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  • Single database, multiple system dependency

    - by davenewza
    Consider an environment where we have a single, core database, with many separate systems using this one database. This leads to all of these systems have a common dependency, which ultimately introduces coupling between them. This means that we cannot always evolve systems independently of each other. Structural changes to the database (even if only intended for one, particular system), requires a full sweep test of ALL systems, and may require that other systems be 'patched' and subsequently released. This is especially tricky when you want to have separate teams working on different projects. What is a good 'pattern' to help in avoiding such coupling? I would imagine that a database should be exclusively depended on by one system. If other systems require data for whatever reason, they should request such from an API service of some kind. A drawback of this approach which comes to mind is performance: routing data between high-throughput systems through service calls is much slower than through a database connection.

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  • Best C# database communication technique

    - by user65439
    A few days ago I read a reply to a question where people said that the days of writing queries within your c# code are long gone. I'm not sure what the specific person meant with the comment but it got me thinking. At the company I'm currently working at we maintain an assembly containing all the queries to the database (let's call it Queries), this assembly is reference by a QueryService (Retrieve the correct queries) assembly which in turn is referenced by a UnitOfWork assembly (The database connector classes, we have different connector classes for SQL, MySQL etc.). We use these three assemblies to perform operations on our database and all queries/commands are written in our C# code. Is there a better way to communicate with the database and is there a better way to communicate with different database types?

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  • Object-Oriented Operating System

    - by nmagerko
    As I thought about writing an operating system, I came across a point that I really couldn't figure out on my own: Can an operating system truly be written in an Object-Oriented Programming (OOP) Language? Being that these types of languages do not allow for direct accessing of memory, wouldn't this make it impossible for a developer to write an entire operating system using only an OOP Language? Take, for example, the Android Operating System that runs many phones and some tablets in use around the world. I believe that this operating system uses only Java, an Object-Oriented language. In Java, I have been unsuccessful in trying to point at and manipulate a specific memory address that the run-time environment (JRE) has not assigned to my program implicitly. In C, C++, and other non-OOP languages, I can do this in a few lines. So this makes me question whether or not an operating system can be written in an OOP, especially Java. Any counterexamples or other information is appreciated.

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  • Object Oriented programming on 8-bit MCU Case Study

    - by Calvin Grier
    I see that there's a lot of questions related to OO Programming here. I'm actually trying to find a specific resource related to embedded OO approaches for an 8 bit MCU. Several years back (maybe 6) I was looking for material related to Object Oriented programming for resource constrained 8051 microprocessors. I found an article/website with a case history of a design group that used a very small RAM part, and implemented many Object based constructs during their C design and development. I believe it was an 8051. The project was a success, and managed to stay inside the very small ROM/RAM they had available. I'm attempting to find it again, but Google can't locate it. The article was well written, and recommended a "mixed" approach using C methods for inheritance and encapsulation - if I recall correctly. Can anyone help me locate this article?

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  • What is Object Oriented Programming ill-suited for?

    - by Richard JP Le Guen
    In Martin Fowler's book Refactoring, Fowler speaks of how when developers learn something new, they don't consider when it's inappropriate for the job: Ten years ago it was like that with objects. If someone asked me when not to use objects, it was hard to answer. [...] It was just that I didn't know what those limitations were, although I knew what the benefits were. Reading this, it occurred to me I don't know what the limitations or potential disadvantages of Object-Oriented Programming are. What are the limitations of Object Oriented Programming? When should one look at a project and think "OOP is not best suited for this"?

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  • In which object should I implement wait()/notify()?

    - by Christopher Francisco
    I'm working in an Android project with multithreading. Basically I have to wait to the server to respond before sending more data. The data sending task is delimited by the flag boolean hasServerResponded so the Thread will loop infinitely without doing anything until the flag becomes true. Since this boolean isn't declared as volatile (yet), and also looping without doing anything wastes resources, I thought maybe I should use AtomicBoolean and also implement wait() / notify() mechanism. Should I use the AtomicBoolean object notify() and wait() methods or should I create a lock Object?

