November 2007 - users-list

[MonetDB-users] Proofreading your professional documents
by Richard Hounslow 24 Feb '24

24 Feb '24

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[MonetDB-users] (no subject)
by Matt Magoffin 11 Aug '08

11 Aug '08

Hello, I am interested in evaluating MonetDB/XQuery. I have some XML collections for a project I work on that are of 1-2 million individual XML documents for which I use XQuery to access for OLAP style reporting operations. This is a Java-based project, and while working on this project I developed a thin XQuery-centric API so that I could evaluate/use many different XQuery implementations, which my company released as an open source project called Xaj (http://sourceforge.net/projects/xaj). Currently I am using a Berkeley DB XML implementation, but am interested in exploring other options. I'd like to implement a MonetDB version of this API now, but I am having some difficulty finding out how to effectively access MonetDB through Java. So far I was able to use the MonetDB JDBC driver to construct XQuery statements and get XML results, and also I was able to construct MonetDB pf:add-doc() statements to add documents, but I am wondering if this is the best approach (and if so, how to add documents to a remote MonetDB server using the pf:add-doc() mechanism). The API I am trying to implement you can view here, to give you an idea what I'm trying to do: http://xaj.svn.sourceforge.net/viewvc/xaj/xaj/src/net/sf/xaj/XmlDb.java?rev… It was somewhat modeled after the defunct XML:DB API, but focused just on add/store/XQuery operations. Any help/advise would be greatly appreciated! -- m@

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[MonetDB-users] db log shrink
by Colin Foss 17 Apr '08

17 Apr '08

Is there any method, besides restarting the database, of shrinking the sql log file? When I am performing a large set of large inserts (via COPY INTO) the log file gets very large. I wish there was a way to cycle the log file. Also during these large batches of inserts the database server becomes less and less responsive until I am forced to restart the server. Upon restart and the normal recovery monet returns to a very responsive state.

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[MonetDB-users] JDBC insert performance
by chinarinde 11 Mar '08

11 Mar '08

Hi all, I am new to monetDB and ran into the following problem (I'll try to be as verbose as I can, perhaps it helps helping me): I've installed MonetDB server 5.0.0, clients and commons 1.18.2 and sql 2.18.2 on Ubuntu Feisty. Then I've taken the JDBC example which is available online and modified it to be able to insert data into a test database. More specifically I'm using prepared statements and executeBatch() together with the monetdb-1.6 JDBC driver. Which is quite successful until about 5 million records are inserted - afterwards the speed of the inserts drops dramatically. I've experimented with different batch sizes (10000 records seems to work ok), and I've tried to understand the chapter about memory tuning for MonetDB (not sure yet about how to use mem_cursize() though). In any case at first inserting 2 million records only takes about 5 minutes (measured with Javas System.timemillis), later on this time increases and the server gets rather unresponsive. I found only two posts concerning the speed of JDBC inserts (from January 2007 I think) and I would be interested if a solution or explanation has been found off-list. Thank you -- View this message in context: http://www.nabble.com/JDBC-insert-performance-tf4589411.html#a13100422 Sent from the monetdb-users mailing list archive at Nabble.com.

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[MonetDB-users] inserting into default schema?
by m h 05 Dec '07

05 Dec '07

If I create a table, by default it goes into the "tmp" schema. But when I try to create a "users" table, it complains, since there is one in the "sys" schema. Why doesn't it create one in the "tmp" schema? ie: CREATE TABLE users (fcol FLOAT(25)); !CREATE TABLE: name 'users' already in use Just wondering about the resolution order. thanks -matt

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[MonetDB-users] Question about used Encoding
by Markus Gritsch 04 Dec '07

04 Dec '07

Hi, I would like to know how encoding related issues are handles in MonetDB. For example, when I run the following Python script # -*- coding: utf-8 -*- import MonetSQLdb x = MonetSQLdb.connect(host = 'localhost', user = 'voc', password = 'voc', lang = 'sql') c = x.cursor() c.execute('DROP TABLE test') c.execute('CREATE TABLE test(id int, name varchar(20))') c.execute('INSERT INTO test (id, name) VALUES (%s, %s)', (0, 'ä ö ü')) c.close() x.close() and then look at the inserted data using DbVisualizer I get Ã¤ Ã¶ Ã¼ in the 'name' column. When I try to edit the value in the DbVisualizer, I get an error message "unexpected end of input". (The SQL statements reads update voc.test set name = 'ö' where id = 0). Is this a JDBC driver problem? When I connect to an MySQL database with the MySQL JDBC driver included in DbVisualizer I can insert arbitrary characters, and they get properly displayed in the GUI. Kind regards, Markus

