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  • How can I do rapid application development with ASP.NET MVC?

    - by Erik Forbes
    I've been given a short amount of time (~80 hours to start with) to replace an existing Access database with a full-blown SQL + Web system, and I'm enumerating my options. I would like to use ASP.NET MVC, but I'm unsure of how to use it effectively with my short timetable. For the database backend I'll be using Linq to SQL as it's a product I already know and can get something working with it quickly. Does anyone have any experience with using ASP.NET MVC in this way and can share some insight? Edit: The reason I've been interested in ASP.NET MVC is because I know (100% confirmed) that there will be more work to do after this first round, and I'd like my maintenance work to be as easy as possible. In my experience Webforms applications tend to break down over repeated maintenance, despite discipline. Maybe there's a middle ground? How difficult would it to be for me to, say, build the app with Webforms, then migrate it to MVC later when I have more time budgeted to the project? Edit 2: Further background: the Access application I'm replacing is used in some capacity by everyone in the building, and since it was upgraded from Access 98 to 2003 it's been crashing daily, causing hours of lost productivity as people have to re-enter data since the last backup. This is the reason for the short amount of time - this is a critical business function, and they can't afford to keep re-entering data on a daily basis.

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  • Visual Studio 2008 project file does not load because of an unexpected encoding change.

    - by Xenan
    In our team we have a database project in visual Studio 2008 which is under source control by Team Foundation Server. Every two weeks or so, after one co-worker checks in, the project file won't load on the other developers machines. The error message is: The project file could not be loaded. Data at the root level is invalid. Line 1, position 1. When I look at the project file in Notepad++, the file looks like this: ??<NUL?NULxNULmNULlNUL NULvNULeNULrNULsNULiNULoNULnNUL ... and so on (you can see <?xml version in this) whereas an normal project file looks like: <?xml version="1.0" encoding="utf-16"?> ... So probably something is wrong with the encoding of the file. This is a problem for us because it turns out to be impossible to get the file encoding correct again. The 'solution' is to throw away the project file an get the last know working version from source control. According to the file, the encoding should be UTF-16. According to Notepad++, the corrupted file is actually UTF-8. My questions are: Why is Visual Studio messing up the encoding of the project file, apparently at random times and at random machines? What should we do to prevent this? When it has happened, is there a possibility to restore the current file in the correct encoding instead of pulling an older version from source control? As a last note: the problem is with one single project file, all other project files don't expose this problem.

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  • How do I pass a lot of parameters to views in Dango?

    - by Mark
    I'm very new to Django and I'm trying to build an application to present my data in tables and charts. Till now my learning process went very smooth, but now I'm a bit stuck. My pageview retrieves large amounts of data from a database and puts it in the context. The template then generates different html-tables. So far so good. Now I want to add different charts to the template. I manage to do this by defining <img src=".../> tags. The Matplotlib chart is generate in my chartview an returned via: response=HttpResponse(content_type='image/png') canvas.print_png(response) return response Now I have different questions: the data is retrieved twice from the database. Once in the pageview to render the tables, and again in the chartview for making the charts. What is the best way to pass the data, already in the context of the page to the chartview? I need a lot of charts, each with different datasets. I could make a chartview for each chart, but probably there is a better way. How do I pass the different dataset names to the chartview? Some charts have 20 datasets, so I don't think that passing these dataset parameters via the url (like: <imgm src="chart/dataset1/dataset2/.../dataset20/chart.png />) is the right way. Any advice?

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  • phppgadmin : How does it kick users out of postgres, so it can db_drop?

    - by egarcia
    I've got one Posgresql database (I'm the owner) and I'd like to drop it and re-create it from a dump. Problem is, there're a couple applications (two websites, rails and perl) that access the db regularly. So I get a "database is being accessed by other users" error. I've read that one possibility is getting the pids of the processes involved and killing them individually. I'd like to do something cleaner, if possible. Phppgadmin seems to do what I want: I am able to drop schemas using its web interface, even when the websites are on, without getting errors. So I'm investigating how its code works. However, I'm no PHP expert. I'm trying to understand the phppgadmin code in order to see how it does it. I found out a line (257 in Schemas.php) where it says: $data->dropSchema(...) $data is a global variable and I could not find where it is defined. Any pointers would be greatly appreciated.

