final IMNodeIterator<ICachedMNode> getChildrenIterator(ICachedMNode parent, boolean needLock)
      throws MetadataException {
    try {
      return new CachedMNodeIterator(parent, needLock);
    } catch (IOException e) {
      throw new MetadataException(e);
    }
  }
Get the target child node from parent. The parent must be pinned before invoking this method.
The method will try to get child node from cache. If there's no matched node in cache or the
node is not cached, which means it has been evicted, then this method will retrieve child node
from PBTree The returned child node will be pinned. If there's no matched child with the given
name, this method will return null.

@param parent parent node
@param name the name or alias of the target child
@return the pinned child node
@throws MetadataException
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/schemaengine/schemaregion/mtree/impl/pbtree/CachedMTreeStore.java