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• partial entity loading and management in silverlight / wcf ria

  - by Dan Wray

  I have a Silverlight 4 app which pulls entities down from a database using WCF RIA services. These data objects are fairly simple, just a few fields but one of those fields contains binary data of an arbitrarily size. The application needs access to this data basically asap after a user has logged in, to display in a list, enable selection etc. My problem is because of the size of this data, the load times are not acceptable and can approach the default timeout of the RIA service. I'd like to somehow partially load the objects into my local data context so that I have the IDs, names etc but not the binary data. I could then at a later point (ie when it's actually needed) populate the binary fields of those objects I need to display. Any suggestions on how to accomplish this would be welcome. Another approach which has occurred to me whilst writing this question (how often does that happen?!) is that I could move the binary data into a seperate database table joined to the original record 1:1 which would allow me to make use of RIA's lazy loading on that binary data. again.. comments welcome! Thanks.

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• Cache consistency & spawning a thread

  - by Dave Keck

  Background I've been reading through various books and articles to learn about processor caches, cache consistency, and memory barriers in the context of concurrent execution. So far though, I have been unable to determine whether a common coding practice of mine is safe in the strictest sense. Assumptions The following pseudo-code is executed on a two-processor machine: int sharedVar = 0; myThread() { print(sharedVar); } main() { sharedVar = 1; spawnThread(myThread); sleep(-1); } main() executes on processor 1 (P1), while myThread() executes on P2. Initially, sharedVar exists in the caches of both P1 and P2 with the initial value of 0 (due to some "warm-up code" that isn't shown above.) Question Strictly speaking – preferably without assuming any particular CPU – is myThread() guaranteed to print 1? With my newfound knowledge of processor caches, it seems entirely possible that at the time of the print() statement, P2 may not have received the invalidation request for sharedVar caused by P1's assignment in main(). Therefore, it seems possible that myThread() could print 0. References These are the related articles and books I've been reading. (It wouldn't allow me to format these as links because I'm a new user - sorry.) Shared Memory Consistency Models: A Tutorial hpl.hp.com/techreports/Compaq-DEC/WRL-95-7.pdf Memory Barriers: a Hardware View for Software Hackers rdrop.com/users/paulmck/scalability/paper/whymb.2009.04.05a.pdf Linux Kernel Memory Barriers kernel.org/doc/Documentation/memory-barriers.txt Computer Architecture: A Quantitative Approach amazon.com/Computer-Architecture-Quantitative-Approach-4th/dp/0123704901/ref=dp_ob_title_bk

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• Movies recommendation engine conceptual database design

  - by Supyxy

  I am working at an movie recommendations engine and i'm facing a DB design issue. My actual database looks like this: MOVIES [ID,TITLE] KEYWORDS_TABLE [ID,KEY_ID] - where ID is Foreign Key for MOVIES.id and KEY_ID is a key for a text keywords table This is not the entire DB, but i showed here what's important for my problem. I have about 50,000 movies and about 1,3 milion keywords correlations, and basically my algorithm consists in extracting all the who have the same keywords with a given movie, then ordering them by the number of keywords correlations. For example i looked for a movie similar to 'Cast away' and it returned 'Six days and six nights' because it had the most keywords correlations (4 keywords): Island Airplane crash Stranded Pilot The algorithm is based on more factors, but this one is the most important and the most difficult for the approach. Basically what i do now is getting all the movies that have at least one keyword similar to the given movie and then ordering them by other factors which are not important for a moment. There wouldn't be any problem if there weren't so many records, a query lasts in many cases up to 10-20 seconds and some of them return even over 5000 movies. Someone already helped me on here (thanks Mark Byers) with optimizing the query but that's not enough because it takes too longer SELECT DISTINCT M.title FROM keywords_table K1 JOIN keywords_table K2 ON K2.key_id = K1.key_id JOIN movies M ON K2.id = M.id WHERE K1.id = 4 So i thought it would be better if i pre-made those lists with movies recommendations for each movie, but i'm not sure how to design the tables.. whatever is it a good idea or how would you take this approach?

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• Localization: How to allow the user to define custom resources without compiling?