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  • Representing complex object dependencies

    - by max
    I have several classes with a reasonably complex (but acyclic) dependency graph. All the dependencies are of the form: class X instance contains an attribute of class Y. All such attributes are set during initialization and never changed again. Each class' constructor has just a couple parameters, and each object knows the proper parameters to pass to the constructors of the objects it contains. class Outer is at the top of the dependency hierarchy, i.e., no class depends on it. Currently, the UI layer only creates an Outer instance; the parameters for Outer constructor are derived from the user input. Of course, Outer in the process of initialization, creates the objects it needs, which in turn create the objects they need, and so on. The new development is that the a user who knows the dependency graph may want to reach deep into it, and set the values of some of the arguments passed to constructors of the inner classes (essentially overriding the values used currently). How should I change the design to support this? I could keep the current approach where all the inner classes are created by the classes that need them. In this case, the information about "user overrides" would need to be passed to Outer class' constructor in some complex user_overrides structure. Perhaps user_overrides could be the full logical representation of the dependency graph, with the overrides attached to the appropriate edges. Outer class would pass user_overrides to every object it creates, and they would do the same. Each object, before initializing lower level objects, will find its location in that graph and check if the user requested an override to any of the constructor arguments. Alternatively, I could rewrite all the objects' constructors to take as parameters the full objects they require. Thus, the creation of all the inner objects would be moved outside the whole hierarchy, into a new controller layer that lies between Outer and UI layer. The controller layer would essentially traverse the dependency graph from the bottom, creating all the objects as it goes. The controller layer would have to ask the higher-level objects for parameter values for the lower-level objects whenever the relevant parameter isn't provided by the user. Neither approach looks terribly simple. Is there any other approach? Has this problem come up enough in the past to have a pattern that I can read about? I'm using Python, but I don't think it matters much at the design level.

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  • would a composite design pattern be useful for group membership?

    - by changokun
    I'm trying to think about the best way to handle group memberships on a website. People sign up and select checkboxes in a list of interests. Every week we send out interest-themed emails to those members that indicated that interest. however i store the information in the database, while i am working with the lists and generating lists of email addresses or manipulating group memberships, the composite design pattern looked interesting. it would be easy to populate the group, then do some aggregating functions that say... generate the list of email addresses based on the interests. but i'm not sure i'm seeing any other advantages. i do need something scalable, and flexible. thoughts?

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  • Passing functions into other functions as parameters, bad practice?

    - by BlueHat
    We've been in the process of changing how our AS3 application talks to our back end and we're in the process of implementing a REST system to replace our old one. Sadly the developer who started the work is now on long term sick leave and it's been handed over to me. I've been working with it for the past week or so now and I understand the system, but there's one thing that's been worrying me. There seems to be a lot of passing of functions into functions. For example our class that makes the call to our servers takes in a function that it will then call and pass an object to when the process is complete and errors have been handled etc. It's giving me that "bad feeling" where I feel like it's horrible practice and I can think of some reasons why but I want some confirmation before I propose a re-work to system. I was wondering if anyone had any experience with this possible problem?

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  • Sharing object between 2 classes

    - by Justin
    I am struggling to wrap my head around being able to share an object between two classes. I want to be able to create only one instance of the object, commonlib in my main class and then have the classes, foo1 and foo2, to be able to mutually share the properties of the commonlib. commonlib is a 3rd party class which has a property Queries that will be added to in each child class of bar. This is why it is vital that only one instance is created. I create two separate queries in foo1 and foo2. This is my setup: abstract class bar{ //common methods } class foo1 extends bar{ //add query to commonlib } class foo2 extends bar{ //add query to commonlib } class main { public $commonlib = new commonlib(); public function start(){ //goal is to share one instance of $this->commonlib between foo1 and foo2 //so that they can both add to the properites of $this->commonlib (global //between the two) //now execute all of the queries after foo1 and foo2 add their query $this->commonlib->RunQueries(); } }

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  • What kind of programs/solutions can only be written with OOP or are too hard to achieve without it?