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  • MySQL GIS and Spatial Extensions - how to map regions and query against them

    - by chibineku
    I am trying to make a smartphone app which will return a list of users within a certain proximity, say 100m. It's easy to get the coordinates of my BlackBerry and write them to a database, but in order to return a list of other users within 100m, I need to pull every other record from the database and compare the distance between the two points, checking to see if it's within range, before outputting that user's information. This is going to be time consuming if there are many users involved. So I would like to map areas (countries, cities, I'm not yet sure of the resolution I'll need) so that I can first target a smaller subset of all users. This will save on processing time. I have read the basics of GIS and spatial querying on the mysql website but to be honest the query is over my head and I hate copying and pasting code without understanding it. Plus it only checks for proximity - I want to first check if a coordinate falls within a certain area. Does anyone have any experience of such matters and feel like giving me some pointers? Resources such as any preexisting databases of points describing countries as polygons would be really helpful too. Many thanks to anyone who takes the time :)

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  • What do these .NET auto-generated table adapter commands do? e.g. UPDATE/INSERT followed by a SELECT

    - by RickL
    I'm working with a legacy application which I'm trying to change so that it can work with SQL CE, whilst it was originally written against SQL Server. The problem I am getting now is that when I try to do dataAdapter.Update, SQL CE complains that it is not expecting the SELECT keyword in the command text. I believe this is because SQL CE does not support batch SELECT statements. The auto-generated table adapter command looks like this... this._adapter.InsertCommand.CommandText = @"INSERT INTO [Table] ([Field1], [Field2]) VALUES (@Value1, @Value2); SELECT Field1, Field2 FROM Table WHERE (Field1 = @Value1)"; What is it doing? It looks like it is inserting new records from the datatable into the database, and then reading that record back from the database into the datatable? What's the point of that? Can I just go through the code and remove all these SELECT statements? Or is there an easier way to solve my problem of wanting to use these data adapters with SQL CE? I cannot regenerate these table adapters, as the people who knew how to have long since left.

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  • Communication between EJB3 Instances (JEE inter-bean communication) possible?

    - by Hank
    I'm designing a part of a JEE6 application, consisting of EJB3 beans. Part of the requirements are multiple parallel (say a few hundred) long running (over days) database hunts. Individual hunts have different search parameters (start time, end time, query filter). Parameters may get changed over time. Currently I'm thinking of the following: SearchController (Stateless Session Bean) formulates a set of search parameters, sends it off to a SearchListener via JMS SearchListener (Message Driven Bean) receives search parameters, instantiates a SearchWorker with the parameters SearchWorker (SLSB) hunts repeatedly through the database; when it finds something, the result is sent off via JMS, and the search continues; when the given 'end-time' has reached, it ends What I'm wondering now: Is there a problem, with EJB3 instances running for days? (Other than that I need to be able to deal with container restarts...) How do I know how many and which EJB instances of SearchWorker are currently running? Is it possible to communicate with them individually (similar to sending a System V signal to a unix process), e.g. to send new parameters, to end an instance, etc..

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  • Python many-to-one mapping (creating equivalence classes)

    - by Adam Matan
    Hi, I have a project of converting one database to another. One of the original database columns defines the row's category. This coulmn should be mapepd to a new category in the new databse. For example, let's assume the original categories are:parrot, spam, cheese_shop, Cleese, Gilliam, Palin Now that's a little verbose for me, And I want to have these rows categorized as sketch, actor - That is, define all the sketches and all the actors as two equivalence classes. >>> monty={'parrot':'sketch', 'spam':'sketch', 'cheese_shop':'sketch', 'Cleese':'actor', 'Gilliam':'actor', 'Palin':'actor'} >>> monty {'Gilliam': 'actor', 'Cleese': 'actor', 'parrot': 'sketch', 'spam': 'sketch', 'Palin': 'actor', 'cheese_shop': 'sketch'} That's quite awkward- I would prefer having something like: monty={ ('parrot','spam','cheese_shop'): 'sketch', ('Cleese', 'Gilliam', 'Palin') : 'actors'} But this, of course, sets the entire tuple as a key: >>> monty['parrot'] Traceback (most recent call last): File "<pyshell#29>", line 1, in <module> monty['parrot'] KeyError: 'parrot' Any ideas how to create an elegant many-to-one dictionary in Python? Thanks, Adam

