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  • Database schema for Product Properties

    - by Chemosh
    As so many people I'm looking for a Products /Product Properties database schema. I'm using Ruby on Rails and (Thinking) Sphinx for faceted searches. Requirements: Adding new product types and their options should not require a change to the database schema Support faceted searches using Sphinx. Solutions I've come across: (See Bill Karwin's answer) Option 1: Single Table Inheritance Not an option really. The table would contain way to many columns. Option 2: Class Table Inheritance Ruby on Rails caches the database schema on start-up which means a restart whenever a new type of product is introduced. If you have a size able product catalog this could mean hundreds of tables. Option 3: Serialized LOB Kills being able to do faceted searches without heavy application logic. Option 4: Entity-Attribute-Value For testing purposes, EAV worked fine. However it could quickly become a mess and a maintenance hell as you add more and more options (e.g. when an option increase the prices or delivery time). What option should I go with? What other solutions are out there? Is there a silver bullet (ha) I overlooked?

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  • What's a good icon to represent a legend or a key for a diagram?

    - by Bears will eat you
    I'm implementing a small web app widget that shows a legend/key for a diagram (or chart/map/graph/whatever), but only during mouseover of the widget. It's basically just going to be a div with a background image. What would be a good icon that communicates "I show the legend" or "I am the legend" to the unfamiliar users? I'm looking for something in the 10x10 to 20x20 pixel range. Assuming that a legend is the same thing as a key (is it?) then I could use a small icon of a key (like you'd unlock a door with) but that seems cheesy or unclear at worst. I'm not sure that's really the clearest way to do it. Is there an icon that should instantly remind users of a legend?

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  • Getting the final value to this MySQL query...

    - by Jack W-H
    I've got my database set up with three tables - code, tags, and code_tags for tagging posts. This will be the SQL query processed when a post is submitted. Each tag is sliced up by PHP and individually inserted using these queries. INSERT IGNORE INTO tags (tag) VALUES ('$tags[1]'); SELECT tags.id FROM tags WHERE tag = '$tags[1]' ORDER BY id DESC LIMIT 1; INSERT INTO code_tags (code_id, tag_id) VALUES ($codeid, WHAT_GOES_HERE?) The WHAT_GOES_HERE? value at the end is what I need to know. It needs to be the ID of the tag that the second query fetched. How can I put that ID into the third query? I hope I explained that correctly. I'll rephrase if necessary.

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  • What is so bad about Singletons

    - by Ewan Makepeace
    The Singleton pattern is a fully paid up member of the GoF Patterns Book but lately seems rather orphaned by the developer world. I still use quite a lot of singletons, especially for Factory classes, and while you have to be a bit careful about multithreading issues (like any class actually) fail to see why they are so awful. This site especially seems to assume that everyone agrees that Singletons are evil. Why?

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  • Process a batch of items, return an object to report on status

    - by Naeem Sarfraz
    I'm looking for a pattern (or good practice) for the following scenario: My function List<BatchItemResponse> Process(List<BatchItem> Data) {..} will process a list of data, and return info on where each item in the batch could be processed. struct BatchItemResponse { int BatchItemID; bool Processed; string Description; } Any thoughts? Is what I've proposed as good as it gets?

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  • designing an ASP.NET MVC partial view - showing user choices within a large set of choices

    - by p.campbell
    Consider a partial view whose job is to render markup for a pizza order. The desire is to reuse this partial view in the Create, Details, and Update views. It will always be passed an IEnumerable<Topping>, and output a multitude of checkboxes. There are lots... maybe 40 in all (yes, that might smell). A-OK so far. Problem The question is around how to include the user's choices on the Details and Update views. From the datastore, we've got a List<ChosenTopping>. The goal is to have each checkbox set to true for each chosen topping. What's the easiest to read, or most maintainable way to achieve this? Potential Solutions Create a ViewModel with the List and List. Write out the checkboxes as per normal. While writing each, check whether the ToppingID exists in the list of ChosenTopping. Create a new ViewModel that's a hybrid of both. Perhaps call it DisplayTopping or similar. It would have property ID, Name and IsUserChosen. The respective controller methods for Create, Update, and Details would have to create this new collection with respect to the user's choices as they see fit. The Create controller method would basically set all to false so that it appears to be a blank slate. The real application isn't pizza, and the organization is a bit different from the fakeshot, but the concept is the same. Is it wise to reuse the control for the 3 different scenarios? How better can you display the list of options + the user's current choices? Would you use jQuery instead to show the user selections? Any other thoughts on the potential smell of splashing up a whole bunch of checkboxes?

