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• Strategies for "Always-Connected" Windows Client Data Architecture

  - by magz2010

  Hi. Let me start by saying: this is my 1st post here, this is a bit lenghty, and I havent done Windows Forms development in years....with that in mind please excuse me if this isn't directly a programming question and please bear with me as I really need the help!! I have been asked to develop a Windows Forms app for our company that talks to a central (local area network) Linux Server hosting a PostgreSQL database. The app is to allow users to authenticate themselves into the system and thereafter conduct the usual transactions with the PG database. Ordinarily, I would propose writing a webforms app against Mono, but the clients need to utilise local resources such as USB peripheral devices, so that is out of the question. While it might not seem clear, my questions are italised below: Dilemma #1: The application is meant to be always connected. How should I structure my DAL/BLL - Should this reside on the server or with the client? Dilemma #2: I have been reading up on Client Application Services (CAS), and it seems like a great fit for authentication, as everything is exposed via URIs. I know that a .NET Data Provider exists for PostgreSQL, but not too sure if CAS will all work on a Linux (Debian) server? Believe me, I would get my hands dirty and try myself, but I need to come up with a logical design first before resources are allocated to me for "trial purposes"! Dilemma #3: If the DAL/BLL is to reside on the server, is there any way I can create data services, and expose only these services to authenticated clients. There is a (security) requirement whereby a connection string with username and password to the database cannot be present on any client machines...even if security on the database side is quite rigid. I'm guessing that the only way for this to work would be to create the various CRUD data service methods that are exposed by an ASP.NET app, and have the WindowsForms make a request for data or persist data to the ASP.NET app (thru a URI) and have that return a resultset or value. Would I be correct in assuming this? Should I be looking into WCF Data Services? and will WCF work with a non-SQL Server database? Thank you for taking the time out to read this, but know that I am desperately seeking any advice on this! THANKS A MILLION!!!!

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• Pass Types as arguments to a function in Haskell?

  - by Charles Peng

  The following two functions are extremely similar. They read from a [String] n elements, either [Int] or [Float]. How can I factor the common code out? I don't know of any mechanism in Haskell that supports passing types as arguments. readInts n stream = foldl next ([], stream) [1..n] where next (lst, x:xs) _ = (lst ++ [v], xs) where v = read x :: Int readFloats n stream = foldl next ([], stream) [1..n] where next (lst, x:xs) _ = (lst ++ [v], xs) where v = read x :: Float I am at a beginner level of Haskell, so any comments on my code are welcome.

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• relating data stored in NoSQL DB to data stored in SQL DB

  - by seanbrant

  Whats the best way to use a SQL DB along side a NoSQL DB? I want to keep my users and other data in postgres but have some data that would be better suited for a NoSQL DB like redis. I see a lot of talk about switching to NoSQL but little talk on integrating it with existing systems. I think it would be foolish to throw the baby out with the bath water and ditch SQL all together, unless it makes things easier to maintain and develop. I'm wondering what the best approach is for relating data stored in SQL to my data in redis. I was thinking of something along the line of this. User object stored in SQL Book object in redis, key sh1 hash of value, value is a JSON string Relations stored in redis, key User.pk:books, value redis set of sha1's Anyone have experience, tips, better ways?

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• SQL Server: Primary Key Schema Largely Guid but Sometimes Integer Types...

  - by Code Sherpa

  OK, this may be a silly question but... I have inherited a project and am tasked with going over the primary key relationships. The project largely uses Guids. I say "largely" because there are examples where tables use integral types to reflect enumerations. For example, dbo.MessageFolder has MessageFolderId of type int to reflect public emum MessageFolderTypes { inbox = 1, sent = 2, trash = 3, etc... } This happens a lot. There are tables with primary keys of type int which is unavoidable because of their reliance on enumerations and tables with primary keys of type Guid which reflect the primary key choice on the part of the previous programmer. Should I care that the PK schema is spotty like this? It doesn't feel right but does it really matter? If this could create a problem, how do I get around it (I really can't move all PKs to type int without serious legwork and I have never heard of enumerations that have guid values)? Thanks.

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• Haskell data serialization of some data implementing a common type class

  - by Evan

  Let's start with the following data A = A String deriving Show data B = B String deriving Show class X a where spooge :: a -> Q [ Some implementations of X for A and B ] Now let's say we have custom implementations of show and read, named show' and read' respectively which utilize Show as a serialization mechanism. I want show' and read' to have types show' :: X a => a -> String read' :: X a => String -> a So I can do things like f :: String -> [Q] f d = map (\x -> spooge $ read' x) d Where data could have been [show' (A "foo"), show' (B "bar")] In summary, I wanna serialize stuff of various types which share a common typeclass so I can call their separate implementations on the deserialized stuff automatically. Now, I realize you could write some template haskell which would generate a wrapper type, like data XWrap = AWrap A | BWrap B deriving (Show) and serialize the wrapped type which would guarantee that the type info would be stored with it, and that we'd be able to get ourselves back at least an XWrap... but is there a better way using haskell ninja-ery? EDIT Okay I need to be more application specific. This is an API. Users will define their As, and Bs and fs as they see fit. I don't ever want them hacking through the rest of the code updating their XWraps, or switches or anything. The most i'm willing to compromise is one list somewhere of all the A, B, etc. in some format. Why? Here's the application. A is "Download a file from an FTP server." B is "convert from flac to mp3". A contains username, password, port, etc. information. B contains file path information. A and B are Xs, and Xs shall be called "Tickets." Q is IO (). Spooge is runTicket. I want to read the tickets off into their relevant data types and then write generic code that will runTicket on the stuff read' from the stuff on disk. At some point I have to jam type information into the serialized data.

