Remove unused track_read_versions (#6871)

Author: achamayou

src/kv/apply_changes.h

@@ -25,10 +25,6 @@ namespace ccf::kv
   // sets to their underlying Maps. Calls f() at most once, iff the writes are
   // applied, to retrieve a unique Version for the write set and return the max
   // version which can have a conflict with the transaction.
-  //
-  // The track_read_versions parameter tells the store if it needs to track the
-  // last read version for every key. This is required for backup execution as
-  // described at the top of tx.h
 
   using VersionLastNewMap = Version;
   using VersionResolver = std::function<std::tuple<Version, VersionLastNewMap>(
@@ -40,7 +36,6 @@ namespace ccf::kv
     ccf::kv::ConsensusHookPtrs& hooks,
     const MapCollection& new_maps,
     const std::optional<Version>& new_maps_conflict_version,
-    bool track_read_versions,
     bool track_deletes_on_missing_keys,
     const std::optional<Version>& expected_rollback_count = std::nullopt)
   {
@@ -88,7 +83,7 @@ namespace ccf::kv
     {
       for (auto it = views.begin(); it != views.end(); ++it)
       {
-        if (!it->second->prepare(track_read_versions))
+        if (!it->second->prepare())
         {
           ok = false;
           break;
@@ -132,40 +127,31 @@ namespace ccf::kv
       std::tie(version, version_last_new_map) =
         version_resolver_fn(!new_maps.empty());
 
-      if (!track_read_versions)
+      // Transfer ownership of these new maps to their target stores, iff we
+      // have writes to them
+      for (const auto& [map_name, map_ptr] : new_maps)
       {
-        // Transfer ownership of these new maps to their target stores, iff we
-        // have writes to them
-        for (const auto& [map_name, map_ptr] : new_maps)
+        const auto it = views.find(map_name);
+        if (it != views.end() && it->second->has_writes())
         {
-          const auto it = views.find(map_name);
-          if (it != views.end() && it->second->has_writes())
-          {
-            map_ptr->get_store()->add_dynamic_map(version, map_ptr);
-          }
+          map_ptr->get_store()->add_dynamic_map(version, map_ptr);
         }
+      }
 
-        for (auto it = views.begin(); it != views.end(); ++it)
-        {
-          it->second->commit(
-            version, track_read_versions, track_deletes_on_missing_keys);
-        }
+      for (auto it = views.begin(); it != views.end(); ++it)
+      {
+        it->second->commit(version, track_deletes_on_missing_keys);
+      }
 
-        // Collect ConsensusHooks
-        for (auto it = views.begin(); it != views.end(); ++it)
+      // Collect ConsensusHooks
+      for (auto it = views.begin(); it != views.end(); ++it)
+      {
+        auto hook_ptr = it->second->post_commit();
+        if (hook_ptr != nullptr)
         {
-          auto hook_ptr = it->second->post_commit();
-          if (hook_ptr != nullptr)
-          {
-            hooks.push_back(std::move(hook_ptr));
-          }
+          hooks.push_back(std::move(hook_ptr));
         }
       }
-      else
-      {
-        // A linearizability violation was detected
-        ok = false;
-      }
     }
 
     for (auto it = changes.begin(); it != changes.end(); ++it)

src/kv/committable_tx.h

@@ -130,7 +130,6 @@ namespace ccf::kv
      */
     CommitResult commit(
       const ccf::ClaimsDigest& claims = ccf::empty_claims(),
-      bool track_read_versions = false,
       std::function<std::tuple<Version, Version>(bool has_new_map)>
         version_resolver = nullptr,
       std::function<void(
@@ -170,7 +169,6 @@ namespace ccf::kv
         hooks,
         pimpl->created_maps,
         new_maps_conflict_version,
-        track_read_versions,
         track_deletes_on_missing_keys);
 
       if (maps_created)
@@ -422,15 +420,13 @@ namespace ccf::kv
         throw std::logic_error("Reserved transaction cannot be empty");
 
       std::vector<ConsensusHookPtr> hooks;
-      bool track_read_versions = false;
       bool track_deletes_on_missing_keys = false;
       auto c = apply_changes(
         all_changes,
         [this](bool) { return std::make_tuple(version, version - 1); },
         hooks,
         pimpl->created_maps,
         version,
-        track_read_versions,
         track_deletes_on_missing_keys,
         rollback_count);
       success = c.has_value();