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  • Messaging strategies to connect different systems

    - by n002213f
    I have a system to handle Applications online and a different system to send SMS/Email notifications to applicants on completion using web services. I can't guarantee the availability of the SMS/Email gateway. Option 1 After an application is complete, place a message on a JMS queue. A Message Driven bean receives the message and make a call for the web service, if it fails leave the message on the queue. I suspect (please correct if incorrect) that if the gate way is offline the continuosly try to send the message which might use up valuable resources. Can the above option be refined are are there any other messaging strategies that can be used?

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  • K-nearest neighbour with closed-loop dimensions

    - by Tomas
    Hi, I've got a K-nearest neighbour problem where some of the dimensions are closed loops. For example one is 'time of day' and I'm matching for similarity so 'very early morning' is close to 'late evening', you can't just make it a linear scale from 'very early morning' at one end to 'late evening' at the other. How can I represent this in the data model? Is there an established way to handle this or a way to work around it?

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  • With MVVM, does each UI window have its own ViewModel?

    - by j0rd4n
    When I'm designing multiple views under the MVVM pattern, does each view get its own ViewModel or do they all share the same one? I understand that this is ultimately a flexible decision, but what is the best practice? My gut tells me to have a ViewModel for each view (i.e. each separate UI window). All of the blog examples of MVVM show a single view but not much beyond that.

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  • Converting ASP.NET MVC to n-Tiered Architecture

    - by Jeff
    I just built an application using ASP.NET MVC. The programmers at my company want to build all future modules using n-Tiered (Presentation Layer, Business Logic Layer, Data Access Layer) architecture. I am not the programmer and need to know why this makes sense? Do I have to completely rewrite the entire code or can it be converted? We are building an HRIS system with Business Intelligence. Somebody please explain why or why not this approach does or does not make sense.

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  • Are bad data issues that common?

    - by Water Cooler v2
    I've worked for clients that had a large number of distinct, small to mid-sized projects, each interacting with each other via properly defined interfaces to share data, but not reading and writing to the same database. Each had their own separate database, their own cache, their own file servers/system that they had dedicated access to, and so they never caused any problems. One of these clients is a mobile content vendor, so they're lucky in a way that they do not have to face the same problems that everyday business applications do. They can create all those separate compartments where their components happily live in isolation of the others. However, for many business applications, this is not possible. I've worked with a few clients, one of whose applications I am doing the production support for, where there are "bad data issues" on an hourly basis. Yeah, it's that crazy. Some data records from one of the instances (lower than production, of course) would have been run a couple of weeks ago, and caused some other user's data to get corrupted. And then, a data script will have to be written to fix this issue. And I've seen this happening so much with this client that I have to ask. I've seen this happening at a moderate rate with other clients, but this one just seems to be out of order. If you're working with business applications that share a large amount of data by reading and writing to/from the same database, are "bad data issues" that common in your environment?

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  • Routing redirection decision

    - by programming late night
    I have really no idea why I'm asking this as this a really completely irrelevant question for which I should have figured out an answer within milliseconds, yet I'm doing it. So in my project I have a Router class which splits up the request and selects the right page to be loaded. Fine so far. Now I have a page displayed when the user requests a page that doesn't exist, you know, 404. So theoretically, if the user entered mydomain.com/404 (I use mod_rewrite with a requests collector via index.php?req=*) the 404 error would be shown to him, but in fact there was no error - the 404 page would be displayed as a perfectly normal page. So if someone would try out requesting the 404 page via /404, he would be shown the page but he can't tell if the 404 page he requested doesn't exist and he is actually getting a, you guessed it, 404 error or if he actually found some flaw in the system that makes him able to see an error page when there is no error. I don't know how dumb this whole thing here is but I'm sure some of you have in fact ran into this problem already. Short version: If the user enters mydomain.com/404 the 404 page is shown even though there is no 404 error. I know this is a completely irrelevant question, please don't tell me, but I just spontaneously wanted to hear your thoughts on it. Strange eh? Should I redirect direct access to my 404-page to the home page? Should I do nothing? Should I just go to bed and stop asking irrelevant stuff?

