I'm using Sqoop 1.4.1 to import a table from MySQL to HDFS. The table contains log entries by users who are identified by an integer user ID but does not have a primary key. Because of the way user ID's were assigned, lower value ID's have more records in the table than larger ID's making parallel imports extremely unbalanced (I'm only running 7 map tasks).
In order balance the parallel import, I created an additional column which I set to be 'mapid = UserID mod 7' producing values 0 - 6 which do have a uniform distribution of records. When I run the Sqoop import with '--split-by mapid -m 7' the job seems to be limited to 6 map tasks. This same behavior is exhibited even if I add 1 to my 'mapid' column so I'm thinking Sqoop is limiting the map tasks to the difference between the minimum and maximum values of the split-by column without adding 1 to the range. I know that I can create a different 'mapid' column or create a primary key, but is there something I can do with Sqoop to correct for this? Thank you, Erik
