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Re: 250bc3b6d74: Ensure that table is truly dropped when using DROP TABLE

To: Michael Widenius <michael.widenus@xxxxxxxxx>
From: Sergei Golubchik <serg@xxxxxxxxxxx>
Date: Fri, 12 Jun 2020 20:09:54 +0200
Cc: maria-developers@xxxxxxxxxxxxxxxxxxx
In-reply-to: <FrerfmsknYH.A.62B.-6i4eB@pweza>
Hi, Michael!

On Jun 11, Michael Widenius wrote:
> revision-id: 250bc3b6d74 (mariadb-10.5.2-390-g250bc3b6d74)
> parent(s): ba2c2cfb20e
> author: Michael Widenius <michael.widenus@xxxxxxxxx>
> committer: Michael Widenius <michael.widenus@xxxxxxxxx>
> timestamp: 2020-06-11 11:33:55 +0300
> message:
> 
> Ensure that table is truly dropped when using DROP TABLE
> 
> MDEV-11412 AliSQL: [Feature] Issue#34 Support force drop table

please, put this line ^^^ first in the comment comment.

> 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

TSQL? Or some other fork?

> 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.

I don't see why is that needed, if .frm exists, it tells exactly what
storage engine to use, there is no point in trying other 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

I don't think this part of the comment makes any sense, when one looks
through git history there is no "original version of this commit".

It's like a rolled back transaction, that value did not exist, unless
you use READ UNCOMMITTED :)

> diff --git a/mysql-test/main/drop_table_force.test b/mysql-test/main/drop_table_force.test
> new file mode 100644
> index 00000000000..8fdd79465b7
> --- /dev/null
> +++ b/mysql-test/main/drop_table_force.test
> @@ -0,1 +1,197 @@
>  +--source include/have_log_bin.inc
> +--source include/have_innodb.inc
> +
> +#
> +# This test is based on the orginal test from Tencent for DROP TABLE ... FORCE
> +# In MariaDB we did reuse the code but MariaDB does not require the FORCE
> +# keyword to drop a table even if the .frm file or some engine files are
> +# missing.
> +# To make it easy to see the differences between the orginal code and
> +# the new one, we have left some references to the original test case
> +#
> +
> +CALL mtr.add_suppression("Operating system error number");
> +CALL mtr.add_suppression("The error means the system cannot");
> +CALL mtr.add_suppression("returned OS error 71");

not sure it's a good idea, error numbers aren't very portable, this will
blow up some day like a time bomb

> +
> +let $DATADIR= `select @@datadir`;
> +
> +--echo #Test1: table with missing .ibd can be dropped directly
> +# drop table without ibd
> +create table t1(a int)engine=innodb;
> +--remove_file $DATADIR/test/t1.ibd
> +drop table t1;
> +--list_files  $DATADIR/test/
> +
> +# Original DROP TABLE .. FORCE required SUPER privilege. MariaDB doesn't
> +--echo # Test droping table without frm without super privilege
> +
> +# create table t1 and rm frm
> +create table t1(a int) engine=innodb;
> +--remove_file $DATADIR/test/t1.frm
> +
> +# create test user
> +create user test identified by '123456';
> +grant all privileges on test.t1 to 'test'@'%'identified by '123456' with grant option;

why with grant option?
better remove it if it's not essential for drop to work.
if it is essential, why is it?

> +
> +# connect as test
> +connect (con_test, localhost, test,'123456', );
> +--connection con_test
> +
> +# drop table with user test
> +drop table t1;
> +--error ER_BAD_TABLE_ERROR
> +drop table t1;
> +
> +# connect as root
> +--connection default
> +
> +--disconnect con_test
> +drop user test;
> +
> +# check files in datadir about t1
> +--list_files  $DATADIR/test/
> +
> +--echo #Test4: drop table can drop consistent table as well
> +create table t1(a int) engine=innodb;
> +drop table t1;

aha, so it works! :)

> +
> +# check files in datadir about t1
> +--list_files  $DATADIR/test/
> +
> +--echo #Test5: drop table with triger, and with missing frm
> +# create table t1 with triger and rm frm
> +create table t1(a int)engine=innodb;
> +create trigger t1_trg before insert on t1 for each row begin end;
> +
> +let $DATADIR= `select @@datadir`;
> +--remove_file $DATADIR/test/t1.frm
> +
> +drop table t1;
> +--error ER_BAD_TABLE_ERROR
> +drop table t1;
> +
> +# check files in datadir about t1
> +--list_files  $DATADIR/test/
> +
> +--echo #Test6: table with foreign key references can not be dropped
> +# create table with foreign key reference and rm frm
> +CREATE TABLE parent (id INT NOT NULL, PRIMARY KEY (id)) ENGINE=INNODB;
> +CREATE TABLE child (id INT, parent_id INT, INDEX par_ind (parent_id), FOREIGN KEY (parent_id) REFERENCES parent(id) ON DELETE CASCADE) ENGINE=INNODB;
> +--remove_file $DATADIR/test/parent.frm
> +
> +# parent can not be dropped when there are foreign key references
> +--error ER_ROW_IS_REFERENCED_2
> +drop table parent;
> +
> +# parent can be dropped when there are no foreign key references
> +drop table child;
> +drop table parent;
> +
> +# check files in datadir about child and parent
> +--list_files  $DATADIR/test/
> +
> +--echo #Test7: drop table twice
> +create table t1(a int)engine=innodb;
> +--remove_file $DATADIR/test/t1.frm
> +
> +# first drop table will success
> +drop table t1;
> +
> +# check files in datadir about t1
> +--list_files  $DATADIR/test/
> +
> +# second drop with if exists will also ok
> +drop table if exists t1;
> +
> +# check files in datadir about t1
> +--list_files  $DATADIR/test/
> +
> +--echo #Test8: check compatibility with if exists
> +create table t1(a int)engine=innodb;
> +--remove_file $DATADIR/test/t1.frm
> +
> +# first drop will success
> +drop table t1;
> +
> +# check files in datadir about t1
> +--list_files  $DATADIR/test/
> +
> +# second drop with if exists will success
> +drop table if exists t1;

you've just tested it in Test7, haven't you?

