MDEV-11412 Ensure that table is truly dropped when using DROP TABLE

The used code is largely based on code from Tencent

The problem is that in some rare cases there may be a conflict between .frm
files and the files in the storage engine. In this case the DROP TABLE
was not able to properly drop the table.

Some MariaDB/MySQL forks has solved this by adding a FORCE option to
DROP TABLE. After some discussion among MariaDB developers, we concluded
that users expects that DROP TABLE should always work, even if the
table would not be consistent. There should not be a need to use a
separate keyword to ensure that the table is really deleted.

The used solution is:
- If a .frm table doesn't exists, try dropping the table from all storage
  engines.
- If the .frm table exists but the table does not exist in the engine
  try dropping the table from all storage engines.
- Update storage engines using many table files (.CVS, MyISAM, Aria) to
  succeed with the drop even if some of the files are missing.
- Add HTON_AUTOMATIC_DELETE_TABLE to handlerton's where delete_table()
  is not needed and always succeed. This is used by ha_delete_table_force()
  to know which handlers to ignore when trying to drop a table without
  a .frm file.

The disadvantage of this solution is that a DROP TABLE on a non existing
table will be a bit slower as we have to ask all active storage engines
if they know anything about the table.

Other things:
- Added a new flag MY_IGNORE_ENOENT to my_delete() to not give an error
  if the file doesn't exist. This simplifies some of the code.
- Don't clear thd->error in ha_delete_table() if there was an active
  error. This is a bug fix.
- handler::delete_table() will not abort if first file doesn't exists.
  This is bug fix to handle the case when a drop table was aborted in
  the middle.
- Cleaned up mysql_rm_table_no_locks() to ensure that if_exists uses
  same code path as when it's not used.
- Use non_existing_Table_error() to detect if table didn't exists.
  Old code used different errors tests in different position.
- Table_triggers_list::drop_all_triggers() now drops trigger file if
  it can't be parsed instead of leaving it hanging around (bug fix)
- InnoDB doesn't anymore print error about .frm file out of sync with
  InnoDB directory if .frm file does not exists. This change was required
  to be able to try to drop an InnoDB file when .frm doesn't exists.
- Fixed bug in mi_delete_table() where the .MYD file would not be dropped
  if the .MYI file didn't exists.
- Fixed memory leak in Mroonga when deleting non existing table
- Fixed memory leak in Connect when deleting non existing table

Bugs fixed introduced by the original version of this commit:
MDEV-22826 Presence of Spider prevents tables from being force-deleted from
           other engines

1 files changed, 25 insertions, 18 deletions

diff --git a/sql/sql_trigger.cc b/sql/sql_trigger.cc
index 0b2d2d8ca1c..779faa96f82 100644
--- a/sql/sql_trigger.cc
+++ b/sql/sql_trigger.cc
@@ -1029,10 +1029,10 @@ bool Trigger::add_to_file_list(void* param_arg)
 */
 
 static bool rm_trigger_file(char *path, const LEX_CSTRING *db,
-                            const LEX_CSTRING *table_name)
+                            const LEX_CSTRING *table_name, myf MyFlags)
 {
   build_table_filename(path, FN_REFLEN-1, db->str, table_name->str, TRG_EXT, 0);
-  return mysql_file_delete(key_file_trg, path, MYF(MY_WME));
+  return mysql_file_delete(key_file_trg, path, MyFlags);
 }
 
 
@@ -1051,10 +1051,11 @@ static bool rm_trigger_file(char *path, const LEX_CSTRING *db,
 */
 
 static bool rm_trigname_file(char *path, const LEX_CSTRING *db,
-                             const LEX_CSTRING *trigger_name)
+                       const LEX_CSTRING *trigger_name, myf MyFlags)
 {
-  build_table_filename(path, FN_REFLEN - 1, db->str, trigger_name->str, TRN_EXT, 0);
-  return mysql_file_delete(key_file_trn, path, MYF(MY_WME));
+  build_table_filename(path, FN_REFLEN - 1, db->str, trigger_name->str,
+                       TRN_EXT, 0);
+  return mysql_file_delete(key_file_trn, path, MyFlags);
 }
 
