Add minLamport for proper GC of deactivated clients (#1060)

This change improves GC handling when nodes from deactivated
clients remain in the document. Previously, GC failed for such nodes because
the min version vector lacked information about deactivated clients.

The solution:
- Introduces minLamport concept for version vector comparison
- When actor info is missing in min version vector, uses minimum value instead
- Removes nodes if minimum value exceeds node's Lamport timestamp
- Ensures safe deletion by confirming all active users received the change

This approach ensures proper cleanup of orphaned nodes while maintaining data
consistency across the system.

pkg/document/time/version_vector.go

@@ -18,6 +18,7 @@ package time
 
 import (
 	"bytes"
+	"math"
 	"sort"
 	"strconv"
 	"strings"
@@ -114,7 +115,15 @@ func (v VersionVector) AfterOrEqual(other VersionVector) bool {
 
 // EqualToOrAfter returns whether this VersionVector's every field is equal or after than given ticket.
 func (v VersionVector) EqualToOrAfter(other *Ticket) bool {
-	return v[other.actorID.bytes] >= other.lamport
+	clientLamport, ok := v[other.actorID.bytes]
+
+	if !ok {
+		minLamport := v.MinLamport()
+
+		return minLamport > other.lamport
+	}
+
+	return clientLamport >= other.lamport
 }
 
 // Min returns new vv consists of every min value in each column.
@@ -167,7 +176,20 @@ func (v VersionVector) Max(other VersionVector) VersionVector {
 	return maxVV
 }
 
-// MaxLamport returns new vv consists of every max value in each column.
+// MinLamport returns min lamport value in version vector.
+func (v VersionVector) MinLamport() int64 {
+	var minLamport int64 = math.MaxInt64
+
+	for _, value := range v {
+		if value < minLamport {
+			minLamport = value
+		}
+	}
+
+	return minLamport
+}
+
+// MaxLamport returns max lamport value in version vector.
 func (v VersionVector) MaxLamport() int64 {
 	var maxLamport int64 = -1
 

test/integration/gc_test.go

@@ -1136,4 +1136,64 @@ func TestGarbageCollection(t *testing.T) {
 			assert.Equal(t, 2, d2.GarbageLen())
 		}
 	})
+
+	t.Run("gc targeting nodes made by deactivated client", func(t *testing.T) {
+		ctx := context.Background()
+		d1 := document.New(helper.TestDocKey(t))
+		assert.NoError(t, c1.Attach(ctx, d1))
+		// d2.vv =[c1:1], minvv =[c1:1], db.vv {c1: [c1:1]}
+		assert.Equal(t, checkVV(d1.VersionVector(), versionOf(d1.ActorID(), 1)), true)
+
+		d2 := document.New(helper.TestDocKey(t))
+		assert.NoError(t, c2.Attach(ctx, d2))
+		// d2.vv =[c1:1, c2:1], minvv =[c1:0, c2:0], db.vv {c1: [c1:1], c2: [c2:1]}
+		assert.Equal(t, checkVV(d2.VersionVector(), versionOf(d1.ActorID(), 1), versionOf(d2.ActorID(), 2)), true)
+
+		err := d1.Update(func(root *json.Object, p *presence.Presence) error {
+			root.SetNewText("text").Edit(0, 0, "a").Edit(1, 1, "b").Edit(2, 2, "c")
+			return nil
+		}, "sets text")
+		//d1.vv = [c1:2]
+		assert.Equal(t, checkVV(d1.VersionVector(), versionOf(d1.ActorID(), 2)), true)
+		assert.NoError(t, err)
+
+		assert.NoError(t, c1.Sync(ctx))
+		// d1.vv =[c1:3, c2:1], minvv =[c1:0, c2:0], db.vv {c1: [c1:2], c2: [c2:1]}
+		assert.Equal(t, checkVV(d1.VersionVector(), versionOf(d1.ActorID(), 3), versionOf(d2.ActorID(), 1)), true)
+
+		assert.NoError(t, c2.Sync(ctx))
+		// d2.vv =[c1:2, c2:3], minvv =[c1:0, c2:0], db.vv {c1: [c1:2], c2: [c1:1, c2:2]}
+		assert.Equal(t, checkVV(d2.VersionVector(), versionOf(d1.ActorID(), 2), versionOf(d2.ActorID(), 3)), true)
+
+		err = d2.Update(func(root *json.Object, p *presence.Presence) error {
+			root.GetText("text").Edit(2, 2, "c")
+			return nil
+		}, "insert c")
+		//d2.vv =[c1:2, c2:4]
+		assert.Equal(t, checkVV(d2.VersionVector(), versionOf(d1.ActorID(), 2), versionOf(d2.ActorID(), 4)), true)
+		assert.NoError(t, err)
+
+		err = d1.Update(func(root *json.Object, p *presence.Presence) error {
+			root.GetText("text").Edit(1, 3, "")
+			return nil
+		}, "delete bd")
+		//d1.vv = [c1:4, c2:1]
+		assert.Equal(t, checkVV(d1.VersionVector(), versionOf(d1.ActorID(), 4), versionOf(d2.ActorID(), 1)), true)
+		assert.NoError(t, err)
+		assert.Equal(t, 2, d1.GarbageLen())
+		assert.Equal(t, 0, d2.GarbageLen())
+
+		assert.NoError(t, c1.Sync(ctx))
+		assert.NoError(t, c2.Sync(ctx))
+		assert.NoError(t, c1.Deactivate(ctx))
+
+		assert.Equal(t, d2.GarbageLen(), 2)
+		assert.Equal(t, len(d2.VersionVector()), 2)
+
+		// TODO(JOOHOJANG): remove below comments after https://github.com/yorkie-team/yorkie/issues/1058 resolved
+		// Due to https://github.com/yorkie-team/yorkie/issues/1058, removing deactivated client's version vector is not working properly now.
+		// assert.NoError(t, c2.Sync(ctx))
+		// assert.Equal(t, d2.GarbageLen(), 0)
+		// assert.Equal(t, len(d2.VersionVector()), 1)
+	})
 }