The document discusses improvements to ORC (Optimized Row Columnar) in Apache Spark 2.3 and 2.4. It covers major features of Spark 2.3 like the vectorized ORC reader and structured streaming with ORC. It summarizes the history of integration between Spark, ORC, and Hive. It also categorizes and discusses previous issues with ORC in Spark, covering topics like writer versions, performance, structured streaming, column names, schema evolution, and robustness. The current approach of supporting two ORC file formats is described.