Bug #40543 ReadCommitted might theoretically read stale data
Submitted: 6 Nov 2008 9:55 Modified: 6 Nov 2008 19:19
Reporter: Jonas Oreland Email Updates:
Status: Closed Impact on me:
Category:MySQL Cluster: Cluster (NDB) storage engine Severity:S3 (Non-critical)
Version:* OS:Any
Assigned to: Jonas Oreland CPU Architecture:Any

[6 Nov 2008 9:55] Jonas Oreland
There is a theoretical possibility for the following scenario
insert t1 values (a=1,b=1)
update t1 set b = 2 where a = 1;
select b from t1 where a = 1; // return 1!!!

The select should of course return 2,
This behavior has never been observed wo/ instrumenting code

How to repeat:
see above

Suggested fix:
For committed read to read from primary replica
[6 Nov 2008 10:04] Bugs System
A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:


2717 Jonas Oreland	2008-11-06
      ndb - bug#40543 ReadCommitted might theoretically read stale data
[6 Nov 2008 10:10] Bugs System
Pushed into 5.1.29-ndb-6.3.19  (revid:jonas@mysql.com-20081106100840-fxb98icp0tgzh5ed) (version source revid:jonas@mysql.com-20081106100948-jdmo3tc971tw2va5) (pib:5)
[6 Nov 2008 10:12] Bugs System
Pushed into 5.1.29-ndb-6.4.0  (revid:jonas@mysql.com-20081106100840-fxb98icp0tgzh5ed) (version source revid:jonas@mysql.com-20081106101337-py5fx94c1sfivcca) (pib:5)
[6 Nov 2008 10:13] Bugs System
Pushed into 5.1.29-ndb-6.2.17  (revid:jonas@mysql.com-20081106100840-fxb98icp0tgzh5ed) (version source revid:jonas@mysql.com-20081106100840-fxb98icp0tgzh5ed) (pib:5)
[6 Nov 2008 19:19] Jon Stephens
Documented in the NDB-6.2.17 and NDB-6.3.19 changelogs as follows:

        It was theoretically possible for stale data to be read from NDBCLUSTER
        tables when the transaction isolation level was set to ReadCommitted.
[12 Dec 2008 23:29] Bugs System
Pushed into 6.0.9-alpha  (revid:jonas@mysql.com-20081106100840-fxb98icp0tgzh5ed) (version source revid:tomas.ulin@sun.com-20081209185954-9svcixh2p5hsfi6w) (pib:5)
[23 Jan 2009 8:34] Tomas Ulin
this commit id is also part of bug fix but has not been tagged as such