Added count functionality

mdb/collection.go

@@ -274,6 +274,10 @@ func (c *Collection[T]) delete(tx *Snapshot, itemID uint64) error {
 	return c.deleteItem(tx, itemID)
 }
 
+func (c *Collection[T]) Count(tx *Snapshot) int {
+	return c.ByID.Count(tx)
+}
+
 func (c *Collection[T]) getByID(tx *Snapshot, itemID uint64) (*T, bool) {
 	x := new(T)
 	c.setID(x, itemID)

mdb/index.go

@@ -192,6 +192,11 @@ func (i *Index[T]) List(tx *Snapshot, args *ListArgs[T], out []*T) []*T {
 	return items
 }
 
+func (i *Index[T]) Count(tx *Snapshot) int {
+	tx = i.ensureSnapshot(tx)
+	return i.btree(tx).Len()
+}
+
 // ----------------------------------------------------------------------------
 
 func (i *Index[T]) insertConflict(tx *Snapshot, item *T) bool {