Stop tracking parents/children outside of txgraph

diff --git a/src/kernel/mempool_entry.h b/src/kernel/mempool_entry.h
index e12047de..b274e1f7 100644
--- a/src/kernel/mempool_entry.h
+++ b/src/kernel/mempool_entry.h
@@ -67,16 +67,11 @@ class CTxMemPoolEntry : public TxGraph::Ref
 {
 public:
     typedef std::reference_wrapper<const CTxMemPoolEntry> CTxMemPoolEntryRef;
-    // two aliases, should the types ever diverge
-    typedef std::set<CTxMemPoolEntryRef, CompareIteratorByHash> Parents;
-    typedef std::set<CTxMemPoolEntryRef, CompareIteratorByHash> Children;
 
 private:
     CTxMemPoolEntry(const CTxMemPoolEntry&) = delete;
 
     const CTransactionRef tx;
-    mutable Parents m_parents;
-    mutable Children m_children;
     const CAmount nFee;             //!< Cached to avoid expensive parent-transaction lookups
     const int32_t nTxWeight;         //!< ... and avoid recomputing tx weight (also used for GetTxSize())
     const size_t nUsageSize;        //!< ... and total memory usage
@@ -142,11 +137,6 @@ public:
 
     bool GetSpendsCoinbase() const { return spendsCoinbase; }
 
-    const Parents& GetMemPoolParentsConst() const { return m_parents; }
-    const Children& GetMemPoolChildrenConst() const { return m_children; }
-    Parents& GetMemPoolParents() const { return m_parents; }
-    Children& GetMemPoolChildren() const { return m_children; }
-
     mutable size_t idx_randomized; //!< Index in mempool's txns_randomized
     mutable Epoch::Marker m_epoch_marker; //!< epoch when last touched, useful for graph algorithms
 };
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 53d92b8d..64acf952 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -90,10 +90,6 @@ void CTxMemPool::UpdateTransactionsFromBlock(const std::vector<Txid>& vHashesToU
 {
     AssertLockHeld(cs);
 
-    // Use a set for lookups into vHashesToUpdate (these entries are already
-    // accounted for in the state of their ancestors)
-    std::set<Txid> setAlreadyIncluded(vHashesToUpdate.begin(), vHashesToUpdate.end());
-
     // Iterate in reverse, so that whenever we are looking at a transaction
     // we are sure that all in-mempool descendants have already been processed.
     for (const Txid& hash : vHashesToUpdate | std::views::reverse) {
@@ -103,20 +99,10 @@ void CTxMemPool::UpdateTransactionsFromBlock(const std::vector<Txid>& vHashesToU
             continue;
         }
         auto iter = mapNextTx.lower_bound(COutPoint(hash, 0));
-        // First calculate the children, and update CTxMemPoolEntry::m_children to
-        // include them, and update their CTxMemPoolEntry::m_parents to include this tx.
-        // we cache the in-mempool children to avoid duplicate updates
         {
-            WITH_FRESH_EPOCH(m_epoch);
             for (; iter != mapNextTx.end() && iter->first->hash == hash; ++iter) {
                 txiter childIter = iter->second;
                 assert(childIter != mapTx.end());
-                // We can skip updating entries we've encountered before or that
-                // are in the block (which are already accounted for).
-                if (!visited(childIter) && !setAlreadyIncluded.count(iter->second->GetTx().GetHash())) {
-                    UpdateChild(it, childIter, true);
-                    UpdateParent(childIter, it, true);
-                }
                 // Add dependencies that are discovered between transactions in the
                 // block and transactions that were in the mempool to txgraph.
                 m_txgraph->AddDependency(/*parent=*/*it, /*child=*/*childIter);
@@ -158,8 +144,6 @@ CTxMemPool::setEntries CTxMemPool::CalculateMemPoolAncestors(const CTxMemPoolEnt
     const CTransaction &tx = entry.GetTx();
 
     // Get parents of this transaction that are in the mempool
-    // GetMemPoolParents() is only valid for entries in the mempool, so we
-    // iterate mapTx to find parents.
     for (unsigned int i = 0; i < tx.vin.size(); i++) {
         std::optional<txiter> piter = GetIter(tx.vin[i].prevout.hash);
         if (piter) {
@@ -177,38 +161,6 @@ CTxMemPool::setEntries CTxMemPool::CalculateMemPoolAncestors(const CTxMemPoolEnt
     return ret;
 }
 
