Use index table repair_run_by_cluster_v2 to obtain UUIDs for cluste…

…r and state and then query the main `repair_runs` table using the found UUIDs.

src/server/src/main/java/io/cassandrareaper/storage/CassandraStorage.java

@@ -424,7 +424,7 @@ private void prepareStatements() {
     getRepairRunForClusterPrepStmt = session.prepare(
         "SELECT * FROM repair_run_by_cluster_v2 WHERE cluster_name = ? limit ?");
     getRepairRunForClusterWhereStatusPrepStmt = session.prepare(
-        "SELECT * FROM repair_run_by_cluster_v2 WHERE cluster_name = ? AND repair_run_state = ? limit ?");
+        "SELECT id FROM repair_run_by_cluster_v2 WHERE cluster_name = ? AND repair_run_state = ? limit ?");
     getRepairRunForUnitPrepStmt = session.prepare("SELECT * FROM repair_run_by_unit WHERE repair_unit_id = ?");
     deleteRepairRunPrepStmt = session.prepare("DELETE FROM repair_run WHERE id = ?");
     deleteRepairRunByClusterPrepStmt
@@ -962,29 +962,52 @@ public Collection<RepairRun> getRepairRunsForCluster(String clusterName, Optiona
 
   @Override
   public List<RepairRun> getRepairRunsForClusterPrioritiseRunning(String clusterName, Optional<Integer> limit) {
-    List<ResultSetFuture> repairRunFutures = Lists.<ResultSetFuture>newArrayList();
+    List<ResultSetFuture> repairUuidFuturesByState = Lists.<ResultSetFuture>newArrayList();
     // We've set up the RunState enum so that values are declared in order of "interestingness",
     // we iterate over the table via the secondary index according to that ordering.
     for (RunState state : RepairRun.RunState.values()) {
-      repairRunFutures.add(
+      repairUuidFuturesByState.add(
+          // repairUUIDFutures will be a List of resultSetFutures, each of which contains a ResultSet of
+          // UUIDs for one status.
           session
               .executeAsync(getRepairRunForClusterWhereStatusPrepStmt
                   .bind(clusterName, state.toString(), limit.orElse(MAX_RETURNED_REPAIR_RUNS)
                   )
               )
       );
     }
-    List<RepairRun> flattenedRows = Lists.<RepairRun>newArrayList();
-    repairRunFutures
+    List<UUID> flattenedUuids = Lists.<UUID>newArrayList();
+    // Flatten the UUIDs from each status down into a single array and trim.
+    for (ResultSetFuture idResSetFuture : repairUuidFuturesByState) {
+      idResSetFuture
+          .getUninterruptibly()
+          .forEach(
+              row -> flattenedUuids.add(row.getUUID("id"))
+        );
+    }
+    flattenedUuids.subList(0, limit.orElse(MAX_RETURNED_REPAIR_RUNS));
+    // Run an async query on each UUID in the flattened list, against the main repair_run table with
+    // all columns required as an input to `buildRepairRunFromRow`.
+    List<ResultSetFuture> repairRunFutures = Lists.<ResultSetFuture>newArrayList();
+    flattenedUuids.forEach(uuid ->
+        repairRunFutures.add(
+            session
+                .executeAsync(getRepairRunPrepStmt.bind(uuid)
+                )
+        )
+    );
+    // Defuture the repair_run rows and build the strongly typed RepairRun objects from the contents.
+    return repairRunFutures
         .stream()
-        .forEach(
-            resSet -> resSet.getUninterruptibly().forEach(
-                row -> flattenedRows.add(buildRepairRunFromRow(row, row.getUUID("id")))
-            )
-      );
-    return flattenedRows.subList(0, limit.orElse(MAX_RETURNED_REPAIR_RUNS));
+        .map(
+            row -> {
+              Row extractedRow = row.getUninterruptibly().one();
+              return buildRepairRunFromRow(extractedRow, extractedRow.getUUID("id"));
+            }
+        ).collect(Collectors.toList());
   }
 
+
   @Override
   public Collection<RepairRun> getRepairRunsForUnit(UUID repairUnitId) {
     List<ResultSetFuture> repairRunFutures = Lists.<ResultSetFuture>newArrayList();