> +
> +--echo #Test9: check compatibility with restrict/cascade
> +# create table with foreign key reference and rm frm
> +CREATE TABLE parent (id INT NOT NULL, PRIMARY KEY (id)) ENGINE=INNODB;
> +CREATE TABLE child (id INT, parent_id INT, INDEX par_ind (parent_id), FOREIGN KEY (parent_id) REFERENCES parent(id) ON DELETE CASCADE) ENGINE=INNODB;
> +
> +# parent can not be dropped when there are froeign key references

typo "foreign"

> +--error ER_ROW_IS_REFERENCED_2
> +drop table parent;
> +--error ER_ROW_IS_REFERENCED_2
> +drop table parent restrict;
> +--error ER_ROW_IS_REFERENCED_2
> +drop table parent cascade;
> +--error ER_ROW_IS_REFERENCED_2
> +drop table parent;
> +--error ER_ROW_IS_REFERENCED_2
> +drop table parent restrict;
> +--error ER_ROW_IS_REFERENCED_2
> +drop table parent cascade;
> +
> +# parent can be dropped when there are no foreign key references
> +drop table child;
> +drop table parent;
> +
> +--echo #Test10: drop non-innodb engine table returns ok
> +# create myisam table t1 and rm .frm
> +create table t1(a int) engine=myisam;
> +--remove_file $DATADIR/test/t1.frm
> +--replace_result \\ /
> +drop table t1;
> +
> +# create myisam table t1 and rm .MYD
> +create table t1(a int) engine=myisam;
> +--remove_file $DATADIR/test/t1.MYD
> +--replace_result \\ /
> +drop table t1;
> +
> +# create myisam table t1 and rm .MYI
> +create table t1(a int) engine=myisam;
> +--remove_file $DATADIR/test/t1.MYI
> +--replace_result \\ /
> +drop table t1;
> +--list_files  $DATADIR/test/
> +
> +# create Aria table t1 and rm .frm and .MAD
> +create table t1(a int) engine=aria;
> +--remove_file $DATADIR/test/t1.frm
> +--remove_file $DATADIR/test/t1.MAD
> +--list_files  $DATADIR/test/
> +--error ER_BAD_TABLE_ERROR
> +drop table t1;
> +--replace_result \\ /
> +show warnings;
> +--list_files  $DATADIR/test/
> +
> +# create Aria table t2 and rm .frm and .MAI
> +create table t2(a int) engine=aria;
> +flush tables;
> +--remove_file $DATADIR/test/t2.frm
> +--remove_file $DATADIR/test/t2.MAI
> +--list_files  $DATADIR/test/
> +--error ER_BAD_TABLE_ERROR
> +drop table t2;
> +--replace_result \\ /
> +show warnings;
> +--list_files  $DATADIR/test/
> +
> +# create Aria table t2 and rm .MAI and .MAD
> +create table t2(a int) engine=aria;
> +flush tables;
> +--remove_file $DATADIR/test/t2.MAD
> +--remove_file $DATADIR/test/t2.MAI
> +--list_files  $DATADIR/test/
> +--replace_result \\ /
> +drop table t2;

may be csv and archive tests too?

> diff --git a/sql/handler.cc b/sql/handler.cc
> index 1af0157783e..5dd02d057c7 100644
> --- a/sql/handler.cc
> +++ b/sql/handler.cc
> @@ -2674,26 +2712,34 @@ const char *get_canonical_filename(handler *file, const char *path,
>  }
>  
>  
> -/** delete a table in the engine
> +/**
> +   Delete a table in the engine
>  
> +   @return 0   Table was deleted
> +   @return -1  Table didn't exists, no error given
> +   @return #   Error from table handler
> +
>    @note
>    ENOENT and HA_ERR_NO_SUCH_TABLE are not considered errors.
> -  The .frm file will be deleted only if we return 0.
> +  The .frm file should be deleted by the caller only if we return <= 0.
>  */
> +
>  int ha_delete_table(THD *thd, handlerton *table_type, const char *path,
> -                    const LEX_CSTRING *db, const LEX_CSTRING *alias, bool generate_warning)
> +                    const LEX_CSTRING *db, const LEX_CSTRING *alias,
> +                    bool generate_warning)
>  {
>    handler *file;
>    char tmp_path[FN_REFLEN];
>    int error;
>    TABLE dummy_table;
>    TABLE_SHARE dummy_share;
> +  bool is_error= thd->is_error();
>    DBUG_ENTER("ha_delete_table");
>  
>    /* table_type is NULL in ALTER TABLE when renaming only .frm files */
>    if (table_type == NULL || table_type == view_pseudo_hton ||
>        ! (file=get_new_handler((TABLE_SHARE*)0, thd->mem_root, table_type)))
> -    DBUG_RETURN(0);
> +    DBUG_RETURN(-1);

"Table didn't exists, no error given"?
if get_new_handler() fails it's OOM.

>  
>    bzero((char*) &dummy_table, sizeof(dummy_table));
>    bzero((char*) &dummy_share, sizeof(dummy_share));
> @@ -2723,8 +2769,10 @@ int ha_delete_table(THD *thd, handlerton *table_type, const char *path,
>      }
>      if (intercept)
>      {
> +      /* Clear error if we got it in this function */
> +      if (!is_error)
>        thd->clear_error();

this is generally a wrong approach. One should use push_internal_handler
to silence errors, not thd->is_error() or thd->clear_error().

In this particilar case there will be no errors if there was no error
before ha_delete_table() - which is correct. But if there was an error
before, this will leave spurious and confusing errors in `SHOW WARNINGS`
output.