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  • Why use hashing to create pathnames for large collections of files?

    - by Stephen
    Hi, I noticed a number of cases where an application or database stored collections of files/blobs using a has to determine the path and filename. I believe the intended outcome is a situation where the path never gets too deep, or the folders ever get too full - too many files (or folders) in a folder making for slower access. EDIT: Examples are often Digital libraries or repositories, though the simplest example I can think of (that can be installed in about 30s) is the Zotero document/citation database. Why do this? EDIT: thanks Mat for the answer - does this technique of using a hash to create a file path have a name? Is it a pattern? I'd like to read more, but have failed to find anything in the ACM Digital Library

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  • Element Content Versus Attribute for Simple XML Value

    - by MB
    I know the elements versus attributes debate has come up many times here and elsewhere (e.g. here, here, here, here, and here) but I haven't seen much discussion of elements versus attributes for simple property values. So which of the following approaches do you think is better for storing a simple value? A: Value in Element Content: <TotalCount>553</TotalCount> <CelsiusTemperature>23.5</CelsiusTemperature> <SingleDayPeriod>2010-05-29</SingleDayPeriod> <ZipCodeLocation>12203</ZipCodeLocation> or B: Value in Attribute: <TotalCount value="553"/> <CelsiusTemperature value="23.5"/> <SingleDayPeriod day="2010-05-29"/> <ZipCodeLocation code="12203"/> I suspect that putting the value in the element content (A) might look a little more familiar to most folks (though I'm not sure about that). Putting the value in an attribute (B) might use less characters, but that depends on the length of the element and attribute names. Putting the value in an attribute (B) might be more extensible, because you could potentially include all sorts of extra information as nested elements. Whereas, by putting the value inside the element content (A), you're restricting extensibility to adding more attributes. But then extensibility often isn't a concern for really simple properties - sometimes you know that you'll never need to add additional data. Bottom line might be that it simply doesn't matter, but it would still be great to hear some thoughts and see some votes for the two options.

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  • C++. How to define template parameter of type T for class A when class T needs a type A template parameter?

    - by jaybny
    Executor class has template of type P and it takes a P object in constructor. Algo class has a template E and also has a static variable of type E. Processor class has template T and a collection of Ts. Question how can I define Executor< Processor<Algo> > and Algo<Executor> ? Is this possible? I see no way to defining this, its kind of an "infinite recursive template argument" See code. template <class T> class Processor { map<string,T> ts; void Process(string str, int i) { ts[str].Do(i); } } template <class P> class Executor { Proc &p; Executor(P &p) : Proc(p) {} void Foo(string str, int i) { p.Process(str,i); } Execute(string str) { } } template <class E> class Algo { static E e; void Do(int i) {} void Foo() { e.Execute("xxx"); } } main () { typedef Processor<Algo> PALGO; // invalid typedef Executor<PALGO> EPALGO; typedef Algo<EPALGO> AEPALGO; Executor<PALGO> executor(PALGO()); AEPALGO::E = executor; }

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  • Brilliant features of C++

    - by John
    (Following Features to remove from C++ and Desired features for C++, I thought why not complete the trio...) What C++ features would you not change? What features are elegantly and brilliantly implemented and still look better than other popular languages?

