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• NoSQL and meteorological data

  - by christian studer

  So there's this new cool thing, these NoSQL-databases. And so there's my data: Rows of rows of rows of meteorological data: Values, representing certain measurements at a certain station (Identified by a WMO number, not coordinates), at a certain time. Not every station measures every parameter, not every parameter is measured all the time. I store this data (30 years worth of hourly values, resulting in ~1 billion values) currently in MySQL. The continous growth and the forseeable addition of even more data give me a little headache. Reading about the document based NoSQL systems which seem to scale rather easily, I was wondering if NoSQL is a viable data storage concept for meteorological data too. Do you have any experience with this?

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• Deleting orphans with JPA

  - by homaxto

  I have a one-to-one relation where I use CascadeType.PERSIST. This has over time build up a huge amount of child records that has not been deleted, to such an extend that it is reflected in the performance. Now I wish to add some code that cleans up the database removing all the child records that are not referenced by a parent. At the moment we are talking 400K+ records, at I need to run the code on all customer installations just to be sure they do not run into the same problem. I think the best solution would be to run a named query (because we support two databases) that deletes the necessary records, and this is where I get into problems, because how should I write it in JPQL? The result I want can be defined like the following sql statement, which unfortunaltely does not run on MySQL. DELETE FROM child c1 WHERE c1.pk NOT IN (SELECT DISTINCT p.pk FROM child c2 JOIN parent p ON p.child = c2.pk);

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• Excel File opened under Ubuntu, read by R, OpenOffice

  - by Vishal Belsare

  I have a bunch of Excel files which are updated on a daily basis on a Windows machine. I transfer them to a Ubuntu machine and want to open them there. Specifically, I want to read the files as a database under R. A couple years ago, I used ODBC under a Windows machine to open Excel files through R. Is there any way, I can do this with R under Ubuntu? I could make a database .ODB file for the corresponding XLS files using OpenOffice, but I don't know of a way to connect to a .ODB database. OpenOffice seems to have ways to connect TO databases, but no way to connect to ODB. Thanks for any potential solutions.

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• Major performance difference between two Oracle database instances

  - by jrdioko

  I am working with two instances of an Oracle database, call them one and two. two is running on better hardware (hard disk, memory, CPU) than one, and two is one minor version behind one in terms of Oracle version (both are 11g). Both have the exact same table table_name with exactly the same indexes defined. I load 500,000 identical rows into table_name on both instances. I then run, on both instances: delete from table_name; This command takes 30 seconds to complete on one and 40 minutes to complete on two. Doing INSERTs and UPDATEs on the two tables has similar performance differences. Does anyone have any suggestions on what could have such a drastic impact on performance between the two databases?

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• OOP function and if statement

  - by Luke

  Not sure if I can ask two questions? If i run the following function in my database class function generateUserArray() { $u = array(); $result = $this->selectAllUsers(); while( $row=mysql_fetch_assoc($result)) { $u[] = $row['username']; } return $u; } Would i call it like this? $u[] = $datebase->generateUserArray(); My second question, will this work: else if($database->addLeagueInformation($subname, $subformat, $subgame, $subseason, $subwindow, $subadmin, $subchampion, $subtype) && $databases->addLeagueTable($name) && $_SESSION['players'] == $subplayers && $comp_name = "$format_$game_$name_$season" && $_SESSION['comp_name'] = $comp_name) Thankyou

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• InnoDB or MyISAM - Why not both?

  - by Skoder

  Hey. I'm new to databases, and I've read various threads about which is better between InnoDB and MyISAM. It seems that the debates are to use or the other. Is it not possible to use both, depending on the table? What would be the disadvantages in doing this? As far as I can tell, the engine can be set during the CREATE TABLE command. Therefore, certain tables which are often read can be set to MyISAM, but tables that need transaction support can use InnoDB. I'm sure there must be a problem, otherwise this would be the ultimate answer :).

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• Hierarchical Data in MySQL is as fast as XML to retrieve?

  - by ajsie

  i've got a list of all countries - states - cities (- subcities/villages etc) in a XML file and to retrieve for example a state's all cities it's really quick with XML (using xml parser). i wonder, if i put all this information in mysql, is retrieving a state's all cities as fast as with XML? cause XML is designed to store hierarchical data while relational databases like mysql are not. the list contains like 500 000 entities. so i wonder if its as fast as XML using either of: Adjacency list model Nested Set model And which one should i use? Cause (theoretically) there could be unlimited levels under a state (i heard that adjacency isn't good for unlimited child-levels). And which is fastest for this huge dataset? Thanks!