  - by gehho

  In our application, we have a collection of data items, each with a DisplayedName property. This property should be localized, i.e. it should be displayed in the language selected by the user. Therefore, another property, DisplayedNameResourceKey, specifies which resource should be returned by the DisplayedName property. In simplified code this means something like this: public string DisplayedName { get { return MyResources.ResourceManager.GetObject(this.DisplayedNameResourceKey); } } public string DisplayedNameResourceKey { get; set; } Now, the problem is: The user should be able to edit these items including the DisplayedName, or more precisely the DisplayedNameResourceKey. And not only this, but the user should also be able to somehow define new resources which he can then reference. That is, he can either choose from a predefined set of resources (some commonly used names), or define a custom resource which then needs to be localized by the user as well. However, the user cannot add custom resources to MyResources at runtime and without compiling. Therefore, another approach is needed. It does not have to be an extremely user-friendly way (e.g. UI is not required) because this will typically be done by our service engineers. I was thinking about using a txt or csv file containing pairs of resource keys and the corresponding translations. A separate file would exist for every language at a predefined location. But I am not really satisfied with that idea because it involves a lot of work to resolve the resources. Does anyone know a good approach for such a situation?

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• ANTLR Tree Grammar and StringTemplate Code Translation

  - by Behrooz Nobakht

  I am working on a code translation project with a sample ANTLR tree grammar as: start: ^(PROGRAM declaration+) -> program_decl_tmpl(); declaration: class_decl | interface_decl; class_decl: ^(CLASS ^(ID CLASS_IDENTIFIER)) -> class_decl_tmpl(cid={$CLASS_IDENTIFIER.text}); The group template file for it looks like: group My; program_decl_tmpl() ::= << *WHAT?* >> class_decl_tmpl(cid) ::= << public class <cid> {} >> Based on this, I have these questions: Everything works fine apart from that what I should express in WHAT? to say that a program is simply a list of class declarations to get the final generated output? Is this approach averagely suitable for not so a high-level language? I have also studied ANTLR Code Translation with String Templates, but it seems that this approach takes much advantage of interleaving code in tree grammar. Is it also possible to do it as much as possible just in String Templates?

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• What is the best way to iterate over a large result set in JDBC/iBatis 3?

  - by paul_sns

  We're trying to iterate over a large number of rows from the database and convert those into objects. Behavior will be as follows: Result will be sorted by sequence id, a new object will be created when sequence id changes. The object created will be sent to an external service and will sometimes have to wait before sending another one (which means the next set of data will not be immediately used) We already have invested code in iBatis 3 so an iBatis solution will be the best approach for us (we've tried using RowBounds but haven't seen how it does the iteration under the hood). We'd like to balance minimizing memory usage and reducing number of DB trips. We're also open to pure JDBC approach but we'd like the solution to work on different databases. UPDATE: We need to make as few calls to DB as possible (1 call would be the ideal scenario) while also preventing the application to use too much memory. Are there any other solutions out there for this type of problem may it be pure JDBC or any other technology? Thanks and hope to hear your insights on this.

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• OpenCV shape matching

  - by MAckerman

  I'm new to OpenCV (am actually using Emgu CV C# wrapper) and am attempting to do some object detection. I'm attempting to determine if an object matches a predefined set of objects (that I will have to define). The background is well lit and does not move. My objects that I am starting with are bottles and cans. My current approach is: Do absDiff with a previously taken background image to separate the background. Then dilate 4x to make the lighter areas (in labels) shrink. Then I do a binary threshold to get a big blog, followed by finding contours in this image. I then take the largest contour and draw it, which becomes my shape to either save to the accepted set or compare with the accepted set. Currently I'm using cvMatchShapes, but the double return value seems to vary widely. I'm guessing it is because it doesn't take into account rotation. Is this approach a good one? It isn't working well for glass bottles since the edges are hard to find... I've read about haar classifiers, but thinking that might be overkill for my task.

