fix bug, revert field deletion, docs

Author: aaronc

iavl/internal/mem_node.go

@@ -44,7 +44,7 @@ func (node *MemNode) Version() uint32 {
 
 // Key implements the Node interface.
 func (node *MemNode) Key() (UnsafeBytes, error) {
-	return WrapUnsafeBytes(node.key), nil
+	return WrapSafeBytes(node.key), nil
 }
 
 // Value implements the Node interface.

iavl/internal/node_pointer.go

@@ -7,9 +7,10 @@ import (
 
 // NodePointer is a pointer to a Node, which may be either in-memory, on-disk or both.
 type NodePointer struct {
-	mem     atomic.Pointer[MemNode]
-	fileIdx uint32 // absolute index in file, 1-based, zero means we don't have an offset
-	id      NodeID
+	mem       atomic.Pointer[MemNode]
+	changeset *Changeset
+	fileIdx   uint32 // absolute index in file, 1-based, zero means we don't have an offset
+	id        NodeID
 }
 
 // NewNodePointer creates a new NodePointer pointing to the given in-memory node.
@@ -19,13 +20,23 @@ func NewNodePointer(memNode *MemNode) *NodePointer {
 	return n
 }
 
-// Resolve resolves the NodePointer to a Node, loading from memory or disk as necessary.
+// Resolve resolves the NodePointer to a Node, loading from memory or disk as necessary
+// as well as a Pin which MUST be unpinned after the caller is done using the node.
+// Resolve will ALWAYS return a valid Pin even if there is an error. For clarity and
+// consistency it is recommended to introduce a defer pin.Unpin() immediately after
+// calling Resolve and BEFORE checking the error return value like this:
+//
+//	node, pin, err := nodePointer.Resolve()
+//	defer pin.Unpin()
+//	if err != nil {
+//	    // handle error
+//	}
 func (p *NodePointer) Resolve() (Node, Pin, error) {
 	mem := p.mem.Load()
 	if mem != nil {
 		return mem, NoopPin{}, nil
 	}
-	panic("not implemented: loading from disk")
+	return nil, NoopPin{}, fmt.Errorf("node not in memory and on-disk loading will be implemented in a future PR")
 }
 
 // String implements the fmt.Stringer interface.