diff --git a/internal/app/datastore.go b/internal/app/datastore.go
index 45eaff6..bfc09b5 100644
--- a/internal/app/datastore.go
+++ b/internal/app/datastore.go
@@ -3,11 +3,14 @@ package app
 import (
 	"database/sql"
 	"errors"
+	"fmt"
 	_ "github.com/mattn/go-sqlite3"
-	"log"
+	"github.com/sirupsen/logrus"
 	"time"
 )
 
+var ErrorRecordNotFound = errors.New("Record not found")
+
 type ImageMetaData struct {
 	ImageId           int
 	PiwigoId          int
@@ -19,11 +22,12 @@ type ImageMetaData struct {
 	CategoryId        int
 }
 
-type ImageMetadataLoader interface {
-	GetImageMetadata(relativePath string) (ImageMetaData, error)
+func (img *ImageMetaData) String() string {
+	return fmt.Sprintf("ImageMetaData{ImageId:%d, PiwigoId:%d, CategoryId:%d, RelPath:%s, File:%s, Md5:%s, Change:%sS, catpath:%s}", img.ImageId, img.PiwigoId, img.CategoryId, img.RelativeImagePath, img.Filename, img.Md5Sum, img.LastChange.String(), img.CategoryPath)
 }
 
-type ImageMetadataSaver interface {
+type ImageMetadataProvider interface {
+	GetImageMetadata(relativePath string) (ImageMetaData, error)
 	SaveImageMetadata(m ImageMetaData) error
 }
 
@@ -50,68 +54,84 @@ func (d *localDataStore) Initialize(connectionString string) error {
 }
 
 func (d *localDataStore) GetImageMetadata(relativePath string) (ImageMetaData, error) {
+	logrus.Debugf("Query image metadata for file %s", relativePath)
+	img := ImageMetaData{}
+
 	db, err := d.openDatabase()
 	if err != nil {
-		return ImageMetaData{}, err
+		return img, err
 	}
 	defer db.Close()
 
-	tx, err := db.Begin()
+	stmt, err := db.Prepare("SELECT imageId, piwigoId, relativePath, fileName, md5sum, lastChanged, categoryPath, categoryId FROM image WHERE relativePath = ?")
 	if err != nil {
-		return ImageMetaData{}, err
+		return img, err
 	}
 
-	//TODO: select entry by path
-	//stmt, err := tx.Prepare("select * from image WHERE relativePath = '?'")
-	//if err != nil {
-	//	log.Fatal(err)
-	//}
-
-	err = tx.Commit()
+	rows, err := stmt.Query(relativePath)
 	if err != nil {
-		log.Fatal(err)
+		return img, err
 	}
+	defer rows.Close()
 
-	return ImageMetaData{}, nil
-}
-
-func (d *localDataStore) SaveImageMetadata(m ImageMetaData) error {
-	db, err := d.openDatabase()
-	if err != nil {
-		return err
-	}
-	defer db.Close()
-
-	tx, err := db.Begin()
-	if err != nil {
-		return err
-	}
-
-	if m.ImageId <= 0 {
-		err = d.insertImageMetaData(tx, m)
+	if rows.Next() {
+		err = rows.Scan(&img.ImageId, &img.PiwigoId, &img.RelativeImagePath, &img.Filename, &img.Md5Sum, &img.LastChange, &img.CategoryPath, &img.CategoryId)
 		if err != nil {
-			return err
+			return img, err
 		}
 	} else {
-		// TODO: update existing entry
+		return img, ErrorRecordNotFound
 	}
+	err = rows.Err()
 
