Dear MonetDB developers,

I am currently experiencing segmentation faults on SQL-based data processing using the MonetDB Nov2009 branch. As the processing is rather complex, I don't know when I will be able to isolate a test case. Based on the clues I gathered (see below), could you give me some pointers on how to investigate further?

It always crashes on this query:

DELETE FROM progress WHERE EXISTS ( SELECT true FROM finalization WHERE finalization.id=progress.id AND finalization.category=active );

The related tables are defined like this:

CREATE TABLE progress ( id VARCHAR(32), attempt INTEGER, clearance INTEGER, PRIMARY KEY (id) );

CREATE TABLE finalization ( category VARCHAR(32), id VARCHAR(32), governing VARCHAR(64), sub_governing VARCHAR(64), domain VARCHAR(64), reason VARCHAR(16), epoch INTEGER, size INTEGER, PRIMARY KEY (category,id,governing,sub_governing,domain,reason,epoch) );

On the crash, the stack backtrace always looks like this:

Program received signal SIGSEGV, Segmentation fault. [Switching to Thread 0x42006940 (LWP 17625)] 0x00002b8e691fdad8 in strCmp (l=0x2aaab97c6a20 "06EED104D173", r=0xdbdbdbdbe98848f3 <Address 0xdbdbdbdbe98848f3 out of bounds>) at gdk_atoms.mx:1855 1855 return GDK_STRCMP(l, r); (gdb) bt #0 0x00002b8e691fdad8 in strCmp (l=0x2aaab97c6a20 "06EED104D173", r=0xdbdbdbdbe98848f3 <Address 0xdbdbdbdbe98848f3 out of bounds>) at gdk_atoms.mx:1855 #1 0x00002b8e693d7322 in BAThashjoin (l=0x2aaab9417188, r=0xd614ba0, estimate=9223372036854775807) at gdk_relop.mx:452 #2 0x00002b8e6940e151 in batjoin (l=0x2aaab9417188, r=0xd614ba0, estimate=9223372036854775807, swap=1 '\001') at gdk_relop.mx:1244 #3 0x00002b8e6940e193 in BATjoin (l=0x2aaab9417188, r=0xd614ba0, estimate=9223372036854775807) at gdk_relop.mx:1251 #4 0x00002aaaaafd105e in CMDjoin () from /opt/monetdb-nov2009/lib64/MonetDB5/lib/lib_algebra.so.5 #5 0x00002aaaaaffcef5 in ALGjoinestimate () from /opt/monetdb-nov2009/lib64/MonetDB5/lib/lib_algebra.so.5 #6 0x00002aaaaaffcfc1 in ALGjoin () from /opt/monetdb-nov2009/lib64/MonetDB5/lib/lib_algebra.so.5 #7 0x00002b8e6868b106 in DFLOWstep () from /opt/monetdb-nov2009/lib64/libmonetdb5.so.5 #8 0x00002b8e6868ed7d in runDFLOWworker () from /opt/monetdb-nov2009/lib64/libmonetdb5.so.5 #9 0x00000039d04064a7 in start_thread () from /lib64/libpthread.so.0 #10 0x00000039cf8d3c2d in clone () from /lib64/libc.so.6

The second argument's address to the comparison at the top has always one or more 0xdb memory deletion markers, so it looks like it is at least overlapping with deleted space.

Please note that I could not create a backtrace with full symbols as the error does not occur with the MonetDB5 module being compiled with debugging enabled.

Best regards,

Isidor