src/kv/kv_types.h

@@ -599,11 +599,8 @@ namespace ccf::kv
     virtual ~AbstractCommitter() = default;
 
     virtual bool has_writes() = 0;
-    virtual bool prepare(bool track_commits) = 0;
-    virtual void commit(
-      Version v,
-      bool track_read_versions,
-      bool track_deletes_on_missing_keys) = 0;
+    virtual bool prepare() = 0;
+    virtual void commit(Version v, bool track_deletes_on_missing_keys) = 0;
     virtual ConsensusHookPtr post_commit() = 0;
   };
 

src/kv/store.h

@@ -123,7 +123,6 @@ namespace ccf::kv
         hooks,
         new_maps,
         std::nullopt,
-        false,
         track_deletes_on_missing_keys);
       if (!c.has_value())
       {

src/kv/untyped_map.h

@@ -143,7 +143,7 @@ namespace ccf::kv::untyped
         return committed_writes || change_set.has_writes();
       }
 
-      bool prepare(bool track_read_versions) override
+      bool prepare() override
       {
         auto& map_roll = map.get_roll();
 
@@ -185,9 +185,7 @@ namespace ccf::kv::untyped
             // conflicts then ensure that the read versions also match.
             if (
               !search.has_value() ||
-              std::get<0>(it->second) != search.value().version ||
-              (track_read_versions &&
-               std::get<1>(it->second) != search.value().read_version))
+              std::get<0>(it->second) != search.value().version)
             {
               LOG_DEBUG_FMT("Read depends on invalid version of entry");
               return false;
@@ -198,12 +196,9 @@ namespace ccf::kv::untyped
         return true;
       }
 
-      void commit(
-        Version v,
-        bool track_read_versions,
-        bool track_deletes_on_missing_keys) override
+      void commit(Version v, bool track_deletes_on_missing_keys) override
       {
-        if (change_set.writes.empty() && !track_read_versions)
+        if (change_set.writes.empty())
         {
           commit_version = change_set.start_version;
           return;
@@ -212,30 +207,6 @@ namespace ccf::kv::untyped
         auto& map_roll = map.get_roll();
         auto state = map_roll.commits->get_tail()->state;
 
-        // To track conflicts the read version of all keys that are read or
-        // written within a transaction must be updated.
-        if (track_read_versions)
-        {
-          for (auto it = change_set.reads.begin(); it != change_set.reads.end();
-               ++it)
-          {
-            auto search = state.get(it->first);
-            if (!search.has_value())
-            {
-              continue;
-            }
-            state =
-              state.put(it->first, VersionV{search->version, v, search->value});
-          }
-          if (change_set.writes.empty())
-          {
-            commit_version = change_set.start_version;
-            map.roll.commits->insert_back(map.roll.create_new_local_commit(
-              commit_version, std::move(state), change_set.writes));
-            return;
-          }
-        }
-
         // Record our commit time.
         commit_version = v;
         committed_writes = true;
@@ -439,14 +410,16 @@ namespace ccf::kv::untyped
         return true;
       }
 
-      bool prepare(bool) override
+      bool prepare() override
       {
         // Snapshots never conflict
         return true;
       }
 
-      void commit(Version, bool, bool) override
+      void commit(Version v, bool track_deletes_on_missing_keys) override
       {
+        (void)v;
+        (void)track_deletes_on_missing_keys;
         // Version argument is ignored. The version of the roll after the
         // snapshot is applied depends on the version of the map at which the
         // snapshot was taken.

src/node/rpc/frontend.h

@@ -777,7 +777,7 @@ namespace ccf
           // else args owns a valid Tx relating to a non-pending response, which
           // should be applied
           ccf::kv::CommittableTx& tx = *args.owned_tx;
-          ccf::kv::CommitResult result = tx.commit(ctx->claims, false);
+          ccf::kv::CommitResult result = tx.commit(ctx->claims);
 
           switch (result)
           {

src/node/snapshotter.h

@@ -157,8 +157,7 @@ namespace ccf
           commit_evidence = commit_evidence_;
         };
 
-      auto rc =
-        tx.commit(cd, false, nullptr, capture_ws_digest_and_commit_evidence);
+      auto rc = tx.commit(cd, nullptr, capture_ws_digest_and_commit_evidence);
       if (rc != ccf::kv::CommitResult::SUCCESS)
       {
         LOG_FAIL_FMT(