> -      error= 0;
> +      error= -1;
>      }
>    }
>    delete file;
> @@ -4365,45 +4413,63 @@ uint handler::get_dup_key(int error)
>  
>    @note
>      We assume that the handler may return more extensions than
> -    was actually used for the file.
> +    was actually used for the file. We also assume that the first
> +    extension is the most important one. If this exist and we can't delete
> +    that one we will abort the delete.

after "the most important one" you can add "(see the comment near
handlerton::tablefile_extensions)"

> +    If the first one doesn't exists, we have to try to delete all other

"doesn't exist"

> +    extension as there is chance that the server had crashed between
> +    the delete of the first file and the next
>  
>    @retval
>      0   If we successfully deleted at least one file from base_ext and
>      didn't get any other errors than ENOENT
> +
>    @retval
>      !0  Error
>  */
> +
>  int handler::delete_table(const char *name)
>  {
> -  int saved_error= 0;
> -  int error= 0;
> -  int enoent_or_zero;
> +  int saved_error= ENOENT;
> +  bool abort_if_first_file_error= 1;
> +  bool some_file_deleted= 0;
> +  DBUG_ENTER("handler::delete_table");
>  
> +  // For discovery tables, it's ok if first file doesn't exists

why would that be ok?

>    if (ht->discover_table)
> -    enoent_or_zero= 0; // the table may not exist in the engine, it's ok
> -  else
> -    enoent_or_zero= ENOENT;  // the first file of bas_ext() *must* exist
> +  {
> +    abort_if_first_file_error= 0;
> +    saved_error= 0;
> +    if (!bas_ext())
> +    {
> +      DBUG_ASSERT(ht->flags & HTON_AUTOMATIC_DELETE_TABLE);
> +      DBUG_RETURN(0);                           // Drop succeded
> +    }
> +  }
>  
>    for (const char **ext= bas_ext(); *ext ; ext++)
>    {
> +    int error;
> -    if (mysql_file_delete_with_symlink(key_file_misc, name, *ext, 0))
> +    if ((error= mysql_file_delete_with_symlink(key_file_misc, name, *ext,
> +                                              MYF(0))))

why do you need this `error` variable, if you never use it?

>      {
>        if (my_errno != ENOENT)
>        {
> +        saved_error= my_errno;
>          /*
> -          If error on the first existing file, return the error.
> +          If error other than file not found on the first existing file,
> +          return the error.
>            Otherwise delete as much as possible.
>          */
> -        if (enoent_or_zero)
> -          return my_errno;
> -        saved_error= my_errno;
> +        if (abort_if_first_file_error)
> +          DBUG_RETURN(saved_error);
>        }
>      }
>      else
> -      enoent_or_zero= 0;                        // No error for ENOENT
> -    error= enoent_or_zero;
> +      some_file_deleted= 1;
> +    abort_if_first_file_error= 0;
>    }
> -  return saved_error ? saved_error : error;
> +  DBUG_RETURN(some_file_deleted && saved_error == ENOENT ? 0 : saved_error);
>  }
>  
>  
> @@ -4439,5 +4505,20 @@ void handler::drop_table(const char *name)
>  
>  
>  /**
> +   Return true if the error from drop table means that the
> +   table didn't exists
> +*/
> +
> +bool non_existing_table_error(int error)
> +{
> +  return (error == ENOENT || error == HA_ERR_NO_SUCH_TABLE ||
> +          error == HA_ERR_UNSUPPORTED ||
> +          error == ER_NO_SUCH_TABLE ||
> +          error == ER_NO_SUCH_TABLE_IN_ENGINE ||
> +          error == ER_WRONG_OBJECT);
> +}

this should, I believe, be inline in handler.h

> +
> +
> +/**
>    Performs checks upon the table.
>  
> @@ -4899,5 +4981,89 @@ handler::ha_drop_table(const char *name)
>  
>  
>  /**
> +   Structure used during force drop table.
> +*/
> +
> +struct st_force_drop_table_params
> +{
> +  const char *path;
> +  const LEX_CSTRING *db;
> +  const LEX_CSTRING *alias;
> +  bool generate_warning;
> +  int error;
> +};
> +
> +
> +/**
> +   Try to delete table from a given plugin
> +   Table types with discovery is ignored as these .frm files would have
> +   been created during discovery and thus doesn't need to be found
> +   for drop table force
> +*/
> +
> +static my_bool delete_table_force(THD *thd, plugin_ref plugin, void *arg)
> +{
> +  handlerton *hton = plugin_hton(plugin);
> +  st_force_drop_table_params *param = (st_force_drop_table_params *)arg;
> +
> +  /*
> +    We have to ignore HEAP tables as these may not have been created yet
> +    We also remove engines that is using discovery (as these will recrate
> +    any missing .frm if needed) and tables marked with
> +    HTON_AUTOMATIC_DELETE_TABLE as for these we can't check if the table
> +    ever existed.
> +  */
> +  if (!hton->discover_table && hton->db_type != DB_TYPE_HEAP &&
> +      !(hton->flags & HTON_AUTOMATIC_DELETE_TABLE))
> +  {
> +    int error;
> +    error= ha_delete_table(thd, hton, param->path, param->db,
> +                           param->alias, param->generate_warning);

This is doing a a lot of extra work. dummy_table/dummy_share, if()s.
Allocating and constructing new handlers.
I suggest the following:

  1. Introduce new handlerton method hton->drop_table().
     By default it'll be

        hton->get_new_handler()
        get_canonical_filename() 
        file->ha_delete_table()

     like now, so all engines will still work. But later we can start
     moving drop table functionality out of the handler. In this commit
     only engines like blackhole will have a dummy drop_table() method.

  2. Here you can do, basically

       hton->drop_table(hton, param->path)

     without checking for discovery, without a new flag
     HTON_AUTOMATIC_DELETE_TABLE. I'm not sure why you check for
     DB_TYPE_HEAP, could you please explain that?

