feat: B-Tree added

[gfant]

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

Added B-Tree structure so data can be mantained ordered without using too much operations.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 63.12%. Comparing base (f6bd2d3) to head (618630c).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2677      +/-   ##
==========================================
+ Coverage   63.08%   63.12%   +0.04%     
==========================================
  Files         563      563              
  Lines       79254    79362     +108     
==========================================
+ Hits        49998    50099     +101     
- Misses      25896    25905       +9     
+ Partials     3360     3358       -2     

Flag	Coverage Δ
contribs/gnodev	60.62% <ø> (ø)
contribs/gnofaucet	14.82% <ø> (ø)
gno.land	67.56% <ø> (ø)
gnovm	67.25% <ø> (ø)
misc/genstd	79.72% <ø> (ø)
misc/logos	19.45% <ø> (ø)
tm2	62.29% <ø> (+0.04%)	⬆️

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[gfant]

Is there something I could do to help with the merging of this PR, @thehowl , @ajnavarro @leohhhn ? (Thank you in advance!)

[gfant]

Updated test to adapt to new error message.

[wyhaines]

There is a bug in the implementation, likely in the delete/fill/merge handling.

If you insert a large number of entries into the tree, and then start deleting them, you will run into a situation where you get a .: test pkg: panic: slice index out of bounds: 3 (len=3) type error.

This is likely related to the recursion near the bottom of the delete function, but there is interplay with the fill/merge functionality. Something is just not quite right, and while it's possible to fix the slice out of bounds, when one does that, after doing a number of deletes, one starts to get keys that are no longer reachable.

This is an incomplete test, but it serves to illustrate the problem:

func TestStress(t *testing.T) {
  tree, _ := NewBTree(4)

  for j := 0; j < 1000; j++ {
    tree.Insert(Content{Key: j, Value: j})
  }

  if tree.GetSize() != 1000 {
    t.Errorf("Expected size of 1000; got %d\n", tree.GetSize())
  }

  for j := 0; j < 1000; j++ {
    found, err := tree.Search(j)
    if found.Key != j {
      t.Errorf("Search for %d expected to find %d, but got %d\n", j, j, found.Key)
    }
  }

  for j := 0; j < 1000; j += 2 {
    tree.Delete(j)
  }
}

[wyhaines]

This still breaks when subjected to the stress test above:

=== RUN   TestStress
.: test pkg: panic: slice index out of bounds: 3 (len=3)
stack:
goroutine 1 [running]:
runtime/debug.Stack()
        /usr/local/go/src/runtime/debug/stack.go:26 +0x5e
main.runTestFiles.func1()
        /media/wyhaines/home/wyhaines/ghq/github.com/wyhaines/gno/gnovm/cmd/gno/test.go:439 +0x58
panic({0xd99c20?, 0xc004b18c90?})
        /usr/local/go/src/runtime/panic.go:785 +0x132
github.com/gnolang/gno/gnovm/pkg/gnolang.(*SliceValue).GetPointerAtIndexInt2(0xc00ba13560, {0x11e4e10?, 0xc0000cce60?}, 0xc0003a81e0?, {0x11d2f10?, 0xc00057e1e0?})
        /media/wyhaines/home/wyhaines/ghq/github.com/wyhaines/gno/gnovm/pkg/gnolang/values.go:442 +0x1be
github.com/gnolang/gno/gnovm/pkg/gnolang.(*TypedValue).GetPointerAtIndex(0xc0003a81b8, 0xc009ceb201?, {0x11e4e10, 0xc0000cce60}, 0xc0003a81e0)
        /media/wyhaines/home/wyhaines/ghq/github.com/wyhaines/gno/gnovm/pkg/gnolang/values.go:1997 +0xa45
github.com/gnolang/gno/gnovm/pkg/gnolang.(*Machine).PopAsPointer(0xc00cc39550?, {0x11d9708?, 0xc00053a1e0?})
        /media/wyhaines/home/wyhaines/ghq/github.com/wyhaines/gno/gnovm/pkg/gnolang/machine.go:2130 +0x193
github.com/gnolang/gno/gnovm/pkg/gnolang.(*Machine).doOpAssign(0xc0003a2488)
        /media/wyhaines/home/wyhaines/ghq/github.com/wyhaines/gno/gnovm/pkg/gnolang/op_assign.go:35 +0x247
github.com/gnolang/gno/gnovm/pkg/gnolang.(*Machine).Run(0xc0003a2488)
        /media/wyhaines/home/wyhaines/ghq/github.com/wyhaines/gno/gnovm/pkg/gnolang/machine.go:1537 +0xd73
github.com/gnolang/gno/gnovm/pkg/gnolang.(*Machine).Eval(0xc0003a2488, {0x11d94e8, 0xc00cb647e0})
        /media/wyhaines/home/wyhaines/ghq/github.com/wyhaines/gno/gnovm/pkg/gnolang/machine.go:884 +0x63c
main.runTestFiles(0xc0003a2488, 0xc000011698, {0xc00047cd40, 0x6}, 0x1, 0x0, 0x0, {0x0, 0x0}, {0x11dbe80, ...})
        /media/wyhaines/home/wyhaines/ghq/github.com/wyhaines/gno/gnovm/cmd/gno/test.go:468 +0x3a5
main.gnoTestPkg({0x11baba0, 0x1}, {0xc0004822d0?, 0x1, 0x8?}, {0x0, 0x0, 0x0?}, 0xc000478780, {0x11dbe80, ...})
        /media/wyhaines/home/wyhaines/ghq/github.com/wyhaines/gno/gnovm/cmd/gno/test.go:309 +0x12b0
main.execTest(0xc000478780, {0xc0004822b0?, 0x1?, 0x1?}, {0x11dbe80, 0xc0003cb720})
        /media/wyhaines/home/wyhaines/ghq/github.com/wyhaines/gno/gnovm/cmd/gno/test.go:207 +0x428
main.newTestCmd.func1({0x0?, 0xc000034130?}, {0xc0004822b0?, 0xc00047af00?, 0x0?})
        /media/wyhaines/home/wyhaines/ghq/github.com/wyhaines/gno/gnovm/cmd/gno/test.go:101 +0x30
github.com/gnolang/gno/tm2/pkg/commands.(*Command).Run(0xc000307ea8?, {0x11cdc60?, 0x18bcce0?})
        /media/wyhaines/home/wyhaines/ghq/github.com/wyhaines/gno/tm2/pkg/commands/command.go:255 +0x18e
github.com/gnolang/gno/tm2/pkg/commands.(*Command).Run(0xc0003971e0?, {0x11cdc60?, 0x18bcce0?})