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  • Performance improvement of client server system

    - by Tanuj
    I have a legacy client server system where the server maintains a record of some data stored in a sqlite database. The data is related to monitoring access patterns of files stored on the server. The client application is basically a remote viewer of the data. When the client is launched, it connects to the server and gets the data from the server to display in a grid view. The data gets updated in real time on the server and the view in the client automatically gets refreshed. There are two problems with the current implementation: When the database gets too big, it takes a lot of time to load the client. What are the best ways to deal with this. One option is to maintain a cache at the client side. How to best implement a cache ? How can the server maintain a diff so that it only sends the diff during the refresh cycle. There can be multiple clients and each client needs to display the latest data available on the server. The server is a windows service daemon. Both the client and the server are implemented in C#

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  • What technologies/tools do people use to implement live websites ?

    - by MadSeb
    Hi, I have the following situation: -I have a server A hooked up to a piece of hardware that sends values and information out of every second. Programs on the server machine can read these values. This server A is in a very remote location so Internet connection is very slow and not reliable but the connection does exist. Let's say it's a weather station in the Arctic. -Users from the home location want to monitorize the weather values somehow. Well, the users can use a remote desktop connection the server A but that would be too too slow. My idea is somehow to have a website on a web server (let's call the webserver - B and B is in a home location ) and make the server A connect to the server B and somehow send values and the web application reads the values and displays them....... but how to do such a system ?? I know I can use MySQL and have the server A connect to a SQL server on server B and send INSERT queries and have the web application running on server B constantly read from the SQL server but I think that would be way way too slow and I think there has to be a better solution. Any ideas ? BTW. The users should be able to send information to the weather station from the website as well ( so an ADMIN user should be allowed to shut down the weather station from the website or whatever) Best regards, MadSeb

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  • Unit Testing User Interface. What is an effective way ?

    - by pierocampanelli
    I have an accounting & payroll client/server application where there are several input form with complex data validation rules. I am finding an effective way to perform unit testing of user interface. For complex validation rules I mean: "Disable button X if I Insert a value in textfield Y" "Enable a combobox if I insert a value in a textfield" ...... ...... Most promising pattern i have found is suggested by M. Fowler (http://martinfowler.com/eaaDev/ModelViewPresenter.html). Have you any experience about Unit Testing of User Interface? As technology stack I am using: .NET 3.5 & Windows Forms Widget Library.

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  • How would you code an efficient Circular Buffer in Java or C#

    - by Cheeso
    I want a simple class that implements a fixed-size circular buffer. It should be efficient, easy on the eyes, generically typed. EDIT: It need not be MT-capable, for now. I can always add a lock later, it won't be high-concurrency in any case. Methods should be: .Add and I guess .List, where I retrieve all the entries. On second thought, Retrieval I think should be done via an indexer. At any moment I will want to be able to retrieve any element in the buffer by index. But keep in mind that from one moment to the next Element[n] may be different, as the Circular buffer fills up and rolls over. This isn't a stack, it's a circular buffer. Regarding "overflow": I would expect internally there would be an array holding the items, and over time the head and tail of the buffer will rotate around that fixed array. But that should be invisible from the user. There should be no externally-detectable "overflow" event or behavior. This is not a school assignment - it is most commonly going to be used for a MRU cache or a fixed-size transaction or event log.

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  • Auto scale and rotate images

    - by Dave Jarvis
    Given: two images of the same subject matter; the images have the same resolution, colour depth, and file format; the images differ in size and rotation; and two lists of (x, y) co-ordinates that correlate the images. I would like to know: How do you transform the larger image so that it visually aligns to the second image? (Optional.) What are the minimum number of points needed to get an accurate transformation? (Optional.) How far apart do the points need to be to get an accurate transformation? The transformation would need to rotate, scale, and possibly shear the larger image. Essentially, I want to create (or find) a program that does the following: Input two images (e.g., TIFFs). Click several anchor points on the small image. Click the several corresponding anchor points on the large image. Transform the large image such that it maps to the small image by aligning the anchor points. This would help align pictures of the same stellar object. (For example, a hand-drawn picture from 1855 mapped to a photograph taken by Hubble in 2000.) Many thanks in advance for any algorithms (preferably Java or similar pseudo-code), ideas or links to related open-source software packages.

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