> +    if (error > 0 && !non_existing_table_error(error))
> +      param->error= error;
> +    if (error == 0)
> +    {
> +      param->error= 0;
> +      return TRUE;                                // Table was deleted
> +    }
> +  }
> +  return FALSE;
> +}
> +
> +/**
> +   @brief
> +   Traverse all plugins to delete table when .frm file is missing.
> +
> +   @return -1  Table was not found in any engine
> +   @return 0  Table was found in some engine and delete succeded
> +   @return #  Error from first engine that had a table but didn't succeed to
> +              delete the table
> +   @return HA_ERR_ROW_IS_REFERENCED if foreign key reference is encountered,
> +
> +*/
> +
> +int ha_delete_table_force(THD *thd, const char *path, const LEX_CSTRING *db,
> +                          const LEX_CSTRING *alias, bool generate_warning)
> +{
> +  st_force_drop_table_params param;
> +  Table_exists_error_handler no_such_table_handler;
> +  DBUG_ENTER("ha_delete_table_force");
> +
> +  param.path=             path;
> +  param.db=               db;
> +  param.alias=            alias;
> +  param.generate_warning= generate_warning;

this is never used, you always invoke ha_delete_table_force() with
generate_warning=0.

> +  param.error=            -1;                   // Table not found
> +
> +  thd->push_internal_handler(&no_such_table_handler);
> +  if (plugin_foreach(thd, delete_table_force, MYSQL_STORAGE_ENGINE_PLUGIN,
> +                     &param))
> +    param.error= 0;                            // Delete succeded
> +  thd->pop_internal_handler();
> +  DBUG_RETURN(param.error);
> +}
> +
> +
> +/**
>    Create a table in the engine: public interface.
>  
> diff --git a/sql/handler.h b/sql/handler.h
> index f592c635c5d..f5ccdbe1ee4 100644
> --- a/sql/handler.h
> +++ b/sql/handler.h
> @@ -1780,6 +1780,13 @@ handlerton *ha_default_tmp_handlerton(THD *thd);
>  */
>  #define HTON_TRANSACTIONAL_AND_NON_TRANSACTIONAL (1 << 17)
>  
> +/*
> +  The engine doesn't keep track of tables, delete_table() is not
> +  needed and delete_table() always returns 0 (table deleted). This flag
> +  mainly used to skip storage engines in case of ha_delete_table_force()
> +*/
> +#define HTON_AUTOMATIC_DELETE_TABLE (1 << 18)
> +
>  class Ha_trx_info;
>  
>  struct THD_TRANS
> diff --git a/sql/sql_table.cc b/sql/sql_table.cc
> index 61b1113f680..7c79acef3ea 100644
> --- a/sql/sql_table.cc
> +++ b/sql/sql_table.cc
> @@ -2327,36 +2329,42 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
>                    thd->find_temporary_table(table) &&
>                    table->mdl_request.ticket != NULL));
>  
> +    /* First try to delete temporary tables and temporary sequences */
> -    if (table->open_type == OT_BASE_ONLY || !is_temporary_table(table) ||
> -        (drop_sequence && table->table->s->table_type != TABLE_TYPE_SEQUENCE))
> -      error= 1;
> -    else
> +    if ((table->open_type != OT_BASE_ONLY && is_temporary_table(table)) &&

unnecessary parentheses

> +        (!drop_sequence || table->table->s->table_type == TABLE_TYPE_SEQUENCE))
>      {
>        table_creation_was_logged= table->table->s->table_creation_was_logged;
>        if (thd->drop_temporary_table(table->table, &is_trans, true))
>        {
> +        /*
> +          This is a very unlikely scenaro as dropping a temporary table
> +          should always work. Would be better if we tried to drop all
> +          temporary tables before giving the error.
> +        */
>          error= 1;
>          goto err;
>        }
> -      error= 0;
>        table->table= 0;
> +      temporary_table_was_dropped= 1;
>      }
>  
> -    if ((drop_temporary && if_exists) || !error)
> +    if ((drop_temporary && if_exists) || temporary_table_was_dropped)
>      {
>        /*
>          This handles the case of temporary tables. We have the following cases:
>  
> -          . "DROP TEMPORARY" was executed and a temporary table was affected
> -          (i.e. drop_temporary && !error) or the if_exists was specified (i.e.
> -          drop_temporary && if_exists).
> -
> -          . "DROP" was executed but a temporary table was affected (.i.e
> -          !error).
> +          - "DROP TEMPORARY" was executed and table was dropped
> +            temporary_table_was_dropped == 1
> +          - "DROP TEMPORARY IF EXISTS" was specified but no temporary table
> +            existed
> +            temporary_table_was_dropped == 0
>        */
>        if (!dont_log_query && table_creation_was_logged)
>        {
>          /*
> +          DROP TEMPORARY succeded. For the moment when we only come
> +          here on success (error == 0)

DBUG_ASSERT(error == 0) please

> +
>            If there is an error, we don't know the type of the engine
>            at this point. So, we keep it in the trx-cache.
>          */
> @@ -2387,7 +2395,8 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
>          is no need to proceed with the code that tries to drop a regular
>          table.
>        */
> -      if (!error) continue;
> +      if (temporary_table_was_dropped)

can temporary_table_was_dropped be false here?

> +        continue;
>      }
>      else if (!drop_temporary)
>      {
> @@ -2402,48 +2411,33 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
>        path_length= build_table_filename(path, sizeof(path) - 1, db.str,
>                                          alias.str, reg_ext, 0);
>      }
> +
>      DEBUG_SYNC(thd, "rm_table_no_locks_before_delete_table");
>      error= 0;
> -    if (drop_temporary ||
> -        (ha_table_exists(thd, &db, &alias, &table_type, &is_sequence) == 0 &&
> +    if (drop_temporary)
> +    {
> +      /* "DROP TEMPORARY" but a temporary table was not found */
> +      error= ENOENT;
> +    }
> +    else if (((frm_exists= ha_table_exists(thd, &db, &alias, &table_type,
> +                                           &is_sequence)) == 0 &&

this is an overkill. ha_table_exists() will do a full table discovery,
you don't need it here, because you'll try to delete anyway.

