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  • Whats the best way to design this database scenario?

    - by ankimal
    I want to setup 2 MySQL databases which differ in schema in that, one is normalized and the other is flat for quicker reads and writes. The information being stored in both DBs is the same, but the representation is obviously different owing to the different design approaches. I need to find a robust solution to sync information in real time from my normalized version to my flatter version.

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  • Efficient way to combine results of two database queries.

    - by ensnare
    I have two tables on different servers, and I'd like some help finding an efficient way to combine and match the datasets. Here's an example: From server 1, which holds our stories, I perform a query like: query = """SELECT author_id, title, text FROM stories ORDER BY timestamp_created DESC LIMIT 10 """ results = DB.getAll(query) for i in range(len(results)): #Build a string of author_ids, e.g. '1314,4134,2624,2342' But, I'd like to fetch some info about each author_id from server 2: query = """SELECT id, avatar_url FROM members WHERE id IN (%s) """ values = (uid_list) results = DB.getAll(query, values) Now I need some way to combine these two queries so I have a dict that has the story as well as avatar_url and member_id. If this data were on one server, it would be a simple join that would look like: SELECT * FROM members, stories WHERE members.id = stories.author_id But since we store the data on multiple servers, this is not possible. What is the most efficient way to do this? Thanks.

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  • Will this make the object thread-safe?

    - by sharptooth
    I have a native Visual C++ COM object and I need to make it completely thread-safe to be able to legally mark it as "free-threaded" in th system registry. Specifically I need to make sure that no more than one thread ever accesses any member variable of the object simultaneously. The catch is I'm almost sure that no sane consumer of my COM object will ever try to simultaneously use the object from more than one thread. So I want the solution as simple as possible as long as it meets the requirement above. Here's what I came up with. I add a mutex or critical section as a member variable of the object. Every COM-exposed method will acquire the mutex/section at the beginning and release before returning control. I understand that this solution doesn't provide fine-grained access and this might slow execution down, but since I suppose simultaneous access will not really occur I don't care of this. Will this solution suffice? Is there a simpler solution?

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  • Static member object of a class in the same class

    - by Luv
    Suppose we have a class as class Egg { static Egg e; int i; Egg(int ii):i(ii) {} Egg(const Egg &); //Prevents copy-constructor to be called public: static Egg* instance() {return &e} }; Egg Egg::e(47); This code guarantees that we cannot create any object, but could use only the static object. But how could we declare static object of the same class in the class. And also one thing more since e is a static object, and static objects can call only static member functions, so how could the constructor been called here for static object e, also its constructors are private.

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  • best web database solution for scala for a high traffic site?

    - by egervari
    I am in charge of a rebuilding a website that gets about 250,000 visitors a day. We'd like to use Scala, but it does not work very well with Spring (in some minor cases) and Hibernate (there is a major and very annoying mismatch here if you want to use scala collections, which we do). The application itself is going to have about 40-50 tables. Other than Hibernate, is there an ORM that works awesome with Scala and is as performant and reliable as Hibernate? Does it also have the same capabilities, or are we going to run into leaky-abstractions if we don't use Hibernate? It would be a big risk for us to go with a framework that is newer and doesn't seem to have a lot of industry backing... and at the same time, Hibernate is a real pain to program against when using Scala. 1) The Java Collection <- Scala Collection is absolutely painful. There is a lot more boilerplate and crap to write. 2) The IDE doesn't import JavaConversions and java interfaces automatically... so we this needs to be done manually. Optimizing Imports in IDEA is going to destroy all the manual work. 3) There is also a performance cost to converting back and forth all the time in your domain objects and your dao classes. 4) Not to mention there needs to be a lot of casting, which produces code ugly as sin. I actually would love to write my own orm that is 100% tailored to scala, but obviously this is really outside of the scope of our project for now. So what is the best approach?

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  • Booking logic and architecture, database sync: Hotels, tennis courts reservation system ...

    - by coulix
    Hello Stackers, Imagine that you want to design a tennis booking system. You have 5 tennis clubs as partenrs with no online api allowing you to check on their side if a court is booked or not: You have to build this part as well. Every time a booking is done on their side you want it to be know by our system. Probably using a POST request form tennis partner to our server. Every time a booking is done on our website, we want to push the booking to their system. The difficulty is that their system need to be online and accessible from outside. Ip may change, we have to use a dns updater. In case their system is not available we still accept the booking and fallback to an async email with 'i confirm booking/reject booking' link sent to the club. I find the whole process quite complex and was wondering about the way online hotel booking system and hotel were working. Do they all have their data open and online ? The good thing is that the data will grow large and fits nicely to some no SQL ;) like couch db

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  • Database(Partitions) related query.... Please suggest..........

