public static PrimitiveTypeInfo deriveMinArgumentCast(
      ExprNodeDesc childExpr, TypeInfo targetType) {
    return deriveMinArgumentCast(childExpr.getTypeInfo(), targetType);
  }
Get Map of ExprNodeColumnDesc HashCode to ExprNodeColumnDesc.

@param exprDesc
@param hashCodeToColumnDescMap
ql/src/java/org/apache/hadoop/hive/ql/plan/ExprNodeDescUtils.java