InfluxDB 1.4 introduces several significant enhancements, including improved InfluxQL capabilities, support for Prometheus read and write endpoints, and performance improvements to compaction. The new version also includes features such as SHOW CARDINALITY queries, EXPLAIN and EXPLAIN ANALYZE commands, and support for unsigned 64-bit integers. Additionally, the InfluxDB CLI now supports Ctrl+C to cancel a running query, and message pack formats can be used for responses by setting `application/x-msgpack` in the Accept header. The release also includes experimental features such as TSI progress, IFQL prototype interfaces, and other changelog tidbits.