Ensure proper deletion of documents in MemDB (#920)

In Dashboard, there was an issue where re-creating and deleting a
previously deleted document did not remove the document as expected.
This issue occurred because the already deleted document was not
properly filtered out and returned again upon re-deletion.

This commit fixes this issue by adding a filter to prevent previously
deleted documents from being returned during document retrieval for
deletion.

server/backend/database/memory/database.go

@@ -683,48 +683,17 @@ func (d *DB) FindDocInfoByKeyAndOwner(
 	txn := d.db.Txn(true)
 	defer txn.Abort()
 
-	// TODO(hackerwins): Removed documents should be filtered out by the query, but
-	// somehow it does not work. This is a workaround.
-	// val, err := txn.First(tblDocuments, "project_id_key_removed_at", projectID.String(), key.String(), gotime.Time{})
-	iter, err := txn.Get(
-		tblDocuments,
-		"project_id_key_removed_at",
-		clientRefKey.ProjectID.String(),
-		key.String(),
-		gotime.Time{},
-	)
-	if err != nil {
-		return nil, fmt.Errorf("find document by key: %w", err)
-	}
-	var raw interface{}
-	for val := iter.Next(); val != nil; val = iter.Next() {
-		if val != nil && val.(*database.DocInfo).RemovedAt.IsZero() {
-			raw = val
-		}
-	}
-
+	info, err := d.findDocInfoByKey(txn, clientRefKey.ProjectID, key)
 	if err != nil {
-		return nil, fmt.Errorf("find document by key: %w", err)
+		return info, err
 	}
-	if !createDocIfNotExist && raw == nil {
-		raw, err = txn.First(
-			tblDocuments,
-			"project_id_key",
-			clientRefKey.ProjectID.String(),
-			key.String(),
-		)
-		if err != nil {
-			return nil, fmt.Errorf("find document by key: %w", err)
-		}
-		if raw == nil {
-			return nil, fmt.Errorf("%s: %w", key, database.ErrDocumentNotFound)
-		}
+	if !createDocIfNotExist && info == nil {
+		return nil, fmt.Errorf("%s: %w", key, database.ErrDocumentNotFound)
 	}
 
-	now := gotime.Now()
-	var docInfo *database.DocInfo
-	if raw == nil {
-		docInfo = &database.DocInfo{
+	if info == nil {
+		now := gotime.Now()
+		info = &database.DocInfo{
 			ID:         newID(),
 			ProjectID:  clientRefKey.ProjectID,
 			Key:        key,
@@ -733,15 +702,38 @@ func (d *DB) FindDocInfoByKeyAndOwner(
 			CreatedAt:  now,
 			AccessedAt: now,
 		}
-		if err := txn.Insert(tblDocuments, docInfo); err != nil {
+		if err := txn.Insert(tblDocuments, info); err != nil {
 			return nil, fmt.Errorf("create document: %w", err)
 		}
 		txn.Commit()
-	} else {
-		docInfo = raw.(*database.DocInfo)
 	}
 
-	return docInfo.DeepCopy(), nil
+	return info.DeepCopy(), nil
+}
+
+// findDocInfoByKey finds the document of the given key.
+func (d *DB) findDocInfoByKey(txn *memdb.Txn, projectID types.ID, key key.Key) (*database.DocInfo, error) {
+	// TODO(hackerwins): Removed documents should be filtered out by the query, but
+	// somehow it does not work. This is a workaround.
+	// val, err := txn.First(tblDocuments, "project_id_key_removed_at", projectID.String(), key.String(), gotime.Time{})
+	iter, err := txn.Get(
+		tblDocuments,
+		"project_id_key_removed_at",
+		projectID.String(),
+		key.String(),
+		gotime.Time{},
+	)
+	if err != nil {
+		return nil, fmt.Errorf("find doc info by key: %w", err)
+	}
+	var docInfo *database.DocInfo
+	for val := iter.Next(); val != nil; val = iter.Next() {
+		if info := val.(*database.DocInfo); info.RemovedAt.IsZero() {
+			docInfo = info
+		}
+	}
+
+	return docInfo, nil
 }
 
 // FindDocInfoByKey finds the document of the given key.
@@ -753,15 +745,15 @@ func (d *DB) FindDocInfoByKey(
 	txn := d.db.Txn(false)
 	defer txn.Abort()
 
-	raw, err := txn.First(tblDocuments, "project_id_key_removed_at", projectID.String(), key.String(), gotime.Time{})
+	info, err := d.findDocInfoByKey(txn, projectID, key)
 	if err != nil {
-		return nil, fmt.Errorf("find document by key: %w", err)
+		return nil, fmt.Errorf("find doc info by key: %w", err)
 	}
-	if raw == nil {
+	if info == nil {
 		return nil, fmt.Errorf("%s: %w", key, database.ErrDocumentNotFound)
 	}
 
-	return raw.(*database.DocInfo).DeepCopy(), nil
+	return info.DeepCopy(), nil
 }
 
 // FindDocInfoByRefKey finds a docInfo of the given refKey.

server/backend/database/testcases/testcases.go

@@ -71,6 +71,26 @@ func RunFindDocInfoTest(
 		assert.NoError(t, err)
 		assert.Equal(t, docKey, docInfo.Key)
 	})
+
+	t.Run("find docInfo by key test", func(t *testing.T) {
+		ctx := context.Background()
+		clientInfo, err := db.ActivateClient(ctx, projectID, t.Name())
+		assert.NoError(t, err)
+
+		// 01. Create a document
+		docKey := helper.TestDocKey(t)
+		info, err := db.FindDocInfoByKeyAndOwner(ctx, clientInfo.RefKey(), docKey, true)
+		assert.NoError(t, err)
+		assert.Equal(t, docKey, info.Key)
+
+		// 02. Remove the document
+		err = db.CreateChangeInfos(ctx, projectID, info, 0, []*change.Change{}, true)
+		assert.NoError(t, err)
+
+		// 03. Find the document
+		info, err = db.FindDocInfoByKey(ctx, projectID, docKey)
+		assert.ErrorIs(t, err, database.ErrDocumentNotFound)
+	})
 }
 
 // RunFindProjectInfoBySecretKeyTest runs the FindProjectInfoBySecretKey test for the given db.