    - by user1598390
    Paraphrasing a recent question: What is Object Oriented Programming ill-suited for? I would like to ask the opposite question: What kind of programs cannot be written unless you use OOP? What kind of programs are not recommended to be written using non-OOP techniques? What kind of programs need OOP in order to even be written? What kind of programs would be too hard to write without OOP ? The answer to this question can help sell the idea of OOP to project leaders that have no special interest in code quality. At least they could buy the idea if one shows them the kind of things that are not even possible unless you use OOP.

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  • Any tips/tricks/resources on actually TEACHING a class on OOP? [closed]

    - by Sempus
    I may slowly be getting into teaching an Object-Orientated Programming class at my school in a year or two. I just graduated and work at my school as an Application Programmer. I'd first start off as a TA/grader and then slowly move into the Professor role. The class would be in Java. I always see resources on this fine site about HOW to program, but does anyone know any tips/tricks/resources on how to TEACH a programming class? It would be full of all different skills levels(but still semi-technical) so it would have to be a little more understandable than if it was just CS kids.

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  • GAE python database object design for simple list of values

    - by Joey
    I'm really new to database object design so please forgive any weirdness in my question. Basically, I am use Google AppEngine (Python) and contructing an object to track user info. One of these pieces of data is 40 Achievement scores. Do I make a list of ints in the User object for this? Or do I make a separate entity with my user id, the achievement index (0-39) and the score and then do a query to grab these 40 items every time I want to get the user data in total? The latter approach seems more object oriented to me, and certainly better if I extend it to have more than just scores for these 40 achievements. However, considering that I might not extend it, should I even consider just doing a simple list of 40 ints in my user data? I would then forgo doing a query, getting the sorted list of achievements, reading the score from each one just to process a response etc. Is doing this latter approach just such a common practice and hand-waved as not even worth batting an eyelash at in terms of thinking it might be more costly or complex processing wise?

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  • SQL SERVER – Error: Fix – Msg 208 – Invalid object name ‘dbo.backupset’ – Invalid object name ‘dbo.backupfile’

    - by pinaldave
    Just a day before I got a very interesting email. Here is the email (modified a bit to make it relevant to this blog post). “Pinal, We are facing a very strange issue. One of our query  related to backup files and backup set has stopped working suddenly in SSMS. It works fine in application where we have and in the stored procedure but when we have it in our SSMS it gives following error. Msg 208, Level 16, State 1, Line 1 Invalid object name ‘dbo.backupfile’. Here are our queries which we are trying to execute. SELECT name, database_name, backup_size, TYPE, compatibility_level, backup_set_id FROM dbo.backupset; SELECT logical_name, backup_size, file_type FROM dbo.backupfile; This query gives us details related to backupset and backup files when the backup was taken.” When I receive this kind of email, usually I have no answers directly. The claim that it works in stored procedure and in application but not in SSMS gives me no real data. I have requested him to very first check following two things: If he is connected to correct server? His answer was yes. If he has enough permissions? His answer was he was logged in as an admin. This means there was something more to it and I requested him to send me a screenshot of the his SSMS. He promptly sends that to me and as soon as I receive the screen shot I knew what was going on. Before I say anything take a look at the screenshot yourself and see if you can figure out why his queries are not working in SSMS. Just to make your life a bit easy, I have already given a hint in the image. The answer is very simple, the context of the database is master database. To execute above two queries the context of the database has to be msdb. Tables backupset and backupfile belong to the database msdb only. Here are two workaround or solution to above problem: 1) Change context to MSDB Above two queries when they will run as following they will not error out and will give the accurate desired result. USE msdb GO SELECT name, database_name, backup_size, TYPE, compatibility_level, backup_set_id FROM dbo.backupset; SELECT logical_name, backup_size, file_type FROM dbo.backupfile; 2) Prefix the query with msdb There are cases above script used in stored procedure or part of big query, it is not possible to change the context of the whole query to any specific database. Use three part naming convention and prefix them with msdb. SELECT name, database_name, backup_size, TYPE, compatibility_level, backup_set_id FROM msdb.dbo.backupset; SELECT logical_name, backup_size, file_type FROM msdb.dbo.backupfile; Very simple solution but sometime keeps people wondering for an answer. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Error Messages, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Pros/Cons of document based database vs relational database

