database: Add auto-create table(bucket) in BoltDB backend

This is in order to auto create tables in case they doesn't exist, it will
only apply for the DbAdd method which will receive a tableID, a key and a
value, we're infering that table must exist, this change make sure that
that table is created.

One the useful cases for this is in the ciao-image, which will dinamically
require new tables(buckets) per tenant or project. It will automatically
create the tenant's table when a new image is registered.

When retrieving all key/value elements from a specific table(bucket),
it will not create the table if it doesn't exist, it will return an empty
array which means that there are no elements from that table.

Signed-off-by: Obed N Munoz <[email protected]>

database/boltdb.go

@@ -127,7 +127,6 @@ func (db *BoltDB) DbTablesInit(tables []string) (err error) {
 
 // DbAdd adds a new element to table in Bolt database
 func (db *BoltDB) DbAdd(table string, key string, value interface{}) (err error) {
-
 	err = db.DB.Update(func(tx *bolt.Tx) error {
 		var v bytes.Buffer
 
@@ -138,7 +137,10 @@ func (db *BoltDB) DbAdd(table string, key string, value interface{}) (err error)
 
 		bucket := tx.Bucket([]byte(table))
 		if bucket == nil {
-			return fmt.Errorf("Bucket %v not found", table)
+			bucket, err = tx.CreateBucketIfNotExists([]byte(table))
+			if err != nil {
+				return fmt.Errorf("Bucket %v creation failed", table)
+			}
 		}
 
 		err = bucket.Put([]byte(key), v.Bytes())
@@ -207,16 +209,19 @@ func (db *BoltDB) DbGetAll(table string, dbTable DbTable) (elements []interface{
 	err = db.DB.View(func(tx *bolt.Tx) error {
 		b := tx.Bucket([]byte(table))
 
-		err := b.ForEach(func(key, value []byte) error {
-			vr := bytes.NewReader(value)
-			elem := dbTable.NewElement()
-			if err := gob.NewDecoder(vr).Decode(elem); err != nil {
-				return err
-			}
-			elements = append(elements, elem)
-			return nil
-		})
-		return err
+		if b != nil {
+			err := b.ForEach(func(key, value []byte) error {
+				vr := bytes.NewReader(value)
+				elem := dbTable.NewElement()
+				if err := gob.NewDecoder(vr).Decode(elem); err != nil {
+					return err
+				}
+				elements = append(elements, elem)
+				return nil
+			})
+			return err
+		}
+		return nil
 	})
 
 	return elements, err