private static void appendKllSketch(StringBuilder rewrittenQueryBuilder, HiveConf conf,
      String columnName, ColumnStatsType columnStatsType, int pos) throws SemanticException {
    appendKllSketch(rewrittenQueryBuilder, conf, columnName, columnStatsType);
    rewrittenQueryBuilder.append(" AS ")
        .append(unparseIdentifier(ColumnStatsField.KLL_SKETCH.getFieldName() + pos, conf));
  }
Generates a SQL statement that will compute the stats for all columns
included in the input table.
ql/src/java/org/apache/hadoop/hive/ql/parse/ColumnStatsSemanticAnalyzer.java