v0.4.0 (Spark 2.4) - 2020-07-24

Added

• Add Spark filter pushdown and projection pushdown to improve efficiency when loading only subgraphs.
  Filters like .where($"revenue".isNotNull) and projections like .select($"subject", $"`dgraph.type`", $"revenue")
  will be pushed to Dgraph and only the relevant graph data will be read (issue #7).
• Improve performance of PredicatePartitioner for multiple predicates per partition.
  Restoring default number of predicates per partition of 1000 from before 0.3.0 (issue #22).
• The PredicatePartitioner combined with UidRangePartitioner is the default partitioner now.
• Add stream-like reading of partitions from Dgraph. Partitions are split into smaller chunks.
  This make Spark read Dgraph partitions of any size.
• Add Dgraph metrics to measure throughput, visible in Spark UI Stages page and through SparkListener.

Security

• Move Google Guava dependency version to 24.1.1-jre due to known security vulnerability fixed in 24.1.1