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  • Large ResultSet on postgresql query

    - by tuler
    I'm running a query against a table in a postgresql database. The database is on a remote machine. The table has around 30 sub-tables using postgresql partitioning capability. The query will return a large result set, something around 1.8 million rows. In my code I use spring jdbc support, method JdbcTemplate.query, but my RowCallbackHandler is not being called. My best guess is that the postgresql jdbc driver (I use version 8.3-603.jdbc4) is accumulating the result in memory before calling my code. I thought the fetchSize configuration could control this, but I tried it and nothing changes. I did this as postgresql manual recomended. This query worked fine when I used Oracle XE. But I'm trying to migrate to postgresql because of the partitioning feature, which is not available in Oracle XE. My environment: Postgresql 8.3 Windows Server 2008 Enterprise 64-bit JRE 1.6 64-bit Spring 2.5.6 Postgresql JDBC Driver 8.3-603

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  • Problem with datagridvieew in vb.net

    - by user225269
    I'm trying to add a datagridview in vb.net, but it does not allow me to change the connection string or the database that should be imported to connect to it. The only thing that I'm seeing is the previous ms sql database that I connected with datagridview and everytime I click the new connection, the window closes and it leaves me with the datagridview with the previous connection that I have. And its not applicable because, now I want to connect it with mysql. Not ms sql. Its some sort of a cache like feature in vb.net, how do I get rid of it. so that I can add the new connection for mysql? Do I need to reinstall visual studio 2008?

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  • the MVCC effect on migration from oracle to db2

    - by Ryan Fernandes
    I have a simple (actually simplified :) ) scenario that is possibly the cause for the headache I've been having for the last few days... My current application (that serves 100's of users) currently uses Oracle as the database. I have no stored procs (I wish actually). Now, I've been asked if the product will work if I migrate to IBM DB2 as the database. So, after taking Oracle for granted all this while.... and having re-read Tom's article on MVCC (Multiversion Concurrency Control) and going through this post stating that DB2 is not 'on the list' or 'just tip-toeing in the area' as it were... I know I can't be sure that the product will work with DB2 as is. Is there no hope.. or is there a nice disclaimer I could use.. ?

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  • Should an event-sourced aggregate root have access to the event sourcing repository?

    - by JD Courtoy
    I'm working on an event-sourced CQRS implementation, using DDD in the application / domain layer. I have an object model that looks like this: public class Person : AggregateRootBase { private Guid? _bookingId; public Person(Identification identification) { Apply(new PersonCreatedEvent(identification)); } public Booking CreateBooking() { // Enforce Person invariants var booking = new Booking(); Apply(new PersonBookedEvent(booking.Id)); return booking; } public void Release() { // Enforce Person invariants // Should we load the booking here from the aggregate repository? // We need to ensure that booking is released as well. var booking = BookingRepository.Load(_bookingId); booking.Release(); Apply(new PersonReleasedEvent(_bookingId)); } [EventHandler] public void Handle(PersonBookedEvent @event) { _bookingId = @event.BookingId; } [EventHandler] public void Handle(PersonReleasedEvent @event) { _bookingId = null; } } public class Booking : AggregateRootBase { private DateTime _bookingDate; private DateTime? _releaseDate; public Booking() { //Enforce invariants Apply(new BookingCreatedEvent()); } public void Release() { //Enforce invariants Apply(new BookingReleasedEvent()); } [EventHandler] public void Handle(BookingCreatedEvent @event) { _bookingDate = SystemTime.Now(); } [EventHandler] public void Handle(BookingReleasedEvent @event) { _releaseDate = SystemTime.Now(); } // Some other business activities unrelated to a person } With my understanding of DDD so far, both Person and Booking are seperate aggregate roots for two reasons: There are times when business components will pull Booking objects separately from the database. (ie, a person that has been released has a previous booking modified due to incorrect information). There should not be locking contention between Person and Booking whenever a Booking needs to be updated. One other business requirement is that a Booking can never occur for a Person more than once at a time. Due to this, I'm concerned about querying the query database on the read side as there could potentially be some inconsistency there (due to using CQRS and having an eventually consistent read database). Should the aggregate roots be allowed to query the event-sourced backing store by id for objects (lazy-loading them as needed)? Are there any other avenues of implementation that would make more sense?