So, basically you only need dd_frm_type() here.

>           table_type == 0) ||
>          (!drop_view && (was_view= (table_type == view_pseudo_hton))) ||
>          (drop_sequence && !is_sequence))
>      {
>        /*
>          One of the following cases happened:
> -          . "DROP TEMPORARY" but a temporary table was not found.
>            . "DROP" but table was not found
>            . "DROP TABLE" statement, but it's a view.
>            . "DROP SEQUENCE", but it's not a sequence
>        */
> -      was_table= drop_sequence && table_type;
> -      if (if_exists)
> -      {
> -        char buff[FN_REFLEN];
> -        int err= (drop_sequence ? ER_UNKNOWN_SEQUENCES :
> -                  ER_BAD_TABLE_ERROR);
> -        String tbl_name(buff, sizeof(buff), system_charset_info);
> -        tbl_name.length(0);
> -        tbl_name.append(&db);
> -        tbl_name.append('.');
> -        tbl_name.append(&table->table_name);
> -        push_warning_printf(thd, Sql_condition::WARN_LEVEL_NOTE,
> -                            err, ER_THD(thd, err),
> -                            tbl_name.c_ptr_safe());
> -
> -        /*
> -          Our job is done here. This statement was added to avoid executing
> -          unnecessary code farther below which in some strange corner cases
> -          caused the server to crash (see MDEV-17896).
> -        */
> -        goto log_query;
> -      }
> -      else
> -      {
> -        non_tmp_error = (drop_temporary ? non_tmp_error : TRUE);
> -        error= 1;
> -      }
> +      wrong_drop_sequence= drop_sequence && table_type;
> +      was_table|= wrong_drop_sequence;
> +      local_non_tmp_error= 1;
> +      error= -1;
> +      if ((!frm_exists && !table_type) ||       // no .frm
> +          if_exists)
> +        error= ENOENT;
>      }
>      else
>      {
> @@ -2509,49 +2507,138 @@ int mysql_rm_table_no_locks(THD *thd, TABLE_LIST *tables, bool if_exists,
>            goto err;
>          }
>        }
> -      else
> +
> +      /*
> +        Delete the .frm file if we managed to delete the table from the
> +        engine or the table didn't exists in the engine
> +      */
> +      if (likely(!error) || non_existing_table_error(error))
>        {
>          /* Delete the table definition file */
>          strmov(end,reg_ext);
>          if (table_type && table_type != view_pseudo_hton &&
> -            table_type->discover_table)
> +            (table_type->discover_table || error))

I don't think this new drop table logic needs to have any special
handling of discovery. If the table didn't exist in engine - it's the
normal case now, discovery or not, it's be handled normally.

>          {
>            /*
> -            Table type is using discovery and may not need a .frm file.
> +            Table type is using discovery and may not need a .frm file
> +            or the .frm file existed but no table in engine.
>              Delete it silently if it exists
>            */
> -          (void) mysql_file_delete(key_file_frm, path, MYF(0));
> +          if (mysql_file_delete(key_file_frm, path,
> +                                MYF(MY_WME | MY_IGNORE_ENOENT)))
> +            error= my_errno;
>          }
>          else if (unlikely(mysql_file_delete(key_file_frm, path,
> -                                            MYF(MY_WME))))
> +                                            !error ? MYF(MY_WME) :
> +                                            MYF(MY_WME | MY_IGNORE_ENOENT))))
>          {
>            frm_delete_error= my_errno;
>            DBUG_ASSERT(frm_delete_error);
>          }
>        }
> +      frm_was_deleted= 1;
>        if (thd->replication_flags & OPTION_IF_EXISTS)
>          log_if_exists= 1;
>  
> -      if (likely(!error))
> +      if (frm_delete_error)
>        {
> -        int trigger_drop_error= 0;
> +        /*
> +          Remember error if unexpected error from dropping the .frm file
> +          or we got an error from ha_delete_table()
> +        */
> +        if (frm_delete_error != ENOENT)
> +          error= frm_delete_error;
> +        else if (if_exists && ! error)
> +          thd->clear_error();

no, please, don't do thd->clear_error().
I've seen and fixed so many bugs because of that. The last one - just an
hour ago. Use push_internal_handler() instead.

