pkg/adt: refactor + add more test cases

auth/range_perm_cache.go

@@ -28,8 +28,8 @@ func getMergedPerms(lg *zap.Logger, tx backend.BatchTx, userName string) *unifie
 		return nil
 	}
 
-	readPerms := &adt.IntervalTree{}
-	writePerms := &adt.IntervalTree{}
+	readPerms := adt.NewIntervalTree()
+	writePerms := adt.NewIntervalTree()
 
 	for _, roleName := range user.Roles {
 		role := getRole(tx, roleName)
@@ -148,6 +148,6 @@ func (as *authStore) invalidateCachedPerm(userName string) {
 }
 
 type unifiedRangePermissions struct {
-	readPerms  *adt.IntervalTree
-	writePerms *adt.IntervalTree
+	readPerms  adt.IntervalTree
+	writePerms adt.IntervalTree
 }

auth/range_perm_cache_test.go

@@ -48,7 +48,7 @@ func TestRangePermission(t *testing.T) {
 	}
 
 	for i, tt := range tests {
-		readPerms := &adt.IntervalTree{}
+		readPerms := adt.NewIntervalTree()
 		for _, p := range tt.perms {
 			readPerms.Insert(p, struct{}{})
 		}
@@ -89,7 +89,7 @@ func TestKeyPermission(t *testing.T) {
 	}
 
 	for i, tt := range tests {
-		readPerms := &adt.IntervalTree{}
+		readPerms := adt.NewIntervalTree()
 		for _, p := range tt.perms {
 			readPerms.Insert(p, struct{}{})
 		}

etcdserver/api/v3rpc/key.go

@@ -179,7 +179,7 @@ func checkTxnRequest(r *pb.TxnRequest, maxTxnOps int) error {
 // there is an overlap, returns an error. If no overlap, return put and delete
 // sets for recursive evaluation.
 func checkIntervals(reqs []*pb.RequestOp) (map[string]struct{}, adt.IntervalTree, error) {
-	var dels adt.IntervalTree
+	dels := adt.NewIntervalTree()
 
 	// collect deletes from this level; build first to check lower level overlapped puts
 	for _, req := range reqs {

mvcc/watcher_group.go

@@ -156,6 +156,7 @@ type watcherGroup struct {
 func newWatcherGroup() watcherGroup {
 	return watcherGroup{
 		keyWatchers: make(watcherSetByKey),
+		ranges:      adt.NewIntervalTree(),
 		watchers:    make(watcherSet),
 	}
 }

pkg/adt/README.md

@@ -0,0 +1,48 @@
+
+## Red-Black Tree
+
+*"Introduction to Algorithms" (Cormen et al, 3rd ed.), Chapter 13*
+
+1. Every node is either red or black.
+2. The root is black.
+3. Every leaf (NIL) is black.
+4. If a node is red, then both its children are black.
+5. For each node, all simple paths from the node to descendant leaves contain the
+same number of black nodes.
+
+For example,
+
+```go
+import (
+    "fmt"
+
+    "go.etcd.io/etcd/pkg/adt"
+)
+
+func main() {
+    ivt := adt.NewIntervalTree()
+    ivt.Insert(NewInt64Interval(510, 511), 0)
+    ivt.Insert(NewInt64Interval(82, 83), 0)
+    ivt.Insert(NewInt64Interval(830, 831), 0)
+    ...
+```
+
+After inserting the values `510`, `82`, `830`, `11`, `383`, `647`, `899`, `261`, `410`, `514`, `815`, `888`, `972`, `238`, `292`, `953`.
+
+![red-black-tree-01-insertion.png](img/red-black-tree-01-insertion.png)
+
+Deleting the node `514` should not trigger any rebalancing:
+
+![red-black-tree-02-delete-514.png](img/red-black-tree-02-delete-514.png)
+
+Deleting the node `11` triggers multiple rotates for rebalancing:
+
+![red-black-tree-03-delete-11.png](img/red-black-tree-03-delete-11.png)
+![red-black-tree-04-delete-11.png](img/red-black-tree-04-delete-11.png)
+![red-black-tree-05-delete-11.png](img/red-black-tree-05-delete-11.png)
+![red-black-tree-06-delete-11.png](img/red-black-tree-06-delete-11.png)
+![red-black-tree-07-delete-11.png](img/red-black-tree-07-delete-11.png)
+![red-black-tree-08-delete-11.png](img/red-black-tree-08-delete-11.png)
+![red-black-tree-09-delete-11.png](img/red-black-tree-09-delete-11.png)
+
+Try yourself at https://www.cs.usfca.edu/~galles/visualization/RedBlack.html.

pkg/adt/example_test.go

@@ -21,8 +21,7 @@ import (
 )
 
 func Example() {
-	ivt := &adt.IntervalTree{}
-
+	ivt := adt.NewIntervalTree()
 	ivt.Insert(adt.NewInt64Interval(1, 3), 123)
 	ivt.Insert(adt.NewInt64Interval(9, 13), 456)
 	ivt.Insert(adt.NewInt64Interval(7, 20), 789)