Re: we control spark file names before we write them - should we opensource it?

[ilaimalka]

Hey Panos,
our solution allows us to analyze the full path and modify the file name.
so for multiple partitions, we can extract the values of the partitions and
then inject them into the file name.

for example, 
for the following file:
s3://some_bucket/some_folder/partition1=value1/partition2=value2/part-123.c001.csv
we will store it like that:
s3://some_bucket/some_folder/value1-value2-part-123.c001.csv

and since we can modify the file name as we want, then theoretically two
files can get the same name.
which will either throw an exception or override of one of the files,
according to the configurations.



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RE: we control spark file names before we write them - should we opensource it?

[ilaimalka]

Hey Stefan,
Thank you for your replay.

May I ask for a use-case or an example of how you would use this ability.
I want to make sure our solution would work for you.



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we control spark file names before we write them - should we opensource it?

[ilaimalka]

Hi, as part of our work we needed more control over the name of the files
written out by Spark, e.g instead of "part-...csv.gz" we want to get
something like this "15988891_1748330679_20200507124153.tsv.gz" where the
first number is hardcoded, the second one is the value from partitionBy and
third is a timestamp in provided SimpleDateFormat.

After a long research for possibilities, the most common way is to find
those files and rename them *after* the spark job has finished. We tried to
find a more efficient way.

We decided to implement a new DataSource which is actually a wrapper to most
standard Spark file formats (csv, json, text, parquet, avro), which allows
us to rename the file before it's written.

In short, this is how it works :
Datasource extends FileFormat and implements prepareWrite - which redirects
to local FileNameOutputWriterFactory
TypeFactory which redirects to original Spark Formats
FileNameOutputWriterFactory which actually do the work and by reflection can
call any implementation to control the file name  

The question is - is this interesting/useful enough for the community?
Should we open-source it?
Thanks!

p.s we wrote the same question on spark channel on ASF if you want to
discuss it there:
https://the-asf.slack.com/archives/CD5UQDNBA/p1589117451069600



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