Major Description
Reasons are discussed in https://issues.apache.org/jira/browse/NUTCH-1541?focusedCommentId=13797768&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-13797768 and following comments.
To summarize, the indexer interface is not aware of tasks so it cannot generate unique output name per reducers.
But it seems achievable because IndexWriters initialize each writer with calls to 2 open functions:
- One passing the general configuration and a "name"
- The second to pass indexer parameters
https://github.com/apache/nutch/blob/master/src/java/org/apache/nutch/indexer/IndexWriters.java#L214
Fortunately, "name" is generated by calling getUniqueFile which does exactly what we want:
I propose we use it instead of "nutch.csv" as CSVIndexWriter output file name. This is a breaking change because it modifies the output name but allows the indexer to work in distributed mode.
PR will follow the ticket creation.