November 2007 - users-list

[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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[MonetDB-users] Howto query with non ascii in python?
by m h 30 Nov '07

30 Nov '07

How do I run non-ascii queries in python? Or from the command line for that matter? Naive tests on my part fail.... python: RuntimeError: !syntax error, unexpected IDENT, expecting INTERSECT or EXCEPT or UNION in: "select name from tables where system=false and name=unitéble2" commandline: sql>select name from tables where system=false and name=unitéble2; !syntax error, unexpected IDENT, expecting INTERSECT or EXCEPT or UNION in: "select name from tables where system=false and name=unitéble2" Thanks -matt

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[MonetDB-users] incorrect handling of NULL values in "IN" statements?
by m h 29 Nov '07

29 Nov '07

My understanding that is that NULL is never equal to anything including itself. Thus to test for NULL values, one must use the IS operator. I'm wondering if the following is a bug. The NOT IN will return the null row, instead of the empty set. Are NULL values outside that query? CREATE TABLE query_users ( user_id INT NOT NULL AUTO_INCREMENT, user_name VARCHAR(20), PRIMARY KEY (user_id) ); INSERT INTO query_users (user_id, user_name) VALUES (1, 'matt'); INSERT INTO query_users (user_id, user_name) VALUES (2, 'fred'); INSERT INTO query_users (user_id, user_name) VALUES (3, null); SELECT user_name FROM query_users WHERE user_name IN ('matt', 'fred'); -- should return empty set, returns null SELECT user_name FROM query_users WHERE user_name NOT IN ('matt', 'fred');

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[MonetDB-users] use column names as column alias?
by m h 29 Nov '07

29 Nov '07

Is it possible to use the column names as the alias? The select query below fails. CREATE TABLE query_users ( user_id INTEGER NOT NULL, user_name VARCHAR(20), PRIMARY KEY (user_id) ); INSERT INTO query_users (user_id, user_name) VALUES (1,'matt'); select query_users.user_id AS "query_users.user_id", query_users.user_name AS "query_users.user_name" from query_users; Here's the error: !Invalid identifier 'query_users.user_id' -matt

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[MonetDB-users] SQL exception during query resolving. Slow join? How to submit external variables?
by Huib Verweij 28 Nov '07

28 Nov '07

Hi everyone, I'm new to MonetDB XQuery and have written a crude Cocoon generator for MonetDB using the example code for the JDBC client from the website. I am using the latest Bug Fix Release of MonetDB as announced by Sjoerd Mullender on 24-10-2007. When I execute the following query I get an error: --------------------------------------------------------- let $zz := doc('vogels.xml')//Vogels[data(Dwaalgast) = 'zeer zeldzaam'] return <vogeltjes>{$zz}</vogeltjes> --------------------------------------------------------- throws: java.sql.SQLException: ERROR: ERROR: XML Generation: NULL BAT has a 4415 head, but tail is NULL. ERROR: ERROR: xquery_print_result_loop: operation failed. However, when I change the XQuery to: --------------------------------------------------------- let $zz := doc('vogels.xml')//Vogels[data(Dwaalgast) = 'zeer zeldzaam'] return <vogeltjes>{$zz}azaz</vogeltjes> --------------------------------------------------------- everything's OK and I get the proper result. (The previous release threw the same error btw.) Also, when I join the results from the above query with another table to resolve some codes to code-descriptions, the query takes from 8.5 up to 11 seconds to execute, vs. <1 second for a query without the join. The result is a little over 1Mb in size. The query I use is this: --------------------------------------------------------- let $zz := doc('vogels.xml')//Vogels[Ecotoop_x0020_nest] return <vogeltjes> {for $vogel in doc('vogels.xml')//Vogels[Ecotoop_x0020_nest], $vc in doc('vogels-code.xml')//Vogels-code[data(Kolomnaam) = 'Ecotoop nest'][data(Code) = $vogel/Ecotoop_x0020_nest]/Codebeschrijving return <vogel> {$vogel/*} {$vc} </vogel> } </vogeltjes> --------------------------------------------------------- The latest preview release of eXist handles the join in 3.1 seconds, any ideas on why this join takes almost three times as long? I have a final question: how do I specify external variables using the JDBC client? Regards, Huib Verweij.

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[MonetDB-users] Why does MonetDB take indexes not into account?
by Markus Gritsch 28 Nov '07

28 Nov '07

Hi, I basically have this schema: CREATE TABLE "act" ( "id" int NOT NULL auto_increment, "title" text NOT NULL, "is_closed" bool NOT NULL, PRIMARY KEY ("id") ); CREATE INDEX act_isClosedIndex ON act (is_closed); CREATE TABLE "entry" ( "id" int NOT NULL auto_increment, "note" text NOT NULL, "act_id" int NOT NULL, PRIMARY KEY ("id"), CONSTRAINT "entry_act_id_exists" FOREIGN KEY ("act_id") REFERENCES "act" ("id") ); CREATE INDEX entry_actIndex ON entry (act_id); Each "act" has several "entries" and each "entry" belongs to one "act". *) full-text search in the "note" column over all entries: SELECT * FROM entry WHERE entry.note LIKE ('%hui%') MySQL: 4.5 Seconds MonetDB: 0.8 Seconds So this is very good and this motivates me to switch to MonetDB. However, the majority of the acts have the "is_closed" field set. The usual case in my application is to take into account only the entries of open acts: *) full-text search in the "note" column over all entries of the open acts: SELECT * FROM entry, act WHERE entry.act_id = act.id AND act.is_closed = 0 AND entry.note LIKE ('%hui%') MySQL: 0.26 Seconds MonetDB: 0.8 Seconds Here, MySQL can take advantage of the index on the is_closed column, whereas MonetDB does not. Is this intended? Databases without indexes seem strange to me. Markus

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[MonetDB-users] python cursor missing lastrowid attribute?
by m h 27 Nov '07

27 Nov '07

In MonetSQLdb BaseCursor.insert_id, the docstring says to use the lastrowid attribute. When I try to access that lastrowid on the cursor instance I get an AttributeError. Should I file a bug for this? matt

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[MonetDB-users] Another query that works in MySQL and SQLite but not in MonetDB
by Markus Gritsch 26 Nov '07

26 Nov '07

Hi, I have another question with an SQL query that works in SQLite and MySQL but does not in MonetDB. SELECT * FROM test WHERE ((1) AND (id=100)) syntax error, unexpected AND in: "prepare select * from test where ((1) and" The query is forged by an ORM. I programmatically put together the WHERE clause. All the contitions are put together using AND, and in the case of no conditions, the WHERE clause simply reads (1), which yields all entries in the table. However, MonetDB cannot parse this. Markus

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[MonetDB-users] Problem with colums named "begin" and "end"
by Markus Gritsch 25 Nov '07

25 Nov '07

Hi, I have a table with columns named "begin" and "end". With SQLite and MySQL the SELECT works all right, but MonetDB cannot parse the SQL: sql>CREATE TABLE "test" ("id" INT, "begin" TIMESTAMP, "end" TIMESTAMP); sql>INSERT INTO test ("id", "begin", "end") VALUES (0, '2003-02-07 12:00:00', '2003-02-07 12:00:00'); sql>SELECT id, begin end FROM test; !syntax error, unexpected BEGIN in: "select id, begin" Kind regards, Markus

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