[ntuple] avoid shared pointer for RColumn::fTeam

tree/ntuple/v7/inc/ROOT/RColumn.hxx

@@ -75,11 +75,11 @@ private:
    NTupleSize_t fFirstElementIndex = 0;
    /// Used to pack and unpack pages on writing/reading
    std::unique_ptr<RColumnElementBase> fElement;
-   /// The column team is a set of columns that serve the same column index for different representation IDs
-   /// Initially, the team has only one member, the very column it belongs to. Through MergeTeams(), two column
+   /// The column team is a set of columns that serve the same column index for different representation IDs.
+   /// Initially, the team has only one member, the very column it belongs to. Through MergeTeams(), two columns
    /// can join forces. The team is used to react on suppressed columns: if the current team member has a suppressed
    /// column for a MapPage() call, it get the page from the active column in the corresponding cluster.
-   std::shared_ptr<std::vector<RColumn *>> fTeam;
+   std::vector<RColumn *> fTeam;
    /// Points into fTeam to the column that successfully returned the last page.
    std::size_t fLastGoodTeamIdx = 0;
 
@@ -117,8 +117,6 @@ private:
       fWritePage[otherIdx].Reset(0);
    }
 
-   void TeamUp(const RColumn &other) { fTeam = other.fTeam; }
-
 public:
    template <typename CppT>
    static std::unique_ptr<RColumn> Create(EColumnType type, std::uint32_t columnIdx, std::uint16_t representationIdx)

tree/ntuple/v7/src/RColumn.cxx

@@ -19,15 +19,13 @@
 
 #include <TError.h>
 
+#include <algorithm>
 #include <cassert>
 #include <utility>
 
 ROOT::Experimental::Internal::RColumn::RColumn(EColumnType type, std::uint32_t columnIndex,
                                                std::uint16_t representationIndex)
-   : fType(type),
-     fIndex(columnIndex),
-     fRepresentationIndex(representationIndex),
-     fTeam(std::make_shared<std::vector<RColumn *>>(std::vector<RColumn *>{this}))
+   : fType(type), fIndex(columnIndex), fRepresentationIndex(representationIndex), fTeam({this})
 {
    // TODO(jblomer): fix for column types with configurable bit length once available
    const auto [minBits, maxBits] = RColumnElementBase::GetValidBitRange(type);
@@ -115,10 +113,10 @@ bool ROOT::Experimental::Internal::RColumn::TryMapPage(NTupleSize_t globalIndex)
    // the page population fails.
    fReadPage = RPage();
 
-   const auto nTeam = fTeam->size();
+   const auto nTeam = fTeam.size();
    std::size_t iTeam = 1;
    do {
-      fReadPage = fPageSource->PopulatePage(fTeam->at(fLastGoodTeamIdx)->GetHandleSource(), globalIndex);
+      fReadPage = fPageSource->PopulatePage(fTeam.at(fLastGoodTeamIdx)->GetHandleSource(), globalIndex);
       if (fReadPage.IsValid())
          break;
       fLastGoodTeamIdx = (fLastGoodTeamIdx + 1) % nTeam;
@@ -135,10 +133,10 @@ bool ROOT::Experimental::Internal::RColumn::TryMapPage(RClusterIndex clusterInde
    // the page population fails.
    fReadPage = RPage();
 
-   const auto nTeam = fTeam->size();
+   const auto nTeam = fTeam.size();
    std::size_t iTeam = 1;
    do {
-      fReadPage = fPageSource->PopulatePage(fTeam->at(fLastGoodTeamIdx)->GetHandleSource(), clusterIndex);
+      fReadPage = fPageSource->PopulatePage(fTeam.at(fLastGoodTeamIdx)->GetHandleSource(), clusterIndex);
       if (fReadPage.IsValid())
          break;
       fLastGoodTeamIdx = (fLastGoodTeamIdx + 1) % nTeam;
@@ -150,6 +148,15 @@ bool ROOT::Experimental::Internal::RColumn::TryMapPage(RClusterIndex clusterInde
 
 void ROOT::Experimental::Internal::RColumn::MergeTeams(RColumn &other)
 {
-   fTeam->emplace_back(&other);
-   other.TeamUp(*this);
+   // We are working on very small vectors here, so quadratic complexity works
+   for (auto *c : other.fTeam) {
+      if (std::find(fTeam.begin(), fTeam.end(), c) == fTeam.end())
+         fTeam.emplace_back(c);
+   }
+
+   for (auto c : fTeam) {
+      if (c == this)
+         continue;
+      c->fTeam = fTeam;
+   }
 }