Problem: memory leak during memiavl import (#1036)

* Problem: memory leak during memiavl import

Solution:
- break up the unnesserary references

* Update CHANGELOG.md

Signed-off-by: yihuang <huang@crypto.com>

* Update memiavl/import.go

Co-authored-by: mmsqe <mavis@crypto.com>
Signed-off-by: yihuang <huang@crypto.com>

---------

Signed-off-by: yihuang <huang@crypto.com>
Co-authored-by: mmsqe <mavis@crypto.com>

CHANGELOG.md

@@ -22,6 +22,7 @@
 
 - [#833](/~https://github.com/crypto-org-chain/cronos/pull/833) Fix rollback command.
 - [#945](/~https://github.com/crypto-org-chain/cronos/pull/945) Fix no handler exists for proposal type error when update-client due to wrong ibc route.
+- [#1036](/~https://github.com/crypto-org-chain/cronos/pull/1036) Fix memiavl import memory leak.
 
 ### Improvements
 

memiavl/import.go

@@ -200,6 +200,11 @@ func (i *importer) Add(n *iavl.ExportNode) error {
 		right:   rightNode,
 	}
 	nodeHash := node.Hash()
+
+	// remove unnecessary reference to avoid memory leak
+	node.left = nil
+	node.right = nil
+
 	preTrees := uint8(len(i.nodeStack) - 2)
 	if err := i.writeBranch(node.version, uint32(node.size), node.height, preTrees, keyLeaf, nodeHash); err != nil {
 		return err