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  • Help me understand Rails eager loading

    - by aaronrussell
    I'm a little confused as to the mechanics of eager loading in active record. Lets say a Book model has many Pages and I fetch a book using this query: @book = Book.find book_id, :include => :pages Now this where I'm confused. My understanding is that @book.pages is already loaded and won't execute another query. But suppose I want to find a specific page, what would I do? @book.pages.find page_id # OR... @book.pages.to_ary.find{|p| p.id == page_id} Am I right in thinking that the first example will execute another query, and therefore making the eager loading pointless, or is active record clever enough to know that it doesn't need to do another query? Also, my second question, is there an argument that in some cases eager loading is more intensive on the database and sometimes multiple small queries will be more efficient that a single large query? Thanks for your thoughts.

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  • Create a service that connects to remote database and uses public key encryption

    - by Leedsoft Solutions
    I have been searching all day and reading many tutorials and still I am confused. I am working on a project that has the following requirements as specified by the client (customer - not to be confused with client app): Connect to a remote server and verify that connection was successful. Connect to Web service on said server via SOAP. Authenticate with service using public key encryption Upon successful authentication, push a list of products and categories to a MSSQL database on remote server via the Web service. The client is a Winforms application written in C#. So far, I have created a WCF Service Application with separate services for the products and categories but I cannot figure the rest out. Can anyone point me in the direction of a tutorial or tutorials that cover these requirements? Many thanks in advance! Joe

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  • Cilk or Cilk++ or OpenMP

    - by Aman Deep Gautam
    I'm creating a multi-threaded application in Linux. here is the scenario: Suppose I am having x instance of a class BloomFilter and I have some y GB of data(greater than memory available). I need to test membership for this y GB of data in each of the bloom filter instance. It is pretty much clear that parallel programming will help to speed up the task moreover since I am only reading the data so it can be shared across all processes or threads. Now I am confused about which one to use Cilk, Cilk++ or OpenMP(which one is better). Also I am confused about which one to go for Multithreading or Multiprocessing

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  • ASP.NET MVC Routes Login/Logout Problem

    - by Tom
    Hi Guys, Relatively new to ASP.NET MVC and little confused about how to do routing. My problem basically relates to "logged in" and "logged out routes" and having both as "/". i.e. I have home/index for logged out user which appears as "/" but this has got me confused as to how I can have home/home for logged in user and still have "/". I keep getting 127.0.0.1/home/home I could modify like 127.0.0.1/home - but I want it like "/". My confusion relates to the fact that the "/" [127.0.0.1/] is bound in the routes collection to home/index. Does anyone know how I can modify the routes dictionary (which will be binded ONCE at the start) so that the "/" can be shared for logged and non-logged users ? Thanks?

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  • Spring + Hibernate + JPA

    - by Albinoswordfish
    As of now I have a working Spring application with persistence. However now I want to use Hibernate with JPA to do all of my database activities. I want to do this using an entitymanager. I've been reading many documents and tutorials on this matter, I've been getting confused on whether I need a persistence.xml file or not. Also I've been getting confused on how to setup my applicationContext.xml file as well. Does anybody know of a good site to look at in order to learn Spring + Hibernate + JPA + using EntityManager?

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  • Confusion with cookie session token and oauth2.0 don't know where to go anymore

    - by byte_slave
    Hi guys, I'm completely confused, frustrated and nothing seems to make sense and work any more. I' dev some iframe fb app and i've been using the javascript sdk (FB.Init()) to get the access_token, but doesn't always work, sometimes i'm already logged into FB and doesn't works... Did some reading, and read also that there is problems using cookies in iframes in Opera and IE, so I was thinking in use the OAuth 2.0 but i'm not sure how via facebook sdk c# and now I'm now completely lost, don't know if i still need to use the javascript FB.Init(). Documentation out there is poor and unclear, a lot of stuff refers to old code, and after hours of reading, jumping on examples, i'm completely messed up and confused. Can some, please, point/explain/enlightening me about this? Thanks a lot guys, appreciated! Merry christmas!

