Fix wrong graphdb refs paths purging

Signed-off-by: Antonio Murdaca <me@runcom.ninja>

graphdb/graphdb.go

@@ -378,12 +378,22 @@ func (db *Database) Purge(id string) (int, error) {
 		tx.Rollback()
 		return -1, err
 	}
-
 	changes, err := rows.RowsAffected()
 	if err != nil {
 		return -1, err
 	}
 
+	// Clear who's using this id as parent
+	refs, err := tx.Exec("DELETE FROM edge WHERE parent_id = ?;", id)
+	if err != nil {
+		tx.Rollback()
+		return -1, err
+	}
+	refsCount, err := refs.RowsAffected()
+	if err != nil {
+		return -1, err
+	}
+
 	// Delete entity
 	if _, err := tx.Exec("DELETE FROM entity where id = ?;", id); err != nil {
 		tx.Rollback()
@@ -394,7 +404,7 @@ func (db *Database) Purge(id string) (int, error) {
 		return -1, err
 	}
 
-	return int(changes), nil
+	return int(changes + refsCount), nil
 }
 
 // Rename an edge for a given path

graphdb/graphdb_test.go

@@ -472,8 +472,8 @@ func TestPurgeId(t *testing.T) {
 
 	db.Set("/webapp", "1")
 
-	if db.Refs("1") != 1 {
+	if c := db.Refs("1"); c != 1 {
-		t.Fatal("Expect reference count to be 1")
+		t.Fatalf("Expect reference count to be 1, got %d", c)
 	}
 
 	db.Set("/db", "2")
@@ -484,7 +484,45 @@ func TestPurgeId(t *testing.T) {
 		t.Fatal(err)
 	}
 	if count != 2 {
-		t.Fatal("Expected 2 references to be removed")
+		t.Fatalf("Expected 2 references to be removed, got %d", count)
+	}
+}
+
+// Regression test https://github.com/docker/docker/issues/12334
+func TestPurgeIdRefPaths(t *testing.T) {
+	db, dbpath := newTestDb(t)
+	defer destroyTestDb(dbpath)
+
+	db.Set("/webapp", "1")
+	db.Set("/db", "2")
+
+	db.Set("/db/webapp", "1")
+
+	if c := db.Refs("1"); c != 2 {
+		t.Fatalf("Expected 2 reference for webapp, got %d", c)
+	}
+	if c := db.Refs("2"); c != 1 {
+		t.Fatalf("Expected 1 reference for db, got %d", c)
+	}
+
+	if rp := db.RefPaths("2"); len(rp) != 1 {
+		t.Fatalf("Expected 1 reference path for db, got %d", len(rp))
+	}
+
+	count, err := db.Purge("2")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if count != 2 {
+		t.Fatalf("Expected 2 rows to be removed, got %d", count)
+	}
+
+	if c := db.Refs("2"); c != 0 {
+		t.Fatalf("Expected 0 reference for db, got %d", c)
+	}
+	if c := db.Refs("1"); c != 1 {
+		t.Fatalf("Expected 1 reference for webapp, got %d", c)
 	}
 }