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  • Passing parameters to web service method in c#

    - by wafa.cs1
    Hello I'm developing an android application .. which will send location data to a web service to store in the server database. In Java: I've used REST protocol so the URI is: HttpPost request = new HttpPost("http://trafficmapsa.com/GService.asmx/GPSdata? lon="+Lon+"&Lat="+Lat+"&speed="+speed); In Asp.net (c#) web service will be: [WebMethod] public CountryName GPSdata(Double Lon, Double Lat, Double speed) { after passing the data from android ..nothing return in back .. and there is no data in the database!! Is there any library missing in the CS file!! I cannot figure out what is the problem.

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  • how to run foreach loop with ternary condition

    - by I Like PHP
    i have two foreach loop to display some data, but i want to use a single foreach on basis of database result. means if there is any row returns from database then forach($first as $fk=>$fv) should execute otherwise foreach($other as $ok) should execute. i m unsing below ternary operator which gives parse error $n=$db->numRows($taskData); // databsse results <?php ($n) ? foreach ($first as $fk=>$fv) : foreach ($other as $ok) { ?> <table><tr><td>......some data...</td></tr></table> <?php } ?> please suggest me how to handle such condition via ternary operator or any other idea. Thanks

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  • What arguments to use to explain why a SQL DB is far better then a flat file

    - by jamone
    The higher ups in my company were told by good friends that flat files are the way to go, and we should switch from MS SQL server to them for everything we do. We have over 300 servers and hundreds of different databases. From just the few I'm involved with we have 10 billion records in quite a few of them with upwards of 100k new records a day and who knows how many updates... Me and a couple others need to come up with a response saying why we shouldn't do this. Most of our stuff is ASP.NET with some legacy ASP. We thought that making a simple console app that tests/times the same interactions between a flat file (stored on the network) and SQL over the network doing large inserts, searches, updates etc along with things like network disconnects randomly. This would show them how bad flat files can be espically when you are dealing with millions of records. What things should I use in my response? What should I do with my demo code to illustrate this? My sort list so far: Security Concurent access Performance with large ammounts of data Ammount of time to do such a massive rewrite/switch Lack of transactions PITA to map relational data to flat files I fear that this will be a great post on the Daily WTF someday if I can't stop it now.

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  • When should I open and close a connection to SQL Server

    - by Martin
    I have a simple static class with a few methods in it. Each of those methods open a SqlConnection, query the database and close the connection. This way, I am sure that I always close the connection to the database, but on the other hand, I don't like to always open and close connection. Below is an example of what my methods look like. public static void AddSomething(string something) { using (SqlConnection connection = new SqlConnection("...")) { connection.Open(); // ... connection.Close(); } } Considering that the methods are inside a static class, should I have a static member containing a single SqlConnection? How and when should I drop it? What are the best practices?

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  • Sign Up/Login system for multi-domain/multi-server

    - by David
    I'm thinking about a good solution for implementing a sign up/login system that works across different domains and servers. A working example is Olx (you can register in one domain, and your login will work in the rest of domains). The scenario is that every domain (one per country) has its own database. And there will be 2 servers (for example), each one will have the 50% of the domains (and so the 50% of databases). What would you suggest to start with? Database: MySQL 5.1 Server-side language: PHP 5.3 (I will be using Symfony 1.4, so if someone has some suggestion for this framework, it will be interesting too, although it is optional)

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  • Core Data: Overkill for simple, static UITableView-based iPhone App?

    - by David Foster
    Hello! I have a rather simple iPhone app consisting of numerous views containing a single, grouped table view. These views are held together in navigation controllers which are grouped in a tab bar. Simple stuff. My table views do little more than list text (like "Dog", "Cat" and "Weasel") and this data is being served from a collection of plists. It's perhaps worth mentioning too that these tables are 'static' in the sense that their data is pre-determined and will only ever be amended—and if so, very rarely indeed—by the developer (in this case, moi). This rudimentary approach has reached its limits though, and I think I'm going to need something a bit more relational. I have worked a tad with Core Data in the past, but only with apps whose data is determined by user input. I have four closely related questions: Is Core Data overkill for an app consisting mainly of a selection of simple table views? Do you recommend using Core Data to manage data which is predetermine and extremely unlikely to ever change? Can one lock Core Data down so that its data can't change, thereby relinquishing my responsibility as the developer to handle the editing and saving of the managed object context? How do I go about giving Core Data my predetermined data, and in a format I know that it can work with? Thanks a bunch guys.

