Move the BatchIndexer class from SF's sfx/lib/migrate.py into Allura core, and use it during import tasks. This should make the solr indexing much better, instead of tons of separate tasks for each individual artifact. If it's easier/better to make the BatchIndexer apply to all background tasks and not just the importer tasks, that'd be fine too.
FYI [#4745] is somewhat related.
Closed #475.
{allura,forge-classic}:je/42cc_6825