btree_txn_get
int btree_txn_get(struct btree *bt, struct btree_txn *txn,
btree_txn_get(bt, NULL, key, data)
if (btree_txn_get(ns->data_db, ns->data_txn, &key, &val) != 0) {
rc = btree_txn_get(NULL, search->data_txn, &key, &val);
if (btree_txn_get(NULL, search->data_txn, &key, &val) == 0) {