Constant BACKEND_COMPARISON_SQL 

pub const BACKEND_COMPARISON_SQL: &str = "SELECT \
  json_extract(payload, '$.backend') AS backend, \
  ROUND(AVG(json_extract(payload, '$.narration_ratio')), 4) AS narration_ratio, \
  ROUND(AVG(json_extract(payload, '$.commit_frequency')), 4) AS commit_frequency, \
  ROUND(AVG(json_extract(payload, '$.first_pass_test_rate')), 4) AS first_pass_test_rate, \
  ROUND(AVG(json_extract(payload, '$.retry_rate')), 4) AS retry_rate, \
  ROUND(AVG(json_extract(payload, '$.time_to_completion_secs')), 2) AS time_to_completion_secs, \
  COUNT(*) AS samples \
FROM events \
WHERE event_type='quality_metrics_recorded' \
GROUP BY backend \
ORDER BY backend;";