Unable to get results of intermediate dataset

[Sunitha Chennareddy]

 Hi Team,

I am new to Spark, my requirement is I have a huge list, which is converted
to spark dataset and I need to operate on this dataset and store computed
values in another object/dataset and store in memory for further processing.

Approach I tried is : list is retrieved from third party in a loop. I
converted this list to dataset and using function I am trying to iterate
and store results in another dataset.
Problem I am facing : I am not able to see any data in newly computed
dataset.

Kindly help me to sort out this issue, please let me know if any better
approach.

Sample Code:

Class Person implements Serializable{
private static final long serialVersionUID = 1L;

private String name;
Private PersonId id;
//getters and setters
}

Class personId
{
private int deptId;
//getters and setters
}

Class PersonDetails implements Serializable{

private static final long serialVersionUID = 1L;
private int deptId;
private BigDecimal sal;
private String name;

//getters and setters
}

In another Class - I have below template code

List personDtlsList = new ArrayList<>();
final Encoder encoder = Encoders.bean(Person.class);
final Encoder< PersonDetails > personDtlsEncoder = Encoders.bean(
PersonDetails .class);

// here I try to hit thrid party Interface and get person information in
list
List personList = getPersonInformation( passing few parameters);

Dataset personDS = sqlContext.createDataset(personList,encoder);
Dataset personDtlsDS = sqlContext.createDataset(
personDtlsList,personDtlsEncoder);


JavaRDD personDtlsRDD = personDS.toDF().toJavaRDD().map(new
Function() {
private static final long serialVersionUID = 2L;

@Override
  public PersonDetails call(Row row)  throws Exception{
PersonDetails personDetails = new PersonDetails();
//setter for personDetails - name, sal and others
personDetails.setName(row.getString(0));
personDetails.setSal(new BigDecimal(1));
 personDtlsDS.union(sqlContext.createDataset(new
ArrayList(){{add(personDetails);}}, personDtlsEncoder));
 return personDetails;
  }
});

personDtlsDS.count();


Regards,
Sunitha.

Re: Help Required on Spark - Convert DataFrame to List with out using collect

[Sunitha Chennareddy]

Hi,

Thank You All..

Here is my requirement, I have a dataframe which contains list of rows
retrieved from oracle table.
I need to iterate dataframe and fetch each record and call a common
function by passing few parameters.

Issue I am facing is : I am not able to call common function

JavaRDD personRDD = person_dataframe.toJavaRDD().map(new
Function<Row, Person>() {
  @Override
  public Person call(Row row)  throws Exception{
  Person person = new Person();
  person.setId(row.getDecimal(0).longValue());
  person.setName(row.getString(1));

personLst.add(person);
return person;
  }
});

personRDD.foreach(new VoidFunction() {
private static final long serialVersionUID = 1123456L;

@Override
public void call(Person person) throws Exception
{
  System.out.println(person.getId());
Here I tried to call common function 
}
   });

I am able to print data in foreach loop, however if I tried to call common
function it gives me below error
Error Message :  org.apache.spark.SparkException: Task not serializable

I kindly request you to share some idea(sample code / link to refer) on how
to call a common function/Interace method by passing values in each record
of the dataframe.

Regards,
Sunitha


On Tue, Dec 19, 2017 at 1:20 PM, Weichen Xu <weichen...@databricks.com>
wrote:

> Hi Sunitha,
>
> In the mapper function, you cannot update outer variables such as 
> `personLst.add(person)`,
> this won't work so that's the reason you got an empty list.
>
> You can use `rdd.collect()` to get a local list of `Person` objects
> first, then you can safely iterate on the local list and do any update you
> want.
>
> Thanks.
>
> On Tue, Dec 19, 2017 at 2:16 PM, Sunitha Chennareddy <
> chennareddysuni...@gmail.com> wrote:
>
>> Hi Deepak,
>>
>> I am able to map row to person class, issue is I want to to call another
>> method.
>> I tried converting to list and its not working with out using collect.
>>
>> Regards
>> Sunitha
>> On Tuesday, December 19, 2017, Deepak Sharma <deepakmc...@gmail.com>
>> wrote:
>>
>>> I am not sure about java but in scala it would be something like
>>> df.rdd.map{ x => MyClass(x.getString(0),.)}
>>>
>>> HTH
>>>
>>> --Deepak
>>>
>>> On Dec 19, 2017 09:25, "Sunitha Chennareddy" <chennareddysunitha@.com
>>> <chennareddysuni...@gmail.com>> wrote:
>>>
>>> Hi All,
>>>
>>> I am new to Spark, I want to convert DataFrame to List with
>>> out using collect().
>>>
>>> Main requirement is I need to iterate through the rows of dataframe and
>>> call another function by passing column value of each row (person.getId())
>>>
>>> Here is the snippet I have tried, Kindly help me to resolve the issue,
>>> personLst is returning 0:
>>>
>>> List personLst= new ArrayList();
>>> JavaRDD personRDD = person_dataframe.toJavaRDD().map(new
>>> Function<Row, Person>() {
>>>   public Person call(Row row)  throws Exception{
>>>   Person person = new Person();
>>>   person.setId(row.getDecimal(0).longValue());
>>>   person.setName(row.getString(1));
>>>
>>> personLst.add(person);
>>> // here I tried to call another function but control never passed
>>> return person;
>>>   }
>>> });
>>> logger.info("personLst size =="+personLst.size());
>>> logger.info("personRDD count ==="+personRDD.count());
>>>
>>> //output is
>>> personLst size == 0
>>> personRDD count === 3
>>>
>>>
>>>
>

Re: Help Required on Spark - Convert DataFrame to List with out using collect

[Sunitha Chennareddy]

Hi Jorn,

In my case I have to call common interface function
by passing the values of each rdd. So I have tried iterating , but I was
not able to trigger common function from call method as commented in the
snippet code in my earlier mail.