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• Extracting note onset from MIDI

  - by Dolphin

  Hi I need to extract musical features (note details-pitch, duration, rhythm, loudness, note start time) from a polyphonic (having 2 scores for treble and bass - bass may also have chords) MIDI file. I'm using the jMusic API to extract these details from a MIDI file. My approach is to go through each score, into parts, then phrases and finally notes and extract the details. With my approach, it's reading all the treble notes first and then the bass notes - but chords are not captured (i.e. only a single note of the chord is taken), and I cannot identify from which point onwards are the bass notes. So what I tried was to get the note onsets (i.e. the start time of note being played) - since the starting time of both the treble and bass notes at the start of the piece should be same - But I cannot extract the note onset using jMusic API. Each time it shows 0.0. Is there any way I can identify the voice (treble or bass) of a note? And also all the notes of a chord? How is the voice or note onset for each note stored in MIDI? Is this different for each MIDI file? Any insight is greatly appreciated. Thanks in advance

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• web design question (php/ajax)

  - by tom smith

  Hi guys... Hope this isn't a waste of your time. I'm working on a project, and it occured to me that there's a chunk of code out there, that should allow me to see how others have implemented this. I've got a project where I'm going to have a page, with a sel box. the user will select an item from the selList, and based on the item selected, a separate section of the page (areaB) will change in terms of the content/tbls being displayed. i then want to allow the user to go through a series of subpages in areaB, where the user goes through a submit/cancel/confirm process, where the stuff in areaB changes, with the rest of the page remaining the same... i'm trying to figure out the best approach to implement the on both client/server side. i could just have an ugly "if block" where i have abunch of logic, and i completely regen the page each time the user selects an action.. i could have an approach that might involve divs/frames, where i then just regen the targeted frame/div area.. is this even possible?? i could have some form of ajaxy process, which would only alter the targeted section(s) of the page... so.. i'm trying to talk to anyone who has ideas on how to do this, or more ideally, if you know of a good code (client/server) side example of this... that i can examine. i'd really appreciate it!! i've got a more detailed overview but didn't know if it would be cool to post it here... thanks.. tom

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• Exporting dataset to Excel file with multiple sheets in ASP.NET

  - by engg

  In C# ASP.NET 3.5 web application, I need to export multiple datatables (or a dataset) to an Excel 2007 file with multiple sheets, and then provide the user with 'Open/Save' dialog box, WITHOUT saving the Excel file on the web server. I have used Excel Interop before. I have been reading that it's not efficient and is not the best approach to achieve this and there are more ways to do it, 2 of them being: 1) Converting data in datatables to an XML string that Excel understands 2) Using OPEN XML SDK 2.0. It looks like OPEN XML SDK 2.0 is better, please let me know. Are there any other ways to do it? I don't want to use any third-party tools. If I use OPEN XML SDK, it creates an excel file, right? I don't want to save it on the (Windows 2003) server hard drive (I don't want to use Server.MapPath, these Excel files are dynamically created, and they are not required on the server, once client gets them). I directly want to prompt the user to open/save it. I know how to do it when the 'XML string' approach is used. Please help. Thank you.

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• Detect IE version in Javascript

  - by Chad Decker

  I want to bounce users of our web site to an error page if they're using a version of Internet Explorer prior to v9. It's just not worth our time and money to support IE pre-v9. Users of all other non-IE browsers are fine and shouldn't be bounced. Here's the proposed code: if(navigator.appName.indexOf("Internet Explorer")!=-1){ //yeah, he's using IE var badBrowser=( navigator.appVersion.indexOf("MSIE 9")==-1 && //v9 is ok navigator.appVersion.indexOf("MSIE 1")==-1 //v10, 11, 12, etc. is fine too ); if(badBrowser){ // navigate to error page } } Will this code do the trick? To head off a few comments that will probably be coming my way: [1] Yes, I know that users can forge their useragent string. I'm not concerned. [2] Yes, I know that programming pros prefer sniffing out feature-support instead of browser-type but I don't feel this approach makes sense in this case. I already know that all (relevant) non-IE browsers support the features that I need and that all pre-v9 IE browsers don't. Checking feature by feature throughout the site would be a waste. [3] Yes, I know that someone trying to access the site using IE v1 (or = 20) wouldn't get 'badBrowser' set to true and the warning page wouldn't be displayed properly. That's a risk we're willing to take. [4] Yes, I know that Microsoft has "conditional comments" that can be used for precise browser version detection. IE no longer supports conditional comments as of IE 10, rendering this approach absolutely useless. Any other obvious issues to be aware of? Thanks.

