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Re: Re: mserver5 stability problems in acting with multithreaded clients
by Sherzod Mutalov 17 Jul '15

17 Jul '15

Thank you for answer, <b>Sjoerd Mullender! You said, > </b>In all, I think the situation is better in Jul2015 Does these problems have been fixed in nightly build? Regards, Sherzod Mutalov

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Re: Re: mserver5 stability problems in acting with multithreaded clients
by Sherzod Mutalov 17 Jul '15

17 Jul '15

You can get MapiDemoCpp source and test it:     https://gist.github.com/shmutalov/3894fdd22ec62334fe17 Regards, Sherzod Mutalov

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mserver5 stability problems in acting with multithreaded clients
by Sherzod Mutalov 17 Jul '15

17 Jul '15

Good day all, I am testing mserver5 with multithreaded client and have stability problems. I wrote a simple app in C#, which uses wrapper around Mapi (pure calls to libmapi.dll functions). The app creates 1000 tasks (threads), each thread opens connection to mserver5, then sends a simple query: "SELECT {0}, NOW();", where "{0}" is thread number, and fetchs the result. Problems are: 1. When my application starts to execute threads, always 1st, 2nd or 3rd connection will be lost, and I can't reconnect from that thread. 2. Sometimes there is error on mserver5, which causes connection lost on the client:     "!SABAOTHgetMyStatus: MALException:sabaoth.getmystatus:could not find my own database?!?" mserver5 is running on the local machine, same as client. I tryied to set a gdk_nr_threads option to 1, 8, 16, and get the same problems. I am running on Windows 7 x64, 16GB RAM, Intel i7-5500 CPU Regards, Sherzod Mutalov

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Job openings at MonetDB Solutions
by Ying Zhang 14 Jul '15

14 Jul '15

Dear all, MonetDB Solutions, the supporting company of MonetDB, is looking for core database developers. If you’re interested, please see the job description here: https://www.monetdbsolutions.com/company/careers Regards, Jennie

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Re: Re: mserver5 crash while login with newly created user
by Sherzod Mutalov 14 Jul '15

14 Jul '15

> > > Adding users on the mal level isn't supported on the sql level. > > Ok, how can I create sql user on server side? Is there a way to obtain this?

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mserver5 crash while login with newly created user
by Sherzod Mutalov 14 Jul '15

14 Jul '15

I want to change default monetdb user password to other and create new database user when starting new database instance, before any client connects to newly created db. I starting server with follow command: mserver5.exe --dbinit="oldpwd := clients.backendsum(\"monetdb\"); newpwd := clients.backendsum(\"secret\"); clients.changePassword(oldpwd, newpwd); usrpwd:=clients.backendsum(\"secret2\");clients.addUser(\"newuser\", usrpwd);" --dbpath="D:\Projects\git\monetdb-latest-dev\NT\build\bin\dbfarm\demo" There are no errors. Then I trying to connect to this server: mclient.exe -u monetdb -P secret No errors, connected. Then, I am trying to open new session: mclient.exe -u newuser -P secret2 Ooops! Client exits with error: Connection terminated Server unexpectedly dies. I restarted server, then try connect one more time, same behaviour: "Connection terminated". Ok. Then I connected to server with default "monetdb" user and checked "users" table: mclient.exe -u monetdb -P secret sql>select * from users; +---------+---------------+----------------+ | name | fullname | default_schema | +=========+===============+================+ | monetdb | MonetDB Admin | 2000 | | newuser | null | null | +---------+---------------+----------------+ 2 tuples (5.332ms) Look, fullname and default_schema for "newuser" is null. I think "null pointer dereference" somewhere in code. If I creating user with SQL (CREATE USER ...) everything works fine, I can connect.