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  • SAS/R calculate distance between two groups

    - by user976856
    I would like to calculate distance between two groups. I am very confused. I have a two data sets. One is about a company and one is about employees. I would like to find out how their age( a company in which an employee is hired and an employee) are similar or not. I think I need to standarize also.. calcuate euclidean distance between each person and a company. (4-5 people in a company) calculate euclidean distance between each person and a company in industry level. My dataset is like this: person person_age company company_age insustry 1 50 1 5 1 2 40 1 5 1 3 30 2 1 1 4 20 2 1 1 5 25 3 8 2 Please help me. I don't mind using SAS or R. I am very confused.

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  • Best Data Access Methods for New Web Application

    - by user98454
    I'm building a new web application project and am confused by the numerous methods of performing data access. I'm backending on SQL and a bit confused whether to use LINQ to SQL or trtaditional ADO.net ? what are the advantages and disadvantages of using LINQ/SQL over ADO.net? If it is ADO.net,then what is the best way to retrieve data means either calling the stored procedures or directly calling the t-sql code? My question is what is cleanes and most effiecient and professional way of creating DAL for webapplication in asp.net? Thanks

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  • Why is this C or C++ macro not expanded by the preprocessor?

    - by Atul
    Can someone points me the problem in the code when compiled with gcc 4.1.0. #define X 10 int main() { double a = 1e-X; return 0; } I am getting error:Exponent has no digits. When i replace X with 10, it works fine. Also i checked with g++ -E command to see the file with preprocessors applied, it has not replaced X with 10. I was under the impression that preprocessor replaces every macro defined in the file with the replacement text with applying any intelligence. Am I wrong? I know this is a really silly question but I am confused and I would rather be silly than confused :). Any comments/suggestions.

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  • how does [<Literal>] differ from other constants in F#

    - by Mitzh
    I am a bit confused by the Literal keyword and why it is necessary in F#. Reading the docs, it sounds to me that [<Literal>] is used to define a constant, however I am a bit confused how this constant differs from all other constants in F#.. Values that are intended to be constants can be marked with the Literal attribute. This attribute has the effect of causing a value to be compiled as a constant. When I think of a constant, I think of something which is immutable.... let x = "a" + "b" //this is a immutable value, its value is constant [<Literal>] let y = "a" + "b" //this is also a immutable value, but why is this a special constant? Is it because the 'normal' F# values are evaluated lazily and the [<Literal>] is not evaluated lazily..? is that what they mean with 'compiled as constant'..? or is there something else to it?

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  • Problem while compiling the code

    - by Atul
    Can someone points me the problem in the code when compiled with gcc 4.1.0. #define X 10 int main() { double a = 1e-X; return 0; } I am getting error:Exponent has no digits. When i replace X with 10, it works fine. Also i checked with g++ -E command to see the file with preprocessors applied, it has not replaced X with 10. I was under the impression that preprocessor replaces every macro defined in the file with the replacement text with applying any intelligence. Am I wrong? I know this is a really silly question but I am confused and I would rather be silly than confused :). Any comments/suggestions.

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  • C# thread safety for class instances

    - by Steveng
    I am learning C# and I am confused with the thread safety of the copies of the class instances as below: eg: classA objA; classA objB = objA; objA.field1 = value2; //do I need lock around modification of field1? //let say we pass the objB to another thread objB.field1 = value1 //do I need a lock for objB because of the modification of field1? I am confused because coming from the background of C++, the class in C# is the reference type. If both objA and objB refer to the same memory underlying, then I would need a lock to protect the simultaneous writing to the field1. Could someone confirm with this or am I missing something? Thanks.

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  • what's the job of std::unique_lock when used with std::conditional_variable::wait()

    - by Mike
    I'm quite confused with the need of a std::unique_lock when wait a std::conditional_variable. So I look into the library code in VS 2013 and get more confused. This is how std::conditional_variable::wait() implemented: void wait(unique_lock<mutex>& _Lck) { // wait for signal _Cnd_waitX(&_Cnd, &_Lck.mutex()->_Mtx); } Is this some kind of joke? Wrap a mutex in a unique_lock and do nothing but get it back latter? Why not just use mutex in the parameter list?

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  • Why is it called NoSQL?

