Apologies if this question has been asked before.
I have a very large table in Oracle with hundreds of partitions and we want to be able to import it to parquet in HDFS a partition at a time as part of a ETL process. The table has evolved over time and there is not a column that doesn't have significant skew meaning that mappers get very uneven numbers when using the standard sqoop connector and split-by. Impala is the target platform that the data is for so we also want to keep the file sizes under the cluster block size to prevent remote streaming when we use the data. I've just discovered OraOop and it sounds like this would be exactly tool we would need to import the data in an efficient and predictable way.
Unfortunately the problem i'm now having is that if i use the partition option to choose just a single partition this always equates to exactly one mapper. The sort of speed and output file sizes we are looking at would equate to something like 40.
Are there any options i can set to increase the number of mappers when pulling data from a single table partition?