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Bug#39953 Triggers are not working properly with multi table

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updates

Attempt to execute trigger or stored function with multi-UPDATE
which used - but didn't update - a table that was also used by
the calling statement led to an error. Read-only reference to
tables used in the calling statement should be allowed.
 
This problem was caused by the fact that check for conflicting
use of tables in SP/triggers was performed in open_tables(),
and in case of multi-UPDATE we didn't know exact lock type at
this stage.

We solve the problem by moving this check to lock_tables(), so
it can be performed after exact lock types for tables used by
multi-UPDATE are determined.
This commit is contained in:
Staale Smedseng 2009-03-27 12:09:15 +01:00
parent 2005f3c72c
commit fce11a8bb1
3 changed files with 91 additions and 26 deletions
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20
mysql-test/r/trigger.result
View file

@ -1961,4 +1961,24 @@ select * from t2;
s1
drop table t1;
drop temporary table t2;
#------------------------------------------------------------------------
# Bug#39953 Triggers are not working properly with multi table updates
#------------------------------------------------------------------------
DROP TABLE IF EXISTS t1;
DROP TRIGGER IF EXISTS t_insert;
DROP TABLE IF EXISTS t2;
CREATE TABLE t1 (a int, date_insert timestamp, PRIMARY KEY (a));
INSERT INTO t1 (a) VALUES (2),(5);
CREATE TABLE t2 (a int, b int, PRIMARY KEY (a));
CREATE TRIGGER t_insert AFTER INSERT ON t2 FOR EACH ROW BEGIN UPDATE t1,t2 SET
date_insert=NOW() WHERE t1.a=t2.b AND t2.a=NEW.a; END |
INSERT INTO t2 (a,b) VALUES (1,2);
DROP TRIGGER t_insert;
CREATE TRIGGER t_insert AFTER INSERT ON t2 FOR EACH ROW BEGIN UPDATE t1,t2 SET
date_insert=NOW(),b=b+1 WHERE t1.a=t2.b AND t2.a=NEW.a; END |
INSERT INTO t2 (a,b) VALUES (3,5);
ERROR HY000: Can't update table 't2' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.
DROP TABLE t1;
DROP TRIGGER t_insert;
DROP TABLE t2;
End of 5.0 tests

33
mysql-test/t/trigger.test
View file

@ -2217,4 +2217,37 @@ select * from t1;
select * from t2;
drop table t1;
drop temporary table t2;
--echo #------------------------------------------------------------------------
--echo # Bug#39953 Triggers are not working properly with multi table updates
--echo #------------------------------------------------------------------------
--disable_warnings
DROP TABLE IF EXISTS t1;
DROP TRIGGER IF EXISTS t_insert;
DROP TABLE IF EXISTS t2;
--enable_warnings
CREATE TABLE t1 (a int, date_insert timestamp, PRIMARY KEY (a));
INSERT INTO t1 (a) VALUES (2),(5);
CREATE TABLE t2 (a int, b int, PRIMARY KEY (a));
DELIMITER |;
CREATE TRIGGER t_insert AFTER INSERT ON t2 FOR EACH ROW BEGIN UPDATE t1,t2 SET
date_insert=NOW() WHERE t1.a=t2.b AND t2.a=NEW.a; END |
DELIMITER ;|
INSERT INTO t2 (a,b) VALUES (1,2);
DROP TRIGGER t_insert;
DELIMITER |;
CREATE TRIGGER t_insert AFTER INSERT ON t2 FOR EACH ROW BEGIN UPDATE t1,t2 SET
date_insert=NOW(),b=b+1 WHERE t1.a=t2.b AND t2.a=NEW.a; END |
DELIMITER ;|
--error ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG
INSERT INTO t2 (a,b) VALUES (3,5);
DROP TABLE t1;
DROP TRIGGER t_insert;
DROP TABLE t2;
--echo End of 5.0 tests

64
sql/sql_base.cc
View file

@ -1596,27 +1596,11 @@ 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))
{
if (check_if_used && table->query_id &&
table->query_id != thd->query_id)
{
/*
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))
@ -1640,13 +1624,13 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
{
best_distance= distance;
best_table= table;
if (best_distance == 0 && !check_if_used)
if (best_distance == 0)
{
/*
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.
We have found a perfect match and can finish iterating
through open tables list. Check for table use conflict
between calling statement and SP/trigger is done in
lock_tables().
*/
break;
}
@ -2944,9 +2928,9 @@ static bool check_lock_and_start_stmt(THD *thd, TABLE *table,
lock_type Lock to use for open
NOTE
This function don't do anything like SP/SF/views/triggers analysis done
in open_tables(). It is intended for opening of only one concrete table.
And used only in special contexts.
This function doesn't do anything like SP/SF/views/triggers analysis done
in open_tables()/lock_tables(). It is intended for opening of only one
concrete table. And used only in special contexts.
RETURN VALUES
table Opened table
@ -3262,8 +3246,36 @@ int lock_tables(THD *thd, TABLE_LIST *tables, uint count, bool *need_reopen)
TABLE_LIST *first_not_own= thd->lex->first_not_own_table();
for (table= tables; table != first_not_own; table= table->next_global)
{
if (!table->placeholder() &&
check_lock_and_start_stmt(thd, table->table, table->lock_type))
if (table->placeholder())
continue;
/*
In a stored function or trigger we should ensure that we won't change
a table that is already used by the calling statement.
*/
if (thd->prelocked_mode &&
table->lock_type >= TL_WRITE_ALLOW_WRITE)
{
for (TABLE* opentab= thd->open_tables; opentab; opentab= opentab->next)
{
/*
issue an error if the tables are the same (by key comparison),
but query_id isn't
*/
if (opentab->query_id &&
table->table->query_id != opentab->query_id &&
table->table->s->key_length == opentab->s->key_length &&
!memcmp(table->table->s->table_cache_key,
opentab->s->table_cache_key, opentab->s->key_length))
{
my_error(ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG, MYF(0),
table->table->s->table_name);
DBUG_RETURN(-1);
}
}
}
if (check_lock_and_start_stmt(thd, table->table, table->lock_type))
{
ha_rollback_stmt(thd);
DBUG_RETURN(-1);