- users-list - monetdb.org

Using MonetDB with Scala/Slick
by Pablo S 05 Aug '16

05 Aug '16

I develop in Scala, and need to access a MonetDB database. I use the Scala standard, Slick, however Slick doesn't have a driver to access MonetDB. I'm interested in developing a Slick/MonetDB driver (it's a JDBC wrapper) but I'd like to know first if someone already started the process (we could join forces). Please let me know. Thanks.

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When would the function group.multicolumn() used?
by Xu,Wenjian 03 Aug '16

03 Aug '16

Hi all, I found the following new MAL function in the new release of version 11.23.3: ============================================================ pattern group.multicolumn(b:bat[:any]...) (ref:bat[:oid],grp:bat[:oid],hist:bat[:any]) address GROUPmulticolumngroup; comment Derivation of a group index over multiple columns. ============================================================ I thought I may be used by queries with multiple attributes in the GROUP BY clause. So I tried to EXPLAIN such a query (e.g., SELECT ... FROM... GROUP BY ColA, ColB), but it is still compiled with multiple group.subgroup() followed by a group.subgroupdone(). So, when would this function group.multicolumn() used? Thanks, Wenjian

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a few good stackoverflow qs without answers..
by Anthony Damico 30 Jul '16

30 Jul '16

http://stackoverflow.com/questions/tagged/monetdb?sort=newest&pageSize=50

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infinity value
by Stefano Fioravanzo 26 Jul '16

26 Jul '16

Hello, I am creating a table from the result of a python function. One column is composed of double values, some of them are np.inf and are translated in monet as inf I cannot find a way to query for these values, how does monetdb handle infinity? Moreover, if I later do some query on this table and apply an arithmetic operation to the inf values, monetdb throws ‘overflow in calculation’ error, I would expect any operation (except for special cases) to result in inf. Is this a known issue or an intended design? Regards, Stefano

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mapi.class.php
by Alberto Ferrari 26 Jul '16

26 Jul '16

For those who are interested, here is (attached) the "php_mapi.inc" which I changed to a php class (OOP) Feel free to use or even upload to any repository. Regards.

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Announcement: New Jun2016-SP1 Bugfix release of MonetDB suite
by Sjoerd Mullender 22 Jul '16

22 Jul '16

The MonetDB team at CWI/MonetDB BV is pleased to announce the Jun2016-SP1 bugfix release of the MonetDB suite of programs. More information about MonetDB can be found on our website at <http://www.monetdb.org/>. For details on this release, please see the release notes at <http://www.monetdb.org/Downloads/ReleaseNotes>. As usual, the download location is <http://dev.monetdb.org/downloads/>. Jun 2016-SP1 bugfix release . * Lots of memory leaks have been plugged across the whole system. Java Module * Corrected PROCEDURE_TYPE output value of method DatabaseMetaData.getProcedures(). It used to return procedureReturnsResult. Now it returns procedureNoResult. Corrected ORDINAL_POSITION output value of method DatabaseMetaData.getProcedureColumns(). It used to start with 0, but as procedures do not return a result value it now starts with 1 for all the procedure arguments, as defined by the JDBC API. * Improved output of method DatabaseMetaData.getProcedures(). The REMARKS column now contains the procedure definition as stored in sys.functions.func. The SPECIFIC_NAME column now contains the procedure unique identifier as stored in sys.functions.id. This allows the caller to retrieve the specific overloaded procedure which has the same name, but different arguments. Also improved output of method DatabaseMetaData.getProcedureColumns(). The SPECIFIC_NAME column now contains the procedure unique identifier as stored in sys.functions.id. This allows the caller to retrieve the proper arguments of the specific overloaded procedure by matching the SPECIFIC_NAME value. * Improved output of method DatabaseMetaData.getFunctions(). The REMARKS column now contains the function definition as stored in sys.functions.func. The SPECIFIC_NAME column now contains the function unique identifier as stored in sys.functions.id. This allows the caller to retrieve the specific overloaded function which has the same name, but different arguments. Also improved output of method DatabaseMetaData.getFunctionColumns(). The SPECIFIC_NAME column now contains the function unique identifier as stored in sys.functions.id. This allows the caller to retrieve the proper arguments of the specific overloaded function by matching the SPECIFIC_NAME value. Bug Fixes * 4014: KILL signal * 4021: Analyze query does not escape input [security] * 4026: JDBC driver incorrectly converts TINYINT fields to String instead of an integer type. * 4028: inputs not the same size * 4031: mclient doesn't accept - argument to refer to stdin * 4032: no decimal places after update. ODBC driver * 4035: SQL Function call bug * 4036: Possible sql_catalog corruption due to unclean backuped tail

