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Fix for bugs#12472/#15137 'CREATE TABLE ... SELECT ... which explicitly

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or implicitly uses stored function gives "Table not locked" error'

CREATE TABLE ... SELECT ... statement which was explicitly or implicitly
(through view) using stored function gave "Table not locked" error.

The actual bug resides in the current locking scheme of CREATE TABLE SELECT
code, which first opens and locks tables of the SELECT statement itself,
and then, having SELECT tables locked, creates the .FRM, opens the .FRM and
acquires lock on it. This scheme opens a possibility for a deadlock, which
was present and ignored since version 3.23 or earlier. This scheme also
conflicts with the invariant of the prelocking algorithm -- no table can
be open and locked while there are tables locked in prelocked mode.

The patch makes an exception for this invariant when doing CREATE TABLE ...
SELECT, thus extending the possibility of a deadlock to the prelocked mode.
We can't supply a better fix in 5.0.


mysql-test/r/sp.result:
  Added tests for bugs#12472/#15137 'CREATE TABLE ... SELECT ... which
  explicitly or implicitly uses stored function gives "Table not locked" error'
mysql-test/t/sp.test:
  Added tests for bugs#12472/#15137 'CREATE TABLE ... SELECT ... which
  explicitly or implicitly uses stored function gives "Table not locked" error'
sql/mysql_priv.h:
  Added flag which can be passed to open_table() routine in order to ignore
  set of locked tables and prelocked mode.
  We don't need declaration of create_table_from_items() any longer as it was
  moved into sql_insert.cc and made static.
sql/sql_base.cc:
  open_table():
    Added flag which allows open table ignoring set of locked tables and
    prelocked mode.
sql/sql_insert.cc:
  Moved create_table_from_items() from sql_table.cc to sql_insert.cc as it was
  not used outside of sql_insert.cc and contains code which is specific for
  CREATE TABLE ... SELECT.
  Also now when we are executing CREATE TABLE ... SELECT ... statement which
  SELECT part requires execution in prelocked mode we ignore set of locked
  tables in order to get access to the table we just have created.
  We probably don't want to do this if we are under real LOCK TABLES since
  it will widen window for deadlock too much.
sql/sql_table.cc:
  Moved create_table_from_items() routine into sql_insert.cc, since it was not
  used anywhere outside of this file and contains logic which is specific for
  CREATE TABLE ... SELECT statement.
This commit is contained in:
unknown
2006-05-09 16:39:11 +04:00
parent 6ef757e411
commit 4f15a043e2
6 changed files with 201 additions and 107 deletions
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147
sql/sql_insert.cc
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@ -2434,6 +2434,153 @@ bool select_insert::send_eof()
CREATE TABLE (SELECT) ...
***************************************************************************/
/*
Create table from lists of fields and items (or open existing table
with same name).
SYNOPSIS
create_table_from_items()
thd in Thread object
create_info in Create information (like MAX_ROWS, ENGINE or
temporary table flag)
create_table in Pointer to TABLE_LIST object providing database
and name for table to be created or to be open
extra_fields in/out Initial list of fields for table to be created
keys in List of keys for table to be created
items in List of items which should be used to produce rest
of fields for the table (corresponding fields will
be added to the end of 'extra_fields' list)
lock out Pointer to the MYSQL_LOCK object for table created
(open) will be returned in this parameter. Since
this table is not included in THD::lock caller is
responsible for explicitly unlocking this table.
NOTES
If 'create_info->options' bitmask has HA_LEX_CREATE_IF_NOT_EXISTS
flag and table with name provided already exists then this function will
simply open existing table.
