I just profiled a CSV upload, and aside from the CSV parsing, Solr adds pretty much no overhead! I was expecting some non-trivial overhead due to Solr's SolrInputDocument, update processing pipeline, and update handler... but profiling showed that it amounted to less than 1%.
85% of the time was spent in Lucene's IndexWriter 12% of the time was spent in the CSV parser2 2% of the time was spent merging segments in the IndexWriter -Yonik http://www.lucidimagination.com