> +      }
> +      if (likely(!error) || !frm_delete_error)
> +        non_tmp_table_deleted= TRUE;
>  
> -      if (likely(!frm_delete_error))
> +      if (likely(!error) || non_existing_table_error(error))
>        {
> +        trigger_drop_executed= 1;
> +
> +        if (Table_triggers_list::drop_all_triggers(thd, &db,
> +                                                   &table->table_name,
> +                                                   MYF(MY_WME |
> +                                                       MY_IGNORE_ENOENT)))
> +          error= error ? error : -1;
> +      }
> +      local_non_tmp_error|= MY_TEST(error);
> +    }
> +
> +    /*
> +      If there was no .frm file and the table is not temporary,
> +      scan all engines try to drop the table from there.
> +      This is to ensure we don't have any partial table files left.
> +
> +      We check for trigger_drop_executed to ensure we don't again try
> +      to drop triggers when it failed above (after sucecssfully dropping
> +      the table).
> +    */
> +    if (non_existing_table_error(error) && !drop_temporary &&
> +        table_type != view_pseudo_hton && !trigger_drop_executed &&
> +        !wrong_drop_sequence)
> +    {
> +      char *end;
> +      int ferror= 0;
> +
> +      /* Remove extension for delete */
> +      *(end = path + path_length - reg_ext_length) = '\0';
> +      ferror= ha_delete_table_force(thd, path, &db,
> +                                    &table->table_name, 0);
> +      if (!ferror)
> +      {
> +        /* Table existed and was deleted */
>            non_tmp_table_deleted= TRUE;
> -          trigger_drop_error=
> -            Table_triggers_list::drop_all_triggers(thd, &db,
> -                                                   &table->table_name);
> +        local_non_tmp_error= 0;
> +        error= 0;
>          }
> +      if (ferror <= 0)
> +      {
> +        ferror= 0;                              // Ignore table not found
>  
> -        if (unlikely(trigger_drop_error) ||
> -            (frm_delete_error && frm_delete_error != ENOENT))
> -          error= 1;
> -        else if (frm_delete_error && if_exists)
> -          thd->clear_error();
> +        /* Delete the table definition file */
> +        if (!frm_was_deleted)
> +        {
> +          strmov(end, reg_ext);
> +          if (mysql_file_delete(key_file_frm, path,
> +                                MYF(MY_WME | MY_IGNORE_ENOENT)))
> +            ferror= my_errno;
>        }
> -      non_tmp_error|= MY_TEST(error);
> +        if (Table_triggers_list::drop_all_triggers(thd, &db,
> +                                                   &table->table_name,
> +                                                   MYF(MY_WME |
> +                                                       MY_IGNORE_ENOENT)))
> +          ferror= -1;

Why do you need two copies of code to drop triggers?
Why cannot you do it once, on the first drop_all_triggers() place?