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[MonetDB-users] offset support?
by m h 04 Dec '07

04 Dec '07

Is there support for OFFSET in queries? The syntax doesn't throw an error, but the expected behavior isn't correct... sql>select * from query_users; +---------+----------+ |user_id |user_name | +=========+==========+ | 1 |john | | 2 |jack | | 3 |ed | | 4 |wendy | | 5 |laura | | 6 |ralph | | 7 |fido | +---------+----------+ Timer 1.820 msec 7 rows sql> Timer 0.294 msec 0 rows sql>SELECT query_users.user_id, query_users.user_name more>FROM query_users ORDER BY query_users.user_id more> LIMIT 3 OFFSET 2; +---------+----------+ |user_id |user_name | +=========+==========+ | 1 |john | | 2 |jack | | 3 |ed | +---------+----------+ -matt

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[MonetDB-users] Server in a weird state....
by m h 01 Dec '07

01 Dec '07

I tried running the SQLAlchemy ORM testsuite. The first time it ran for a while and then mserver segfaulted. (It also grew to using 700+Megs of memory. Am assumming this is a monetdb issue, since after each test the tables are usually dropped). The server now has issues. It appears to start fine: # MonetDB server v5.2.3, based on kernel v1.20.1 # Serving database 'demo' # Compiled for i686-pc-linux-gnu/32bit with 32bit OIDs dynamically linked # Copyright (c) 1993-2007 CWI, all rights reserved # Visit http://monetdb.cwi.nl/ for further information #warning: please don't forget to set your vault key! #(see /root/MonetDB/etc/monetdb5.conf) # Listening for connection requests on mapi:monetdb://127.0.0.1:50000/ # MonetDB/SQL module v2.20.3 loaded When I try to connect with the command line client it complains repeatedly: !ERROR: BUNdelete: access denied to tmp_537, aborting. !ERROR: BUNdelete: access denied to tmp_537, aborting. ....

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[MonetDB-users] Preferred bulk load method?
by m h 01 Dec '07

01 Dec '07

Good afternoon- Just wondering if there is a preferred method to load large datasets into monetdb? Piping SQL through mclient? thanks much -matt

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[MonetDB-users] Difficulty with External C Function
by Thomas J. Schulte 30 Nov '07

30 Nov '07

I'm having difficulty linking a custom external C function into MonetDB without crashing the database connection. If anyone knows of a documented end-to-end example of adding external functions compiled with GCC, please let me know. I've documented a minimal example below that crashes the connection for me each time. Software: Red Hat Linux knock-off CentOS, i386. Most recent MonetDB download from Sourceforge (server 5.2.2, client 1.20.2, common 1.20.0). GCC 4.1.1 1. Create a simple C file named te.c. int TEtest( ) { return 4; } 2. Compile file, move it to the proper directory, and create symlinks. $ gcc -c -fPIC te.c -o te.o $ gcc -shared -Wl,-soname,lib_te.so.0 -o lib_te.so.0.0.0 te.o (also tried with soname = libte.so.0, leaving output as lib_te.so.0.0.0) $ cp lib_te.so.0.0.0 $mhome/lib/MonetDB5/lib $ cd $mhome/lib/MonetDB5/lib $ ln -s lib_te.so.0.0.0 lib_te.so.0 $ ln -s lib_te.so.0.0.0 lib_te.so 3. Create a MAL file, saved as $mhome/lib/MonetDB5/te.mal module te; command test( ):int address TEtest(); command doesnotexist( ):int address TEdoesnotexist; 4. Update mal_init.mal by adding the following 2 lines: library te; include te; 5. Start a random DB and try to invoke the test function. Merovingian log show database dino killed by signal 11 afterwards. $ cd $mhome/bin $ ./merovingian & [1] xxxx $ ./mclient -lmal --database=dino -h COS1 mal> te.test( ); MAPI = monetdb@COS1:50001 ACTION= read_line QUERY = te.test(); ERROR = Connection terminated If I instead invoke te.doesnotexist(), I get a different error (below.) This leads me to think that MonetDB is findng and loading my compiled .so file, but it wasn't compiled correctly or otherwise isn't providing what MonetDB expects. mal> te.doesnotexist(); MAPI = monetdb@COS1:50001 QUERY = te.doesnotexist(); ERROR = !TypeException:user.main[1]:'te.doesnotexist' undefined in: _1:int := te.doesnotexist() Any pointers are appreciated. Thomas Schulte

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