This version of ZomboDB improves cross-index join performance by using RoaringBitmaps (https://github.com/RoaringBitmap/) and CompactHashSets (https://ontopia.wordpress.com/2009/09/23/a-faster-and-more-compact-set/).
These changes allowed for significant code cleanup opportunities and overall provides tremendous performance and memory usage improvements. In one particularly nasty query using
#expand(), we've gone from consuming ~7.2G of memory to ~580 bytes.
Please download from https://www.zombodb.com/releases