…roperty: oak.indexer.pipelined.mongoParallelDump.

…ests.

… to be used for tests.

… declaration where this makes code more clear.

…tegration tests.

…every 10k to every 20k.

…nd $lte(Long.MAX_VALUE) instead $exits(_modified). $exists also checks for the property being equals to null, which cannot be verified just by looking at an index, because indexes in MongoDB do not contain null values. Using $exists requires retrieving the full document from the column store, which dramatically slows down the traversal.

…on. Ensures that both download threads are shutdown gracefully.

Small refactoring.

…ch any documents.

Add additional comments.

…ment to reduce its size.

…traversal (retry on connection errors false). Documents without _modified field are not needed to build the FFS and like this there is no need to do a null check when calling getModified on the documents.