tx::Engine - commit log encapsulation

Reviewers: buda

Reviewed By: buda

Subscribers: pullbot

Differential Revision: https://phabricator.memgraph.io/D460

src/database/graph_db_accessor.hpp

@@ -265,7 +265,7 @@ class GraphDbAccessor {
       auto wait_transaction = db_.tx_engine.Begin();
       for (auto id : wait_transaction->snapshot()) {
         if (id == transaction_->id_) continue;
-        while (wait_transaction->engine_.clog_.fetch_info(id).is_active())
+        while (wait_transaction->engine_.clog().fetch_info(id).is_active())
           // TODO reconsider this constant, currently rule-of-thumb chosen
           std::this_thread::sleep_for(std::chrono::microseconds(100));
       }

src/mvcc/record.hpp

@@ -129,8 +129,8 @@ class Record : public Version<T> {
     //       snapshot (consequently also not in the snapshots of
     //       newer transactions)
     return (exp_id != 0 && exp_id < snapshot.back() &&
-            engine.clog_.is_committed(exp_id) && !snapshot.contains(exp_id)) ||
-           engine.clog_.is_aborted(tx.cre());
+            engine.clog().is_committed(exp_id) && !snapshot.contains(exp_id)) ||
+           engine.clog().is_aborted(tx.cre());
   }
 
   // TODO: Test this
@@ -230,7 +230,7 @@ class Record : public Version<T> {
     if (!hint_bits.is_unknown()) return hint_bits.is_committed();
 
     // if hints are not set consult the commit log
-    auto info = engine.clog_.fetch_info(id);
+    auto info = engine.clog().fetch_info(id);
 
     // committed
     if (info.is_committed()) return hints.set_committed(), true;

src/transactions/commit_log.hpp

@@ -31,17 +31,21 @@ class CommitLog {
 
   CommitLog operator=(CommitLog) = delete;
 
-  Info fetch_info(transaction_id_t id) { return Info{log.at(2 * id, 2)}; }
+  Info fetch_info(transaction_id_t id) const { return Info{log.at(2 * id, 2)}; }
 
-  bool is_active(transaction_id_t id) { return fetch_info(id).is_active(); }
+  bool is_active(transaction_id_t id) const {
+    return fetch_info(id).is_active();
+  }
 
-  bool is_committed(transaction_id_t id) {
+  bool is_committed(transaction_id_t id) const {
     return fetch_info(id).is_committed();
   }
 
   void set_committed(transaction_id_t id) { log.set(2 * id); }
 
-  bool is_aborted(transaction_id_t id) { return fetch_info(id).is_aborted(); }
+  bool is_aborted(transaction_id_t id) const {
+    return fetch_info(id).is_aborted();
+  }
 
   void set_aborted(transaction_id_t id) { log.set(2 * id + 1); }
 

src/transactions/engine.hpp

@@ -137,15 +137,13 @@ class Engine : Lockable<SpinLock> {
     return active_.size();
   }
 
-  // TODO make this private and expose "const CommitLog"
-  // through a getter. To do that you need to make the
-  // appropriate CommitLog functions const. To do THAT,
-  // you need to make appropriate DynamicBitset functions
-  // const. While doing that, clean the DynamicBitset up.
-  /** Commit log of this engine */
-  CommitLog clog_;
+  /** Returns this engine's commit log */
+  auto &clog() const { return clog_; }
 
  private:
+  // commit log of this engine
+  CommitLog clog_;
+
   // Performs cleanup common to ending the transaction
   // with either commit or abort
   void Finalize(const Transaction &t) {