 
@@ -1172,7 +1173,7 @@ bool Table_triggers_list::drop_trigger(THD *thd, TABLE_LIST *tables,
       parse_file.cc functionality (because we will need it
       elsewhere).
     */
-    if (rm_trigger_file(path, &tables->db, &tables->table_name))
+    if (rm_trigger_file(path, &tables->db, &tables->table_name, MYF(MY_WME)))
       return 1;
   }
   else
@@ -1181,7 +1182,7 @@ bool Table_triggers_list::drop_trigger(THD *thd, TABLE_LIST *tables,
       return 1;
   }
 
-  if (rm_trigname_file(path, &tables->db, sp_name))
+  if (rm_trigname_file(path, &tables->db, sp_name, MYF(MY_WME)))
     return 1;
 
   delete trigger;
@@ -1322,9 +1323,9 @@ bool Table_triggers_list::prepare_record_accessors(TABLE *table)
     This could be avoided if there is no triggers for UPDATE and DELETE.
 
   @retval
-    False   success
+    False   no triggers or triggers where correctly loaded
   @retval
-    True    error
+    True    error (wrong trigger file)
 */
 
 bool Table_triggers_list::check_n_load(THD *thd, const LEX_CSTRING *db,
@@ -1638,7 +1639,7 @@ err_with_lex_cleanup:
   }
 
 error:
-    if (unlikely(!thd->is_error()))
+  if (unlikely(!thd->is_error()))
   {
     /*
       We don't care about this error message much because .TRG files will
@@ -1815,7 +1816,8 @@ bool add_table_for_trigger(THD *thd,
 */
 
 bool Table_triggers_list::drop_all_triggers(THD *thd, const LEX_CSTRING *db,
-                                            const LEX_CSTRING *name)
+                                            const LEX_CSTRING *name,
+                                            myf MyFlags)
 {
   TABLE table;
   char path[FN_REFLEN];
@@ -1824,11 +1826,13 @@ bool Table_triggers_list::drop_all_triggers(THD *thd, const LEX_CSTRING *db,
 
   table.reset();
   init_sql_alloc(key_memory_Table_trigger_dispatcher,
-                 &table.mem_root, 8192, 0, MYF(0));
+                 &table.mem_root, 8192, 0, MYF(MY_WME));
 
   if (Table_triggers_list::check_n_load(thd, db, name, &table, 1))
   {
     result= 1;
+    /* We couldn't parse trigger file, best to just remove it */
+    rm_trigger_file(path, db, name, MyFlags);
     goto end;
   }
   if (table.triggers)
@@ -1848,7 +1852,7 @@ bool Table_triggers_list::drop_all_triggers(THD *thd, const LEX_CSTRING *db,
             Such triggers have zero-length name and are skipped here.
           */
           if (trigger->name.length &&
-              rm_trigname_file(path, db, &trigger->name))
+              rm_trigname_file(path, db, &trigger->name, MyFlags))
           {
             /*
               Instead of immediately bailing out with error if we were unable
@@ -1862,7 +1866,7 @@ bool Table_triggers_list::drop_all_triggers(THD *thd, const LEX_CSTRING *db,
         }
       }
     }
-    if (rm_trigger_file(path, db, name))
+    if (rm_trigger_file(path, db, name, MyFlags))
       result= 1;
     delete table.triggers;
   }
@@ -1923,9 +1927,10 @@ change_table_name_in_triggers(THD *thd,
   if (save_trigger_file(thd, new_db_name, new_table_name))
     return TRUE;
 
-  if (rm_trigger_file(path_buff, old_db_name, old_table_name))
+  if (rm_trigger_file(path_buff, old_db_name, old_table_name, MYF(MY_WME)))
   {
-    (void) rm_trigger_file(path_buff, new_db_name, new_table_name);
+    (void) rm_trigger_file(path_buff, new_db_name, new_table_name,
+                           MYF(MY_WME));
     return TRUE;
   }
   return FALSE;
@@ -2034,9 +2039,11 @@ bool Trigger::change_on_table_name(void* param_arg)
   /* Remove stale .TRN file in case of database upgrade */
   if (param->old_db_name)
   {
-    if (rm_trigname_file(trigname_buff, param->old_db_name, &name))
+    if (rm_trigname_file(trigname_buff, param->old_db_name, &name,
+                         MYF(MY_WME)))
     {
-      (void) rm_trigname_file(trigname_buff, param->new_db_name, &name);
+      (void) rm_trigname_file(trigname_buff, param->new_db_name, &name,
+                              MYF(MY_WME));
       return 1;
     }
   }