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  • Search book by title, and author

    - by Swoosh
    I got a table with columns: author firstname, author lastname, and booktitle Multiple users are inserting in the database, through an import, and I'd like to avoid duplicates. So I'm trying to do something like this: I have a record in the db: First Name: "Isaac" Last Name: "Assimov" Title: "I, Robot" If the user tries to add it again, it would be basically a non-split-text (would not be split up into author firstname, author lastname, and booktitle) So it would basically look like this: "Isaac Asimov - I Robot" or "Asimov, Isaac - I Robot" or "I Robot by Isaac Asimov" You see where I am getting at? (I cannot force the user to split up all the books into into author firstname, author lastname, and booktitle, and I don't even like the idea to force the user, because it's not too user-friendly) What is the best way (in SQL) to compare all this possible bookdata scenarios to what I have in the database, not to add the same book twice. I was thinking about a possibility of suggesting the user: "is THIS the book you are trying to add?" (imagine a list instead of the THIS word, just like on stackoverflow - ask question - Related Questions. I was thinking about soundex and maybe even the like operators, but so far i didn't get the results i was hoping.

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  • PHP not obeying my defined ETags

    - by Sam Bisbee
    What I'm doing I'm pulling an image from the database and sending it to the browser with all the proper headers - the image displays fine. I also send an ETag header, using the SHA1 of the image's content as the tag. The images are getting called semi regularly, so caching is a bit of an issue (won't kill the site, but nice to have). The Problem $_SERVER['HTTP_IF_NONE_MATCH'] is not available to me. As far as I can tell, this is because of PHP's "disobey the cache controls" life style. I can't mess with the session cache limiter, because I don't have access. But, even if I did have access, I wouldn't want to touch it: 99% of the site is under WordPress. The Environment PHP 4 (don't ask) Apache 2.2 WordPress The images live in the database (largeblog), which I can't change. Any guidance, tip/tricks, etc. would be helpful. I don't have much room to change the environmental/structural stuff. Cheers.

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  • Putting a C++ Vector as a Member in a Class that Uses a Memory Pool

    - by Deep-B
    Hey, I've been writing a multi-threaded DLL for database access using ADO/ODBC for use with a legacy application. I need to keep multiple database connections for each thread, so I've put the ADO objects for each connection in an object and thinking of keeping an array of them inside a custom threadInfo object. Obviously a vector would serve better here - I need to delete/rearrange objects on the go and a vector would simplify that. Problem is, I'm allocating a heap for each thread to avoid heap contention and stuff and allocating all my memory from there. So my question is: how do I make the vector allocate from the thread-specific heap? (Or would it know internally to allocate memory from the same heap as its wrapper class - sounds unlikely, but I'm not a C++ guy) I've googled a bit and it looks like I might need to write an allocator or something - which looks like so much of work I don't want. Is there any other way? I've heard vector uses placement-new for all its stuff inside, so can overloading operator new be worked into it? My scant knowledge of the insides of C++ doesn't help, seeing as I'm mainly a C programmer (even that - relatively). It's very possible I'm missing something elementary somewhere. If nothing easier comes up - I might just go and do the array thing, but hopefully it won't come to that. I'm using MS-VC++ 6.0 (hey, it's rude to laugh! :-P ). Any/all help will be much appreciated.

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  • When is Facebook Connect supposed to call its delegate methods?

    - by RickiG
    Hi The Facebook connect code is eluding me a bit. I have no problem doing a login, and a wall post, however, I simply can not figure out how the delegate methods for the FBDialog andFBStreamDialog is supposed to work. - (void)postToWall { FBStreamDialog *dialog = [[[FBStreamDialog alloc] init] autorelease]; dialog.delegate = self; dialog.userMessagePrompt = @"Enter your message:"; dialog.attachment = [NSString stringWithFormat:@"JSONpost code"]; [dialog show]; } I adhere to these protocols in my controller: <FBDialogDelegate, FBSessionDelegate, FBRequestDelegate> I then implement the two methods: - (void) dialogDidCancel:(FBDialog *)dialog { NSLog(@"Failed"); } - (void) dialogDidSucceed:(FBDialog *)dialog { NSLog(@"Success"); } After I tap "publish" and the postToWall methods is done executing the Facebook "pop up" in the UI is empty, except a small "X" in the top right corner and a "F" (facebook logo) in the top left corner. The UI will stay there until I tap the "X", this results in the dialogDidCancel delegate method being called. The post data is showing up on the Facebook page, everything seems to work. Why is thedialogDidSucceedmethod never called? I need this to release my facebook controller and restore the UI back to where the user was before "starting" FB Connect. Thank You:)

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  • How can I write System preferences with Java? Can I invoke UAC?

