On 06 Jun 2016, at 21:36, Martin Kersten <martin@monetdb.org> wrote:

Hi

Please provide information on which MonetDB release and platform you are using.

Ou, sorry for forgetting this. This is Ubuntu, 14.04.3 LTS. 

uname -a
Linux ip-10-0-0-47 3.13.0-74-generic #118-Ubuntu SMP Thu Dec 17 22:52:10 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

MonetDB version, as I said:

2016-06-06 19:05:27 MSG merovingian[1255]: Merovingian 1.7 (Jul2015-SP4) starting
2016-06-06 19:05:27 MSG merovingian[1255]: monitoring dbfarm /mnt/mysql-copy
2016-06-06 19:05:27 MSG merovingian[1255]: accepting connections on TCP socket 0.0.0.0:50000
2016-06-06 19:05:27 MSG merovingian[1255]: accepting connections on UNIX domain socket /tmp/.s.monetdb.50000
2016-06-06 19:05:27 MSG discovery[1255]: listening for UDP messages on 0.0.0.0:50000
2016-06-06 19:05:27 MSG control[1255]: accepting connections on UNIX domain socket /tmp/.s.merovingian.50000
2016-06-06 19:05:27 MSG discovery[1255]: new neighbour ip-10-0-0-47 (ip-10-0-0-47.eu-west-1.compute.internal)
2016-06-06 19:05:29 MSG discovery[1255]: new database mapi:monetdb://ip-10-0-0-47:50000/mysql-copy (ttl=660s)
2016-06-06 19:05:44 MSG merovingian[1255]: starting database 'mysql-copy', up min/avg/max: 5m/8h/22h, crash average: 1.00 0.90 0.97 (126-4=122)
2016-06-06 19:05:45 MSG mysql-copy[1263]: arguments: /usr/bin/mserver5 --dbpath=/mnt/mysql-copy/mysql-copy --set merovingian_uri=mapi:monetdb://ip-10-0-0-47:50000/mysql-copy --set mapi_open=false --set mapi_port=0 --set mapi_usock=/mnt/mysql-copy/mysql-copy/.mapi.sock --set monet_vault_key=/mnt/mysql-copy/mysql-copy/.vaultkey --set gdk_nr_threads=4 --set max_clients=64 --set sql_optimizer=default_pipe --set monet_daemon=yes
2016-06-06 19:05:45 MSG mysql-copy[1263]: # MonetDB 5 server v11.21.19 "Jul2015-SP4"
2016-06-06 19:05:45 MSG mysql-copy[1263]: # Serving database 'mysql-copy', using 4 threads
2016-06-06 19:05:45 MSG mysql-copy[1263]: # Compiled for x86_64-pc-linux-gnu/64bit with 64bit OIDs and 128bit integers dynamically linked
2016-06-06 19:05:45 MSG mysql-copy[1263]: # Found 15.672 GiB available main-memory.


Overall, the symptoms provided do not ring a bell on a possible problem.

Assuming you were able to create this database, it might by a good idea to trim down
the problem by growing the database in a few steps to isolate if size is the problem.

Are there any known limits of tables sizes? Row-wise or size-wise?

You also could check the system logs and/or merovingian.log of your instance to determine
if the DBMS received an OOM kill signal from the OS.

merovingan.log:
2016-06-06 19:05:53 MSG merovingian[1255]: database 'mysql-copy' (1263) was killed by signal SIGSEGV

dmesg:
[  310.163434] mserver5[1268]: segfault at 0 ip 00007f19deb63712 sp 00007f19ddc12a80 error 4 in lib_sql.so[7f19deb35000+199000]

No mentions of oom_killer.


The last resort is to attach a debugger to the server before you issue the query to catch
a stack trace where it happens in the code base.

Do you have any how-to doc for that?

Thank you for your help,

Nikita


regards, Martin


On 06/06/16 18:13, Nikita Salnikov-Tarnovski wrote:
Hello. I am evaluating MonetDB to use in our project, but so far have some real problems with MonetDB constantly having segmentation faults. Here is my setup:

I am using AWS EC2 instance with 16GB of RAM, monetdb farm is location on ESB volume.

Welcome to mclient, the MonetDB/SQL interactive terminal (Jul2015-SP4)
Database: MonetDB v11.21.19 (Jul2015-SP4), 'mapi:monetdb://ip-10-0-0-47:50000/mysql-copy'

In there I have several tables, among them is one table I am most interested in, problemsview, with total columnsize of 120GB, largest column is around 11GB.

The moment I execute “select count(1) from problemsview;” I get segmentation fault:

mserver5[1300]: segfault at 0 ip 00007f86a0ca0712 sp 00007f869b6faa80 error 4 in lib_sql.so[7f86a0c72000+199000]

Next
select * from problemsview limit 10;

wait for 20-30 seconds, and then segmentation fault:
mserver5[1313]: segfault at 18 ip 00007f68cf2a0726 sp 00007f68ce14ea80 error 4 in lib_sql.so[7f68cf272000+199000]

So essentially I cannot do anything, I always get segmentation fault. Can this be fixed somehow?

Thank you in advance,

Nikita Salnikov-Tarnovski
Plumbr Founder and Master Developer
@JavaPlumbr/@iNikem



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