@Override
  public Object clone() {
    List<VirtualColumn> vcs = new ArrayList<VirtualColumn>(getVirtualCols());
    return new TableScanDesc(getAlias(), vcs, this.tableMetadata, this.probeDecodeContext);
  }
A boolean variable set to true by the semantic analyzer only in case of the analyze command.
ql/src/java/org/apache/hadoop/hive/ql/plan/TableScanDesc.java