    - by Jonas
    How can I write system preferences with Java, using Preferences.systemRoot()? I tried with: Preferences preferences = Preferences.systemRoot(); preferences.put("/myapplication/databasepath", pathToDatabase); But I got this error message: 2010-maj-29 19:02:50 java.util.prefs.WindowsPreferences openKey VARNING: Could not open windows registry node Software\JavaSoft\Prefs at root 0x80000002. Windows RegOpenKey(...) returned error code 5. Exception in thread "AWT-EventQueue-0" java.lang.SecurityException: Could not open windows registry node Software\JavaSoft\Prefs at root 0x80000002: Access denied at java.util.prefs.WindowsPreferences.openKey(Unknown Source) at java.util.prefs.WindowsPreferences.openKey(Unknown Source) at java.util.prefs.WindowsPreferences.openKey(Unknown Source) at java.util.prefs.WindowsPreferences.putSpi(Unknown Source) at java.util.prefs.AbstractPreferences.put(Unknown Source) at biz.accountia.pos.install.Setup$2.actionPerformed(Setup.java:43) I would like to do this, because I want to install an embedded JavaDB database, and let multiple users on the computer to use the same database with the application. How to solve this? Can I invoke UAC and do this as Administrator from Java? And if I log in as Administrator when writing, can I read the values with my Java application if I'm logged in as a User?

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  • How to port an Ajax CMS based on metadata in Asp.Net MVC?

    - by Maushu
    I'm maintaining a CMS where I have this feeling it was made in the age of dinosaurs (Asp.net 1.0?) and decided to upgrade it with Asp.Net MVC and jQuery. But I have some problems regarding the design/specifications of the CMS which I cannot change. The CMS The CMS uses JavaScript. Alot. As in "I don't load pages, I request new pages using Ajax and render the information using javascript" alot. Not to mention the animations, the weird horizontal apresentation of structures... anyways, besides the first page (that is the login page) every other "page" is just data requested from a WebService that comes with the website. Would MVC have any problems with this design? The Database The database is in a SQL Server 2k8 and, like the CMS, this part is also... interesting. Basically, the user can create data structures using metadata (and saved on the Structure table). These structures are saved on tables that are created (and regenerated when changed) at runtime using said metadata. I don't know how I would implement this part in MVC. The question is, can and should I convert this project to MVC? Any tips regarding the metadata and overuse of ajax?

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  • Programatically create web application & sub site

    - by Tejas
    I am using the following code to programatically create a web application & sub site, try { SPWebApplicationBuilder webAppBuilder = new SPWebApplicationBuilder(SPFarm.Local); SPWebApplication newApplication; int myPort = 3333; webAppBuilder.Port = myPort; //Port No. webAppBuilder.RootDirectory = new System.IO.DirectoryInfo("C:\\Inetpub\\wwwroot\\wss\\VirtualDirectories\\" + myPort); webAppBuilder.CreateNewDatabase = true; // Create new database webAppBuilder.DatabaseName = "WSS_Content_372772890a5a4a04abb460cd9ea3bd22"; // Database name webAppBuilder.DatabaseServer = webAppBuilder.DefaultZoneUri.Host; // DatabaseServer Host name/computer name webAppBuilder.UseNTLMExclusively = true; // Use NTLM authentication newApplication = webAppBuilder.Create(); // Create new web application newApplication.Provision(); // Provision it into web farm using (var mySiteCollection = newApplication.Sites.Add("/", "Site 3", "Site 3 Decscription", 1033, "STS#1", "In-Wai-Svr2\\Administrator", "Administrator", "[email protected]")) { using (var rootWeb = mySiteCollection.RootWeb) { // Code customizing root site goes here using (var subSite = rootWeb.Webs.Add("Site3.1", "Site 3.1", "Site 3.1 Description", 1033, "STS#1", true, false)) { // Code customizing sub site goes here } } } } catch(Exception ex) { ; } It works fine i.e. it creates the web application on the specified port with sub site but this sub site will not be shown under Sites menu of Quick launch bar also it will not be shown as a separate tab on the Home Page. Is it possible to do it programatically?

