Removed tdc_increment_refresh_version()

It is never called after 7fb9d64, which makes the whole refresh version
infrastructure useless.

Removed:
- tdc_version_t
- TDC_VERSION_MAX
- tdc_version
- TDC_element::version
- tdc_increment_refresh_version()
- tdc_refresh_version()
- refresh_version argument of tdc_wait_for_old_version()
- Flush_commands status variable
- refresh version from COM_STATISTICS
- refresh version from dbug printouts

Part of MDEV-17882 - Cleanup refresh version

sql/mysqld.cc

@@ -7050,16 +7050,6 @@ static int show_table_definitions(THD *thd, SHOW_VAR *var, char *buff,
 }
 
 
-static int show_flush_commands(THD *thd, SHOW_VAR *var, char *buff,
-                               enum enum_var_type scope)
-{
-  var->type= SHOW_LONGLONG;
-  var->value= buff;
-  *((longlong *) buff)= (longlong)tdc_refresh_version();
-  return 0;
-}
-
-
 #if defined(HAVE_OPENSSL) && !defined(EMBEDDED_LIBRARY)
 
 /*
@@ -7439,7 +7429,6 @@ SHOW_VAR status_vars[]= {
   {"Feature_trigger",          (char*) offsetof(STATUS_VAR, feature_trigger), SHOW_LONG_STATUS},
   {"Feature_window_functions", (char*) offsetof(STATUS_VAR, feature_window_functions), SHOW_LONG_STATUS},
   {"Feature_xml",              (char*) offsetof(STATUS_VAR, feature_xml), SHOW_LONG_STATUS},
-  {"Flush_commands",           (char*) &show_flush_commands, SHOW_SIMPLE_FUNC},
   {"Handler_commit",           (char*) offsetof(STATUS_VAR, ha_commit_count), SHOW_LONG_STATUS},
   {"Handler_delete",           (char*) offsetof(STATUS_VAR, ha_delete_count), SHOW_LONG_STATUS},
   {"Handler_discover",         (char*) offsetof(STATUS_VAR, ha_discover_count), SHOW_LONG_STATUS},

sql/sql_base.cc

@@ -1404,9 +1404,9 @@ bool wait_while_table_is_used(THD *thd, TABLE *table,
 {
   DBUG_ENTER("wait_while_table_is_used");
   DBUG_ASSERT(!table->s->tmp_table);
-  DBUG_PRINT("enter", ("table: '%s'  share: %p  db_stat: %u  version: %lld",
+  DBUG_PRINT("enter", ("table: '%s'  share: %p  db_stat: %u",
                        table->s->table_name.str, table->s,
-                       table->db_stat, table->s->tdc->version));
+                       table->db_stat));
 
   if (thd->mdl_context.upgrade_shared_lock(
              table->mdl_ticket, MDL_EXCLUSIVE,
@@ -2013,8 +2013,6 @@ retry_share:
   {
     if (share->tdc->flushed)
     {
-      DBUG_PRINT("info", ("Found old share version: %lld  current: %lld",
-                          share->tdc->version, tdc_refresh_version()));
       /*
         We already have an MDL lock. But we have encountered an old
         version of table in the table definition cache which is possible

sql/sql_parse.cc

@@ -2223,13 +2223,12 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
 #endif
     my_snprintf(buff, buff_len - 1,
                         "Uptime: %lu  Threads: %d  Questions: %lu  "
-                        "Slow queries: %lu  Opens: %lu  Flush tables: %lld  "
+                        "Slow queries: %lu  Opens: %lu  "
                         "Open tables: %u  Queries per second avg: %u.%03u",
                         uptime,
                         (int) thread_count, (ulong) thd->query_id,
                         current_global_status_var->long_query_count,
                         current_global_status_var->opened_tables,
-                        tdc_refresh_version(),
                         tc_records(),
                         (uint) (queries_per_second1000 / 1000),
                         (uint) (queries_per_second1000 % 1000));

sql/sql_test.cc

@@ -110,8 +110,6 @@ static void print_cached_tables(void)
 
   tdc_iterate(0, (my_hash_walk_action) print_cached_tables_callback, NULL, true);
 
-  printf("\nCurrent refresh version: %ld\n",
-         (long) tdc_refresh_version());
   fflush(stdout);
   /* purecov: end */
   return;

sql/table_cache.cc

@@ -68,7 +68,6 @@ I_P_List <TDC_element,
           I_P_List_null_counter,
           I_P_List_fast_push_back<TDC_element> > unused_shares;
 