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• Building a formset dynamically

  - by vorpyg

  I initially wrote code to build a form dynamically, based on data from the DB, similar to what I described in my previous SO post. As SO user Daniel Roseman points out, he would use a formset for this, and now I've come to the realization that he must be completely right. :) My approach works, basically, but I can't seem to get validation across the entire form to be working properly (I believe it's possible, but it's getting quite complex, and there has to be a smarter way of doing it = Formsets!). So now my question is: How can I build a formset dynamically? Not in an AJAX way, I want each form's label to be populated with an FK value (team) from the DB. As I have a need for passing parameters to the form, I've used this technique from a previous SO post. With the former approach, my view code is (form code in previous link): def render_form(request): teams = Team.objects.filter(game=game) form_collection = [] for team in teams: f = SuggestionForm(request.POST or None, team=team, user=request.user) form_collection.append(f) Now I want to do something like: def render_form(request): teams = Team.objects.filter(game=game) from django.utils.functional import curry from django.forms.formsets import formset_factory formset = formset_factory(SuggestionForm) for team in teams: formset.form.append(staticmethod(curry(SuggestionForm, request.POST or None, team=team, user=request.user))) But the append bit doesn't work. What's the proper way of doing this? Thanks!

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• How to restrict access to a class's data based on state?

  - by Marcus Swope

  In an ETL application I am working on, we have three basic processes: Validate and parse an XML file of customer information from a third party Match values received in the file to values in our system Load customer data in our system The issue here is that we may need to display the customer information from any or all of the above states to an internal user and there is data in our customer class that will never be populated before the values have been matched in our system (step 2). For this reason, I would like to have the values not even be available to be accessed when the customer is in this state, and I would like to have to avoid some repeated logic everywhere like: if (customer.IsMatched) DisplayTextOnWeb(customer.SomeMatchedValue); My first thought for this was to add a couple interfaces on top of Customer that would only expose the properties and behaviors of the current state, and then only deal with those interfaces. The problem with this approach is that there seems to be no good way to move from an ICustomerWithNoMatchedValues to an ICustomerWithMatchedValues without doing direct casts, etc... (or at least I can't find one). I can't be the first to have come across this, how do you normally approach this? As a last caveat, I would like for this solution to play nice with FluentNHibernate :) Thanks in advance...

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• Format for storing contacts in a database

  - by Gart

  I'm thinking of the best way to store personal contacts in a database for a business application. The traditional and straightforward approach would be to create a table with columns for each element, i.e. Name, Telephone Number, Job title, Address, etc... However, there are known industry standards for this kind of data, like for example vCard, or hCard, or vCard-RDF/XML or even Windows Contacts XML Schema. Utilizing an standard format would offer some benefits, like inter-operablilty with other systems. But how can I decide which method to use? The requirements are mainly to store the data. Search and ordering queries are highly unlikely but possible. The volume of the data is 100,000 records at maximum. My database engine supports native XML columns. I have been thinking to use some XML-based format to store the personal contacts. Then it will be possible to utilize XML indexes on this data, if searching and ordering is needed. Is this a good approach? Which contacts format and schema would you recommend for this?

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• SQL Query: How to determine "Seen during N hour" if given two DateTime time stamps?

  - by efess

  Hello all. I'm writing a statistics application based off a SQLite database. There is a table which records when users Login and Logout (SessionStart, SessionEnd DateTimes). What i'm looking for is a query that can show what hours user have been logged in, in sort of a line graph way- so between the hours of 12:00 and 1:00AM there were 60 users logged in (at any point), between the hours of 1:00 and 2:00AM there were 54 users logged in, etc... And I want to be able to run a SUM of this, which is why I can't bring the records into .NET and iterate through them that way. I've come up with a rather primative approach, a subquery for each hour of the day, however this approach has proved to be slow and slow. I need to be able to calculate this for a couple hundred thousand records in a split second.. SELECT case when (strftime('%s',datetime(date(sessionstart), '+0 hours')) > strftime('%s',sessionstart) AND strftime('%s',datetime(date(sessionstart), '+0 hours')) < strftime('%s',sessionend)) OR (strftime('%s',datetime(date(sessionstart), '+1 hours')) > strftime('%s',sessionstart) AND strftime('%s',datetime(date(sessionstart), '+1 hours')) < strftime('%s',sessionend)) OR (strftime('%s',datetime(date(sessionstart), '+0 hours')) < strftime('%s',sessionstart) AND strftime('%s',datetime(date(sessionstart), '+1 hours')) > strftime('%s',sessionend)) then 1 else 0 end as hour_zero, ... hour_one, ... hour_two, ........ hour_twentythree FROM UserSession I'm wondering what better way to determine if two DateTimes have been seen durring a particular hour (best case scenario, how many times it has crossed an hour if it was logged in multiple days, but not necessary)? The only other idea I had is have a "hour" table specific to this, and just tally up the hours the user has been seen at runtime, but I feel like this is more of a hack than the previous SQL. Any help would be greatly appreciated!