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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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  • What is optimal hardware configuration for heavy load LAMP application

    - by Piotr Kochanski
    I need to run Linux-Apache-PHP-MySQL application (Moodle e-learning platform) for a large number of concurrent users - I am aiming 5000 users. By concurrent I mean that 5000 people should be able to work with the application at the same time. "Work" means not only do database reads but writes as well. The application is not very typical, since it is doing a lot of inserts/updates on the database, so caching techniques are not helping to much. We are using InnoDB storage engine. In addition application is not written with performance in mind. For instance one Apache thread usually occupies about 30-50 MB of RAM. I would be greatful for information what hardware is needed to build scalable configuration that is able to handle this kind of load. We are using right now two HP DLG 380 with two 4 core processors which are able to handle much lower load (typically 300-500 concurrent users). Is it reasonable to invest in this kind of boxes and build cluster using them or is it better to go with some more high-end hardware? I am particularly curious how many and how powerful servers are needed (number of processors/cores, size of RAM) what network equipment should be used (what kind of switches, network cards) any other hardware, like particular disc storage solutions, etc, that are needed Another thing is how to put together everything, that is what is the most optimal architecture. Clustering with MySQL is rather hard (people are complaining about MySQL Cluster, even here on Stackoverflow).

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  • Setting nested object to null when selected option has empty value

    - by Javi
    Hello, I have a Class which models a User and another which models his country. Something like this: public class User{ private Country country; //other attributes and getter/setters } public class Country{ private Integer id; private String name; //other attributes and getter/setters } I have a Spring form where I have a combobox so the user can select his country or can select the undefined option to indicate he doen't want to provide this information. So I have something like this: <form:select path="country"> <form:option value="">-Select one-</form:option> <form:options items="${countries}" itemLabel="name" itemValue="id"/> </form:select> In my controller I get the autopopulated object with the user information and I want to have country set to null when the "-Select one-" option has been selected. So I have set a initBinder with a custom editor like this: @InitBinder protected void initBinder(WebDataBinder binder) throws ServletException { binder.registerCustomEditor(Country.class, "country", new CustomCountryEditor()); } and my editor do something like this: public class CustomCountryEditor(){ @Override public String getAsText() { //I return the Id of the country } @Override public void setAsText(String str) { //I search in the database for a country with id = new Integer(str) //and set country to that value //or I set country to null in case str == null } } When I submit the form it works because when I have country set to null when I have selected "-Select one-" option or the instance of the country selected. The problem is that when I load the form I have a method like the following one to load the user information. @ModelAttribute("user") public User getUser(){ //loads user from database } The object I get from getUser() has country set to a specific country (not a null value), but in the combobox is not selected any option. I've debugged the application and the CustomCountryEditor works good when setting and getting the text, thoughgetAsText method is called for every item in the list "countries" not only for the "country" field. Any idea? Is there a better way to set null the country object when I select no country option in the combobox? Thanks

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  • Computing complex math equations in python

    - by dassouki
    Are there any libraries or techniques that simplify computing equations ? Take the following two examples: F = B * { [ a * b * sumOf (A / B ''' for all i ''' ) ] / [ sumOf(c * d * j) ] } where: F = cost from i to j B, a, b, c, d, j are all vectors in the format [ [zone_i, zone_j, cost_of_i_to_j], [..]] This should produce a vector F [ [1,2, F_1_2], ..., [i,j, F_i_j] ] T_ij = [ P_i * A_i * F_i_j] / [ SumOf [ Aj * F_i_j ] // j = 1 to j = n ] where: n is the number of zones T = vector [ [1, 2, A_1_2, P_1_2], ..., [i, j, A_i_j, P_i_j] ] F = vector [1, 2, F_1_2], ..., [i, j, F_i_j] so P_i would be the sum of all P_i_j for all j and Aj would be sum of all P_j for all i I'm not sure what I'm looking for, but perhaps a parser for these equations or methods to deal with multiple multiplications and products between vectors? To calculate some of the factors, for example A_j, this is what i use from collections import defaultdict A_j_dict = defaultdict(float) for A_item in TG: A_j_dict[A_item[1]] += A_item[3] Although this works fine, I really feel that it is a brute force / hacking method and unmaintainable in the case we want to add more variables or parameters. Are there any math equation parsers you'd recommend? Side Note: These equations are used to model travel. Currently I use excel to solve a lot of these equations; and I find that process to be daunting. I'd rather move to python where it pulls the data directly from our database (postgres) and outputs the results into the database. All that is figured out. I'm just struggling with evaluating the equations themselves. Thanks :)

