should prefer this, instead of relying on a local SQLite database and installation.

I'm gonna fix this actual issue before i potentially start work on a mock, as the mock isn't really high-priority right now. Basically we would just ship the mock in react-native-quick-sqlite and then we would need to setup the mock in jestSetup.js, same as the other mocks.

[tgolen]

Ah, I see. So the in memory database would still use the exact same SQLite interface? If so, then I agree that would be fine.

…

On Fri, Mar 29, 2024 at 4:35 AM Christoph Pader ***@***.***> wrote: Interesting issue! I'm not sure I fully understand it, even after reading it a couple of times, but as long as you have some tests that prove the bug and the fix, then I'm good with it. As for the SQLite mock, I think it would be ideal to be able to spin up an actual SQLite database and run tests directly against it. That would give us extremely accurate and reliable tests. What would need to happen to have that? The idea about an in-memory SQLite database is as in https://www.sqlite.org/inmemorydb.html. It's possible to temporarily store the database only in-memory and this seems more than sufficient for testing/mocking purposes. If this is possible, i think we should prefer this, instead of relying on a local SQLite database and installation. I'm gonna fix this actual issue before i potentially start work on a mock, as the mock isn't really high-priority right now. Basically we would just ship the mock in react-native-quick-sqlite and then we would need to setup the mock in jestSetup.js, same as the other mocks. — Reply to this email directly, view it on GitHub <#526 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAJMABZUKY5RY73R63C6NKTY2UYXVAVCNFSM6AAAAABFNHI4VGVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDAMRXGA2DONRZHE> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[chrispader]

Ah, I see. So the in memory database would still use the exact same SQLite

interface? If so, then I agree that would be fine.

yes 👍

[mountiny]

@chrispader Lint is failing

[chrispader]

@mountiny @tgolen i'm gonna finish up the PR Author checklist by the end of the day, but this is already working.

I've tested this thoroughly and it's working fine.

Basically how you can test this is either through this test branch that i created or in some other way. This branch basically just applies some delta changes to a key with Onyx.merge and prints out the value that's actually in Storage. To make this work, you will need to manually export the Storage from lib/storage in Onyx and use it within E/App

[mountiny]

@chrispader Changes look good to me, one comment, is there a way to test these in App now?

[chrispader]

@mountiny addressed your comments.

@chrispader Changes look good to me, one comment, is there a way to test these in App now?

There isn't really a use-case in which you can test exactly this fixed behavior in E/App, since at the time this only occurs in SQLite on native platforms.

Therefore, in this test PR i do some Onyx operations and then fetch the value from storage directly instead of using something like withOnyx, Onyx.connect or Onyx.get, since for these functions the cache would be used first...

[mountiny]

@chrispader thanks! I have spotted one little typo before merging then

[mountiny]

Thanks

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🚀Published to npm in v2.0.27