MySQL Bugs: #9045: Lock wait timeout when using table with TEXT column

Bug #9045	Lock wait timeout when using table with TEXT column
Submitted:	8 Mar 2005 10:09	Modified:	8 Mar 2005 10:37
Reporter:	Magnus Blåudd	Email Updates:
Status:	Won't fix	Impact on me:	None
Category:	MySQL Cluster: Cluster (NDB) storage engine	Severity:	S3 (Non-critical)
Version:		OS:	Any
Assigned to:	Assigned Account	CPU Architecture:	Any

Description:
When performing an updating transaction on a table with TEXT column and selecting on the same table from another thread the error "Lock wait timeout exceeded is returned"(ndb error: 274  message: Time-out in NDB, probably caused by deadlock)

This can seem normal, but if the TEXT column is changed to a varchar(20), the same test works without this problem.

How to repeat:
Run the below test uing mysql-test-run:

-- source include/have_ndb.inc

--disable_warnings
drop table if exists t1, t5;
--enable_warnings

CREATE TABLE t1 (
  pk int not null primary key,
  a1 int,
  b1 int not null,
  c1 varchar(20)
) ENGINE=ndb;
CREATE TABLE t5 (
  pk int not null primary key,
  a5 int,
  b5 int not null,
  c5 TEXT 
) ENGINE=ndbcluster;

## NOTE! If the TEXT column is changed to varchar(20), test passes

insert into t1 value (1, 2, 3, 'First row');
insert into t5 value (1, 2, 3, '5 - First row');

connect (con1,localhost,root,,);
connection con1;
begin;
update t1 set a1=9 where pk=1;
update t5 set a5=9 where pk=1;
connect (con2,localhost,root,,);
connection con2;
use test;
select * from t1 order by pk desc;
# This is the failing query
select * from t5;
connection con1;
select * from t1 order by pk desc;
select * from t5;
commit;

drop table t1, t5;

Hi magnus!

This bug is due to the impl. of blobs as "separate" rows.
(Text are impl. as blobs)

Since it's multiple rows, one can not read committed (i.e wo/ lock)

This can be fixed using sequence no's, but that's quite a big job.

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