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Fix for bug #11896 "Partial locking in case of recursive trigger definitions".

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If we are in stored function or trigger we should ensure that we won't change
table that is already used by calling statement (this can damage table or
easily cause infinite loops). Particularly this means that recursive triggers
should be disallowed.
This commit is contained in:
dlenev@mysql.com
2005-08-18 19:07:23 +04:00
parent 1006063ef1
commit 6c39364f85
6 changed files with 188 additions and 24 deletions
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74
sql/sql_base.cc
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@@ -1046,35 +1046,61 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
{ // Using table locks
TABLE *best_table= 0;
int best_distance= INT_MIN;
bool check_if_used= thd->prelocked_mode &&
((int) table_list->lock_type >=
(int) TL_WRITE_ALLOW_WRITE);
for (table=thd->open_tables; table ; table=table->next)
{
if (table->s->key_length == key_length &&
!memcmp(table->s->table_cache_key, key, key_length) &&
!my_strcasecmp(system_charset_info, table->alias, alias) &&
table->query_id != thd->query_id && /* skip tables already used */
!(thd->prelocked_mode && table->query_id))
!memcmp(table->s->table_cache_key, key, key_length))
{
int distance= ((int) table->reginfo.lock_type -
(int) table_list->lock_type);
/*
Find a table that either has the exact lock type requested,
or has the best suitable lock. In case there is no locked
table that has an equal or higher lock than requested,
we us the closest matching lock to be able to produce an error
message about wrong lock mode on the table. The best_table is changed
if bd < 0 <= d or bd < d < 0 or 0 <= d < bd.
distance < 0 - No suitable lock found
distance > 0 - we have lock mode higher then we require
distance == 0 - we have lock mode exactly which we need
*/
if (best_distance < 0 && distance > best_distance ||
distance >= 0 && distance < best_distance)
if (check_if_used && table->query_id &&
table->query_id != thd->query_id)
{
best_distance= distance;
best_table= table;
if (best_distance == 0) // Found perfect lock
break;
/*
If we are in stored function or trigger we should ensure that
we won't change table that is already used by calling statement.
So if we are opening table for writing, we should check that it
is not already open by some calling stamement.
*/
my_error(ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG, MYF(0),
table->s->table_name);
DBUG_RETURN(0);
}
if (!my_strcasecmp(system_charset_info, table->alias, alias) &&
table->query_id != thd->query_id && /* skip tables already used */
!(thd->prelocked_mode && table->query_id))
{
int distance= ((int) table->reginfo.lock_type -
(int) table_list->lock_type);
/*
Find a table that either has the exact lock type requested,
or has the best suitable lock. In case there is no locked
table that has an equal or higher lock than requested,
we us the closest matching lock to be able to produce an error
message about wrong lock mode on the table. The best_table
is changed if bd < 0 <= d or bd < d < 0 or 0 <= d < bd.
distance < 0 - No suitable lock found
distance > 0 - we have lock mode higher then we require
distance == 0 - we have lock mode exactly which we need
*/
if (best_distance < 0 && distance > best_distance ||
distance >= 0 && distance < best_distance)
{
best_distance= distance;
best_table= table;
if (best_distance == 0 && !check_if_used)
{
/*
If we have found perfect match and we don't need to check that
table is not used by one of calling statements (assuming that
we are inside of function or trigger) we can finish iterating
through open tables list.
*/
break;
}
}
}
}
}