Derive local buckets from one scan

Four of a period's figures — the hour histogram, the busiest day, the per-day counts and the total — are all questions about the same rows of an append-only event table (local-listening-analytics), and all four are questions about local time. Written as SQL aggregates that is four scans, each needing a local-time conversion inside the engine. Written as one query returning the raw pairs, it is one scan and no conversion at all:

// adapted — the only query in this family that returns rows rather than a number
@Query("SELECT timestamp, listenedSecond FROM activity_event" +
       " WHERE timestamp BETWEEN :startTimestamp AND :endTimestamp")
suspend fun getSamplesInRange(startTimestamp: LocalDateTime, endTimestamp: LocalDateTime): List<Sample>