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Determining join order
by Moritz Bruder 20 Jul '16

20 Jul '16

Hi, in the process of writing a MAL backend for a query compiler, I'm trying to optimize the join order of arbitrary theta joins on whole relations (i.e. predicates may be arbitrary). To implement this, I use a simple heuristic for 2-way theta joins on relations: First the cheap predicates are identified, then the necessary joins are performed on the columns. After that all results of the cheap predicates are merged via joins on the OIDs. Finally, expensive predicates (i.e. with a lot of qualifying tuples) are implemented by applying a binary scalar operation and using a *subselect* and a *projection*/*leftfetchjoin*, since all columns are aligned now. To conclude: 2-way joins may not be atomic MAL joins (i.e. not column-wise), but they very well could be. So, what I'm looking for is some facility in MonetDB, with which I am able to break down a n-way join into 2-way joins, with the smallest possible intermediate results, without assuming too much about how those 2-way joins are implemented. The first thing I found was the *scheduler* module, which is also on the official website ( https://www.monetdb.org/Documentation/Manuals/MonetDB/Optimizers/Memoization ). But that seems no more up to date, since most of the functions are missing and the semantics of join operators in MAL has changed quite a bit. Is there anything else I can use for this task (aside from implementing some dynamic programming algorithm within MAL)? Kind regards, Moritz

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Limits on loaded shared libraries
by Anderson, David B 20 Jul '16

20 Jul '16

All, I was planning on loading a shared library within either an R or Python function inside a MonetDB server. Is this supported? What kinds of constraints do I need to worry about? Guessing any memory problems will impact the server, but not sure about thread safety etc. Thanks, Dave

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MERGE TABLE ERROR
by Ariel Abadi 20 Jul '16

20 Jul '16

Hi! We are facing a problem with MERGE Tables. We have a process in php which connects to the DB using the mapi ( https://www.monetdb.org/Documentation/Manuals/SQLreference/Programming/MAPI <https://www.google.com/url?q=https%3A%2F%2Fwww.monetdb.org%2FDocumentation%…> ) The process creates a new table everyday as follows: CREATE TABLE cub8_20160717 AS (SELECT * FROM cub8) WITH NO DATA; Then, attaches that new table to the MERGE table called cub8_cubo as follows: ALTER TABLE cub8_cubo ADD TABLE cub8_20160717 ; Once all this is created, it start inserting data. Everything works fine, with NO errors. BUT if I run a query against cub8_cubo I dont see cub8_20160717 data. So I run this query in order to check if the new table was attached to the merge: SELECT a.name, b.name, s.name FROM sys.tables as a JOIN sys.dependencies d ON a.id = d.depend_id JOIN sys.tables as b ON b.id= d.id JOIN sys.schemas as s ON a.schema_id = s.id WHERE a.type= 3 AND a.name ILIKE '%cub8%' ORDER BY 1,2; +-----------+---------------+ | name | name | +===========+===============+ | cub8_cubo | cub8_20160710 | | cub8_cubo | cub8_20160711 | | cub8_cubo | cub8_20160712 | | cub8_cubo | cub8_20160713 | | cub8_cubo | cub8_20160714 | | cub8_cubo | cub8_20160715 | | cub8_cubo | cub8_20160716 | | cub8_cubo | cub8_20160717 | So I try to detached from cub8_cubo, with the command: ALTER TABLE cub8_cubo DROP TABLE cub8_20160717; ALTER TABLE: table 'sb_traf.cub8_20160717' isn't part of the MERGE TABLE 'sb_traf.cub8_cubo' So I ADD it again: ALTER TABLE cub8_cubo ADD TABLE cub8_20160717; and now yes... I can see the data. If I need to detach that table, I need to run ALTER ... DROP twice or three times to get it done. It seems to be a bug?, are we doing something wrong ?? Thks in advance! *PS.:We are using * *MonetDB Database Server v1.7 (Jun2016)* *Welcome to mclient, the MonetDB/SQL interactive terminal (Jun2016)*

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embedded py/R on stable release
by Stefano Fioravanzo 17 Jul '16

17 Jul '16

Hello, Are ambedded python/R included in the latest stable release of MonetDB or do I have to install the dev version from source? Thank you Regards, Stefano Fioravanzo

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