>      }
> +      if (!error)
> +        error= ferror;
> +    }
> +
> +    /*
> +      Don't give an error if we are using IF EXISTS for a table that
> +      didn't exists
> +    */
> +
> +    if (if_exists && non_existing_table_error(error))
> +    {
> +      char buff[FN_REFLEN];
> +      int err= (drop_sequence ? ER_UNKNOWN_SEQUENCES :
> +                ER_BAD_TABLE_ERROR);
> +      String tbl_name(buff, sizeof(buff), system_charset_info);
> +      tbl_name.length(0);
> +      tbl_name.append(&db);
> +      tbl_name.append('.');
> +      tbl_name.append(&table->table_name);
> +      push_warning_printf(thd, Sql_condition::WARN_LEVEL_NOTE,
> +                          err, ER_THD(thd, err),
> +                          tbl_name.c_ptr_safe());
> +      error= 0;
> +      local_non_tmp_error= 0;
> +      drop_table_not_done= 1;
> +    }
> +    non_tmp_error|= local_non_tmp_error;
>  
>      if (error)
>      {
> diff --git a/storage/blackhole/ha_blackhole.cc b/storage/blackhole/ha_blackhole.cc
> index 15548350b20..98589f1d043 100644
> --- a/storage/blackhole/ha_blackhole.cc
> +++ b/storage/blackhole/ha_blackhole.cc
> @@ -399,7 +399,7 @@ static int blackhole_init(void *p)
>    blackhole_hton= (handlerton *)p;
>    blackhole_hton->db_type= DB_TYPE_BLACKHOLE_DB;
>    blackhole_hton->create= blackhole_create_handler;
> -  blackhole_hton->flags= HTON_CAN_RECREATE;
> +  blackhole_hton->flags= HTON_CAN_RECREATE | HTON_AUTOMATIC_DELETE_TABLE;
>  
>    mysql_mutex_init(bh_key_mutex_blackhole,
>                     &blackhole_mutex, MY_MUTEX_INIT_FAST);
> diff --git a/storage/blackhole/ha_blackhole.h b/storage/blackhole/ha_blackhole.h
> index 6ee30877b64..646fba6da9f 100644
> --- a/storage/blackhole/ha_blackhole.h
> +++ b/storage/blackhole/ha_blackhole.h
> @@ -95,6 +95,10 @@ class ha_blackhole: public handler
>    THR_LOCK_DATA **store_lock(THD *thd,
>                               THR_LOCK_DATA **to,
>                               enum thr_lock_type lock_type);
> +  int delete_table(const char *name)
> +  {
> +    return 0;
> +  }
>  private:
>    virtual int write_row(const uchar *buf);
>    virtual int update_row(const uchar *old_data, const uchar *new_data);
> diff --git a/storage/connect/ha_connect.cc b/storage/connect/ha_connect.cc
> index 0194b08c792..b1b44085e53 100644
> --- a/storage/connect/ha_connect.cc
> +++ b/storage/connect/ha_connect.cc
> @@ -5192,7 +5192,8 @@ int ha_connect::delete_or_rename_table(const char *name, const char *to)
>          } // endif pos
>  
>        } // endif open_table_def
> -
> +      else
> +        rc= ENOENT;
>      free_table_share(share);
>    } else              // Temporary file
>      ok= true;
> diff --git a/storage/connect/mysql-test/connect/r/drop-open-error.result b/storage/connect/mysql-test/connect/r/drop-open-error.result
> index f0ad8553d8b..34f58a845dc 100644
> --- a/storage/connect/mysql-test/connect/r/drop-open-error.result
> +++ b/storage/connect/mysql-test/connect/r/drop-open-error.result
> @@ -2,6 +2,8 @@ create table t1 (c varchar(8));
>  create table tcon engine=connect table_type=mysql CONNECTION='mysql://root@localhost/test/t1' SRCDEF='select c from t1 where c in ("foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", 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"foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar", "foo", "bar", "qux", "foobar")';
>  ERROR HY000: Too long value for 'SRCDEF'
>  drop table mdev9949;
> +Warnings:
> +Warning 1017    Can't find file: './test/mdev9949.dos' (errno: 2 "No such file or directory")
>  drop table t1;
>  select @@secure_file_priv 'must be NULL';
>  must be NULL
> diff --git a/storage/federated/ha_federated.cc b/storage/federated/ha_federated.cc
> index 00168791d35..b62b74d12bb 100644
> --- a/storage/federated/ha_federated.cc
> +++ b/storage/federated/ha_federated.cc
> @@ -484,7 +484,8 @@ int federated_db_init(void *p)
>    federated_hton->commit= federated_commit;
>    federated_hton->rollback= federated_rollback;
>    federated_hton->create= federated_create_handler;
> -  federated_hton->flags= HTON_ALTER_NOT_SUPPORTED | HTON_NO_PARTITION;
> +  federated_hton->flags= (HTON_ALTER_NOT_SUPPORTED | HTON_NO_PARTITION |
> +                          HTON_AUTOMATIC_DELETE_TABLE);
>  
>    /*
>      Support for transactions disabled until WL#2952 fixes it.
> diff --git a/storage/federated/ha_federated.h b/storage/federated/ha_federated.h
> index 080d0ebd5f0..2e785f87858 100644
> --- a/storage/federated/ha_federated.h
> +++ b/storage/federated/ha_federated.h
> @@ -244,7 +244,10 @@ class ha_federated: public handler
>    void update_auto_increment(void);
>    int repair(THD* thd, HA_CHECK_OPT* check_opt);
>    int optimize(THD* thd, HA_CHECK_OPT* check_opt);
> -
> +  int delete_table(const char *name)
> +  {
> +    return 0;
> +  }
>    int delete_all_rows(void);
>    int truncate();
>    int create(const char *name, TABLE *form,
> diff --git a/storage/federatedx/ha_federatedx.cc b/storage/federatedx/ha_federatedx.cc
> index 6547964cc11..2370473236e 100644
> --- a/storage/federatedx/ha_federatedx.cc
> +++ b/storage/federatedx/ha_federatedx.cc
> @@ -438,7 +438,8 @@ int federatedx_db_init(void *p)
>    federatedx_hton->rollback= ha_federatedx::rollback;
>    federatedx_hton->discover_table_structure= ha_federatedx::discover_assisted;
>    federatedx_hton->create= federatedx_create_handler;
> -  federatedx_hton->flags= HTON_ALTER_NOT_SUPPORTED;
> +  federatedx_hton->flags= (HTON_ALTER_NOT_SUPPORTED |
> +                           HTON_AUTOMATIC_DELETE_TABLE);
>    federatedx_hton->create_derived= create_federatedx_derived_handler;
>    federatedx_hton->create_select= create_federatedx_select_handler;
>  
> diff --git a/storage/federatedx/ha_federatedx.h b/storage/federatedx/ha_federatedx.h
> index a62456e1c33..67fe5f8cc22 100644
> --- a/storage/federatedx/ha_federatedx.h
> +++ b/storage/federatedx/ha_federatedx.h
> @@ -431,7 +431,10 @@ class ha_federatedx: public handler
>    void update_auto_increment(void);
>    int repair(THD* thd, HA_CHECK_OPT* check_opt);
>    int optimize(THD* thd, HA_CHECK_OPT* check_opt);
> -
> +  int delete_table(const char *name)
> +  {
> +    return 0;
> +  }
>    int delete_all_rows(void);
>    int create(const char *name, TABLE *form,
>               HA_CREATE_INFO *create_info);                      //required
> diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