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• Take Current Snapshot of DB and send it to FTP in same PHP Scripts: Advice Needed

  - by Rachel

  Not sure if I can do it this way. I want to get current snapshot of the database and send it via FTP Server, both of this functionality should be implemented in PHP scripts. Here are the steps I am thinking on right now. In my php scripts(basically am extending an PDO into my Dao class and then preparing the query), $qry = SELECT * FROM MyTablename; $stmt = $this->prepare($qry); $stmt = $this->execute(); Now I will store $stmt in csv file using fputcsv or I will execute the sql command from the script itself and than try to store the result in the $file(csv file) note here that I do not have any csv file with me at this point to basically I will have to create one and let's say its $file, so then $file = fputcsv($stmt); or $file = exec("Select * from MyTablename"); Will this put all records in the file ? If yes, then I will use FTP Functionality to transfer file to the FTP Folder. I am not sure if this approach would work and also have concerns regarding the need of preparing the $qry Any suggestions or different approach advised would be highly appreciated. Thanks !!!

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• Build number increment not reflected in AssemblyVersion

  - by awshepard

  I've browsed through some of the discussion on auto-incrementing build numbers, but in the impatience of youth decided to roll my own and re-invent the wheel. I know there are probably better ways to go about this (which I'm definitely going to investigate), but my question centers more around the Assembly and/or Version classes. My approach was to write a separate exe (BuildIncrementer) that takes a command line parameter for file name, does a regex match on the contents to grab the [assembly: AssemblyVersion...] string, do the modifications that I want (increment the build number, etc.), then write the contents back to the file. This approach works as-is. The next thing I did was in the project that I wanted to use this on, I set up a pre-build command line that is simply the command to execute that BuildIncrementer.exe on this project's AssemblyInfo.cs file. This too works, updating the assembly info as desired. The problem comes when I run the project, it sends an email containing the current version, obtained with Assembly.GetExecutingAssembly().GetName().Version.ToString(). BUT, the version showing up is the previous version. When my AssemblyInfo.cs says [assembly: AssemblyVersion("1.0.2.49667")], I get sent 1.0.1.45660, which was the previous build. Anyone have any ideas why that might be?

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• working with large sprite sheets on iphone

  - by lukya

  Hi All, I am trying to use sprite sheet animation in my application. The first POC with a small sprite sheet worked fine but as i change the sprite sheet to a bigger one, i get "check_safe_call: could not restore current frame" warning and the application quits. A quick search revealed that this problem meant my app is taking too much memory or the image is too huge in dimension. My image is 4.9 Mb and dimensions are 6720 * 10080 (oops!!). i read that iphone allows maximum 3 Mb image with dimensions up to 1024 * 1024. Also that the sprite sheet image dimensions should be a power of two. So please let me know how i can use a sprite sheet this big. One approach could be to cut the sprite sheet into many smaller sprite sheets and use them one at a time. Please suggest if you know any other/better approach to accommodate bigger sprite sheets and whether the problem with my sprite sheet is size (4.9 Mb) OR dimensions (6720 * 10080). (Just FYI, i am not trying to play a movie so using MP4 file instead is not an option for me. i need to animate the sprite sheet based on accelerometer input and i have been able to achieve that in my POC with smaller sprite sheet.) Thanks, Swapnil

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• How to configure database connection securely

