public function getHistoryStatement()
{
$sql = <<<'EOT'
SELECT
run.uuid AS run_uuid,
run.date AS run_date,
run.context AS context,
environment.value AS vcs_branch,
run.nb_subjects AS nb_subjects,
run.nb_iterations AS nb_iterations,
run.nb_revolutions AS nb_revolutions,
run.min_time AS min_time,
run.max_time AS max_time,
run.mean_time AS mean_time,
run.mean_rstdev AS mean_rstdev,
run.total_time AS total_time
FROM run
LEFT OUTER JOIN environment ON environment.provider = "vcs" AND environment.run_id = run.id AND environment.ekey = "branch"
ORDER BY run.date DESC
EOT;
$conn = $this->manager->getConnection();
$stmt = $conn->query($sql);
return $stmt;
}