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  • building a web application in eclipse

    - by Noona
    As a concluding assignment for the technologies taught in a data management course, we have to write a web application using the technologies taught throughout the course, this mostly includes xhtml, css, JSP, servelets, JDBC, AJAX, webservices. the project will eventually be deployed using tomcat. we are given the option of choosing the technologies that we see fit. since this is my first time developing a web application I am having some uncertainties about where to start, so for example now I am writing the object classes that will be used in the database and implementing the operations that will be performed on the database, but I am not sure about how to make these operations available to a client through the website, I mean I think I have to write a servlet through which I can extract the request parameters and set the response accordingly, but I would still like a more specific overview of what I am going to do, so if someone can link me to a tutorial with an example that makes use of these technologies while illustrating the stages of the design so that I can see how all these things are linked together in a web project. thanks

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  • Should I be concerned about performance with connections to multiple databases?

    - by Josh Ryan
    I have a PHP app that is running on an Apache server with MySQL databases. Based on the subdomain that users access, I am connecting them to a database (sub1.domain.com connects to database_sub1 and sub2.domain.com connects to database_sub2). Right now there are 10 subdomain-database combos, but that number could potentially grow to well over 100. So, is this a bad thing? Considering my situation, is myslq_pconnect a better way to go? Thanks, and please let me know if more info would be helpful. Josh

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  • asp.net webservice user management across pages

    - by nakori
    I'm developing a site that will display confidential readonly information, with data fetched from a WCF service. My question: What is the best approach to user management across different information pages. The service returns a collection with customer info after a secure login. My idea is to have a Customer object class that is stored in session. Is it possible to use things like HttpContext.Current.User.Identity.IsAuthenticated followed by HttpContext.Current.Session["UserId"] without using a database with role-based security? Would I be better off with a combination of local database, Linq to SQL or datasets rather than using just class objects for data fetched from service? thanks, nakori

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  • How to implement a syndication receiver? (multi-client / single server)

    - by LeonixSolutions
    I have to come up with a system architecture. A few hundred remote devices will be communicating over internet with a central server which will receive data and store it in a database. I could write my own TCP/IP based protocol use SOAP use AJAX use RSS anything else? This is currently seen as one way (telemetry, as opposed to SCADA). Would it make a difference if we make it bi-directional. There are no plans to do so, but Murphy's law makes me wary of a uni-directional solution (on the data plane; I imagine that the control plane is bi-directional in all solutions (?)). I hope that this is not too subjective. I would like a solution which is quick and easy to implement and for others to support and where the general "communications pipeline" from remote deceives to database server can be re-used as the core of future projects. I have a strong background in telecomms protocols, in C/C++ and PHP.

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  • How to consolidate multiple LOG files into one .LDF file in SQL2000

    - by John Galt
    Here is what sp_helpfile says about my current database (recovery model is Simple) in SQL2000: name fileid filename size maxsize growth usage MasterScratchPad_Data 1 C:\SQLDATA\MasterScratchPad_Data.MDF 6041600 KB Unlimited 5120000 KB data only MasterScratchPad_Log 2 C:\SQLDATA\MasterScratchPad_Log.LDF 2111304 KB Unlimited 10% log only MasterScratchPad_X1_Log 3 E:\SQLDATA\MasterScratchPad_X1_Log.LDF 191944 KB Unlimited 10% log only I'm trying to prepare this for a detach then an attach to a sql2008 instance but I don't want to have the 2nd .LDF file (I'd like to have just one file for the log). I have backed up the database. I have issued: BACKUP LOG MasterScratchPad WITH TRUNCATE_ONLY. I have run multiple DBCC SHRINKFILE commands on both of the LOG files. How can I accomplish this goal of having just one .LDF? I cannot find anything on how to delete the one with fileid of 3 and/or how to consolidate multiple files into one log file.

