Title pretty much says it all; I've configured the DIH in 3.1.0, and it works great, except the delta-imports are always from the last time a full-import happened, not a delta-import. After a delta-import, dataimport.properties is completely untouched. The documentation implies that the delta-import should update the last_index_time:
"The DataImportHandler exposes a variable called last_index_time which is a timestamp value denoting the last time full-import 'or' delta-import was run" - http://wiki.apache.org/solr/DataImportHandler#Delta-Import_Example Is there a configuration preventing delta-import from updating dataimport.properties? It updates properly on each full-import.
