MDEV-4456 Reverse discovery of ARCHIVE table on SELECT after disappearance of ARZ file

Implement discovery of table non-existence, and related changes:

1. Split GTS_FORCE_DISCOVERY (that was meaning two different things in
two different functions) into GTS_FORCE_DISCOVERY and GTS_USE_DISCOVERY.
2. Move GTS_FORCE_DISCOVERY implementation into open_table_def().
3. In recover_from_failed_open() clear old errors *before* discovery,
not after successful discovery. The final error should come
from the discovery.
4. On forced discovery delete table .frm first. Discovery will write
a new one, if desired.
5. If the frm file exists, but not the table in the engine, force
rediscovery if the engine supports it.

mysql-test/suite/archive/discover.result

@@ -124,3 +124,9 @@ drop table `a/../`;
 create database test1;
 create table test1.t1 (i int) engine=archive;
 drop database test1;
+create table t1 (a int) engine=archive;
+select * from t1;
+a
+flush tables;
+select * from t1;
+ERROR 42S02: Table 'test.t1' doesn't exist

mysql-test/suite/archive/discover.test

@@ -107,3 +107,14 @@ create database test1;
 create table test1.t1 (i int) engine=archive;
 drop database test1;
 
+#
+# MDEV-4456 Reverse discovery of ARCHIVE table on SELECT after disappearance of ARZ file
+#
+create table t1 (a int) engine=archive;
+select * from t1;
+flush tables;
+remove_file $mysqld_datadir/test/t1.ARZ;
+--error ER_NO_SUCH_TABLE
+select * from t1;
+--list_files $mysqld_datadir/test
+

sql/sql_base.cc

@@ -632,10 +632,8 @@ TABLE_SHARE *get_table_share(THD *thd, const char *db, const char *table_name,
     mysql_mutex_lock(&share->LOCK_ha_data);
     mysql_mutex_unlock(&LOCK_open);
 
-    if (flags & GTS_FORCE_DISCOVERY)
-      ha_discover_table(thd, share); // don't read the frm at all
-    else
-      open_table_def(thd, share, flags | GTS_FORCE_DISCOVERY); // frm or discover
+    /* note that get_table_share() *always* uses discovery */
+    open_table_def(thd, share, flags | GTS_USE_DISCOVERY);
 
     mysql_mutex_unlock(&share->LOCK_ha_data);
     mysql_mutex_lock(&LOCK_open);
@@ -3992,15 +3990,16 @@ recover_from_failed_open(THD *thd)
 
         tdc_remove_table(thd, TDC_RT_REMOVE_ALL, m_failed_table->db,
                          m_failed_table->table_name, FALSE);
+
+        thd->warning_info->clear_warning_info(thd->query_id);
+        thd->clear_error();                 // Clear error message
+
         if ((result=
              !get_table_share(thd, m_failed_table->db,
                               m_failed_table->table_name,
                               GTS_TABLE | GTS_FORCE_DISCOVERY | GTS_NOLOCK)))
           break;
 
-
-        thd->warning_info->clear_warning_info(thd->query_id);
-        thd->clear_error();                 // Clear error message
         thd->mdl_context.release_transactional_locks();
         break;
       }
@@ -5967,7 +5966,7 @@ TABLE *open_table_uncached(THD *thd, handlerton *hton,
                        strend(saved_cache_key)+1, tmp_path);
   share->db_plugin= ha_lock_engine(thd, hton);
 
-  if (open_table_def(thd, share, GTS_TABLE | GTS_FORCE_DISCOVERY) ||
+  if (open_table_def(thd, share, GTS_TABLE | GTS_USE_DISCOVERY) ||
       open_table_from_share(thd, share, table_name,
                             (uint) (HA_OPEN_KEYFILE | HA_OPEN_RNDFILE |
                                     HA_GET_INDEX),

sql/table.cc

@@ -606,10 +606,19 @@ enum open_frm_error open_table_def(THD *thd, TABLE_SHARE *share, uint flags)
   share->error= OPEN_FRM_OPEN_ERROR;
 
   strxmov(path, share->normalized_path.str, reg_ext, NullS);
-  file= mysql_file_open(key_file_frm, path, O_RDONLY | O_SHARE, MYF(0));
+  if (flags & GTS_FORCE_DISCOVERY)
+  {
+    DBUG_ASSERT(flags & GTS_TABLE);
+    DBUG_ASSERT(flags & GTS_USE_DISCOVERY);
+    mysql_file_delete_with_symlink(key_file_frm, path, MYF(0));
+    file= -1;
+  }
+  else
+    file= mysql_file_open(key_file_frm, path, O_RDONLY | O_SHARE, MYF(0));
+
   if (file < 0)
   {
-    if ((flags & GTS_TABLE) && (flags & GTS_FORCE_DISCOVERY))
+    if ((flags & GTS_TABLE) && (flags & GTS_USE_DISCOVERY))
     {
       ha_discover_table(thd, share);
       error_given= true;
@@ -2803,8 +2812,22 @@ partititon_err:
                        !(ha_open_flags & HA_OPEN_FOR_REPAIR));
       outparam->file->print_error(ha_err, MYF(0));
       error_reported= TRUE;
+
       if (ha_err == HA_ERR_TABLE_DEF_CHANGED)
         error= OPEN_FRM_DISCOVER;
+
+      /*
+        We're here, because .frm file was successfully opened.
+
+        But if the table doesn't exist in the engine and the engine
+        supports discovery, we force rediscover to discover
+        the fact that table doesn't in fact exist and remove
+        the stray .frm file.
+      */
+      if (share->db_type()->discover_table &&
+          (ha_err == ENOENT || ha_err == HA_ERR_NO_SUCH_TABLE))
+        error= OPEN_FRM_DISCOVER;
+          
       goto err;
     }
   }

sql/table.h

@@ -2495,7 +2495,8 @@ enum get_table_share_flags {
   GTS_TABLE                = 1,
   GTS_VIEW                 = 2,
   GTS_NOLOCK               = 4,
-  GTS_FORCE_DISCOVERY      = 8
+  GTS_USE_DISCOVERY        = 8,
+  GTS_FORCE_DISCOVERY      = 16
 };
 
 size_t max_row_length(TABLE *table, const uchar *data);