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  • Shared Variable Among Ruby Processes

    - by Jesse J
    I have a Ruby program that loads up two very large yaml files, so I can get some speed-up by taking advantage of the multiple cores by forking off some processes. I've tried looking, but I'm having trouble figuring how, or even if, I can share variables in different processes. The following code is what I currently have: @proteins = "" @decoyProteins = "" fork do @proteins = YAML.load_file(database) exit end fork do @decoyProteins = YAML.load_file(database) exit end p @proteins["LVDK"] P displays nil though because of the fork. So is it possible to have the forked processes share the variables? And if so, how?

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  • Sparse (Pseudo) Infinite Grid Data Structure for Web Game

    - by Ming
    I'm considering trying to make a game that takes place on an essentially infinite grid. The grid is very sparse. Certain small regions of relatively high density. Relatively few isolated nonempty cells. The amount of the grid in use is too large to implement naively but probably smallish by "big data" standards (I'm not trying to map the Internet or anything like that) This needs to be easy to persist. Here are the operations I may want to perform (reasonably efficiently) on this grid: Ask for some small rectangular region of cells and all their contents (a player's current neighborhood) Set individual cells or blit small regions (the player is making a move) Ask for the rough shape or outline/silhouette of some larger rectangular regions (a world map or region preview) Find some regions with approximately a given density (player spawning location) Approximate shortest path through gaps of at most some small constant empty spaces per hop (it's OK to be a bad approximation often, but not OK to keep heading the wrong direction searching) Approximate convex hull for a region Here's the catch: I want to do this in a web app. That is, I would prefer to use existing data storage (perhaps in the form of a relational database) and relatively little external dependency (preferably avoiding the need for a persistent process). Guys, what advice can you give me on actually implementing this? How would you do this if the web-app restrictions weren't in place? How would you modify that if they were? Thanks a lot, everyone!

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  • Working with hibernate/DAO problems

    - by Gandalf StormCrow
    Hello everyone here is my DAO class : public class UsersDAO extends HibernateDaoSupport { private static final Log log = LogFactory.getLog(UsersDAO.class); protected void initDao() { //do nothing } public void save(User transientInstance) { log.debug("saving Users instance"); try { getHibernateTemplate().saveOrUpdate(transientInstance); log.debug("save successful"); } catch (RuntimeException re) { log.error("save failed", re); throw re; } } public void update(User transientInstance) { log.debug("updating User instance"); try { getHibernateTemplate().update(transientInstance); log.debug("update successful"); } catch (RuntimeException re) { log.error("update failed", re); throw re; } } public void delete(User persistentInstance) { log.debug("deleting Users instance"); try { getHibernateTemplate().delete(persistentInstance); log.debug("delete successful"); } catch (RuntimeException re) { log.error("delete failed", re); throw re; } } public User findById( java.lang.Integer id) { log.debug("getting Users instance with id: " + id); try { User instance = (User) getHibernateTemplate() .get("project.hibernate.Users", id); return instance; } catch (RuntimeException re) { log.error("get failed", re); throw re; } } } Now I wrote a test class(not a junit test) to test is everything working, my user has these fields in the database : userID which is 5characters long string and unique/primary key, and fields such as address, dob etc(total 15 columns in database table). Now in my test class I intanciated User added the values like : User user = new User; user.setAddress("some address"); and so I did for all 15 fields, than at the end of assigning data to User object I called in DAO to save that to database UsersDao.save(user); and save works just perfectly. My question is how do I update/delete users using the same logic? Fox example I tried this(to delete user from table users): User user = new User; user.setUserID("1s54f"); // which is unique key for users no two keys are the same UsersDao.delete(user); I wanted to delete user with this key but its obviously different can someone explain please how to do these. thank you

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  • Catching constraint violations in JPA 2.0.