  - by chiccodoro

  Similar but not the same: How to securely store database connection details Securely connecting to database within a application Hi all, I have a C# WinForms application connecting to a database server. The database connection string, including a generic user/pass, is placed in a NHibernate configuration file, which lies in the same directory as the exe file. Now I have this issue: The user that runs the application should not get to know the username/password of the general database user because I don't want him to rummage around in the database directly. Alternatively I could hardcode the connection string, which is bad because the administrator must be able to change it if the database is moved or if he wants to switch between dev/test/prod environments. So long I've found three possibilities: The first referenced question was generally answered by making the file only readable for the user that runs the application. But that's not not enough in my case (the user running the application is a person. The database user/pass are general and shouldn't even be accessible by the person.) The first answer additionally proposed to encrypt the connection data before writing it to the file. With this approach, the administrator is not able anymore to configure the connection string because he cannot encrypt it by hand. The second referenced question provides an approach for this very scenario but it seems very complicated. My questions to you: This is a very general issue, so isn't there any general "how-to-do-it" way, somehow a "design pattern"? Is there some support in .NET's config infrastructure? (optional, maybe out of scope) Can I combine that easily with the NHibernate configuration mechanism?

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• Presenting an image cropping interface

  - by wkw

  I'm trying to engineer a UI for cropping images in iphone OS and suspect I'm going about things the hard way. My goal is pretty much what the Tapbots duo have done with Pastebot. In that app, they dim the source image but provide a movable and resizable cropping view and the image you're cropping is in a zoomable scrollview; when you resize or move the underlying image, the cropping view adjusts appropriately. I mocked up a composite image which will give a sense of the design I'm after, along with how I presently have my view hierarchy setup, viewable here The approach I've started with is the following: UIImageView with the image to crop is in a scrollview, a plain UIView with black fill and suitable transparency/alpha setting is added in front of the imageview. I then use a custom UIView which is a sibling to the scrollview at a higher level, which implements the drawRect: method and for the most part calls CGImageCreateWithImageInRect to get the portion of the image's bitmap that matches the position of the cropping view and draws that to the CGContext. in the viewcontroller I'm using the UIScrollViewDelegate methods to track scrolling and passing those changes to the custom cropping UIView so it stays in sync with the scroll contentOffset. That much is finally working. But trying to keep in sync as the scrollview zoomScale changes is when I figured I should ask for help. Looking for suggestions or guidance. My initial approach just seems like more work than is required. Could this be done with a masking layer in the ImageView? And if so, how would I setup the tracking for moving and resizing the cropping rect? My experience working with layers is non-nil, but very limited thus far.

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• what kind of relationship is there between a common wall and the rooms that located next to it?

  - by siamak

  I want to know whats the Relationship between a common wall (that are located In an adjoining room ) and the rooms. As i know the relationship between a room and its walls is Composition not Aggregation (am i right ?) And according to the definition of Composition the contained object can't be shared between two containers, whereas in aggregation it is possible. now i am confused that whats the best modeling approach to represent the relationship between a common wall and the rooms located next to it ? It would be highly Appreciated if you could provide your advices with some code. |--------|--------| Approch1: (wall class ---- room class) /Composition Approach2: wall class ----- room class /Aggregation Approch3: we have a wall class and a Common wall class , Common wall class inherits from wall class adjoining room class ---- (1) Common wall class /Aggregation adjoining room class ---- (6) wall class / composition Approach4: I am a developer not a designer :) so this is my idea : class Room { private wall _firstwall ; private wall _secondtwall; private wall _thirdwall ; private wall _commonwall ; public Room( CommonWall commonwall) { _firstwall=new Wall(); _secondtwall=new Wall(); _thirdwall=new Wall(); _commonwall=commonwall; } } Class CommonWall:Wall { //... } // in somewher : static void main() { Wall _commonWall=new Wall(); Room room1=new Room(_commonWall); Room room2=new Room(_commonWall); Room [] adjacentRoom =new Room[2]{room1,room2}; } Edit 1: I think this is a clear question but just for more clarification : The point of the question is to find out whats the best pattern or approach to model a relationship for an object that is a component of two other objects in the same time. and about my example : waht i mean by a "room" ?,surely i mean an enclosed square room with 4 walls and one door.but in this case one of these walls is a common wall and is shared between two adjacent rooms.

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• Recursively MySQL Query

  - by Rachel

  How can I implement recursive MySQL Queries. I am trying to look for it but resources are not very helpful. Trying to implement similar logic. public function initiateInserts() { //Open Large CSV File(min 100K rows) for parsing. $this->fin = fopen($file,'r') or die('Cannot open file'); //Parsing Large CSV file to get data and initiate insertion into schema. $query = ""; while (($data=fgetcsv($this->fin,5000,";"))!==FALSE) { $query = $query + "INSERT INTO dt_table (id, code, connectid, connectcode) VALUES (" + $data[0] + ", " + $data[1] + ", " + $data[2] + ", " + $data[3] + ")"; } $stmt = $this->prepare($query); // Execute the statement $stmt->execute(); $this->checkForErrors($stmt); } @Author: Numenor Error Message: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '0' at line 1 This Approach inspired to look for an MySQL recursive query approach.

