Hello Jon Olav!
* Dmitry Lenev <Dmitry.Lenev@stripped> [10/10/05 10:38]:
> * Jon Olav Hauglid <jon.hauglid@stripped> [10/10/04 13:32]:
> > === modified file 'sql/sql_base.cc'
> > --- a/sql/sql_base.cc 2010-09-30 13:29:12 +0000
> > +++ b/sql/sql_base.cc 2010-10-04 09:23:26 +0000
> > @@ -2742,8 +2742,11 @@ bool open_table(THD *thd, TABLE_LIST *ta
> > 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 (((best_distance < 0 && distance > best_distance)
> ||
> > + (distance >= 0 && distance < best_distance))
> &&
> > + ((flags & (MYSQL_OPEN_FORCE_SHARED_MDL |
> > + MYSQL_OPEN_FORCE_SHARED_HIGH_PRIO_MDL)) ||
> > +
> table->mdl_ticket->has_stronger_or_equal_type(table_list->mdl_request.type)))
> > {
> > best_distance= distance;
> > best_table= table;
> >
>
> The following patch:
>
> === modified file 'sql/sql_base.cc'
> --- sql/sql_base.cc 2010-09-30 13:29:12 +0000
> +++ sql/sql_base.cc 2010-10-05 05:59:40 +0000
> @@ -2730,6 +2730,12 @@ bool open_table(THD *thd, TABLE_LIST *ta
> int distance= ((int) table->reginfo.lock_type -
> (int) table_list->lock_type);
>
> + if (table_list->mdl_request.type >= MDL_SHARED_NO_WRITE &&
> + ! (flags & (MYSQL_OPEN_FORCE_SHARED_MDL |
> + MYSQL_OPEN_FORCE_SHARED_HIGH_PRIO_MDL)) &&
> + ! table->mdl_ticket->is_upgradable_or_exclusive())
> + distance= -1;
> +
> /*
> Find a table that either has the exact lock type requested,
> or has the best suitable lock. In case there is no locked
>
>
> fixes the bug as well.
>
> OTOH it doesn't change error codes and messages in so many cases.
>
> So maybe we should follow this approach instead?
I have discussed this bug with Kostja.
He thinks that solution for this MERGE-specific problem should be
localized to MERGE-specific code rather than change code handling
general case.
So here is yet another alternative fix which satisfies this
requirement:
=== modified file 'mysql-test/r/merge.result'
--- mysql-test/r/merge.result 2010-09-30 10:43:43 +0000
+++ mysql-test/r/merge.result 2010-10-05 08:22:56 +0000
@@ -3486,12 +3486,13 @@ ALTER TABLE m1 ADD INDEX (c1);
UNLOCK TABLES;
DROP TABLE m1, t1;
#
-# Locking the merge table will implicitly lock children.
+# Locking the merge table won't implicitly lock children.
#
CREATE TABLE t1 (c1 INT);
CREATE TABLE m1 (c1 INT) ENGINE=MRG_MyISAM UNION=(t1);
LOCK TABLE m1 WRITE;
ALTER TABLE t1 ADD INDEX (c1);
+ERROR HY000: Table 't1' was locked with a READ lock and can't be updated
LOCK TABLE m1 WRITE, t1 WRITE;
ALTER TABLE t1 ADD INDEX (c1);
UNLOCK TABLES;
=== modified file 'mysql-test/t/merge.test'
--- mysql-test/t/merge.test 2010-09-30 10:43:43 +0000
+++ mysql-test/t/merge.test 2010-10-05 08:22:19 +0000
@@ -2600,11 +2600,12 @@ UNLOCK TABLES;
DROP TABLE m1, t1;
--echo #
---echo # Locking the merge table will implicitly lock children.
+--echo # Locking the merge table won't implicitly lock children.
--echo #
CREATE TABLE t1 (c1 INT);
CREATE TABLE m1 (c1 INT) ENGINE=MRG_MyISAM UNION=(t1);
LOCK TABLE m1 WRITE;
+--error ER_TABLE_NOT_LOCKED_FOR_WRITE
ALTER TABLE t1 ADD INDEX (c1);
LOCK TABLE m1 WRITE, t1 WRITE;
ALTER TABLE t1 ADD INDEX (c1);
=== modified file 'storage/myisammrg/ha_myisammrg.cc'
--- storage/myisammrg/ha_myisammrg.cc 2010-09-08 08:25:37 +0000
+++ storage/myisammrg/ha_myisammrg.cc 2010-10-05 08:05:35 +0000
@@ -478,8 +478,10 @@ int ha_myisammrg::add_children_list(void
/* Set the expected table version, to not cause spurious re-prepare.
* */
child_l->set_table_ref_id(mrg_child_def->get_child_table_ref_type(),
mrg_child_def->get_child_def_version());
- /* Use the same metadata lock type for children. */
- child_l->mdl_request.set_type(parent_l->mdl_request.type);
+
+ if (! thd->locked_tables_mode &&
+ parent_l->mdl_request.type == MDL_SHARED_NO_WRITE)
+ child_l->mdl_request.set_type(MDL_SHARED_NO_WRITE);
/* Link TABLE_LIST object into the children list. */
if (this->children_last_l)
child_l->prev_global= this->children_last_l;
What do you think about this approach?
--
Dmitry Lenev, Software Developer
Oracle Development SPB/MySQL, www.mysql.com
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