    - by Dennetik
    Consider the following entity class, used with, for example, EclipseLink 2.0.2 - where the link attribute is not the primary key, but unique nontheless. @Entity public class Profile { @Id private Long id; @Column(unique = true) private String link; // Some more attributes and getter and setter methods } When I insert records with a duplicate value for the link attribute, EclipseLink does not throw a EntityExistsException, but throws a DatabaseException, with the message explaining that the unique constraint was violated. This doesn't seem very usefull, as there would not be a simple, database independent, way to catch this exception. What would be the advised way to deal with this? A few things that I have considered are: Checking the error code on the DatabaseException - I fear that this error code, though, is the native error code for the database; Checking the existence of a Profile with the specific value for link beforehand - this obviously would result in an enormous amount of superfluous queries.

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  • End User Ad-Hoc Reporting Tool: Microsoft SQL Server Management Studio or Microsoft Access?

    - by schultkl
    Our centralized IT department has suggested two primary ad hoc query tools for our general user base of approximately 200 staff members: Microsoft SQL Server Management Studio 2008 (SSMS) Microsoft Access 2003 Environment The backend database is a read-only Microsoft SQL Server 2005 database. The schema is 400+ tables; allowing access to the raw data for our general staff would be a disaster. We will be building an "abstraction layer" over the raw data for our general staff to run ad hoc queries against. The abstraction layer will most likely contain a number of views. A number of users have basic knowledge in Microsoft Access; none have used SSMS. Which of the above tools (or alternative) would be best for a decidedly non-techie user base of approximately 200 people? What are the pros and cons of each? Also, the IT department has suggested teaching people T-SQL so they may use SSMS. Is this reasonable?

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  • Recommend me an architecture for this Facebook application

    - by andybaird
    Firstly, this question is subjective. There is not a right answer for this question and it really depends on what works for you. I'm hoping to use this thread as a breeding ground for ideas. I hope this is acceptable in this medium. I'm working on building a Facebook app that will be replacing an already popular app that gets ~50k hits a day. The original app is using a very typical LAMP setup with help from some Zend libraries for database layer extraction. For the most part the app worked well, except to solve a lot of issues I ended up fragmenting tables to speed things up. As a result, I couldn't do a lot of things with the app that I wanted to (namely any processing using aggregate data that needed to be returned quickly) So I'm starting to design plans for the next version of this application, and I have a whole bunch of new and cool features that I know would choke my current setup. I'm looking for technological recommendations of data storage methods that scale well. The database does not necessarily need to be relational, simple key/value storage would suffice (although at present time I know little to nothing about KV stores) What's your recommendation? How would you tackle this? I'd like to take a completely free approach to this -- although I am most familiar and comfortable using PHP, I want to leave all technical options open.

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  • Iphone & Web App synch

    - by Jack Welsh
    I am trying to build an Iphone App client for our CRM solution so our sales people would be able to access the information available in our CRM through an Iphone App. I am trying to find out what is the recommended approach to architect the application when it comes to the database. I am not sure where should the data reside, should I save a subset of the data on the iPhone, or should I just rely on webservices and pull the information I need from the database whenever I need it. Also, is there any best practices or frameworks to build such applications on the Iphone.

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  • Counting the most tagged tag with MySQL

    - by Jack W-H
    Hi folks My problem is that I'm trying to count which tag has been used most in a table of user-submitted code. But the problem is with the database structure. The current query I'm using is this: SELECT tag1, COUNT(tag1) AS counttag FROM code GROUP BY tag1 ORDER BY counttag DESC LIMIT 1 This is fine, except, it only counts the most often occurence of tag1 - and my database has 5 tags per post - so there's columns tag1, tag2, tag3, tag4, tag5. How do I get the highest occurring tag value from all 5 columns in one query? Jack

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  • How do I display a field's hidden characters in the result of a query in Oracle?

    - by Chris Williams
    I have two rows that have a varchar column that are different according to a Java .equals(). I can't easily change or debug the Java code that's running against this particular database but I do have access to do queries directly against the database using SQLDeveloper. The fields look the same to me (they are street addresses with two lines separated by some new line or carriage feed/new line combo). Is there a way to see all of the hidden characters as the result of a query?I'd like to avoid having to use the ascii() function with substr() on each of the rows to figure out which hidden character is different. I'd also accept some query that shows me which character is the first difference between the two fields.

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