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• Can I use a class as an object in .NET to create instances of that class?

  - by Troy

  I'm writing a fairly uncomplicated program which can "connect" to several different types of data sources including text files and various databases. I've decided to implement each of these connection types as a class inherited from an interface I called iConnection. So, for example, I have TextConnection, MySQLConnection, &c... as classes. In another static class I've got a dictionary with human-readable names for these connections as keys. For the value of each dictionary entry, I want the class itself. That way, I can do things like: newConnection = new dict[connectionTypeString](); Is there a way to do something like this? I'm fairly new to C# so I'd appreciate any help.

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• What is the relationship between IRimTable and PersistenceStore?

  - by Martin

  The BlackBerry Desktop API has the interface IRimTable which apparently maps an "application database" on a BlackBerry device to a virtual structure (i.e, IRimTable has IRimRecords, each of which has IRimField) that developer can browse the handheld device data when it is connected to a desktop computer. Meanwhile, applications in the handheld device can store its data in PersistenceStore databases. The point where I'm stuck is the PersistenceStore API doesn't define any Table or Records or Fields. Does anybody knows what is the relationship between these two classes? And how does the mapping work (if at all) ?

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• What are the main benefits of implementing a virtual machine as part of an application?

  - by Marplesoft

  Several databases I've been looking at recently implement a virtual machine internally to perform the respective data reads and writes. For an example, check out this article on SQLite's virtual machine they call the 'VDBE'. I'm curious as to what the benefits of such an architecture are. I would assume performance is one but why would a virtual machine like this run faster? In fact, it seems to be that this extra layer could cause it to run slower. So perhaps it's for security? Or portability? Anyway, just curious about this.

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• How to connect 2 mysql tables with 2 connection string

  - by denonth

  Hi all I need to connect 2 tables from 2 mysql databases that have 2 different connection strings and each is on the different server. I have this query: cmd = new MySqlCommand(String.Format("INSERT INTO {0} (a,b,c,d) SELECT (a,b,c,d) FROM {1}", ConfigSettings.ReadSetting("main_table"), ConfigSettings.ReadSetting("main_table")), con); So both table have the same columns. Thats why I have only one ConfigSettings.ReadSetting("main_table") for both of them as they are same. I have 2 connection strings and each is pointing to their server: con.ConnectionString = ConfigurationManager.ConnectionStrings["con1"].ConnectionString; con2.ConnectionString = ConfigurationManager.ConnectionStrings["con2"].ConnectionString; How to make this cmd to be workking with 2 different connection strings and with the same name for the table. Table name will change that's why it is saved in config.

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• How do I send a file as an email attachment using Linux command line?

  - by Kit Roed

  I've created a script that runs every night on my Linux server that uses mysqldump to back up each of my MySQL databases to .sql files and packages them together as a compressed .tar file. The next step I want to accomplish is to send that tar file through email to a remote email server for safekeeping. I've been able to send the raw script in the body an email by piping the backup text file to mailx like so: $ cat mysqldbbackup.sql | mailx [email protected] cat echoes the backup file's text which is piped into the mailx program with the recipient's email address passed as an argument. While this accomplishes what I need, I think it could be one step better, Is there any way, using shell scripts or otherwise, to send the compressed .tar file to an outgoing email message as an attachment? This would beat having to deal with very long email messages which contain header data and often have word-wrapping issues etc.

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• Record locking problem between linux and Windows

  - by PabloG

  I need to run a bunch of old DOS FoxPro / Clipper applications in linux under DOSEMU. The programs access their "databases" located on a network server (could be a Windows or Linux server) Actually, the programs ran fine, but I cannot manage to make the record locking work as supposed: I can run a program in two terminals (or the server and any terminal for instance) and lock the same record in both. Now, I'm using Tiny Core Linux as terminal and Windows XP as server, accesing the shared files via CIFS and the latest DOSEMU (1.4.0), but I tried with various combinations of server (Ubuntu 7 to 9, Damn Small Linux, XP) <- protocol (CIFS, samba, various versions of smbclient) <- client (same as server) with no luck I tried to configure the server part to work without oplocks in samba (after reading the entire O'Reilly Samba book locking chapter in http://oreilly.com/catalog/samba/chapter/book/ch05_05.html ) and in XP (\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\UseOpportunisticLocking = 0) but the problem persist. Any ideas? TIA, Pablo