Request you please share your views.

Regards
Sunitha

On Tuesday, December 19, 2017, Jörn Franke <jornfra...@gmail.com> wrote:

> This is correct behavior. If you need to call another method simply append
> another map, flatmap or whatever you need.
>
> Depending on your use case you may use also reduce and reduce by key.
> However you never (!) should use a global variable as in your snippet.
> This can to work because you work in a distributed setting.
> Probably the code will fail on a cluster or at random.
>
> On 19. Dec 2017, at 07:16, Sunitha Chennareddy <
> chennareddysuni...@gmail.com> wrote:
>
> Hi Deepak,
>
> I am able to map row to person class, issue is I want to to call another
> method.
> I tried converting to list and its not working with out using collect.
>
> Regards
> Sunitha
> On Tuesday, December 19, 2017, Deepak Sharma <deepakmc...@gmail.com>
> wrote:
>
>> I am not sure about java but in scala it would be something like
>> df.rdd.map{ x => MyClass(x.getString(0),.)}
>>
>> HTH
>>
>> --Deepak
>>
>> On Dec 19, 2017 09:25, "Sunitha Chennareddy" <chennareddysunitha@.com
>> <chennareddysuni...@gmail.com>> wrote:
>>
>> Hi All,
>>
>> I am new to Spark, I want to convert DataFrame to List with
>> out using collect().
>>
>> Main requirement is I need to iterate through the rows of dataframe and
>> call another function by passing column value of each row (person.getId())
>>
>> Here is the snippet I have tried, Kindly help me to resolve the issue,
>> personLst is returning 0:
>>
>> List personLst= new ArrayList();
>> JavaRDD personRDD = person_dataframe.toJavaRDD().map(new
>> Function<Row, Person>() {
>>   public Person call(Row row)  throws Exception{
>>   Person person = new Person();
>>   person.setId(row.getDecimal(0).longValue());
>>   person.setName(row.getString(1));
>>
>> personLst.add(person);
>> // here I tried to call another function but control never passed
>> return person;
>>   }
>> });
>> logger.info("personLst size =="+personLst.size());
>> logger.info("personRDD count ==="+personRDD.count());
>>
>> //output is
>> personLst size == 0
>> personRDD count === 3
>>
>>
>>

Re: Help Required on Spark - Convert DataFrame to List with out using collect

[Sunitha Chennareddy]

Hi Deepak,

I am able to map row to person class, issue is I want to to call another
method.
I tried converting to list and its not working with out using collect.

Regards
Sunitha
On Tuesday, December 19, 2017, Deepak Sharma <deepakmc...@gmail.com> wrote:

> I am not sure about java but in scala it would be something like
> df.rdd.map{ x => MyClass(x.getString(0),.)}
>
> HTH
>
> --Deepak
>
> On Dec 19, 2017 09:25, "Sunitha Chennareddy" <chennareddysunitha@.com
> <chennareddysuni...@gmail.com>> wrote:
>
> Hi All,
>
> I am new to Spark, I want to convert DataFrame to List with out
> using collect().
>
> Main requirement is I need to iterate through the rows of dataframe and
> call another function by passing column value of each row (person.getId())
>
> Here is the snippet I have tried, Kindly help me to resolve the issue,
> personLst is returning 0:
>
> List personLst= new ArrayList();
> JavaRDD personRDD = person_dataframe.toJavaRDD().map(new
> Function<Row, Person>() {
>   public Person call(Row row)  throws Exception{
>   Person person = new Person();
>   person.setId(row.getDecimal(0).longValue());
>   person.setName(row.getString(1));
>
> personLst.add(person);
> // here I tried to call another function but control never passed
> return person;
>   }
> });
> logger.info("personLst size =="+personLst.size());
> logger.info("personRDD count ==="+personRDD.count());
>
> //output is
> personLst size == 0
> personRDD count === 3
>
>
>

Help Required on Spark - Convert DataFrame to List with out using collect

[Sunitha Chennareddy]

Hi All,

I am new to Spark, I want to convert DataFrame to List with out
using collect().

Main requirement is I need to iterate through the rows of dataframe and
call another function by passing column value of each row (person.getId())

Here is the snippet I have tried, Kindly help me to resolve the issue,
personLst is returning 0:

List personLst= new ArrayList();
JavaRDD personRDD = person_dataframe.toJavaRDD().map(new
Function() {
  public Person call(Row row)  throws Exception{
  Person person = new Person();
  person.setId(row.getDecimal(0).longValue());
  person.setName(row.getString(1));

personLst.add(person);
// here I tried to call another function but control never passed
return person;
  }
});
logger.info("personLst size =="+personLst.size());
logger.info("personRDD count ==="+personRDD.count());

//output is
personLst size == 0
personRDD count === 3