NIFI：将SQL查询中的每月转储作为CSV文件接收到SFTP服务器中

Question

I am in a situation where I would like to store data as respective monthly CSVs using SQL query into SFTP server.

For instance, my query is :

    select fooId, bar from FooBar 
where query_date>=20180101 and query_date<20180201 --(for the month of January 2018)

I would like to store it as 20180101_FooBar.csv on to my SFTP server. Similarly, other files for other months follow the same process with different query_date interval.

Important consideration to make : I have to store the *fooId* as MD5 Hash string.

How may I automate this flow in NIFI?

Roughly, the flow that I foresee is:

*ExecuteSQL*(but not sure how to paramterize the counter for query_date) 
-> *ConvertAvroToJson* 
-> *EvaluateJsonPath* (to extract the fooID ) 
-> *HashContent* 
-> *MergeContent* 
-> *PutSFTP*

Please advicee on how I may take this forward.

Answer 1

For this case I could think of three approaches.

Approach 1 : execute SQL query with MD5 function to get hash value of fooId:

Flow:

1. GenerateFlowFile //add startdate,enddate attributes

    startdate -> ${now():format("yyyyMM"):minus(1):append("01")} enddate -> ${now():format("yyyyMM"):append("01")} 

2. ExecuteSQL //select md5(fooId) foodId, bar from FooBar where

    query_date>=${startdate} and query_date<${enddate} 

   Change the above query as per your source to get md5 hash value for column

3. ConvertRecord //convert Avro format to Json format

4. UpdateAttribute //change the filename
5. PutSFTP //store the file.

Approach 2 : Create MD5 hash value in NiFi

Flow:

1. GenerateFlowFile //add startdate,enddate attributes

    startdate -> ${now():format("yyyyMM"):minus(1):append("01")} enddate -> ${now():format("yyyyMM"):append("01")} 

2. ExecuteSQL //select fooId, bar from FooBar

   where query_date>=${startdate} and query_date

   change the above query as per your source to get md5 hash value for column

3. ConvertRecord //convert Avro format to Json format

4. SplitJson //split the array of json into individual flowfiles
5. EvaluateJsonPath //extract all the key values as flowfile attributes except for fooId key.
6. EvaluateJsonPath //overwrite the flowfile content with fooId value
7. HashContent //get the hash value for the flowfile content with MD5 algorithm
8. AttributesToJson //recreate the json message with new hash md5 value
9. MergeContent //create json array with defragement strategy
10. UpdateAttribute //change the filename
11. PutSFTP ////store the file.

Another way is to write a script that can parse the json array messages and create md5 hashvalue for the fooId key and write the json message with the new md5 hashvalue.

I uploaded both approaches Approach1 and Approach2 templates, Save and Upload to NiFi instance for more reference and use the approach that best fits for your case.