-void CTxMemPool::UpdateAncestorsOf(bool add, txiter it)
-{
-    const CTxMemPoolEntry::Parents& parents = it->GetMemPoolParentsConst();
-    // add or remove this tx as a child of each parent
-    for (const CTxMemPoolEntry& parent : parents) {
-        UpdateChild(mapTx.iterator_to(parent), it, add);
-    }
-}
-
-void CTxMemPool::UpdateChildrenForRemoval(txiter it)
-{
-    const CTxMemPoolEntry::Children& children = it->GetMemPoolChildrenConst();
-    for (const CTxMemPoolEntry& updateIt : children) {
-        UpdateParent(mapTx.iterator_to(updateIt), it, false);
-    }
-}
-
-void CTxMemPool::UpdateForRemoveFromMempool(const setEntries &entriesToRemove, bool updateDescendants)
-{
-    for (txiter removeIt : entriesToRemove) {
-        // Note that UpdateAncestorsOf severs the child links that point to
-        // removeIt in the entries for the parents of removeIt.
-        UpdateAncestorsOf(false, removeIt);
-    }
-    // After updating all the ancestor sizes, we can now sever the link between each
-    // transaction being removed and any mempool children (ie, update CTxMemPoolEntry::m_parents
-    // for each direct child of a transaction being removed).
-    for (txiter removeIt : entriesToRemove) {
-        UpdateChildrenForRemoval(removeIt);
-    }
-}
-
 static CTxMemPool::Options&& Flatten(CTxMemPool::Options&& opts, bilingual_str& error)
 {
     opts.check_ratio = std::clamp<int>(opts.check_ratio, 0, 1'000'000);
@@ -271,10 +223,8 @@ void CTxMemPool::addNewTransaction(CTxMemPool::txiter newit)
     cachedInnerUsage += entry.DynamicMemoryUsage();
 
     const CTransaction& tx = newit->GetTx();
-    std::set<Txid> setParentTransactions;
     for (unsigned int i = 0; i < tx.vin.size(); i++) {
         mapNextTx.insert(std::make_pair(&tx.vin[i].prevout, newit));
-        setParentTransactions.insert(tx.vin[i].prevout.hash);
     }
     // Don't bother worrying about child transactions of this one.
     // Normal case of a new transaction arriving is that there can't be any
@@ -283,12 +233,6 @@ void CTxMemPool::addNewTransaction(CTxMemPool::txiter newit)
     // In that case, our disconnect block logic will call UpdateTransactionsFromBlock
     // to clean up the mess we're leaving here.
 
-    // Update ancestors with information about this tx
-    for (const auto& pit : GetIterSet(setParentTransactions)) {
-        UpdateParent(newit, pit, true);
-    }
-    UpdateAncestorsOf(true, newit);
-
     nTransactionsUpdated++;
     totalTxSize += entry.GetTxSize();
     m_total_fee += entry.GetFee();
@@ -344,7 +288,6 @@ void CTxMemPool::removeUnchecked(txiter it, MemPoolRemovalReason reason)
     totalTxSize -= it->GetTxSize();
     m_total_fee -= it->GetFee();
     cachedInnerUsage -= it->DynamicMemoryUsage();
-    cachedInnerUsage -= memusage::DynamicUsage(it->GetMemPoolParentsConst()) + memusage::DynamicUsage(it->GetMemPoolChildrenConst());
     mapTx.erase(it);
     nTransactionsUpdated++;
 }
@@ -483,8 +426,8 @@ void CTxMemPool::check(const CCoinsViewCache& active_coins_tip, int64_t spendhei
         check_total_fee += it->GetFee();
         innerUsage += it->DynamicMemoryUsage();
         const CTransaction& tx = it->GetTx();
-        innerUsage += memusage::DynamicUsage(it->GetMemPoolParentsConst()) + memusage::DynamicUsage(it->GetMemPoolChildrenConst());
-        CTxMemPoolEntry::Parents setParentCheck;
+        std::set<CTxMemPoolEntry::CTxMemPoolEntryRef, CompareIteratorByHash> setParentCheck;
+        std::set<CTxMemPoolEntry::CTxMemPoolEntryRef, CompareIteratorByHash> setParentsStored;
         for (const CTxIn &txin : tx.vin) {
             // Check that every mempool transaction's inputs refer to available coins, or other mempool tx's.
             indexed_transaction_set::const_iterator it2 = mapTx.find(txin.prevout.hash);
@@ -507,19 +450,26 @@ void CTxMemPool::check(const CCoinsViewCache& active_coins_tip, int64_t spendhei
         auto comp = [](const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) -> bool {
             return a.GetTx().GetHash() == b.GetTx().GetHash();
         };
-        assert(setParentCheck.size() == it->GetMemPoolParentsConst().size());
-        assert(std::equal(setParentCheck.begin(), setParentCheck.end(), it->GetMemPoolParentsConst().begin(), comp));
+        for (auto &txentry : GetParents(*it)) {
+            setParentsStored.insert(dynamic_cast<const CTxMemPoolEntry&>(txentry.get()));
+        }
+        assert(setParentCheck.size() == setParentsStored.size());
+        assert(std::equal(setParentCheck.begin(), setParentCheck.end(), setParentsStored.begin(), comp));
 