    - by beef jerky
    I've recently worked with MongoDB and learned about its schemaless design. However, I'm confused with the term NoSQL? Why is it called that? Doesn't it use SQL or SQL-like queries? I've also read from an article that the main difference lies in how data is stored. In the case of MongoDB, it's stored like JSON documents. Is this true? Also, I'm confused why I always see 'NoSQL vs relational databases'. Aren't NoSQL databases relational? I believe documents in MongoDB are still related/linked through some keys (please correct me if I'm wrong). So why is it labeled as non-relational? Thanks in advance!

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  • How to implement a genetic algorithm with distance, time, and cost

    - by ari
    I want to make a solution to find the optimum route of school visit. For example, I want to visit 5 schools (A, B, C, D, E) in my city. Then I must find out what school I should visit first, then the second, then the third etc. with distance, time, and cost criteria. The problem is, I am confused about how to use distance with time and cost (fuel usage) estimation in genetic algorithm to find the optimum route?

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  • Comparison of Architecture presentation patterns MVP(SC),MVP(PV),PM,MVVM and MVC

    This article will compare four important architecture presentation patterns i.e. MVP(SC),MVP(PV),PM,MVVM and MVC. Many developers are confused around what is the difference between these patterns and when should we use what. This article will first kick start with a background and explain different...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Comparison of Architecture presentation patterns MVP(SC),MVP(PV),PM,MVVM and MVC

    This article will compare four important architecture presentation patterns i.e. MVP(SC),MVP(PV),PM,MVVM and MVC. Many developers are confused around what is the difference between these patterns and when should we use what. This article will first kick start with a background and explain different...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • SQL SERVER – SQL Server High Availability Options – Notes from the Field #032

    - by Pinal Dave
    [Notes from Pinal]: When it is about High Availability or Disaster Recovery, I often see people getting confused. There are so many options available that when the user has to select what is the most optimal solution for their organization they are often confused. Most of the people even know the salient features of various options, but when they have to figure out one single option to use they are often not sure which option to use. I like to give ask my dear friend time all these kinds of complicated questions. He has a skill to make a complex subject very simple and easy to understand. Linchpin People are database coaches and wellness experts for a data driven world. In this 26th episode of the Notes from the Fields series database expert Tim Radney (partner at Linchpin People) explains in a very simple words the best High Availability Option for your SQL Server.  Working with SQL Server a common challenge we are faced with is providing the maximum uptime possible.  To meet these demands we have to design a solution to provide High Availability (HA). Microsoft SQL Server depending on your edition provides you with several options.  This could be database mirroring, log shipping, failover clusters, availability groups or replication. Each possible solution comes with pro’s and con’s.  Not anyone one solution fits all scenarios so understanding which solution meets which need is important.  As with anything IT related, you need to fully understand your requirements before trying to solution the problem.  When it comes to building an HA solution, you need to understand the risk your organization needs to mitigate the most. I have found that most are concerned about hardware failure and OS failures. Other common concerns are data corruption or storage issues.  For data corruption or storage issues you can mitigate those concerns by having a second copy of the databases. That can be accomplished with database mirroring, log shipping, replication or availability groups with a secondary replica.  Failover clustering and virtualization with shared storage do not provide redundancy of the data. I recently created a chart outlining some pros and cons of each of the technologies that I posted on my blog. I like to use this chart to help illustrate how each technology provides a certain number of benefits.  Each of these solutions carries with it some level of cost and complexity.  As a database professional we should all be familiar with these technologies so we can make the best possible choice for our organization. If you want me to take a look at your server and its settings, or if your server is facing any issue we can Fix Your SQL Server. Note: Tim has also written an excellent book on SQL Backup and Recovery, a must have for everyone. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: Notes from the Field, PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: Shrinking Database

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  • 'Photo editor' and 'RAW editor' in Shotwell

    - by Chris Wilson
    The preference menu in Shotwell allows the user to specify both an 'External photo editor' and an 'External RAW editor', but I'm confused as to why two external editors would be required. I'm not a photographer, so this confusion may simply be a result of my ignorance, but I thought RAW images were unprocessed photographs, in which case two editors would be kinda redundant. Am I simply missing one of the finer details of photograph processing?

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