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Putting SequenceFile key value into a data frame

Expert Contributor

I saved thousands of small json files in SequenceFile format to resolve the "small file issue". I use the following pyspark code to parse the json data from saved sequence files.

 

 

reader= sc.sequenceFile("/mysequencefile_dir", "org.apache.hadoop.io.Text", "org.apache.hadoop.io.Text")
rdd=reader.map(lambda x: x[1])
mydf=spark.read.schema(myschema).json(rdd)
mydf.show(truncate=False)

 

 The code worked. However, I do not know how to put the key value from the sequence file, which is actually the original json file name, into the mydf dataframe. Please advise. Thank you.

 

Regards,

1 ACCEPTED SOLUTION

Master Collaborator

@Seaport ,

 

Please try the below:

import json

def jsonize(k, v):
    ret = json.loads(v)
    ret.update({'key': k})
    return ret

...
rdd = reader.map(lambda x: jsonize(*x))
...

 

You need to make sure your schema includes the added key column.

 

Cheers,

André

 

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View solution in original post

3 REPLIES 3

Expert Contributor

I did a workaround by injecting the myfilepath element into the json string.

rdd=reader.map(lambda x: str(x[1])[0]+'"myfilepath":"'+x[0]+'",'+str(x[1])[1:])

It does not look like a very clean solution. Is there a better one? Thanks.

 

Regards

Master Collaborator

@Seaport ,

 

Please try the below:

import json

def jsonize(k, v):
    ret = json.loads(v)
    ret.update({'key': k})
    return ret

...
rdd = reader.map(lambda x: jsonize(*x))
...

 

You need to make sure your schema includes the added key column.

 

Cheers,

André

 

--
Was your question answered? Please take some time to click on "Accept as Solution" below this post.
If you find a reply useful, say thanks by clicking on the thumbs up button.

Expert Contributor

André,

 

Thanks for the elegant solution.

 

Regards,