MySQL Bugs: #34275: mysqld leak if doing multiple statements within same transaction (or wo/ trans)

Bug #34275	mysqld leak if doing multiple statements within same transaction (or wo/ trans)
Submitted:	4 Feb 2008 12:35	Modified:	20 Feb 2008 21:07
Reporter:	Jonas Oreland	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Cluster: Cluster (NDB) storage engine	Severity:	S3 (Non-critical)
Version:	5.1	OS:	Any
Assigned to:	Tomas Ulin	CPU Architecture:	Any

Description:
begin;
select * from kalle; // here 32 bytes are allocated
select * from kalle; // here 32 bytes are allocated
...

commit; // here 32 x X bytes are released

How to repeat:
run above, watch mysqld memory consumption

Suggested fix:
dont clear open_tables hash at every statement
this leads to get_open_table not finding it in hash, making allocate 32 bytes
  and transaction memroot.

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:

  http://lists.mysql.com/commits/41652

ChangeSet@1.2674, 2008-02-04 15:40:04+01:00, tomas@poseidon.ndb.mysql.com +2 -0
  Bug #34275 mysqld leak if doing multiple statements within same transaction (or wo/ trans)
  - in autocommit do not allocate statistics share, but instead use one directly on the handler

Documented bugfix in 5.1.23-ndb-6.3.9 changelog as follows:

        Performing many SQL statements within a single transaction, or
        in AUTOCOMMIT mode, on NDB tables caused a memory leak in
        mysqld.

Left in PQ status pending further merges.

Also documented for 5.1.23-ndb-6.2.12.

I stand corrected, problem only occurs in auto-commit mode.
I.e not when starting with "begin"

Pushed into 5.1.24-rc

Pushed into 6.0.5-alpha

Updated changelog entry per note from Jonas.

Fix also now documented for 5.1.24 and 6.0.5.