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From eSKa <eska...@gmail.com>
Subject Additional data read inside dataset transformations
Date Thu, 07 Sep 2017 06:42:14 GMT

I will describe my use case shortly with steps for easier understanding:
1) currently my job is loading data from parquet files using
HadoopInputFormat along with AvroParquetInputFormat, with current approach:
        AvroParquetInputFormat<GenericRecord> inputFormat = new
        AvroParquetInputFormat.setAvroReadSchema(job, schema);
        HadoopInputFormat<Void, GenericRecord> hadoopInputFormat =
HadoopInputs.createHadoopInput(inputFormat, Void.class, GenericRecord.class,
        return environment.createInput(hadoopInputFormat);
2) data is loaded into DataSource and after various transformations is
grouped by my "user_id" key,
3) in GroupReduceFunction I am dealing with values for given user,
4) for each group in reduce function I am extracting the key (which has been
used for earlier grouping) and would like to read additional data (parquet
files from HDFS for specific key extracted before), which are required for
further grouped data processing
5) after processing inside reduce function, I would like to store results in
parquet files using AvroParquerWriter class.

My question is how additional data loading inside reduce function (or any
other transformation) can be achieved in step number 4). 
In my perfect scenario I would like to use HadoopInputFormat (just like for
loading initial data in first step), however I am missing environment
context here (probably?). Is there any way to achieve this or this scenarios
is completely wrong and therefore badly designed?

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