Also note that create, open and lock sequence in this function is not
atomic and thus contains gap for deadlock and can cause other troubles.
Since this function contains some logic specific to CREATE TABLE ... SELECT
it should be changed before it can be used in other contexts.
RETURN VALUES
non-zero Pointer to TABLE object for table created or opened
0 Error
*/
static TABLE *create_table_from_items(THD *thd, HA_CREATE_INFO *create_info,
TABLE_LIST *create_table,
List<create_field> *extra_fields,
List<Key> *keys, List<Item> *items,
MYSQL_LOCK **lock)
{
TABLE tmp_table; // Used during 'create_field()'
TABLE *table= 0;
uint select_field_count= items->elements;
/* Add selected items to field list */
List_iterator_fast<Item> it(*items);
Item *item;
Field *tmp_field;
bool not_used;
DBUG_ENTER("create_table_from_items");
tmp_table.alias= 0;
tmp_table.timestamp_field= 0;
tmp_table.s= &tmp_table.share_not_to_be_used;
tmp_table.s->db_create_options=0;
tmp_table.s->blob_ptr_size= portable_sizeof_char_ptr;
tmp_table.s->db_low_byte_first= test(create_info->db_type == DB_TYPE_MYISAM ||
create_info->db_type == DB_TYPE_HEAP);
tmp_table.null_row=tmp_table.maybe_null=0;
while ((item=it++))
{
create_field *cr_field;
Field *field;
if (item->type() == Item::FUNC_ITEM)
field=item->tmp_table_field(&tmp_table);
else
field=create_tmp_field(thd, &tmp_table, item, item->type(),
(Item ***) 0, &tmp_field, 0, 0, 0, 0, 0);
if (!field ||
!(cr_field=new create_field(field,(item->type() == Item::FIELD_ITEM ?
((Item_field *)item)->field :
(Field*) 0))))
DBUG_RETURN(0);
if (item->maybe_null)
cr_field->flags &= ~NOT_NULL_FLAG;
extra_fields->push_back(cr_field);
}
/*
create and lock table
We don't log the statement, it will be logged later.
If this is a HEAP table, the automatic DELETE FROM which is written to the
binlog when a HEAP table is opened for the first time since startup, must
not be written: 1) it would be wrong (imagine we're in CREATE SELECT: we
don't want to delete from it) 2) it would be written before the CREATE
TABLE, which is a wrong order. So we keep binary logging disabled when we
open_table().
NOTE: By locking table which we just have created (or for which we just have
have found that it already exists) separately from other tables used by the
statement we create potential window for deadlock.
TODO: create and open should be done atomic !
*/
{
tmp_disable_binlog(thd);
if (!mysql_create_table(thd, create_table->db, create_table->table_name,
create_info, *extra_fields, *keys, 0,
select_field_count))
{
/*
If we are here in prelocked mode we either create temporary table
or prelocked mode is caused by the SELECT part of this statement.
*/
DBUG_ASSERT(!thd->prelocked_mode ||
create_info->options & HA_LEX_CREATE_TMP_TABLE ||
thd->lex->requires_prelocking());
/*
NOTE: We don't want to ignore set of locked tables here if we are
under explicit LOCK TABLES since it will open gap for deadlock
too wide (and also is not backward compatible).
*/
if (! (table= open_table(thd, create_table, thd->mem_root, (bool*) 0,
(MYSQL_LOCK_IGNORE_FLUSH |
((thd->prelocked_mode == PRELOCKED) ?
MYSQL_OPEN_IGNORE_LOCKED_TABLES:0)))))
quick_rm_table(create_info->db_type, create_table->db,
table_case_name(create_info, create_table->table_name));
}
reenable_binlog(thd);
if (!table) // open failed
DBUG_RETURN(0);
}
/*
FIXME: What happens if trigger manages to be created while we are
obtaining this lock ? May be it is sensible just to disable
trigger execution in this case ? Or will MYSQL_LOCK_IGNORE_FLUSH
save us from that ?
*/
table->reginfo.lock_type=TL_WRITE;
if (! ((*lock)= mysql_lock_tables(thd, &table, 1,
MYSQL_LOCK_IGNORE_FLUSH, &not_used)))
{
VOID(pthread_mutex_lock(&LOCK_open));
hash_delete(&open_cache,(byte*) table);
VOID(pthread_mutex_unlock(&LOCK_open));
quick_rm_table(create_info->db_type, create_table->db,
table_case_name(create_info, create_table->table_name));
DBUG_RETURN(0);
}
table->file->extra(HA_EXTRA_WRITE_CACHE);
DBUG_RETURN(table);
}
int
select_create::prepare(List<Item> &values, SELECT_LEX_UNIT *u)
{