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  • Hadoop Map/Reduce - simple use example to do the following...

    - by alexeypro
    I have MySQL database, where I store the following BLOB (which contains JSON object) and ID (for this JSON object). JSON object contains a lot of different information. Say, "city:Los Angeles" and "state:California". There are about 500k of such records for now, but they are growing. And each JSON object is quite big. My goal is to do searches (real-time) in MySQL database. Say, I want to search for all JSON objects which have "state" to "California" and "city" to "San Francisco". I want to utilize Hadoop for the task. My idea is that there will be "job", which takes chunks of, say, 100 records (rows) from MySQL, verifies them according to the given search criteria, returns those (ID's) which qualify. Pros/cons? I understand that one might think that I should utilize simple SQL power for that, but the thing is that JSON object structure is pretty "heavy", if I put it as SQL schemas, there will be at least 3-5 tables joins, which (I tried, really) creates quite a headache, and building all the right indexes eats RAM faster than I one can think. ;-) And even then, every SQL query has to be analyzed to be utilizing the indexes, otherwise with full scan it literally is a pain. And with such structure we have the only way "up" is just with vertical scaling. But I am not sure it's the best option for me, as I see how JSON objects will grow (the data structure), and I see that the number of them will grow too. :-) Help? Can somebody point me to simple examples of how this can be done? Does it make sense at all? Am I missing something important? Thank you.

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  • Collecting high-volume video viewing data

    - by DanK
    I want to add tracking to our Flash-based media player so that we can provide analytics that show what sections of videos are being watched (at the moment, we just register a view when a video starts playing) For example, if a viewer watches the first 30 seconds of a video and then clicks away to something else, we want the data to reflect that. Likewise, if someone watches the first 10 seconds, then scrubs the timeline to the last minute of the video and watches that, we want to register viewing on the parts watched and not the middle section. My first thought was to collect up the viewing data in the player and send it all to the server at the end of a viewing session. Unfortunately, Flash does not seem to have an event that you can hook into when a viewer clicks away from the page the movie is on (probably a good thing - it would be open to abuse) So, it looks like we're going to have to make regular requests to the server as the video is playing. This is obviously going to lead to a high volume of requests when there are large numbers of simultaneous viewers. The simple approach of dumping all these 'heartbeat' events from clients to a database feels like it will quickly become unmanageable so I'm wondering whether I should be taking an approach where viewing sessions are cached in memory and flushed to database when they become inactive (based on a timeout). That way, the data could be stored as time spans rather than individual heartbeats. So, to the question - what is the best way to approach dealing with this kind of high-volume viewing data? Are there any good existing architectures/patterns? Thanks, Dan.

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  • Saving multiple objects in a single call in rails

    - by CaptnCraig
    I have a method in rails that is doing something like this: a = Foo.new("bar") a.save b = Foo.new("baz") b.save ... x = Foo.new("123", :parent_id => a.id) x.save ... z = Foo.new("zxy", :parent_id => b.id) z.save The problem is this takes longer and longer the more entities I add. I suspect this is because it has to hit the database for every record. Since they are nested, I know I can't save the children before the parents are saved, but I would like to save all of the parents at once, and then all of the children. It would be nice to do something like: a = Foo.new("bar") b = Foo.new("baz") ... saveall(a,b,...) x = Foo.new("123", :parent_id => a.id) ... z = Foo.new("zxy", :parent_id => b.id) saveall(x,...,z) That would do it all in only two database hits. Is there an easy way to do this in rails, or am I stuck doing it one at a time?

