For the CDS view extraction from SAP S/4HANA we are going to use ABAP CDS Reader operator in DI. It is a standard operator to read data from a CDS view.

Problem description:

Using this operator, you will not see any headers in the file by default.

There are three versions of ABAP CDS Reader operator. The main difference here is the output data type. But independent of version you are using, the headers are still not visible in the file.This problem we are going to solve in this post.

Solution:

Among these three versions, only ABAP CDS Reader V2 has an information about fields in its output. The output data type of this operator is message. A message has a body and attributes. The body of the output deliveries data, and attribute some information about fields, last batch etc.There is no standard solution to get headers using Generation 1 graph, we must use a python script.

The pipeline looks like:

1. First operator is standard ABAP CDS Reader V2 operator.
2. Second operator is python operator with input “input2” as message type and output “outData” as message type.

   from io import StringIO
   import csv
   import pandas as pd
   import json
   
   
   def on_input(inData):
       
       # Read Body 
       data = StringIO(inData.body)
       
       # Read Attributes
       var = json.dumps(inData.attributes)
       attributes = inData.attributes
       # Parse JSON
       result = json.loads(var)
       ABAP= result['ABAP']
       
       if len(ABAP) == 3:
           Field = ABAP['Fields']
           columns = []
           
           for item in Field:
               columns.append(item['Name'])
               
           df= pd.read_csv(data,index_col= False, names = columns)
   
           df_csv = df.to_csv(index = False, header= True)
       
           api.send('outData',api.Message(attributes =  attributes, body = df_csv))
           
       if len(ABAP) == 2:
       
           api.send('outData',api.Message(attributes =  attributes, body = ''))
       
   api.set_port_callback("input2", on_input)

3. Third operator is standard write file operator as csv.
4. Fourth operator is again python operator with input “input1” as message type and output “outData1” as message type.to read the last batch information.

   from io import StringIO
   import csv
   import pandas as pd
   import json
   
   
   def on_input(inData):
       
       # Read Attributes
       attr = inData.attributes
       result = attr['message.lastBatch']
       
       if str(result) == 'True':
           api.send('outData1','stop')
       
   api.set_port_callback("input1", on_input)​

5. Last operator is Graph Terminator which will be terminated when last batch is true.

Conclusion:

Using the above approach, data is written into CSV file with headers and graph will be terminated. This can be helpful for initial load.

Hope you find the content of this blog helpful. Feel free to comment for further clarifications.