From 4f58f7a437e8affb797d07e40c1348dda5219ac1 Mon Sep 17 00:00:00 2001
From: Yoshini Bailung <yoshini.bailung@cern.ch>
Date: Wed, 8 Jul 2026 15:58:59 +0200
Subject: [PATCH] PWGDQ: Update track indexing for derived tables

---
 PWGDQ/Tasks/qaMatching.cxx | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/PWGDQ/Tasks/qaMatching.cxx b/PWGDQ/Tasks/qaMatching.cxx
index acd5924db7d..f9d9fb23ca2 100644
--- a/PWGDQ/Tasks/qaMatching.cxx
+++ b/PWGDQ/Tasks/qaMatching.cxx
@@ -3018,7 +3018,7 @@ struct QaMatching {
 
     int debugCounter{0};
     fillQaMatchingAodEventForCollision(collisionInfo, collision, collisionInfo.reducedEventId, debugCounter);
-    fillQaMatchingMchTracksForCollision(collisionInfo, collision, muonTracks, taggedMuons, collisionInfo.reducedEventId);
+    fillQaMatchingMchTracksForCollision(collisionInfo, collision, muonTracks, taggedMuons, collisionInfo.reducedEventId, collisionInfo.reducedMchTrackIds);
 
     registry.get<TH1>(HIST("tracksMultiplicityMFT"))->Fill(collisionInfo.mftTracks.size());
     registry.get<TH1>(HIST("tracksMultiplicityMCH"))->Fill(collisionInfo.mchTracks.size());
@@ -3221,21 +3221,18 @@ struct QaMatching {
                                            TCOLLISION const& collision,
                                            TMUON const& muonTracks,
                                            const std::vector<int64_t>& taggedMuons,
-                                           int32_t reducedEventId)
+                                           int32_t reducedEventId,
+                                           const std::map<int64_t, int64_t>& reducedMchTrackIds)
   {
-    std::vector<int64_t> mchIds;
-    for (const auto& mchTrack : collisionInfo.mchTracks) {
-      if (std::find(mchIds.begin(), mchIds.end(), mchTrack.first) == mchIds.end()) {
-        mchIds.emplace_back(mchTrack.first);
-      }
-    }
-    for (const auto& candidate : collisionInfo.matchingCandidates) {
-      if (std::find(mchIds.begin(), mchIds.end(), candidate.first) == mchIds.end()) {
-        mchIds.emplace_back(candidate.first);
-      }
+    std::vector<std::pair<int64_t, int64_t>> orderedMchIds;
+    orderedMchIds.reserve(reducedMchTrackIds.size());
+    for (const auto& [mchIndex, reducedMchTrackId] : reducedMchTrackIds) {
+      orderedMchIds.emplace_back(reducedMchTrackId, mchIndex);
     }
+    std::sort(orderedMchIds.begin(), orderedMchIds.end());
 
-    for (const auto& mchIndex : mchIds) {
+    for (const auto& [reducedMchTrackId, mchIndex] : orderedMchIds) {
+      (void)reducedMchTrackId;
       auto const& mchTrack = muonTracks.rawIteratorAt(mchIndex);
       int mftMchMatchAttempts = 0;
       if (const auto& mchTrackInfoIt = collisionInfo.mchTracks.find(mchIndex); mchTrackInfoIt != collisionInfo.mchTracks.end()) {