090322 20:24:24 [Note] Event Scheduler: Loaded 0 events                         
090322 20:24:24 [Note] 6.0in/libexec/mysqld: ready for connections.             
Version: '6.0.11-alpha-debug'  socket: '/tmp/mysql.sock'  port: 3306  Source distribution
090322 20:25:10 - mysqld got signal 11 ;                                                 
This could be because you hit a bug. It is also possible that this binary                
or one of the libraries it was linked against is corrupt, improperly built,              
or misconfigured. This error can also be caused by malfunctioning hardware.              
We will try our best to scrape up some info that will hopefully help diagnose            
the problem, but since we have already crashed, something is definitely wrong            
and this may fail.                                                                       

key_buffer_size=8384512
read_buffer_size=131072
max_used_connections=1 
max_threads=151        
thread_count=1         
connection_count=1     
It is possible that mysqld could use up to 
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 338433 K
bytes of memory                                                               
Hope that's ok; if not, decrease some variables in the equation.              

thd: 0x421ad38
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went   
terribly wrong...                                                      
stack_bottom = 0x40e1a100 thread_stack 0x40000                         
6.0in/libexec/mysqld(my_print_stacktrace+0x32) [0xdcae84]              
6.0in/libexec/mysqld(handle_segfault+0x2a6) [0x75ba88]                 
/lib/libpthread.so.0 [0x7f0aa84590f0]                                  
6.0in/libexec/mysqld [0x801c9d]                                        
6.0in/libexec/mysqld [0x8040ff]                                        
6.0in/libexec/mysqld(JOIN::optimize()+0xb50) [0x8079bc]                
6.0in/libexec/mysqld(subselect_single_select_engine::exec()+0xe2) [0x707060]
6.0in/libexec/mysqld(Item_subselect::exec()+0x6e) [0x70c0a6]                
6.0in/libexec/mysqld(Item_exists_subselect::val_bool()+0x47) [0x70422b]     
6.0in/libexec/mysqld(Item_cond_and::val_int()+0x65) [0x6c658f]              
6.0in/libexec/mysqld [0x7f87bb]                                             
6.0in/libexec/mysqld(JOIN::optimize()+0x12fe) [0x80816a]                    
6.0in/libexec/mysqld(mysql_select(THD*, Item***, TABLE_LIST*, unsigned int, List<Item>&, Item*, unsigned int, st_order*, st_order*, Item*, st_order*, unsigned long long, select_result*, st_select_lex_unit*, st_select_lex*)+0x27d) [0x80c3ce]                                          
6.0in/libexec/mysqld(handle_select(THD*, LEX*, select_result*, unsigned long)+0x1de) [0x811dad]                                              
6.0in/libexec/mysqld [0x76d237]                                                                                                              
6.0in/libexec/mysqld(mysql_execute_command(THD*)+0x7e5) [0x76e826]                                                                           
6.0in/libexec/mysqld(Prepared_statement::execute(String*, bool)+0x510) [0x825894]                                                            
6.0in/libexec/mysqld(Prepared_statement::execute_loop(String*, bool, unsigned char*, unsigned char*)+0xf6) [0x82978a]                        
6.0in/libexec/mysqld(mysql_sql_stmt_execute(THD*)+0x156) [0x829a07]                                                                          
6.0in/libexec/mysqld(mysql_execute_command(THD*)+0x810) [0x76e851]                                                                           
6.0in/libexec/mysqld(mysql_parse(THD*, char const*, unsigned int, char const**)+0x273) [0x7769c9]                                            
6.0in/libexec/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0xa69) [0x7775c6]                                      
6.0in/libexec/mysqld(do_command(THD*)+0x22b) [0x778b5d]                                                                                      
6.0in/libexec/mysqld(handle_one_connection+0x11c) [0x765965]                                                                                 
/lib/libpthread.so.0 [0x7f0aa84513ea]                                                                                                        
/lib/libc.so.6(clone+0x6d) [0x7f0aa73c3cbd]                                                                                                  
Trying to get some variables.                                                                                                                
Some pointers may be invalid and cause the dump to abort...
thd->query at 0x4495230 = select distinct t1.partner_id
from t1 left join t3 on t1.id = t3.id
     left join t1 pp on pp.id = t3.preceeding_id
where
  exists (
    select *
    from t2 as pl_inner
    where pl_inner.id = t1.id
    and pl_inner.sequence <= (
      select min(sequence) from t2 pl_seqnr
      where pl_seqnr.id = t1.id
    )
    and exists (
      select * from t4
      where t4.article_id = pl_inner.article_id
      and t4.user_id = ?
    )
  )
  and t1.id = ?
group by t1.id
having count(pp.id) = 0
thd->thread_id=1
thd->killed=NOT_KILLED
The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains
information that should help you find out what is causing the crash.
Segmentation fault
miguel@hegel:~/dbs$