Add missing AllocateIDs API.

impl/memory/datastore.go

Index: impl/memory/datastore.go
diff --git a/impl/memory/datastore.go b/impl/memory/datastore.go
index 5ca321b66498c2269da173818c22654c8304fa3c..62c9a99825b8b045c832d76958bc1c816d827563 100644
--- a/impl/memory/datastore.go
+++ b/impl/memory/datastore.go
@@ -40,6 +40,11 @@ type dsImpl struct {
 
 var _ ds.RawInterface = (*dsImpl)(nil)
 
+func (d *dsImpl) AllocateIDs(incomplete *ds.Key, n int) (int64, error) {
+	start := d.data.allocateIDs(incomplete, n)
+	return start, nil
+}
+
 func (d *dsImpl) PutMulti(keys []*ds.Key, vals []ds.PropertyMap, cb ds.PutMultiCB) error {
 	d.data.putMulti(keys, vals, cb)
 	return nil
@@ -108,6 +113,11 @@ type txnDsImpl struct {
 
 var _ ds.RawInterface = (*txnDsImpl)(nil)
 
+func (d *txnDsImpl) AllocateIDs(incomplete *ds.Key, n int) (int64, error) {
+	start := d.data.parent.allocateIDs(incomplete, n)
+	return start, nil
+}
+
 func (d *txnDsImpl) PutMulti(keys []*ds.Key, vals []ds.PropertyMap, cb ds.PutMultiCB) error {
 	return d.data.run(func() error {
 		d.data.putMulti(keys, vals, cb)