> index 6940f8ff3bd..97cfdb01d9f 100644
> --- a/storage/innobase/handler/ha_innodb.cc
> +++ b/storage/innobase/handler/ha_innodb.cc
> @@ -13347,5 +13347,18 @@ ha_innobase::discard_or_import_tablespace(
>  }
>  
>  /**
> +   @return 1 if frm file exists
> +   @return 0 if it doesn't exists
> +*/
> +
> +static bool frm_file_exists(const char *path)
> +{
> +  char buff[FN_REFLEN];
> +  strxnmov(buff, FN_REFLEN, path, reg_ext, NullS);
> +  return !access(buff, F_OK);
> +}
> +
> +
> +/**
>  Drops a table from an InnoDB database. Before calling this function,
>  MySQL calls innobase_commit to commit the transaction of the current user.
> @@ -13446,7 +13459,9 @@ inline int ha_innobase::delete_table(const char* name, enum_sql_command sqlcom)
>                  }
>          }
>  
> -        if (err == DB_TABLE_NOT_FOUND) {
> +        if (err == DB_TABLE_NOT_FOUND &&
> +            frm_file_exists(name))
> +        {
>                  /* Test to drop all tables which matches db/tablename + '#'.
>                  Only partitions can have '#' as non-first character in
>                  the table name!
> diff --git a/storage/mroonga/mrn_table.cpp b/storage/mroonga/mrn_table.cpp
> index b1b2db6161b..037a6a59487 100644
> --- a/storage/mroonga/mrn_table.cpp
> +++ b/storage/mroonga/mrn_table.cpp
> @@ -1080,6 +1080,7 @@ TABLE_SHARE *mrn_create_tmp_table_share(TABLE_LIST *table_list, const char *path
>    if (open_table_def(thd, share, GTS_TABLE))
>    {
>      *error = ER_CANT_OPEN_FILE;
> +    mrn_free_tmp_table_share(share);
>      DBUG_RETURN(NULL);
>    }
>    DBUG_RETURN(share);
> diff --git a/storage/myisam/mi_delete_table.c b/storage/myisam/mi_delete_table.c
> index 7990c3e8a80..d318b44720a 100644
> --- a/storage/myisam/mi_delete_table.c
> +++ b/storage/myisam/mi_delete_table.c
> @@ -28,19 +28,23 @@
>  
>  int mi_delete_table(const char *name)
>  {
> +  int error= 0;
>    DBUG_ENTER("mi_delete_table");
>  
>  #ifdef EXTRA_DEBUG
>    check_table_is_closed(name,"delete");
>  #endif
>  
> -  if (mysql_file_delete_with_symlink(mi_key_file_kfile, name, MI_NAME_IEXT, MYF(MY_WME)) ||
> -      mysql_file_delete_with_symlink(mi_key_file_dfile, name, MI_NAME_DEXT, MYF(MY_WME)))
> -    DBUG_RETURN(my_errno);
> +  if (mysql_file_delete_with_symlink(mi_key_file_kfile, name, MI_NAME_IEXT,
> +                                     MYF(MY_WME)))
> +    error= my_errno;
> +  if (mysql_file_delete_with_symlink(mi_key_file_dfile, name, MI_NAME_DEXT,
> +                                     MYF(MY_WME)))
> +    error= my_errno;
>  
>    // optionally present:
>    mysql_file_delete_with_symlink(mi_key_file_dfile, name, ".OLD", MYF(0));
>    mysql_file_delete_with_symlink(mi_key_file_dfile, name, ".TMD", MYF(0));
>  
> -  DBUG_RETURN(0);
> +  DBUG_RETURN(error);
>  }
> diff --git a/storage/perfschema/ha_perfschema.cc b/storage/perfschema/ha_perfschema.cc
> index 33d4c854c8b..c4c59d109f5 100644
> --- a/storage/perfschema/ha_perfschema.cc
> +++ b/storage/perfschema/ha_perfschema.cc
> @@ -95,10 +95,11 @@ static int pfs_init_func(void *p)
>  
>    pfs_hton->create= pfs_create_handler;
>    pfs_hton->show_status= pfs_show_status;
> -  pfs_hton->flags= HTON_ALTER_NOT_SUPPORTED |
> +  pfs_hton->flags= (HTON_ALTER_NOT_SUPPORTED |
>      HTON_TEMPORARY_NOT_SUPPORTED |
>      HTON_NO_PARTITION |
> -    HTON_NO_BINLOG_ROW_OPT;
> +                    HTON_NO_BINLOG_ROW_OPT |
> +                    HTON_AUTOMATIC_DELETE_TABLE);
>  
>    /*
>      As long as the server implementation keeps using legacy_db_type,
> diff --git a/storage/sequence/sequence.cc b/storage/sequence/sequence.cc
> index 8684a5c60b9..31522b8f3b7 100644
> --- a/storage/sequence/sequence.cc
> +++ b/storage/sequence/sequence.cc
> @@ -69,10 +69,15 @@ class ha_seq: public handler
>  
>    /* open/close/locking */
>    int create(const char *name, TABLE *table_arg,
> -             HA_CREATE_INFO *create_info) { return HA_ERR_WRONG_COMMAND; }
> +             HA_CREATE_INFO *create_info)
> +  { return HA_ERR_WRONG_COMMAND; }
>  
>    int open(const char *name, int mode, uint test_if_locked);
>    int close(void);
> +  int delete_table(const char *name)
> +  {
> +    return 0;
> +  }
>    THR_LOCK_DATA **store_lock(THD *, THR_LOCK_DATA **, enum thr_lock_type);
>  
>    /* table scan */
> @@ -503,6 +508,7 @@ static int init(void *p)
>    hton->savepoint_set= hton->savepoint_rollback= hton->savepoint_release=
>      dummy_savepoint;
>    hton->create_group_by= create_group_by_handler;
> +  hton->flags= HTON_AUTOMATIC_DELETE_TABLE;
>    return 0;
>  }
>  
> @@ -526,4 +532,3 @@ maria_declare_plugin(sequence)
>    MariaDB_PLUGIN_MATURITY_STABLE
>  }
>  maria_declare_plugin_end;
> -
> diff --git a/storage/sphinx/ha_sphinx.cc b/storage/sphinx/ha_sphinx.cc
> index 8403c767796..d60a4d229e6 100644
> --- a/storage/sphinx/ha_sphinx.cc
> +++ b/storage/sphinx/ha_sphinx.cc
> @@ -696,7 +696,7 @@ handlerton sphinx_hton =
>          NULL,   // create_cursor_read_view
>          NULL,   // set_cursor_read_view
>          NULL,   // close_cursor_read_view
> -        HTON_CAN_RECREATE
> +        HTON_CAN_RECREATE | HTON_AUTOMATIC_DELETE_TABLE
>  };
>  #else
>  static handlerton * sphinx_hton_ptr = NULL;
> @@ -749,7 +749,7 @@ static int sphinx_init_func ( void * p )
>                  hton->close_connection = sphinx_close_connection;
>                  hton->show_status = sphinx_show_status;
>                  hton->panic = sphinx_panic;
> -                hton->flags = HTON_CAN_RECREATE;
> +                hton->flags = HTON_CAN_RECREATE | HTON_AUTOMATIC_DELETE_TABLE;
>                  #endif
>          }
>          SPH_RET(0);
> diff --git a/storage/spider/spd_table.cc b/storage/spider/spd_table.cc
> index 1607dd07902..583bfebbed6 100644
> --- a/storage/spider/spd_table.cc
> +++ b/storage/spider/spd_table.cc
> @@ -7249,7 +7249,7 @@ int spider_db_init(
>    DBUG_ENTER("spider_db_init");
>    spider_hton_ptr = spider_hton;
>  
> -  spider_hton->flags = HTON_NO_FLAGS;
> +  spider_hton->flags = HTON_NO_FLAGS | HTON_AUTOMATIC_DELETE_TABLE;
>  #ifdef HTON_CAN_READ_CONNECT_STRING_IN_PARTITION
>    spider_hton->flags |= HTON_CAN_READ_CONNECT_STRING_IN_PARTITION;
>  #endif
 
Regards,
Sergei
VP of MariaDB Server Engineering
and security@xxxxxxxxxxx
Follow ups

Re: 250bc3b6d74: Ensure that table is truly dropped when using DROP TABLE
From: Michael Widenius, 2020-06-13