Replace Add/Set/Delete with single method for batch ops

extension/storage/README.md

@@ -17,11 +17,12 @@ Delete(context.Context, string) error
 Close(context.Context) error
 ```
 
-As well as their batch counterparts (executed in a single transaction):
+It is possible to execute several operations in a single transaction via `BatchOp`. The method takes
+two collections as arguments:
+* list of keys for which the values are retrieved and returned,
+* a map, which specifies the key/value pairs that are going to be updated; when a value is `nil`, the key is deleted.
 ```
-GetBatch(context.Context, []string) ([][]byte, error)
-SetBatch(context.Context, map[string][]byte) error
-DeleteBatch(context.Context, []string) error
+BatchOp(context.Context, []string, map[]string[]byte) ([][]byte, error)
 ```
 
 Note: All methods should return error only if a problem occurred. (For example, if a file is no longer accessible, or if a remote service is unavailable.)

extension/storage/nop_client.go

@@ -45,17 +45,7 @@ func (c nopClient) Close(context.Context) error {
 	return nil
 }
 
-// GetBatch does nothing, and returns nil, nil
-func (c nopClient) GetBatch(ctx context.Context, strings []string) ([][]byte, error) {
+// Batch does nothing, and returns nil, nil
+func (c nopClient) Batch(ctx context.Context, strings []string, entries map[string][]byte) ([][]byte, error) {
 	return nil, nil // no result, but no problem
 }
-
-// SetBatch does nothing and returns nil
-func (c nopClient) SetBatch(ctx context.Context, entries map[string][]byte) error {
-	return nil // no problem
-}
-
-// DeleteBatch does nothing and returns nil
-func (c nopClient) DeleteBatch(ctx context.Context, strings []string) error {
-	return nil // no problem
-}

extension/storage/storage.go

@@ -33,9 +33,11 @@ type Extension interface {
 // Client is the interface that storage clients must implement
 // All methods should return error only if a problem occurred.
 // This mirrors the behavior of a golang map:
-//   - Set and SetBatch don't error if a key already exists - they just overwrite the value.
-//   - Get and GetBatch don't error if a key is not found - they just returns nil.
-//   - Delete and DeleteBatch don't error if the key doesn't exist - they just no-ops.
+//   - Set doesn't error if a key already exists - it just overwrites the value.
+//   - Get doesn't error if a key is not found - it just returns nil.
+//   - Delete doesn't error if the key doesn't exist - it just no-ops.
+// Similarly:
+//   - Batch doesn't error if any of the above happens for either retrieved or updated keys
 // This also provides a way to differentiate data operations
 //   [overwrite | not-found | no-op] from "real" problems
 type Client interface {
@@ -51,17 +53,10 @@ type Client interface {
 	// Delete will delete data associated with the specified key
 	Delete(context.Context, string) error
 
-	// GetBatch will retrieve data from storage that corresponds to the
-	// collection of keys. It will return an array of results, where each
+	// Batch will, respectively - get values for selected keys or upsert key/values. When the value specified
+	// is nil, the key is being deleted. It will return an array of results, where each
 	// one corresponds to a key at a given position and will be nil, if key is not found
-	GetBatch(context.Context, []string) ([][]byte, error)
-
-	// SetBatch will store data provided in the map.
-	// When a value for a given key is nil, the entry will be deleted
-	SetBatch(context.Context, map[string][]byte) error
-
-	// DeleteBatch will delete data associated with specified collection of keys
-	DeleteBatch(context.Context, []string) error
+	Batch(context.Context, []string, map[string][]byte) ([][]byte, error)
 
 	// Close will release any resources held by the client
 	Close(context.Context) error