versioning: use @@timestamp

Don't use hidden system time in versioning,
but keep the system time logic in THD
to workaround low-res system clock and
replication not versioned to versioned.

This reverts MDEV-14788 (System versioning cannot
be based on local timestamps, as it is now).
Versioning is based on local timestamps again,
but timestamps are protected by MDEV-15923
(option to control who can set session @@timestamp).

5 files changed, 29 insertions, 41 deletions

diff --git a/sql/partition_info.cc b/sql/partition_info.cc
index 746d00ef8d1..5c1cb106b28 100644
--- a/sql/partition_info.cc
+++ b/sql/partition_info.cc
@@ -859,7 +859,7 @@ void partition_info::vers_set_hist_part(THD *thd)
 
   if (vers_info->interval.is_set())
   {
-    if (vers_info->hist_part->range_value > thd->systime())
+    if (vers_info->hist_part->range_value > thd->query_start())
       return;
 
     partition_element *next= NULL;
@@ -870,7 +870,7 @@ void partition_info::vers_set_hist_part(THD *thd)
     while ((next= it++) != vers_info->now_part)
     {
       vers_info->hist_part= next;
-      if (next->range_value > thd->systime())
+      if (next->range_value > thd->query_start())
         return;
     }
     goto warn;
diff --git a/sql/sql_class.h b/sql/sql_class.h
index 6241e80052c..22b8e3e18f0 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -3437,16 +3437,13 @@ public:
   { query_start_sec_part_used=1; return start_time_sec_part; }
   MYSQL_TIME query_start_TIME();
 
+private:
   struct {
     my_hrtime_t start;
     my_time_t sec;
     ulong sec_part;
   } system_time;
 
-  ulong systime_sec_part() { query_start_sec_part_used=1; return system_time.sec_part; }
-  my_time_t systime() { return system_time.sec; }
-
-private:
   void set_system_time()
   {
     my_hrtime_t hrtime= my_hrtime();
@@ -3471,29 +3468,9 @@ private:
     }
   }
 
-  void set_system_time_from_user_time(bool with_sec_part)
-  {
-    if (with_sec_part)
-    {
-      system_time.sec= start_time;
-      system_time.sec_part= start_time_sec_part;
-    }
-    else
-    {
-      if (system_time.sec == start_time)
-        system_time.sec_part++;
-      else
-      {
-        system_time.sec= start_time;
-        system_time.sec_part= 0;
-      }
-    }
-  }
-
 public:
   inline void set_start_time()
   {
-    set_system_time();
     if (user_time.val)
     {
       start_time= hrtime_to_my_time(user_time);
@@ -3501,6 +3478,7 @@ public:
     }
     else
     {
+      set_system_time();
       start_time= system_time.sec;
       start_time_sec_part= system_time.sec_part;
     }
@@ -3511,6 +3489,7 @@ public:
     set_start_time();
     start_utime= utime_after_lock= microsecond_interval_timer();
   }
+  /* only used in SET @@timestamp=... */
   inline void set_time(my_hrtime_t t)
   {
     user_time= t;
@@ -3526,13 +3505,22 @@ public:
       set_time();                 // note that BINLOG itself requires SUPER
     else
     {
-      start_time= t;
-      start_time_sec_part= sec_part > TIME_MAX_SECOND_PART ? 0 : sec_part;
+      if (sec_part <= TIME_MAX_SECOND_PART)
+      {
+        start_time= system_time.sec= t;
+        start_time_sec_part= system_time.sec_part= sec_part;
+      }
+      else if (t != system_time.sec)
+      {
+        start_time= system_time.sec= t;
+        start_time_sec_part= system_time.sec_part= 0;
+      }
+      else
+      {
+        start_time= t;
+        start_time_sec_part= ++system_time.sec_part;
+      }
       user_time.val= hrtime_from_time(start_time) + start_time_sec_part;
-      if (slave_thread)
-        set_system_time_from_user_time(sec_part <= TIME_MAX_SECOND_PART);
-      else // BINLOG command
-        set_system_time();
       PSI_CALL_set_thread_start_time(start_time);
       start_utime= utime_after_lock= microsecond_interval_timer();
     }
diff --git a/sql/sql_partition.cc b/sql/sql_partition.cc
index c2534a9962e..f7cd6c2a71e 100644
--- a/sql/sql_partition.cc
+++ b/sql/sql_partition.cc
@@ -1571,7 +1571,7 @@ static bool check_vers_constants(THD *thd, partition_info *part_info)
       my_tz_OFFSET0->TIME_to_gmt_sec(&ltime, &error);
     if (error)
       goto err;
-    if (vers_info->hist_part->range_value <= thd->systime())
+    if (vers_info->hist_part->range_value <= thd->query_start())
       vers_info->hist_part= el;
   }
   return 0;
@@ -5310,7 +5310,7 @@ that are reorganised.
           if (*fast_alter_table && tab_part_info->vers_info->interval.is_set())
           {
             partition_element *hist_part= tab_part_info->vers_info->hist_part;
-            if (hist_part->range_value <= thd->systime())
+            if (hist_part->range_value <= thd->query_start())
               hist_part->part_state= PART_CHANGED;
           }
         }
diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
index 9608620d88c..9e6d53883ad 100644
--- a/sql/sql_yacc.yy
+++ b/sql/sql_yacc.yy
@@ -5907,7 +5907,7 @@ opt_versioning_rotation:
 opt_versioning_interval_start:
          /* empty */
          {
-           $$= thd->systime();
+           $$= thd->query_start();
          }
        | STARTS_SYM ulong_num
          {
diff --git a/sql/table.cc b/sql/table.cc
index 74b4ce3c842..bc61e77c972 100644
--- a/sql/table.cc
+++ b/sql/table.cc
@@ -7752,8 +7752,8 @@ void TABLE::vers_update_fields()
   {
     if (!vers_write)
       return;
-    if (vers_start_field()->store_timestamp(in_use->systime(),
-                                            in_use->systime_sec_part()))
+    if (vers_start_field()->store_timestamp(in_use->query_start(),
+                                            in_use->query_start_sec_part()))
       DBUG_ASSERT(0);
   }
   else
@@ -7768,8 +7768,8 @@ void TABLE::vers_update_fields()
 
 void TABLE::vers_update_end()
 {
-  if (vers_end_field()->store_timestamp(in_use->systime(),
-                                        in_use->systime_sec_part()))
+  if (vers_end_field()->store_timestamp(in_use->query_start(),
+                                        in_use->query_start_sec_part()))
     DBUG_ASSERT(0);
 }
 
@@ -8611,9 +8611,9 @@ bool TR_table::update(ulonglong start_id, ulonglong end_id)
   if (!table && open())
     return true;
 
-  timeval start_time= {thd->systime(), long(thd->systime_sec_part())};
+  timeval start_time= {thd->query_start(), long(thd->query_start_sec_part())};
   thd->set_start_time();
-  timeval end_time= {thd->systime(), long(thd->systime_sec_part())};
+  timeval end_time= {thd->query_start(), long(thd->query_start_sec_part())};
   store(FLD_TRX_ID, start_id);
   store(FLD_COMMIT_ID, end_id);
   store(FLD_BEGIN_TS, start_time);