-static tdc_version_t tdc_version;  /* Increments on each reload */
 static bool tdc_inited;
 
 
@@ -624,7 +623,6 @@ bool tdc_init(void)
   tdc_inited= true;
   mysql_mutex_init(key_LOCK_unused_shares, &LOCK_unused_shares,
                    MY_MUTEX_INIT_FAST);
-  tdc_version= 1L;  /* Increments on each reload */
   lf_hash_init(&tdc_hash, sizeof(TDC_element) +
                           sizeof(Share_free_tables) * (tc_instances - 1),
                LF_HASH_UNIQUE, 0, 0,
@@ -850,7 +848,6 @@ retry:
     element->share= share;
     share->tdc= element;
     element->ref_count++;
-    element->version= tdc_refresh_version();
     element->flushed= false;
     mysql_mutex_unlock(&element->LOCK_table_share);
 
@@ -965,9 +962,9 @@ void tdc_release_share(TABLE_SHARE *share)
 
   mysql_mutex_lock(&share->tdc->LOCK_table_share);
   DBUG_PRINT("enter",
-             ("share: %p  table: %s.%s  ref_count: %u  version: %lld",
+             ("share: %p  table: %s.%s  ref_count: %u",
               share, share->db.str, share->table_name.str,
-              share->tdc->ref_count, share->tdc->version));
+              share->tdc->ref_count));
   DBUG_ASSERT(share->tdc->ref_count);
 
   if (share->tdc->ref_count > 1)
@@ -1217,7 +1214,7 @@ bool tdc_remove_table(THD *thd, enum_tdc_remove_table_type remove_type,
 */
 
 int tdc_wait_for_old_version(THD *thd, const char *db, const char *table_name,
-                             ulong wait_timeout, uint deadlock_weight, tdc_version_t refresh_version)
+                             ulong wait_timeout, uint deadlock_weight)
 {
   TDC_element *element;
 
@@ -1225,7 +1222,7 @@ int tdc_wait_for_old_version(THD *thd, const char *db, const char *table_name,
     return FALSE;
   else if (element == MY_ERRPTR)
     return TRUE;
-  else if (element->flushed && refresh_version > element->version)
+  else if (element->flushed)
   {
     struct timespec abstime;
     set_timespec(abstime, wait_timeout);
@@ -1236,20 +1233,6 @@ int tdc_wait_for_old_version(THD *thd, const char *db, const char *table_name,
 }
 
 
-tdc_version_t tdc_refresh_version(void)
-{
-  return (tdc_version_t)my_atomic_load64_explicit(&tdc_version, MY_MEMORY_ORDER_RELAXED);
-}
-
-
-tdc_version_t tdc_increment_refresh_version(void)
-{
-  tdc_version_t v= (tdc_version_t)my_atomic_add64_explicit(&tdc_version, 1, MY_MEMORY_ORDER_RELAXED);
-  DBUG_PRINT("tcache", ("incremented global refresh_version to: %lld", v));
-  return v + 1;
-}
-
-
 /**
   Iterate table definition cache.
 

sql/table_cache.h

@@ -26,14 +26,11 @@ struct Share_free_tables
   char pad[CPU_LEVEL1_DCACHE_LINESIZE];
 };
 
-typedef int64 tdc_version_t;
-#define TDC_VERSION_MAX INT_MAX64
 
 struct TDC_element
 {
   uchar m_key[NAME_LEN + 1 + NAME_LEN + 1];
   uint m_key_length;
-  tdc_version_t version;
   bool flushed;
   TABLE_SHARE *share;
 
@@ -90,10 +87,7 @@ extern bool tdc_remove_table(THD *thd, enum_tdc_remove_table_type remove_type,
 
 extern int tdc_wait_for_old_version(THD *thd, const char *db,
                                     const char *table_name,
-                                    ulong wait_timeout, uint deadlock_weight,
+                                    ulong wait_timeout, uint deadlock_weight);
-                                    tdc_version_t refresh_version= TDC_VERSION_MAX);
-extern tdc_version_t tdc_refresh_version(void);
-extern tdc_version_t tdc_increment_refresh_version(void);
 extern int tdc_iterate(THD *thd, my_hash_walk_action action, void *argument,
                        bool no_dups= false);