         // Check children against mapNextTx
-        CTxMemPoolEntry::Children setChildrenCheck;
+        std::set<CTxMemPoolEntry::CTxMemPoolEntryRef, CompareIteratorByHash> setChildrenCheck;
+        std::set<CTxMemPoolEntry::CTxMemPoolEntryRef, CompareIteratorByHash> setChildrenStored;
         auto iter = mapNextTx.lower_bound(COutPoint(it->GetTx().GetHash(), 0));
         for (; iter != mapNextTx.end() && iter->first->hash == it->GetTx().GetHash(); ++iter) {
             txiter childit = iter->second;
             assert(childit != mapTx.end()); // mapNextTx points to in-mempool transactions
             setChildrenCheck.insert(*childit);
         }
-        assert(setChildrenCheck.size() == it->GetMemPoolChildrenConst().size());
-        assert(std::equal(setChildrenCheck.begin(), setChildrenCheck.end(), it->GetMemPoolChildrenConst().begin(), comp));
+        for (auto &txentry : GetChildren(*it)) {
+            setChildrenStored.insert(dynamic_cast<const CTxMemPoolEntry&>(txentry.get()));
+        }
+        assert(setChildrenCheck.size() == setChildrenStored.size());
+        assert(std::equal(setChildrenCheck.begin(), setChildrenCheck.end(), setChildrenStored.begin(), comp));
 
         TxValidationState dummy_state; // Not used. CheckTxInputs() should always pass
         CAmount txfee = 0;
@@ -777,7 +727,6 @@ void CTxMemPool::RemoveUnbroadcastTx(const Txid& txid, const bool unchecked) {
 
 void CTxMemPool::RemoveStaged(setEntries &stage, bool updateDescendants, MemPoolRemovalReason reason) {
     AssertLockHeld(cs);
-    UpdateForRemoveFromMempool(stage, updateDescendants);
     for (txiter it : stage) {
         removeUnchecked(it, reason);
     }
@@ -812,28 +761,6 @@ int CTxMemPool::Expire(std::chrono::seconds time)
     return stage.size();
 }
 
-void CTxMemPool::UpdateChild(txiter entry, txiter child, bool add)
-{
-    AssertLockHeld(cs);
-    CTxMemPoolEntry::Children s;
-    if (add && entry->GetMemPoolChildren().insert(*child).second) {
-        cachedInnerUsage += memusage::IncrementalDynamicUsage(s);
-    } else if (!add && entry->GetMemPoolChildren().erase(*child)) {
-        cachedInnerUsage -= memusage::IncrementalDynamicUsage(s);
-    }
-}
-
-void CTxMemPool::UpdateParent(txiter entry, txiter parent, bool add)
-{
-    AssertLockHeld(cs);
-    CTxMemPoolEntry::Parents s;
-    if (add && entry->GetMemPoolParents().insert(*parent).second) {
-        cachedInnerUsage += memusage::IncrementalDynamicUsage(s);
-    } else if (!add && entry->GetMemPoolParents().erase(*parent)) {
-        cachedInnerUsage -= memusage::IncrementalDynamicUsage(s);
-    }
-}
-
 CFeeRate CTxMemPool::GetMinFee(size_t sizelimit) const {
     LOCK(cs);
     if (!blockSinceLastRollingFeeBump || rollingMinimumFeeRate == 0)
@@ -900,7 +827,6 @@ void CTxMemPool::TrimToSize(size_t sizelimit, std::vector<COutPoint>* pvNoSpends
         for (auto ref : worst_chunk) {
             stage.insert(mapTx.iterator_to(static_cast<const CTxMemPoolEntry&>(*ref)));
         }
-        UpdateForRemoveFromMempool(stage, false);
         for (auto e : stage) {
             removeUnchecked(e, MemPoolRemovalReason::SIZELIMIT);
         }
diff --git a/src/txmempool.h b/src/txmempool.h
index 0c0ec241..1891c8d4 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -296,9 +296,6 @@ private:
     typedef std::map<txiter, setEntries, CompareIteratorByHash> cacheMap;
 
 
-    void UpdateParent(txiter entry, txiter parent, bool add) EXCLUSIVE_LOCKS_REQUIRED(cs);
-    void UpdateChild(txiter entry, txiter child, bool add) EXCLUSIVE_LOCKS_REQUIRED(cs);
-
     std::vector<indexed_transaction_set::const_iterator> GetSortedScoreWithTopology() const EXCLUSIVE_LOCKS_REQUIRED(cs);
 
     /**
@@ -584,15 +581,6 @@ private:
      */
     void RemoveStaged(setEntries& stage, bool updateDescendants, MemPoolRemovalReason reason) EXCLUSIVE_LOCKS_REQUIRED(cs);
 
-    /** Update ancestors of hash to add/remove it as a descendant transaction. */
-    void UpdateAncestorsOf(bool add, txiter hash) EXCLUSIVE_LOCKS_REQUIRED(cs);
-    /** For each transaction being removed, update ancestors and any direct children.
-      * If updateDescendants is true, then also update in-mempool descendants'
-      * ancestor state. */
-    void UpdateForRemoveFromMempool(const setEntries &entriesToRemove, bool updateDescendants) EXCLUSIVE_LOCKS_REQUIRED(cs);
-    /** Sever link between specified transaction and direct children. */
-    void UpdateChildrenForRemoval(txiter entry) EXCLUSIVE_LOCKS_REQUIRED(cs);
-
     /** Before calling removeUnchecked for a given transaction,
      *  UpdateForRemoveFromMempool must be called on the entire (dependent) set
      *  of transactions being removed at the same time.  We use each