Bleve has support for querying across multiple indexes (shards) but does not prescribe any mechanism to split the data. So, it's up the application to divide the data how it sees fit, but you can use Bleve functionality to execute the same query across multiple indexes and merge the results.

Merging is required and is indeed somewhat resource intensive. Bleve's current indexing approach has no segments, instead all index data is serialized into a key/value store. This approach allowed us to experiment and plug-in a variety of implementations. Unfortunately, the key/value abstraction limits the way you interact with data, so there are a number of drawbacks. One key gain we get from the segmented approach vs the key/value store approach is that we no longer need to maintain a backindex to handle updates/deletes.