-	err = tx.Commit()
-	return err
+	return img, err
 }
 
-func (d *localDataStore) insertImageMetaData(tx *sql.Tx, m ImageMetaData) error {
+func (d *localDataStore) SaveImageMetadata(img ImageMetaData) error {
+	logrus.Debugf("Saving imagemetadata: %s", img.String())
+	db, err := d.openDatabase()
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+
+	tx, err := db.Begin()
+	if err != nil {
+		return err
+	}
+
+	if img.ImageId <= 0 {
+		err = d.insertImageMetaData(tx, img)
+	} else {
+		err = d.updateImageMetaData(tx, img)
+	}
+
+	if err != nil {
+		logrus.Errorf("Rolling back transaction for metadata of %s", img.RelativeImagePath)
+		errTx := tx.Rollback()
+		if errTx != nil {
+			logrus.Errorf("Rollback of transaction for metadata of %s failed!", img.RelativeImagePath)
+		}
+		return err
+	}
+
+	logrus.Debugf("Commiting metadata for image %s", img.String())
+	return tx.Commit()
+}
+
+func (d *localDataStore) insertImageMetaData(tx *sql.Tx, data ImageMetaData) error {
 	stmt, err := tx.Prepare("INSERT INTO image (piwigoId, relativePath, fileName, md5sum, lastChanged, categoryPath, categoryId) VALUES (?,?,?,?,?,?,?)")
 	if err != nil {
 		return err
 	}
-	_, err = stmt.Exec(m.PiwigoId, m.RelativeImagePath, m.Filename, m.Md5Sum, m.LastChange, m.CategoryPath, m.CategoryId)
+	_, err = stmt.Exec(data.PiwigoId, data.RelativeImagePath, data.Filename, data.Md5Sum, data.LastChange, data.CategoryPath, data.CategoryId)
 	return err
 }
 
 func (d *localDataStore) openDatabase() (*sql.DB, error) {
 	db, err := sql.Open("sqlite3", d.connectionString)
 	if err != nil {
+		logrus.Warnf("Could not open database %s", d.connectionString)
 		return nil, err
 	}
 	db.SetMaxOpenConns(1)
@@ -121,7 +141,7 @@ func (d *localDataStore) openDatabase() (*sql.DB, error) {
 