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  • Mysql InnoDB performance optimization and indexing

    - by Davide C
    Hello everybody, I have 2 databases and I need to link information between two big tables (more than 3M entries each, continuously growing). The 1st database has a table 'pages' that stores various information about web pages, and includes the URL of each one. The column 'URL' is a varchar(512) and has no index. The 2nd database has a table 'urlHops' defined as: CREATE TABLE urlHops ( dest varchar(512) NOT NULL, src varchar(512) DEFAULT NULL, timestamp timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, KEY dest_key (dest), KEY src_key (src) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 Now, I need basically to issue (efficiently) queries like this: select p.id,p.URL from db1.pages p, db2.urlHops u where u.src=p.URL and u.dest=? At first, I thought to add an index on pages(URL). But it's a very long column, and I already issue a lot of INSERTs and UPDATEs on the same table (way more than the number of SELECTs I would do using this index). Other possible solutions I thought are: -adding a column to pages, storing the md5 hash of the URL and indexing it; this way I could do queries using the md5 of the URL, with the advantage of an index on a smaller column. -adding another table that contains only page id and page URL, indexing both columns. But this is maybe a waste of space, having only the advantage of not slowing down the inserts and updates I execute on 'pages'. I don't want to slow down the inserts and updates, but at the same time I would be able to do the queries on the URL efficiently. Any advice? My primary concern is performance; if needed, wasting some disk space is not a problem. Thank you, regards Davide

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  • DataGridView not displaying a row after it is created

    - by joslinm
    Hi, I'm using Visual Studio 10 and I just created a Database using SQL Server CE. Within it, I made a table CSLDataTable and that automatically created a CSLDataSet & CSLDataTableTableAdapter. The three variables were automatically created in my MainWindow.cs class: cSLDataSet cSLDataTableTableAdapter cSLDataTableBindingSource I have added a DataGridView in my Form called dataGridView and datasource cSLDataTableBindingSource. In my MainWindow(), I tried adding a row as a test: public MainWindow() { InitializeComponent(); CSLDataSet.CSLDataTableRow row = cSLDataSet.CSLDataTable.NewCSLDataTableRow(); row.File_ = "file"; row.Artist = "artist11"; row.Album = "album"; row.Save_Structure = "save"; row.Sent = false; row.Error = true; row.Release_Format = "release"; row.Bit_Rate = "bitrate.."; row.Year = "year"; row.Physical_Format = "format"; row.Bit_Format = "bitformat"; row.File_Path = "File!!path"; row.Site_Origin = "what"; cSLDataSet.CSLDataTable.Rows.Add(row); cSLDataSet.AcceptChanges(); cSLDataTableTableAdapter.Fill(cSLDataSet.CSLDataTable); cSLDataTableTableAdapter.Update(cSLDataSet); dataGridView.Refresh(); dataGridView.Update(); } In regards to the DataSet methods I tried calling, I had been trying to find a "correct" way to interact with the adapter, dataset, and datatable to successfully show the row, but to no avail. I'm rather new to using SQL Server CE Database, and read a lot of the MSDN sites & thought I was on the right track, but I've had no luck. The DataGridView shows the headers correctly, but that new row does not show up.

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  • Using Rails, problem testing has_many relationship

    - by east
    The summary is that I've code that works when manually testing, but isn't doing what I would think it should when trying to build an automated test. Here are the details: I've two models: Payment and PaymentTranscation. class Payment ... has_many :transactions, :class_name => 'PaymentTransaction' class PaymentTranscation ... belongs_to payment The PaymentTransaction is only created in a Payment model method, like so: def pay_up ... transactions.create!(params...) ... end I've manually tested this code, inspected the database, and everything works well. The failing automated test looks like this: def test_pay_up purchase = Payment.new(...) assert purchase.save assert_equal purchase.state, :initialized.to_s assert purchase.pay_up # this should create a new PaymentTransaction... assert_equal purchase.state, :succeeded.to_s assert_equal purchase.transactions.count, 1 # FAILS HERE; transactions is an empty array end If I step through the code, it's clear that the PaymentTransaction is getting created correctly (though I can't see it in the database because everything is in a testing transaction). What I can't figure out is why transactions is returning an empty array in the test when I know a valid PaymentTransaction is getting created. Anybody have some suggestions? Thanks in advance, east

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