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1

I have a U-SQL script which processes some data using some UDOs and then finally outputs a file back to Azure Data Lake.

The expected behaviour is that if the file that is generated is empty, the script should fail, however I am unable to get it to do so.

I tried implementing a simple reducer which counts the number of rows and throws an exception when the count is zero. However, it doesnt get called during execution since the file is empty, and the script succeeds.

Any ideas on how to get this done?

The reduce function is below:

public override IEnumerable<IRow> Reduce(...)

 long count = 0;

 foreach (var row in input.Rows)
 
 count++;
 break;
 

 if (count == 0)
 
 throw new Exception("Zero rows found in table");
 
 else
 
 output.Set("Count", count);
 yield return output.AsReadOnly();
 

c# azure azure-data-lake u-sql

share|improve this question

asked Mar 25 at 21:37

mksh15mksh15

5088 bronze badges

add a comment | 

1

I have a U-SQL script which processes some data using some UDOs and then finally outputs a file back to Azure Data Lake.

The expected behaviour is that if the file that is generated is empty, the script should fail, however I am unable to get it to do so.

I tried implementing a simple reducer which counts the number of rows and throws an exception when the count is zero. However, it doesnt get called during execution since the file is empty, and the script succeeds.

Any ideas on how to get this done?

The reduce function is below:

public override IEnumerable<IRow> Reduce(...)

 long count = 0;

 foreach (var row in input.Rows)
 
 count++;
 break;
 

 if (count == 0)
 
 throw new Exception("Zero rows found in table");
 
 else
 
 output.Set("Count", count);
 yield return output.AsReadOnly();
 

c# azure azure-data-lake u-sql

share|improve this question

asked Mar 25 at 21:37

mksh15mksh15

5088 bronze badges

add a comment | 

I have a U-SQL script which processes some data using some UDOs and then finally outputs a file back to Azure Data Lake.

The expected behaviour is that if the file that is generated is empty, the script should fail, however I am unable to get it to do so.

I tried implementing a simple reducer which counts the number of rows and throws an exception when the count is zero. However, it doesnt get called during execution since the file is empty, and the script succeeds.

Any ideas on how to get this done?

The reduce function is below:

public override IEnumerable<IRow> Reduce(...)

 long count = 0;

 foreach (var row in input.Rows)
 
 count++;
 break;
 

 if (count == 0)
 
 throw new Exception("Zero rows found in table");
 
 else
 
 output.Set("Count", count);
 yield return output.AsReadOnly();
 

c# azure azure-data-lake u-sql

share|improve this question

asked Mar 25 at 21:37

mksh15mksh15

5088 bronze badges

public override IEnumerable<IRow> Reduce(...)

 long count = 0;

 foreach (var row in input.Rows)
 
 count++;
 break;
 

 if (count == 0)
 
 throw new Exception("Zero rows found in table");
 
 else
 
 output.Set("Count", count);
 yield return output.AsReadOnly();
 

share|improve this question

asked Mar 25 at 21:37

mksh15mksh15

5088 bronze badges

share|improve this question

asked Mar 25 at 21:37

mksh15mksh15

5088 bronze badges

asked Mar 25 at 21:37

mksh15mksh15

5088 bronze badges

asked Mar 25 at 21:37

mksh15mksh15

5088 bronze badges

1 Answer
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2

You have to declare a c# function to raise custom error , like we used to do it in sql:(You can modify the raise error function as per your need)

DECLARE @RaiseError Func<string, int> = (error) => 
 
 throw new Exception(error);
 return 0;
 ;

and then something like below

@Query = 
 SELECT @RaiseError(value) AS ErrorCode
 FROM (VALUES ("my custom error description")) AS T(value);

OUTPUT @Query TO "/Output/errors.txt" USING Outputters.Csv(quoting : true);

Hope it helps.

share|improve this answer

answered Mar 26 at 6:28

Mohit Verma - MSFTMohit Verma - MSFT

2,65622 gold badges66 silver badges1818 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Please accept as an answer if it helped. It will help others who have the same ask.
  
  – Mohit Verma - MSFT
  Mar 27 at 4:09
  

  
  
  
  

add a comment | 

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2

You have to declare a c# function to raise custom error , like we used to do it in sql:(You can modify the raise error function as per your need)

DECLARE @RaiseError Func<string, int> = (error) => 
 
 throw new Exception(error);
 return 0;
 ;

and then something like below

@Query = 
 SELECT @RaiseError(value) AS ErrorCode
 FROM (VALUES ("my custom error description")) AS T(value);

OUTPUT @Query TO "/Output/errors.txt" USING Outputters.Csv(quoting : true);

Hope it helps.

share|improve this answer

answered Mar 26 at 6:28

Mohit Verma - MSFTMohit Verma - MSFT

2,65622 gold badges66 silver badges1818 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Please accept as an answer if it helped. It will help others who have the same ask.
  
  – Mohit Verma - MSFT
  Mar 27 at 4:09
  

  
  
  
  

add a comment | 

2

You have to declare a c# function to raise custom error , like we used to do it in sql:(You can modify the raise error function as per your need)

DECLARE @RaiseError Func<string, int> = (error) => 
 
 throw new Exception(error);
 return 0;
 ;

and then something like below

@Query = 
 SELECT @RaiseError(value) AS ErrorCode
 FROM (VALUES ("my custom error description")) AS T(value);

OUTPUT @Query TO "/Output/errors.txt" USING Outputters.Csv(quoting : true);

Hope it helps.

share|improve this answer

answered Mar 26 at 6:28

Mohit Verma - MSFTMohit Verma - MSFT

2,65622 gold badges66 silver badges1818 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Please accept as an answer if it helped. It will help others who have the same ask.
  
  – Mohit Verma - MSFT
  Mar 27 at 4:09
  

  
  
  
  

add a comment | 

You have to declare a c# function to raise custom error , like we used to do it in sql:(You can modify the raise error function as per your need)

DECLARE @RaiseError Func<string, int> = (error) => 
 
 throw new Exception(error);
 return 0;
 ;

and then something like below

@Query = 
 SELECT @RaiseError(value) AS ErrorCode
 FROM (VALUES ("my custom error description")) AS T(value);

OUTPUT @Query TO "/Output/errors.txt" USING Outputters.Csv(quoting : true);

Hope it helps.

share|improve this answer

answered Mar 26 at 6:28

Mohit Verma - MSFTMohit Verma - MSFT

2,65622 gold badges66 silver badges1818 bronze badges

DECLARE @RaiseError Func<string, int> = (error) => 
 
 throw new Exception(error);
 return 0;
 ;

@Query = 
 SELECT @RaiseError(value) AS ErrorCode
 FROM (VALUES ("my custom error description")) AS T(value);

OUTPUT @Query TO "/Output/errors.txt" USING Outputters.Csv(quoting : true);

share|improve this answer

answered Mar 26 at 6:28

Mohit Verma - MSFTMohit Verma - MSFT

2,65622 gold badges66 silver badges1818 bronze badges

answered Mar 26 at 6:28

Mohit Verma - MSFTMohit Verma - MSFT

2,65622 gold badges66 silver badges1818 bronze badges

answered Mar 26 at 6:28

Mohit Verma - MSFTMohit Verma - MSFT

2,65622 gold badges66 silver badges1818 bronze badges