 func (d *localDataStore) createTablesIfNeeded(db *sql.DB) error {
 	_, err := db.Exec("CREATE TABLE IF NOT EXISTS image (" +
-		"imageId INTEGER PRIMARY KEY AUTOINCREMENT," +
+		"imageId INTEGER PRIMARY KEY," +
 		"piwigoId INTEGER NULL," +
 		"relativePath NVARCHAR(1000) NOT NULL," +
 		"fileName NVARCHAR(255) NOT NULL," +
@@ -130,5 +150,19 @@ func (d *localDataStore) createTablesIfNeeded(db *sql.DB) error {
 		"categoryPath NVARCHAR(1000) NOT NULL," +
 		"categoryId INTEGER NULL" +
 		");")
+	if err != nil {
+		return err
+	}
+
+	_, err = db.Exec("CREATE UNIQUE INDEX IF NOT EXISTS UX_ImageRelativePath ON image (relativePath);")
+	return err
+}
+
+func (d *localDataStore) updateImageMetaData(tx *sql.Tx, data ImageMetaData) error {
+	stmt, err := tx.Prepare("UPDATE image SET piwigoId = ?, relativePath = ?, fileName = ?, md5sum = ?, lastChanged = ?, categoryPath = ?, categoryId = ? WHERE imageId = ?")
+	if err != nil {
+		return err
+	}
+	_, err = stmt.Exec(data.PiwigoId, data.RelativeImagePath, data.Filename, data.Md5Sum, data.LastChange, data.CategoryPath, data.CategoryId, data.ImageId)
 	return err
 }
diff --git a/internal/app/datastore_test.go b/internal/app/datastore_test.go
new file mode 100644
index 0000000..74785bb
--- /dev/null
+++ b/internal/app/datastore_test.go
@@ -0,0 +1,136 @@
+package app
+
+import (
+	"os"
+	"strings"
+	"testing"
+	"time"
+)
+
+var databaseFile = "./metadatatest.db"
+var dbinitOk bool
+
+func TestDataStoreInitialize(t *testing.T) {
+	_ = setupDatabase(t)
+	cleanupDatabase(t)
+}
+
+func TestSaveAndLoadMetadata(t *testing.T) {
+	if !dbinitOk {
+		t.Skip("Skipping test as TestDataStoreInitialize failed!")
+	}
+	dataStore := setupDatabase(t)
+
+	filePath := "blah/foo/bar.jpg"
+	img := getExampleImageMetadata(filePath)
+
+	saveImageShouldNotFail("insert", dataStore, img, t)
+	img.ImageId = 1
+
+	imgLoad := loadMetadataShouldNotFail("insert", dataStore, filePath, t)
+	EnsureMetadataAreEqual("insert", img, imgLoad, t)
+
+	// updated the image again
+	img.Md5Sum = "123456"
+	saveImageShouldNotFail("update", dataStore, img, t)
+
+	imgLoad = loadMetadataShouldNotFail("update", dataStore, filePath, t)
+	EnsureMetadataAreEqual("update", img, imgLoad, t)
+
+	cleanupDatabase(t)
+}
+
+func TestLoadMetadataNotFound(t *testing.T) {
+	if !dbinitOk {
+		t.Skip("Skipping test as TestDataStoreInitialize failed!")
+	}
+	dataStore := setupDatabase(t)
+
+	filePath := "blah/foo/bar.jpg"
+	imgLoad, err := dataStore.GetImageMetadata(filePath)
+	if err != ErrorRecordNotFound {
+		t.Errorf("Unexpected error on loading non existing file %s: %s", filePath, err)
+	}
+	if imgLoad.ImageId > 0 {
+		t.Error("Found an image metadata that should not exist on an emtpy database.")
+	}
+
+	cleanupDatabase(t)
+}
+
+func TestUniqueIndexOnRelativeFilePath(t *testing.T) {
+	if !dbinitOk {
+		t.Skip("Skipping test as TestDataStoreInitialize failed!")
+	}
+	dataStore := setupDatabase(t)
+
+	filePath := "blah/foo/bar.jpg"
+	img := getExampleImageMetadata(filePath)
+
+	saveImageShouldNotFail("insert", dataStore, img, t)
+
+	err := dataStore.SaveImageMetadata(img)
+	if err == nil {
+		t.Errorf("Could save duplicated image metadata. Expected error but got none!")
+	}
+
+	// check if the error contains the expected column as name. If not, this indicates another problem than
+	// the expected duplicated insert error.
+	if !strings.Contains(err.Error(), "relativePath") {
+		t.Errorf("Got a unexpected error on saving duplicate records: %s", err)
+	}
+
+	cleanupDatabase(t)
+}
+
+func saveImageShouldNotFail(action string, dataStore *localDataStore, img ImageMetaData, t *testing.T) {
+	err := dataStore.SaveImageMetadata(img)
+	if err != nil {
+		t.Errorf("%s: Could not save Metadata: %s", action, err)
+	}
+}
+
+func loadMetadataShouldNotFail(action string, dataStore *localDataStore, filePath string, t *testing.T) ImageMetaData {
+	imgLoad, err := dataStore.GetImageMetadata(filePath)
+	if err != nil {
+		t.Errorf("%s: Could not load saved Metadata: %s - %s", action, filePath, err)
+	}
+	return imgLoad
+}
+
+func EnsureMetadataAreEqual(action string, img ImageMetaData, imgLoad ImageMetaData, t *testing.T) {
+	// check if both instances serialize to the same string representation
+	if img.String() != imgLoad.String() {
+		t.Errorf("%s: Invalid image loaded! expected (ignore ImageId) %s but got %s", action, img.String(), imgLoad.String())
+	}
+}
+
+func getExampleImageMetadata(filePath string) ImageMetaData {
+	return ImageMetaData{
+		RelativeImagePath: filePath,
+		PiwigoId:          1,
+		Md5Sum:            "aabbccddeeff",
+		LastChange:        time.Now().UTC(),
+		Filename:          "bar.jpg",
+		CategoryPath:      "blah/foo",
+		CategoryId:        100,
+	}
+}
+
+func cleanupDatabase(t *testing.T) {
+	err := os.Remove(databaseFile)
+	if err != nil {
+		t.Errorf("Failed remove test database %s: %s", databaseFile, err)
+	}
+}
+
+func setupDatabase(t *testing.T) *localDataStore {
+	dataStore := &localDataStore{}
+	err := dataStore.Initialize(databaseFile)
+	if err != nil {
+		t.Errorf("Failed to init datastore: %s", err)
+		return nil
+	}
+	dbinitOk = true
+	return dataStore
+}