private static MFieldSchema getColumnFromTableColumns(List<MFieldSchema> cols, String col) {
    if (cols == null) {
      return null;
    }
    for (MFieldSchema mfs : cols) {
      if (mfs.getName().equalsIgnoreCase(col)) {
        return mfs;
      }
    }
    return null;
  }
Called right before an action that would drop a storage descriptor.
This function makes the SD's reference to a CD null, and then deletes the CD
if it no longer is referenced in the table.
@param msd the storage descriptor to drop
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/ObjectStore.java