Merge pull request #541 from hisundar/moss_child_colls

Add Snapshot interface methods for moss child collections feature

index/store/moss/lower.go

@@ -102,8 +102,9 @@ type llStore struct {
 // llSnapshot represents a lower-level snapshot, wrapping a bleve
 // store.KVReader, and implements the moss.Snapshot interface.
 type llSnapshot struct {
-	llStore  *llStore // Holds 1 refs on the llStore.
-	kvReader store.KVReader
+	llStore        *llStore // Holds 1 refs on the llStore.
+	kvReader       store.KVReader
+	childSnapshots map[string]*llSnapshot
 
 	m    sync.Mutex // Protects fields that follow.
 	refs int
@@ -316,6 +317,29 @@ func (llss *llSnapshot) decRef() {
 	llss.m.Unlock()
 }
 
+// ChildCollectionNames returns an array of child collection name strings.
+func (llss *llSnapshot) ChildCollectionNames() ([]string, error) {
+	var childCollections = make([]string, len(llss.childSnapshots))
+	idx := 0
+	for name, _ := range llss.childSnapshots {
+		childCollections[idx] = name
+		idx++
+	}
+	return childCollections, nil
+}
+
+// ChildCollectionSnapshot returns a Snapshot on a given child
+// collection by its name.
+func (llss *llSnapshot) ChildCollectionSnapshot(childCollectionName string) (
+	moss.Snapshot, error) {
+	childSnapshot, exists := llss.childSnapshots[childCollectionName]
+	if !exists {
+		return nil, nil
+	}
+	childSnapshot.addRef()
+	return childSnapshot, nil
+}
+
 func (llss *llSnapshot) Close() error {
 	llss.decRef()