Prioritize tasks that have never run at all

src/database-backends/postgresql/queries/get-task-stream.js

@@ -60,18 +60,12 @@ function makeFillQuery(withDependencies) {
 						SELECT item_id FROM tag_candidates
 					`
 				}
-			)
+			),
+			tasks AS NOT MATERIALIZED (
 				SELECT
-			:task AS task,
-			item_id
-		FROM full_candidates
-		WHERE NOT EXISTS (
-			SELECT item_id FROM srap_task_results AS results
-			WHERE
-				item_id = full_candidates.item_id
-				AND results.task = :task
-				AND results.task_version = :taskVersion
-				AND (
+					item_id,
+					is_successful,
+					(
 						results.is_successful = FALSE
 						OR (
 							results.is_successful = TRUE
@@ -81,8 +75,19 @@ function makeFillQuery(withDependencies) {
 								OR results.expires_at IS NULL
 							)
 						)
+					) AS is_completed
+				FROM srap_task_results AS results
+				WHERE
+					results.task = :task
+					AND results.task_version = :taskVersion
 			)
-		)
+		SELECT
+			:task AS task,
+			full_candidates.item_id
+		FROM full_candidates
+		LEFT JOIN tasks ON full_candidates.item_id = tasks.item_id
+		WHERE tasks.is_completed IS NOT TRUE
+		ORDER BY tasks.is_successful NULLS FIRST
 	`;
 }