Merge pull request #5583 from venkatesh-prasad-v/8.0-PS-9719

[8.0] PS-9719: changing binlog_transaction_dependency_tracking hit segmentation fault

Author: Venkatesh Prasad

sql/rpl_trx_tracking.cc

@@ -245,6 +245,7 @@ void Writeset_trx_dependency_tracker::get_dependency(THD *thd,
       // it did not broke past the capacity already
       !write_set_ctx->was_write_set_limit_reached();
   bool exceeds_capacity = false;
+  auto writeset_history = std::atomic_load(&m_writeset_history);
 
   if (can_use_writesets) {
     /*
@@ -253,7 +254,7 @@ void Writeset_trx_dependency_tracker::get_dependency(THD *thd,
      using its information for current transaction.
     */
     exceeds_capacity =
-        m_writeset_history.size() + writeset->size() > m_opt_max_history_size;
+        writeset_history->size() + writeset->size() > m_opt_max_history_size;
 
     /*
      Compute the greatest sequence_number among all conflicts and add the
@@ -262,15 +263,15 @@ void Writeset_trx_dependency_tracker::get_dependency(THD *thd,
     int64 last_parent = m_writeset_history_start;
     for (std::vector<uint64>::iterator it = writeset->begin();
          it != writeset->end(); ++it) {
-      Writeset_history::iterator hst = m_writeset_history.find(*it);
-      if (hst != m_writeset_history.end()) {
+      Writeset_history::iterator hst = writeset_history->find(*it);
+      if (hst != writeset_history->end()) {
         if (hst->second > last_parent && hst->second < sequence_number)
           last_parent = hst->second;
 
         hst->second = sequence_number;
       } else {
         if (!exceeds_capacity)
-          m_writeset_history.insert(
+          writeset_history->insert(
               std::pair<uint64, int64>(*it, sequence_number));
       }
     }
@@ -292,13 +293,16 @@ void Writeset_trx_dependency_tracker::get_dependency(THD *thd,
 
   if (exceeds_capacity || !can_use_writesets) {
     m_writeset_history_start = sequence_number;
-    m_writeset_history.clear();
+    if (writeset_history) {
+      writeset_history->clear();
+    }
   }
 }
 
 void Writeset_trx_dependency_tracker::rotate(int64 start) {
   m_writeset_history_start = start;
-  m_writeset_history.clear();
+  auto new_map = std::make_shared<Writeset_history>();
+  std::atomic_store(&m_writeset_history, new_map);
 }
 
 /**

sql/rpl_trx_tracking.h

@@ -127,7 +127,10 @@ class Commit_order_trx_dependency_tracker {
 class Writeset_trx_dependency_tracker {
  public:
   Writeset_trx_dependency_tracker(ulong max_history_size)
-      : m_opt_max_history_size(max_history_size), m_writeset_history_start(0) {}
+      : m_opt_max_history_size(max_history_size), m_writeset_history_start(0) {
+    std::atomic_store(&m_writeset_history,
+                      std::make_shared<Writeset_history>());
+  }
 
   /**
     Main function that gets the dependencies using the WRITESET tracker.
@@ -161,7 +164,7 @@ class Writeset_trx_dependency_tracker {
     in the database, using row hashes from the writeset as the index.
   */
   typedef std::unordered_map<uint64, int64> Writeset_history;
-  Writeset_history m_writeset_history;
+  std::shared_ptr<Writeset_history> m_writeset_history;
 };
 
 /**