    - by AGeek
    The Query is as follows:- We have an oracle schema, with tables partitioned. -- Need to make one of the partition offline. (How to achieve this,, or have thought of assigning each partition, a different tablespace, and then making that tablespace offline) any other way out possible so as to avoid making so many tablespaces???? -- Then, copy the data files/ logs related to that partition to the temporary storage..... how to achieve this thing... any docs related to the same.... -- Then We make this partition / related tablespace online... -- Then we create a second schema with the same tables as above..... -- Copy the partition data from temporary storage to this table. (How this can be achieved,,, any specific doc??? -- Then verifying to the data is accessible in all respects..... If possible, let's discuss to find out the solution........ Thanks....

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  • Scalably processing large amount of comlpicated database data in PHP, many times a day.

    - by Eph
    I'm soon to be working on a project that poses a problem for me. It's going to require, at regular intervals throughout the day, processing tens of thousands of records, potentially over a million. Processing is going to involve several (potentially complicated) formulas and the generation of several random factors, writing some new data to a separate table, and updating the original records with some results. This needs to occur for all records, ideally, every three hours. Each new user to the site will be adding between 50 and 500 records that need to be processed in such a fashion, so the number will not be steady. The code hasn't been written, yet, as I'm still in the design process, mostly because of this issue. I know I'm going to need to use cron jobs, but I'm concerned that processing records of this size may cause the site to freeze up, perform slowly, or just piss off my hosting company every three hours. I'd like to know if anyone has any experience or tips on similar subjects? I've never worked at this magnitude before, and for all I know, this will be trivial to the server and not pose much of an issue. As long as ALL records are processed before the next three hour period occurs, I don't care if they aren't processed simultaneously (though, ideally, all records belonging to a specific user should be processed in the same batch), so I've been wondering if I should process in batches every 5 minutes, 15 minutes, hour, whatever works, and how best to approach this (and make it scalable in a way that is fair to all users)?

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  • database design: table with large amount of columns (50+) or many sub tables with small amount of co

    - by Guillaume
    In our oroject we already have a lots of tables (100+). Some of them contains a lot of columns (50-100) and we are facing the need of adding more columns from time to time. What do you think is best - from maintenance and performance point of view - to split these huge tables in smaller entities or to keep the tables the way they are ? We are using an ORM tools, so we don't need to write custom request.

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  • Windows 7 & Sql 2008 - set database access to normal user

    - by simon_
    I use Windows 7 & Sql Server 2008. If I run Management Studio as normal user and try to connect to database 'MyDatabase', I get this error message 'The database MyDatabase is not accessible'. I I run Management Studio per right click 'Run as administrator', then 'MyDatabase' is accessible. Where & what should I set, to be able to access MyDatabase as normal user?

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  • Database for Large number of 1kB data chunks (MySQL?)

    - by The Unknown
    I have a very large dataset, each item in the dataset being roughly 1kB in size. The data needs to be queried rapidly by many applications distributed over a network. The dataset has more than a million items (so 500 million+ 1kB data chunks). What would be the best method to storing this dataset (need to allow adding more items, and reading them rapidly, but never modifying already added data)? Would using a MySQL DB using the binary blob format be appropriate? Or should each of these be stored as files on a file system? edit: the number is 1 million items now, but needs to be able to scale to well over 500 million items easily.

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  • Is Cassandra database row size limited by available memory?

    - by Adam Hollidge
    I'm working with very long time series -- hundreds of millions of data points in one series -- and am considering Cassandra as a data store. In this question, one of the Cassandra committers (the über helpful jbellis) says that Cassandra rows can be very large, and that column slicing operations are faster than row slices, hence my question: Is the row size still limited by available memory?

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  • SQL Database application written in Visual Basic in Visual Studio 2010

    - by TID
    Hello, I am writing a program and part of it is to store the keyed entry in a database on an sql server when the enter key is hit. The database is small and simple with only three entry spots in the table. one for the tracking number, one for the date entered, and one for the time entered. The only thing the user will see is the tracking number text box and an enter button. the date and time will be auto entered when the enter key is hit. i am relatively new to databases so i cannot figure out how to send the data to the database. The database is already configured, just need to get the program and the database talking to eachother. Thanks.

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  • Any dynamic database frontend tool from which you can update directly?