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• How to convert a MSSQL database (including procedures, functions and triggers) to a firebird databas

  - by user193655

  I am considering migrating to Firebird. To have a "quick start" approach I downloaded the trial of a conversion tool (DBConvert) and tried it. I just picked up a random tool, this tool doesn't convert procedures, functions and triggers (I don't think it is a limit of the trial since there is not an explicit reference to sp, sf and triggers in the link above). Anyway by trying that tool I had the message: "The DB cannot be converted succesfully because some FK names are too long." This is because in some tables I have FK whose description is 32 chars. Is this a real firebird limit or it is possible to overcome it somehow (of course renaming the FK is an extreme option because it is extra work)? Anyway how to convert a MS SQL DB fully to FIREBIRD? Is there a valid tool? Did someone succed in a conversion of non trivial databases?

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• Stored Procedure with ALTER TABLE

  - by psayre23

  I have a need to sync auto_increment fields between two tables in different databases on the same MySQL server. The hope was to create a stored procedure where the permissions of the admin would let the web user run ALTER TABLE [db1].[table] AUTO_INCREMENT = [num]; without giving it permissions (That just smells of SQL injection). My problem is I'm receiving errors when creating the store procedure. Is this something that is not allowed by MySQL? DROP PROCEDURE IF EXISTS sync_auto_increment; CREATE PROCEDURE set_auto_increment (tableName VARCHAR(64), inc INT) BEGIN ALTER TABLE tableName AUTO_INCREMENT = inc; END;

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• SQL Server 2005: When copy table structure to other database "CONSTRAINT" keywords lost

  - by StreamT

  Snippet of original table: CREATE TABLE [dbo].[Batch]( [CustomerDepositMade] [money] NOT NULL CONSTRAINT [DF_Batch_CustomerDepositMade] DEFAULT (0) Snippet of copied table: CREATE TABLE [dbo].[Batch]( [CustomerDepositMade] [money] NOT NULL, Code for copy database: Server server = new Server(SourceSQLServer); Database database = server.Databases[SourceDatabase]; Transfer transfer = new Transfer(database); transfer.CopyAllObjects = true; transfer.CopySchema = true; transfer.CopyData = false; transfer.DropDestinationObjectsFirst = true; transfer.DestinationServer = DestinationSQLServer; transfer.CreateTargetDatabase = true; Database ddatabase = new Database(server, DestinationDatabase); ddatabase.Create(); transfer.DestinationDatabase = DestinationDatabase; transfer.Options.IncludeIfNotExists = true; transfer.TransferData();

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• What does xp_qv do in SQL Server?

  - by Chris

  Last night one of our SQL servers developed some major problems and after a colleague stopped, started, and all the usual things it started checking and rebuilding databases and is now running an extended stored procedure called "xp_qv". The internet seems to be very short of information on what this procedure does or anythign like that so I was hoping somebody here might be able to help. I should add that I assume it is meant to be running so the question isn't "Can I stop it" or anything like that, its just curiosity in what it is doing in the hope that it will help determine how long before things are usable again...

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• JSON documents and SQL database tables

  - by Sharmi

  Do JSON documents in RavenDB cost more than the SQL Server tables in terms of the storage and query costs. And also for centralized access, which one is better? What are the disadvantages of NON-SQL databases like RavenDB,CouchDB,MongoDB, etc... ? I can get that some of these are open source and support more datatypes like enums,objects,etc. but otherwise i don't see any big advantage? Currently there is a problem of storing huge amount of logs from various locations. I am planning to suggest these to my manager so just need a clear idea.

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• How to retrieve MYSQL records as an INSERT statement.

  - by Aglystas

  I'm trying come up with the best method of synchronizing particular rows of 2 different database tables. So, for example there's 2 product tables in different databases as such... Origin Database product{ merchant_id, product_id, ... additional fields } Destination Database product{ merchant_id product_id ... additional fields } So, the database schema is the same for both. However I'm looking to select records with a particular merchant_id, remove all records from the destination table that have that merchant_id and replace those records with records from the origin database of the same merchant_id. My first thought was using mysqldump, parsing out the create table statements, and only running the Insert Statements. Seems like a pain though. So I was wondering if there is a better technique to do this. I would think mysql has some method of creating INSERT statements as output from a SELECT statement, so you can define how to insert specific record information into a new db. Any help would be appreciated, thank you much.