    - by damian
    I've been trying to see if I can accomplish some requirements with a document based database, in this case CouchDB. Two generic requirements: CRUD of entities with some fields which have unique index on it ecommerce web app like eBay (better description here). And I'm begining to think that a Document-based database isn't the best choice to address these requirements. Furthermore, I can´t imagine a use for a Document based database (maybe my imagination is too little). Can you explain me if I am asking pears to an elm when I try to use a Document based database for this requirements?

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  • Postgresql - one database for everyone, or one-database per customer

    - by user337876
    I'm working on a web-based business application where each customer will need to have their own data (think basecamphq.com type model) For scalability and ease-of-upgrades, I'd prefer to have a single database where each customer gets a filtered version of the data. The problem is how to guarantee that they stay sandboxed to their own data. Trying to enforce it in code seems like a disaster waiting to happen. I know Oracle has a way to append a where clause to every query based on a login id, but does Postgresql have anything similar? If not, is there a different design pattern I could use (like creating a view of each table for each customer that filters)? Worse case scenario, what is the performance/memory overhead of having 1000 100M databases vs having a single 1Tb database? I will need to provide backup/restore functionality on a per-customer basis which is dead-simple on a single database but quite a bit trickier if they are sharing the database with other customers.

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  • SQL Server replication - how to sync tables from internal database to read-only website database

    - by frankadelic
    I have an internal SQL Server 2005 database "ADMIN_DATA" that is used by admin users. We would like to sync three of the database tables in ADMIN_DATA out to another SQL Server 2005 database "WEB_DATA", which is used by a public web app. WEB_DATA is read-only - only SELECT statements are allowed, while ADMIN_DATA is updated all the time. What is the best solution? How can this be accomplished with minimal custom coding and/or changes to database tables? Notes: ADMIN_DATA and WEB_DATA are different physical machines and on different subnets. The syncing operation doesn't need to be instantaneous.

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  • VS2010 ultimate DataBase Project + SQL Server 2008: Updating Project from Database

    - by josecortesp
    Hello everyone, this is a quick question: I have this Database Project in a Web app solution with the real database. I want to update the database using SQL server managment studio, and then update the corresponding VS project. This can be done? I know that you can update the scripts in the project, but I'm not the SQL kind of guy, i rather do this changes using Mangment studio... Thanks in advance

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  • Server database -> client database update based on version

    - by user296191
    Hi, What is the recommended method of collecting items in a server database, versioning the database then deploying only the version differences to a client ? Should it by a field in the table (ie. Version: 3.3.9876) against each record ? Should it be DateTime (server based) in each record ? And whats the best way to just deploy the changes to a client with an older version of the database ? Is it a DUMP to a file with a Bulk import of some description ? Open to comments.. Suggestions. Database can be anything (firebird, mysql, sqlserver, sqlite)... Any info greatly appreciated.

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  • Transferring a flat file database to a MySQL database

    - by Jon
    I have a flat file database (yeah gross I know - the worst part is that it's 1.4GB), and I'm in the process of moving it to a MySQL database. The problem is that I'm not sure how to go about doing this - and I've checked through every related question on here but none relate to what I want to do, nor how my database is currently setup. My current flat file database is setup to where a normal MySQL row is its own file, and a MySQL table would be the directory. So for example if you have a user named Jon, there would be a file for the user in a directory named /members/. Within that file would be various information for the user including the users id, rank etc - all separated by tabs, all on separate lines (userid\t4). So here's an example user file: userid 4 notes staff notes: bla bla staff2 notes: bla bla bla username Example So how can I convert the above into their own rows and fields in MySQL? And if possible, could I do thousands of these files at once? Thanks.

