perf: optimize iteration on nested cache context (backport #13881)

[mergify]

This is an automatic backport of pull request #13881 done by Mergify.
Cherry-pick of cbee1b3 has failed:

On branch mergify/bp/release/v0.46.x/pr-13881
Your branch is up to date with 'origin/release/v0.46.x'.

You are currently cherry-picking commit cbee1b3ea.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	new file:   store/cachekv/benchmark_test.go
	new file:   store/cachekv/internal/btree.go
	new file:   store/cachekv/internal/btree_test.go
	new file:   store/cachekv/internal/memiterator.go
	renamed:    store/cachekv/mergeiterator.go -> store/cachekv/internal/mergeiterator.go
	deleted:    store/cachekv/memiterator.go
	modified:   store/cachekv/search_benchmark_test.go

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	both modified:   CHANGELOG.md
	both modified:   go.mod
	both modified:   go.sum
	deleted by us:   simapp/go.mod
	deleted by us:   simapp/go.sum
	both modified:   store/cachekv/store.go
	both modified:   store/cachekv/store_test.go
	deleted by us:   tests/go.mod
	deleted by us:   tests/go.sum

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

---

Mergify commands and options

More conditions and actions can be found in the documentation.

You can also trigger Mergify actions by commenting on this pull request:

• @Mergifyio refresh will re-evaluate the rules
• @Mergifyio rebase will rebase this PR on its base branch
• @Mergifyio update will merge the base branch into this PR
• @Mergifyio backport <destination> will backport this PR on <destination> branch

Additionally, on Mergify dashboard you can:

• look at your merge queues
• generate the Mergify configuration with the config editor.

Finally, you can contact us on https://mergify.com

[tac0turtle]

We need to do some testing with this change. I can test on umee

[yihuang]

Suggested change

	<<<<<<< HEAD
	=======
	if len(store.cache) == 0 && len(store.deleted) == 0 && len(store.unsortedCache) == 0 {
	store.sortedCache = internal.NewBTree()
	return
	}
	>>>>>>> cbee1b3ea (perf: optimize iteration on nested cache context (#13881))
	if len(store.cache) == 0 && len(store.deleted) == 0 && len(store.unsortedCache) == 0 {
	store.sortedCache = internal.NewBTree()
	return
	}

[yihuang]

this part is added by #12494

[tac0turtle]

unfortunately this backport requires go 1.18 which is a change we cant force on users in a minor release. We would need to fork tidal or revert to google/btree. @yihuang do you have a preference

[yihuang]

unfortunately this backport requires go 1.18 which is a change we cant force on users in a minor release. We would need to fork tidal or revert to google/btree. @yihuang do you have a preference

The reason to use tidal is it provides the Iter() api, which can be used to implement iterator without using a go-routine, the google version only supports visit with callbacks.

[yihuang]

unfortunately this backport requires go 1.18 which is a change we cant force on users in a minor release. We would need to fork tidal or revert to google/btree. @yihuang do you have a preference

I think 0.46 is using 1.18 already?