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• Does a PHP library exist to work with PRC/.mobi files?

  - by Chris Clarke

  I'm writing a WordPress plugin to create an eBook from a selected category in most major eBook formats. I would like to support MobiPocket since that's the format used by the Kindle but I'm not sure how to go about it. From what I've read .mobi files are actually Palm Resource Databases (PRC) but I haven't been able to find a PHP class to work with these. I thought about using exec along with KindleGen but that would be undesirable as it would complicate initial setup. I've also thought about hosting a web service somewhere and using XML-RPC to accomplish this but that also complicates things. My question is: is there a PHP class/library (PHP-only preferred) that can work with PRC or even better, a class that specialises in creating MobiPocket ebooks? (needs to be open source since I'm releasing under the GPL) I've tried searching but haven't been able to find anything.

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• Bulletproof way to DROP and CREATE a database under Continuous Integration.

  - by H. Abraham Chavez

  I am attempting to drop and recreate a database from my CI setup. But I'm finding it difficult to automate the dropping and creation of the database, which is to be expected given the complexities of the db being in use. Sometimes the process hangs, errors out with "db is currently in use" or just takes too long. I don't care if the db is in use, I want to kill it and create it again. Does some one have a straight shot method to do this? alternatively does anyone have experience dropping all objects in the db instead of dropping the db itself? USE master --Create a database IF EXISTS(SELECT name FROM sys.databases WHERE name = 'mydb') BEGIN ALTER DATABASE mydb SET SINGLE_USER --or RESTRICTED_USER --WITH ROLLBACK IMMEDIATE DROP DATABASE uAbraham_MapSifterAuthority END CREATE DATABASE mydb;

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• What format do I use to store a relatively small amount of user data

  - by wcm

  I am writing a small program for our local high school (pro bono). The program has an interface allows the user to enter school holidays. This is a simple stand alone Windows app. What format should I use to store the data? A big relational data is obviously overkill. My initial plan was to store the data in an XML file. Co-workers have been suggesting that I use JSON files, Access Databases, SQL Lite, and SQL Server Express. There was even a suggestion of old school INI files.

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• How do you access config outside of a request in CherryPy?

  - by OrganicPanda

  I've got a webapp running on CherryPy that needs to access the CherryPy config files before a user creates a request. The docs say to use: host = cherrypy.request.app.config['database']['host'] But that won't work outside of a user request. You can also use the application object when you start the app like so: ... application = cherrypy.tree.mount(root, '/', app_conf) host = application.config['database']['host'] ... But I can see no way of accessing 'application' from other classes outside of a user request. I ask because our app looks at several databases and we set them up when the app starts rather than on user request. I have a feeling this would be useful in other places too; so is there any way to store a reference to 'application' somewhere or access it through the CherryPy API?

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• How to optimize this user ranking query

  - by James Simpson

  I have 2 databases (users, userRankings) for a system that needs to have rankings updated every 10 minutes. I use the following code to update these rankings which works fairly well, but there is still a full table scan involved which slows things down with a few hundred thousand users. mysql_query("TRUNCATE TABLE userRankings"); mysql_query("INSERT INTO userRankings (userid) SELECT id FROM users ORDER BY score DESC"); mysql_query("UPDATE users a, userRankings b SET a.rank = b.rank WHERE a.id = b.userid"); In the userRankings table, rank is the primary key and userid is an index. Both tables are MyISAM (I've wondered if it might be beneficial to make userRankings InnoDB).

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• SQL Server switch to MySQL/PostgreSQL for startup?

  - by chopps

  I just checked out the licensing for SQL Server and well...i can't afford it since im funding this project myself. I have been tinkering with MySQL and PostgreSQL a bit the past few weeks and at this point I can't really decide which to go with. MySQL has a large user base and lots of people using it so finding out how to do various items will not be to hard o find. I will be using ASP.NET with this project. Anyone have experience going from SQL Server to either of these databases? Is one stronger than the other? Thoughts?

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