    - by Enjoy coding
    Hi Gurus, This is with reference to this question where I got one tabular report format. I need to update the user entered values correctly back to the same table rows. I am in the process of doing this by using general form post data methods by using some logics which I think will not be easy to maintain. So, just out of curiosity, Is there a front end creator javascript libraries or frameworks which can create the front end for any query's resultset and updates the corresponding rows when the user updates them from front end. This need not have all the full functionality, any one usable, customizable thing will reduce the code maintenance problems. I have googled for some javascript libraris for this but not able to get which will be suitable. Please suggest any useful tools. My environment is Mysql, PHP, JQuery, XAMPP server on Windows. Is JQuery provides one. Thanks in advance.

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  • OBject access from different functions in VC++

    - by sijith
    Hi, I have 3 function in my class B. These three function have to access member function of other class A. I did this by creating object of class A in class B constructor and tried to access that object in functions of class B. But its showing error. How can i assess the same object in these three functions. Where i have to create object of class A B::B() { A a; } B:: function() { a.fun(); //fun belongs to class A } B:: function1() { a.fun1(); //fun1 belongs to class A } I am getting error, How can i implement the same where i can access object a in both function.

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  • Pointer to struct, containing pointer to an object, for which I want to call a function

    - by user1795609
    So I've created an ADT which is a singly linked list made up of nodes. These Nodes each have a pointer to an object in them called data. Class Structure { struct Node { Object *data; Node *next; }; }; Node *head; I am trying to call a function in the object, like this: head = new Node; head -> data = new Object(); head -> next = NULL; cout << head -> data.print(); I keep getting the following error at compile. error: request for member 'print' in 'head-Structure::Node::data', which is of non-class type 'Object'*

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  • Persistent Objects in ASP.NET

    - by user204588
    Hello, I'm trying to find the best way to persist an object or in use the same object at a later point in the code. So, I create an object, then you're redirected to another page(a form) that needs to use variables from that object. That form is submitted to a third party and there is stuff done on their end and then they request a page on my application that runs some more code and needs the objects variables again. I thought about Database but this is all done at once. This is done during a user checkout process and after it's over, there's no reason to retrieve this object again. So adding and retrieving from a database seems like it would be overkill and I think it would make the process slower. Right now I'm using Session but I keep hearing not to use that but no one is really saying why I shouldn't except it is bad practice. I can't really use post back values because the pages don't work that way. The checkout process starts off in a dll code that redirects to the form that is submitted to the third party and the a page is requested by the third party. So, I'm not really sure of the best way. What are all the options and what does everyone recommend as the best way?

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  • Entity framework Update fails when object is linked to a missing child

    - by McKay
    I’m having trouble updating an objects child when the object has a reference to a nonexising child record. eg. Tables Car and CarColor have a relationship. Car.CarColorId CarColor.CarColorId If I load the car with its color record like so this var result = from x in database.Car.Include("CarColor") where x.CarId = 5 select x; I'll get back the Car object and it’s Color object. Now suppose that some time ago a CarColor had been deleted but the Car record in question still contains the CarColorId value. So when I run the query the Color object is null because the CarColor record didn’t exist. My problem here is that when I attach another Color object that does exist I get a Store update, insert error when saving. Car.Color = newColor Database.SaveChanges(); It’s like the context is trying to delete the nonexisting color. How can I get around this?

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  • The database 'DB Name' is not accessible.

    - by Gurucharan
    I am getting following error each time I tried to select database. The database 'DB Name' is not accessible. (Microsoft.SqlServer.Express.ObjectExplorer) Note: My OS is Win Vista. When I tried to open SQL Mgmt Studio as Run as administrator than I can able to access database properly. Any idea why it is giving error. I am also getting following error when my asp.net application is trying to access database. Cannot open database "DBName" requested by the login. The login failed. Login failed for user 'PCName\abcd'. I am not very good with SQL Server, please let me know how to create user and grant them permission in case that is what causing the problem. Thanks.

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  • Create object of unknown class (two inherited classes)

    - by Paul
    I've got the following classes: class A { void commonFunction() = 0; } class Aa: public A { //Some stuff... } class Ab: public A { //Some stuff... } Depending on user input I want to create an object of either Aa or Ab. My imidiate thought was this: A object; if (/*Test*/) { Aa object; } else { Ab object; } But the compiler gives me: error: cannot declare variable ‘object’ to be of abstract type ‘A’ because the following virtual functions are pure within ‘A’: //The functions... Is there a good way to solve this?

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