fix THD::system_time to follow, well, system time

Because NOW() is set to system time, unless overriden.
And both should follow big manual system time changes,
while still coping with lowres system clocks.

Ignoring system time changes is both confusing and
breaks with restarts.

sql/partition_info.cc

@@ -900,7 +900,7 @@ void partition_info::vers_set_hist_part(THD *thd)
 
   if (vers_info->interval.is_set())
   {
-    if (vers_info->hist_part->range_value > thd->system_time)
+    if (vers_info->hist_part->range_value > thd->systime())
       return;
 
     partition_element *next= NULL;
@@ -911,7 +911,7 @@ 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->system_time)
+      if (next->range_value > thd->systime())
         return;
     }
     goto warn;

sql/sql_class.cc

@@ -819,8 +819,7 @@ THD::THD(my_thread_id id, bool is_wsrep_applier, bool skip_global_sys_var_lock)
   // Must be reset to handle error with THD's created for init of mysqld
   lex->current_select= 0;
   start_utime= utime_after_query= 0;
-  system_time= 0;
-  system_time_sec_part= 0;
+  system_time.start.val= system_time.sec= system_time.sec_part= 0;
   utime_after_lock= 0L;
   progress.arena= 0;
   progress.report_to_client= 0;

sql/sql_class.h

@@ -2418,8 +2418,6 @@ class THD :public Statement,
   // track down slow pthread_create
   ulonglong  prior_thr_create_utime, thr_create_utime;
   ulonglong  utime_after_query;
-  my_time_t  system_time;
-  ulong      system_time_sec_part;
 
   // Process indicator
   struct {
@@ -3430,30 +3428,37 @@ class THD :public Statement,
   { query_start_sec_part_used=1; return start_time_sec_part; }
   MYSQL_TIME query_start_TIME();
 
-private:
-  bool system_time_ge(my_time_t secs, ulong usecs)
-  {
-    return (system_time == secs && system_time_sec_part >= usecs) ||
-        system_time > secs;
-  }
+  struct {
+    my_hrtime_t start;
+    my_time_t sec;
+    ulong sec_part;
+  } system_time;
+
+  ulong systime_sec_part() { return system_time.sec_part; }
+  my_time_t systime() { return system_time.sec; }
 
+private:
   void set_system_time()
   {
     my_hrtime_t hrtime= my_hrtime();
-    my_time_t secs= hrtime_to_my_time(hrtime);
-    ulong usecs= hrtime_sec_part(hrtime);
-    if (system_time_ge(secs, usecs))
+    my_time_t sec= hrtime_to_my_time(hrtime);
+    ulong sec_part= hrtime_sec_part(hrtime);
+    if (sec > system_time.sec ||
+        (sec == system_time.sec && sec_part > system_time.sec_part) ||
+        hrtime.val < system_time.start.val)
     {
-      if (++system_time_sec_part == HRTIME_RESOLUTION)
-      {
-        ++system_time;
-        system_time_sec_part= 0;
-      }
+      system_time.sec= sec;
+      system_time.sec_part= sec_part;
     }
     else
     {
-      system_time= secs;
-      system_time_sec_part= usecs;
+      if (system_time.sec_part < TIME_MAX_SECOND_PART)
+        system_time.sec_part++;
+      else
+      {
+        system_time.sec++;
+        system_time.sec_part= 0;
+      }
     }
   }
 
@@ -3468,8 +3473,8 @@ class THD :public Statement,
     }
     else
     {
-      start_time= system_time;
-      start_time_sec_part= system_time_sec_part;
+      start_time= system_time.sec;
+      start_time_sec_part= system_time.sec_part;
     }
     PSI_CALL_set_thread_start_time(start_time);
   }

sql/sql_partition.cc

@@ -1574,7 +1574,7 @@ 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->system_time)
+    if (vers_info->hist_part->range_value <= thd->systime())
       vers_info->hist_part= el;
   }
   return 0;
@@ -5314,7 +5314,7 @@ 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->system_time)
+            if (hist_part->range_value <= thd->systime())
               hist_part->part_state= PART_CHANGED;
           }
         }

sql/sql_yacc.yy

@@ -5872,7 +5872,7 @@ opt_versioning_rotation:
 opt_versioning_interval_start:
          /* empty */
          {
-           $$= thd->system_time;
+           $$= thd->systime();
          }
        | remember_tok_start STARTS_SYM ulong_num
          {

sql/table.cc

@@ -7764,8 +7764,8 @@ void TABLE::vers_update_fields()
   {
     if (!vers_write)
       return;
-    if (vers_start_field()->store_timestamp(in_use->system_time,
-                                            in_use->system_time_sec_part))
+    if (vers_start_field()->store_timestamp(in_use->systime(),
+                                            in_use->systime_sec_part()))
       DBUG_ASSERT(0);
   }
   else
@@ -7780,8 +7780,8 @@ void TABLE::vers_update_fields()
 
 void TABLE::vers_update_end()
 {
-  if (vers_end_field()->store_timestamp(in_use->system_time,
-                                        in_use->system_time_sec_part))
+  if (vers_end_field()->store_timestamp(in_use->systime(),
+                                        in_use->systime_sec_part()))
     DBUG_ASSERT(0);
 }
 
@@ -8622,9 +8622,9 @@ bool TR_table::update(ulonglong start_id, ulonglong end_id)
   if (!table && open())
     return true;
 
-  timeval start_time= {thd->system_time, long(thd->system_time_sec_part)};
+  timeval start_time= {thd->systime(), long(thd->systime_sec_part())};
   thd->set_start_time();
-  timeval end_time= {thd->system_time, long(thd->system_time_sec_part)};
+  timeval end_time= {thd->systime(), long(thd->systime_sec_part())};
   store(FLD_TRX_ID, start_id);
   store(FLD_COMMIT_ID, end_id);
   store(FLD_BEGIN_TS, start_time);