The JDBC driver sends java.sql.Timestamp with nanoseconds as a string
(e.g. '2026-03-15 10:13:58.105931162') which DateTime('UTC') rejects.
Add bucketTimestamp() helper that truncates to seconds for all rollup
query parameters.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>