private boolean fileExist() {
      return !rewritePosDataFiles.isEmpty() || !rewriteDataFiles.isEmpty();
    }
Complete this binary tree to make every subTree of this Tree As a Full Binary Tree(FBT), if
any data exists in this subTree.

<p>A Full Binary Tree(FBT) is a binary tree in which all the nodes have either 0 or 2
offspring. In other terms, it is a binary tree in which all nodes, except the leaf nodes,
have two offspring.

<p>To Complete the tree is to avoid ancestor node's data can't be covered when split subTree.
amoro-format-iceberg/src/main/java/org/apache/amoro/optimizing/plan/MixedIcebergPartitionPlan.java