MySQL Bugs: #44081: Lock with Unique Key in NDB Cluster

Bug #44081	Lock with Unique Key in NDB Cluster
Submitted:	3 Apr 2009 18:28	Modified:	9 Apr 2009 13:55
Reporter:	Emerson Yoshinaga	Email Updates:
Status:	Won't fix	Impact on me:	None
Category:	MySQL Cluster: Cluster (NDB) storage engine	Severity:	S2 (Serious)
Version:	mysql-5.1-telco-6.3.14, 6.4.2	OS:	Linux (Ubuntu Hardy )
Assigned to:	Assigned Account	CPU Architecture:	Any
Tags:	lock, ndb, unique key

Description:
We are facing problems while a transaction is started and selecting a row using a unique key field. This select is not using "for update" command.
In a second client we try to update the same row but the statement keeps locked while the transaction is not release for any reason.

We also tried in a innodb engine in the other hand the statement was not locked.

Is this a cluster limitation or a bug?

How to repeat:
1. Create table nbdcluster engine:
create table t1 (
	col1 tinyint unsigned not null, 
	col2 tinyint unsigned not null, 
	col3 varchar(100), 
	unique key uk1 (col2), 
	primary key (col1)
) engine=ndbcluster;

2. Insert data into the table

insert into t1 values (1,1,'foo1');

start transaction; select * from t1 where col2 = 1;

3. In antoher client session try to update the same row:

update t1 set col3 = 'foo123' where col1 = 1;

Here we have our statement locked!!!

4. Release the transaction in the first client.

rollback;

5. Now we have the update statement executed in the second client!!!

Thank you for the report.

Verified as described.

Hi,

This behavior is a "fact" about our unique index impl.
I.e it has been this since day one.

This bug is not scheduled to be fixed at this time.