public static MapJoinOperator convertJoinOpMapJoinOp(HiveConf hconf,
      JoinOperator op, boolean leftInputJoin, String[] baseSrc, List<String> mapAliases,
      int mapJoinPos, boolean noCheckOuterJoin) throws SemanticException {
    return convertJoinOpMapJoinOp(hconf, op, leftInputJoin, baseSrc, mapAliases,
        mapJoinPos, noCheckOuterJoin, true);
  }
convert a regular join to a a map-side join.

@param op
         join operator
@param mapJoinPos
         position of the source to be read as part of map-reduce framework. All other sources
         are cached in memory
@param noCheckOuterJoin
@param validateMapJoinTree
ql/src/java/org/apache/hadoop/hive/ql/optimizer/MapJoinProcessor.java