v5.53.1 increases tests time execution by ~25%

[janowskipio]

Hello again!
We've recently tried to update to the newest version of the tanstack query and during this, we've found out that the change introduced in the v5.53.1, https://github.com/TanStack/query/pull/7966/files, increases our tests time execution by ~25%.

For now, we've disabled structuralSharing in the tanstack query config used for the test env

if (process.env.NODE_ENV === 'test') {
  queryClient.setDefaultOptions({
    queries: { retry: false, structuralSharing: false },
  })
}

As I've not found any similar issue reported yet, I'm not sure if this issue affects everyone in the same manner, thus I've decided to start a discussion here (it may have to do with our large codebase and specific implementations).

Do you think it would be beneficial to mention the potential perf downside of using structuralSharing in the docs?

Or include it in the testing part of the docs , to maybe even disable it by default for the tests?

Also, I see a big performance downgrade in some parts of the app itself as well - based on the specific tests that have now big execution time. I think it may be unexpected behavior for the developers - wasting time wondering what may cause such a perf problem during development mode - but I'd need to dig deeper to find out why specific parts of the app are affected that much. Although it may be connected with some of the ~"big data" we are using, I don't see any direct connection with the tanstack query on the first glance.

Looking forward to hearing your opinion and ideas! Thank you for your great work 🙇

[janowskipio]

ok, seems like disabling structuralSharing also causes other issues to popup (so it has its own value in our project 🤝 )

FYI, for now, we have just used replaceEqualDeep

if (process.env.NODE_ENV === 'test') {
  queryClient.setDefaultOptions({
    queries: { retry: false, structuralSharing: replaceEqualDeep },
  })
}

to skip these expensive (in our case) changes from v5.53.1

[TkDodo]

I think stringifying prevData is actually unnecessary, so we could remove that:

query/packages/query-core/src/utils.ts

Line 359 in 48702e4

JSON.stringify(prevData)

want to file a PR ?

[janowskipio]

I'm sorry, but I'm currently overwhelmingly busy with my work (did this upgrade in between the sprints). The least I could do was to share my findings, but I won't have time this month to engage more on this topic 🤝 🙇

[TkDodo]

we've already shipped an improvement