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• Passing data between ViewControllers versus doing local Fetch in each VC

  - by Tofrizer

  Hi All, I'm developing an iPhone app using Core Data and I'm looking for some general advice and recommendations on whether its acceptable to pass data between ViewControllers versus doing a local fetch in each ViewController as you navigate to it. Ordinarily I would say it all depends on various factors (e.g. performance etc) but the passing data approach is so prevalent in my app and I'm spooked by all the stories about Apple rejecting apps because of not conforming to their standard guidelines. So let me put another way -- is it non-standard to pass data between VC's? The reason I pass data so much is because each ViewController is just another view on to data present in my object model / graph. Once I have a handle on my first object in the first view controller (which I of course do have to fetch), I can use the existing object composition / relationships to drill down into the next level of detail into data and so I just pass these objects to the next VC. Separately, one possible downside with this passing-data-to-each-VC approach is I don't benefit from (what I perceive to be) the optimisation/benefits that NSFetchedResultsController provides in terms of efficient memory usage and section handling. My app is read-only but I do have one table with 5000 rows and I'm curious if I am missing out on NSFetchedResultsController benefits. Any thoughts on this as well? Can I somehow still benefit from NSFetchedResultsController goodness without having to do a full fetch (as I would have already passed in the data from my previous VC)? Thanks a lot.

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• Temporary users table or legitimate users table?

  - by John

  I have a freelance web application that lets users register for events. In my database, I have a t_events_applicants table with the column t_events_applications.user_id with a foreign key constraint linked to the t_users.user_id column. So this means only users who have registered with my web application can register for my web application's events. My client would now like to allow non-registered users, users who do not have an entry in my t_user table, to register for events. These non-registered users only need to provide their name and email address to register for events. Should I create a t_temporary_user table with columns name and email and then remove the t_events_applicants.user_id fk constraint? Or should I add un-registered users to the t_user table and then add a column called t_user.type where type can be 'registered' or 'non-registered'? How do I decide which approach to go with? A lot of times, I hesitate with either approach. I ask myself, "What if at a later time, a temporary user is allowed to become a fully registered user? Then maybe I should have only a t_user table. But then I also don't feel good about storing a lot of temporary users in t_user."

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• Optimizing processing and management of large Java data arrays

  - by mikera

  I'm writing some pretty CPU-intensive, concurrent numerical code that will process large amounts of data stored in Java arrays (e.g. lots of double[100000]s). Some of the algorithms might run millions of times over several days so getting maximum steady-state performance is a high priority. In essence, each algorithm is a Java object that has an method API something like: public double[] runMyAlgorithm(double[] inputData); or alternatively a reference could be passed to the array to store the output data: public runMyAlgorithm(double[] inputData, double[] outputData); Given this requirement, I'm trying to determine the optimal strategy for allocating / managing array space. Frequently the algorithms will need large amounts of temporary storage space. They will also take large arrays as input and create large arrays as output. Among the options I am considering are: Always allocate new arrays as local variables whenever they are needed (e.g. new double[100000]). Probably the simplest approach, but will produce a lot of garbage. Pre-allocate temporary arrays and store them as final fields in the algorithm object - big downside would be that this would mean that only one thread could run the algorithm at any one time. Keep pre-allocated temporary arrays in ThreadLocal storage, so that a thread can use a fixed amount of temporary array space whenever it needs it. ThreadLocal would be required since multiple threads will be running the same algorithm simultaneously. Pass around lots of arrays as parameters (including the temporary arrays for the algorithm to use). Not good since it will make the algorithm API extremely ugly if the caller has to be responsible for providing temporary array space.... Allocate extremely large arrays (e.g. double[10000000]) but also provide the algorithm with offsets into the array so that different threads will use a different area of the array independently. Will obviously require some code to manage the offsets and allocation of the array ranges. Any thoughts on which approach would be best (and why)?

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