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mserver5 crash while login with newly created user
by Sherzod Mutalov 14 Jul '15

14 Jul '15

I tested with monetdb v11.19.13 and v11.19.15 (Windows 7 x64, MSVC2013)

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Hash join implementation
by Xu,Wenjian 11 Jul '15

11 Jul '15

Hi Stefan, Thank you very much for your suggestions. They are very helpful. I am also trying to understand the hashjoin() implementation in gdk/gdk_join.c. I am aware of the classical *multi-pass partitioned hash join* as described in the literature: [1] Main memory hash joins on multi-core CPUs: tuning to the underlying hardware. Cagri Balkesen et al. ICDE13 [2] Optimizing main-memory join on modern hardware. Stefan Manegold et al. TKDE (2002) I was trying to follow the idea in these papers to understand the implementation of hash join in MonetDB but failed. Do you have any suggestions? Are there any other papers/documents I can refer to? Thanks. Best regards, XU Wenjian >Hi Wenjian, >you might want to consider studying the logical (relational) >and physical (MAL) plans, or debug your SQL queries; for >details see >https://www.monetdb.org/Documentation/Manuals/SQLreference/Runtime >You might also want to consider using the MAL debugger >directly; cf., >https://www.monetdb.org/Documentation/Manuals/MonetDB/debugger >Also, a combination of mserver5's --trace and ->gdk_debug=2097152 ("ALGOMASK") >might be useful. >Best, >Stefan ----- On Jul 8, 2015, at 11:42 AM, Xu,Wenjian zeroxwj at gmail.com <https://www.monetdb.org/mailman/listinfo/developers-list> wrote: >>* Hi, *>> >>* My objective is to investigate that, given an SPJ query, how are BATs *>>* *physically* processed (changed) among relational algebra operators (e.g., *>>* select, join). I do not care about how query is translated into execution plan *>>* in MAL, what I care is the interaction of operators in the kernel (aka., gdk) . *>> >>* My current plan is to add some debug information in those operators (e.g., *>>* functions in src/gdk_join.c, src/gdk_select.c) and re-compile the system. Then, *>>* I will pose an SPJ query (through console) and check the system log to see how *>>* those operators are invoked in sequence. *>> >>* But this method seems inefficient and I would like to ask if there are any *>>* alternatives, for example, is it possible to debug the system *step-by-step* *>>* given an input query (or its logical query plan). *>> >>* Thank you very much for any kind help. *>> >>* Best regards, *>>* Wenjian *>> >> >*>*

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Interaction of operators in the kernel.
by Xu,Wenjian 08 Jul '15

08 Jul '15

Hi, My objective is to investigate that, given an SPJ query, how are BATs *physically* processed (changed) among relational algebra operators (e.g., select, join). I do not care about how query is translated into execution plan in MAL, what I care is the interaction of operators in the kernel (aka., gdk) . My current plan is to add some debug information in those operators (e.g., functions in src/gdk_join.c, src/gdk_select.c) and re-compile the system. Then, I will pose an SPJ query (through console) and check the system log to see how those operators are invoked in sequence. But this method seems inefficient and I would like to ask if there are any alternatives, for example, is it possible to debug the system *step-by-step* given an input query (or its logical query plan). Thank you very much for any kind help. Best regards, Wenjian

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Transaction-replication, monetdbd database properties and other changes on default
by Dimitar Nedev 23 Jun '15

23 Jun '15

Hello everyone, We've recently merged the transaction-replicaiton branch into the default. That means that you can try out the new, still experimental, transaction-replication if you build the MonetDB default branch. Since there is already a release branch for the next feature release (July2015), the transaction-replicaiton support will not be part of the next major release. In general, most changes affect a database instance if it runs as a slave, master instances should function just as before. So unless you flip the right switches (and it cannot happen accidentally*) you shouldn't notice any differences. Most code changes are in gdk_logger, where a few large functions (including logger_new) were split into smaller one to accommodate for the need of new read-only logger. That is, a logger that only reads transactions and persists them in the data store. In additional, you can now set any property to a database (mserver5) instance running under the MonetDB-Daemon (monetdbd). Previously only a few preset properties could be set via the monetdbd. The current preset properties will still function as before, both in terms of mapping monetdb-to-mserver5 names and allowed values. * I will provide more information how to turn on and try out the transaction-replication in a blog post on the website very soon. Best regards, Dimitar

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