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  • Add properties to stdClass object from another object

    - by Florin
    I would like to be able to do the following: $obj = new stdClass; $obj->status = "success"; $obj2 = new stdClass; $obj2->message = "OK"; How can I extend $obj so that it contains the properties of $obj2, eg: $obj->status //"success" $obj->message // "OK" I know I could use an array, add all properties to the array and then cast that back to object, but is there a more elegant way, something like this: extend($obj, $obj2); //adds all properties from $obj2 to $obj Thanks!

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  • Save objects to a database?

    - by Eric
    So far in my .Net coding adventures I've only had a need to save information to files. So I've used XmlSerializer and DataContractSerializer to serialize attributed classes to XML files. My next project, however, requires that I save and retrieve information from a SQL server database. I'm wondering what my options are for doing this. The current version of the app, which was not created by me, uses a lot of hard coded SQL commands. But now I'm trying to avoid doing anything where I have to read or write individual fields to or from the database or objects. I especially want to avoid a lot of hard coded SQL in my code. I like how the serializer classes just figure out how to read and write XML files based on the attributes and or public properties of the class. Is there something similar for a database rather then XML?

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  • Sun Oracle Database Machine a román Banca Transilvaniánál

    - by Fekete Zoltán
    Oracle sajtóhír: Banca Transilvania, first institution in Romania to use Sun Oracle Database Machine (English version) Sikersztori, ügyféltörténet pdf-ben. Az Database Machine V2 megjelenését 2009 szeptemberben jelentette az Oracle. A világon az elso bank, ahol már élesben muködik a Database Machine V2, a romániai Banca Transilvania! Olvassa el a sajtóhírt. A Banca Transilvania 1,5 milló ügyféllel rendelkezik. "This system, product of Oracle and Sun, is the fastest server in the world for data storage, online transactions processing and data warehousing applications." Robert C. Rekkers, Banca Transilvania CEO, ezt nyilatkozta:"Business information is accessed 30 times faster using the new system, leading to quicker decisions and a better data base segmentation", azaz a Database Machine segítségével az üzleti kérséseket 30-szor gyorsabban tudják megválaszolni, mint a korábbi rendszerrel. Leontin Toderici, Banca Transilvania COO mondta a következot: "The acquisition price was excellent, as the costs were below those of an ordinary system", azaz a rendszer ára kiváló volt, kisebb volt a kötsége, mint a hagyományos rendszereké. Sorin Mindrutescu, az Oracle Romania vezetoje büszke arra, hogy egy romániai cég is az innovatív rendszer felhasználói között lehet.: "Oracle Exadata V2 is the result of over 30 years of experience in hardware and software development of two leader companies. I am glad that a top Romanian company is amongst the first in the world to use this innovative product." Az Exadata termékcsalád és a Database Machine kiváló eszköz OLTP rendszerek, adattárházak, konszolidációs megoldások adatbázisainak futtatására. Egy csomagban a tartalmazza a szoftvert és az "okos" hardvert, az adatfeldoldozó, a tároló (storage) komponenseket, mindezt az extrém gyors Infiniband kapcsolatokkal összekötve. A Banca Transilvani az Oracle readingi (Nagy-Britannia) központjában tesztelte a Database Machine rendszert, s a korábbi rendszernél tízszer, néhol hetvenkettoször gyorsabb teljesítményt kaptak, 10-72-szeres teljesítménynövekedés!, említette Tudor Iliescu, Trend Import - Export CEO. A központi Oracle sajtóhír: Customers Select Oracle® Exadata for Extreme Performance of Data Warehouse and OLTP Applications

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