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• EXC_MEMORY_ACCESS when trying to delete from Core Data ($cash solution)

  - by llloydxmas

  I have an application that downloads an xml file, parses the file, and creates core data objects while doing so. In the parse code I have a function called 'emptydatacontext' that removes all items from Core Data before creating replacements items from the xml data. This method looks like this: -(void) emptyDataContext { NSFetchRequest * allCon = [[NSFetchRequest alloc] init]; [allCon setEntity:[NSEntityDescription entityForName:@"Condition" inManagedObjectContext:managedObjectContext]]; NSError * error = nil; NSArray * conditions = [managedObjectContext executeFetchRequest:allCon error:&error]; DebugLog(@"ERROR: %@",error); DebugLog(@"RETRIEVED: %@", conditions); [allCon release]; for (NSManagedObject * condition in conditions) { [managedObjectContext deleteObject:condition]; } // Update the data model effectivly removing the objects we removed above. //NSError *error; if (![managedObjectContext save:&error]) { DebugLog(@"%@", [error domain]); } } The first time this runs it deletes all objects and functions as it should - creating new objects from the xml file. I created a 'update' button that starts the exact same process of retrieving the file the proceeding with the parse & build. All is well until its time to delete the core data objects. This 'deleteObject' call creates a "EXC_BAD_ACCESS" error each time. This only happens on the second time through. Captured errors return null. If I log the 'conditions' array I get a list of NSManagedObjects on the first run. On the second this log request causes a crash exactly as the deleteObject call does. I have a feeling it is something very simple I'm missing or not doing correctly to cause this behavior. The data works great on my tableviews - its only when trying to update I get the crashes. I have spent days & days on this trying numerous alternative methods. Whats left of my hair is falling out. I'd be willing to ante up some cash for anyone willing to look at my code and see what I'm doing wrong. Just need to get past this hurdle. Thanks in advance for the help!

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• Looping through array in PHP to post several multipart form-data

  - by Léon Pelletier

  I'm trying in an asp web application to code a function that would loop through a list of files in a multiple upload form and send them one by one. Is this something that can be done in ASP? Because I've read some posts about how to attach several files together, but saw nothing about looping through the files. I can easily imagine it in C# via HttpWebRequest or with socket, but in php, I guess there are already function designed to handle it? // This is false/pseudo-code :) for (int index = 0; index < number_of_files; index++) { postfile(file[index]); } And in each iteration, it should send a multipart form-data POST. postfile(TheFileInfos) should make a POST like it: POST /afs.aspx?fn=upload HTTP/1.1 [Header stuff] Content-Type: multipart/form-data; boundary=----------Ef1Ef1cH2Ij5GI3ae0gL6KM7GI3GI3 [Header stuff] ------------Ef1Ef1cH2Ij5GI3ae0gL6KM7GI3GI3 Content-Disposition: form-data; name="Filename" myimage1.png ------------Ef1Ef1cH2Ij5GI3ae0gL6KM7GI3GI3 Content-Disposition: form-data; name="fileid" 58e21ede4ead43a5201206101806420000007667212251 ------------Ef1Ef1cH2Ij5GI3ae0gL6KM7GI3GI3 Content-Disposition: form-data; name="Filedata"; filename="myimage1.png" Content-Type: application/octet-stream [Octet Stream] [Edit] I'll try it: <html> <head> <title>Untitled Document</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> </head> <body> <form name="form1" enctype="multipart/form-data" method="post" action="processFiles.php"> <p> <? // start of dynamic form $uploadNeed = $_POST['uploadNeed']; for($x=0;$x<$uploadNeed;$x++){ ?> <input name="uploadFile<? echo $x;?>" type="file" id="uploadFile<? echo $x;?>"> </p> <? // end of for loop } ?> <p><input name="uploadNeed" type="hidden" value="<? echo $uploadNeed;?>"> <input type="submit" name="Submit" value="Submit"> </p> </form> </body> </html>

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• Storing data locally and synchronizing it with data base on linux server

  - by Miraaj

  Hi all, I have developed a mac application, which is continuously interacting with database on linux server. As data is increasing it has become costlier affair in terms of time to fetch data from server. So I am planning to store required data locally, say on mysqlite and find some mechanism through which I can synchronize it with database on linux server. Can anyone suggest me some way to accomplish it? Thanks, Miraaj

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• Transforming OLTP Relational Database to Data Warehousing Model

  - by Russ Cam

  What are the common design approaches taken in loading data from a typical Entity-Relationship OLTP database model into a Kimball star schema Data Warehouse/Marts model? Do you use a staging area to perform the transformation and then load into the warehouse? How do you link data between the warehouse and the OLTP database? Where/How do you manage the transformation process - in the database as sprocs, dts/ssis packages, or SQL from application code?

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• data to be saved in SQLite and want to retrive data from there

  - by Mona

  In android, is it possible that we insert our database in SQLite and get back that data on our EditText boxes. I want to get data from database and populate it in my application activity. How can i do that. I want to save, update and delete my database in SQLite and most important i want to get data from database that is saved in SQLite tables. How can it be possible. Kindly guide. I will be thankfull to you

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• Ways to store data in .NET

  - by Audel

  I am looking for ways to store data in a windows form application in .NET. I want to make the input data of a system persistent, so when I close my program and open it again, the data is retrieved. Which ways are of doing this besides creating a linked database? Examples are gladly appreciated regards

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• Looking for a list of free data api's and web services

  - by darren

  I'm wondering if anybody has come across a comprehensive list of free sources for data (as a web api) or web services. I'm looking to start a new project to tinker with in my spare time and I am wondering what interesting data is available to play with. It seems like many api services such as last.fm or google search don't exist or are no longer free. Possible examples of what I am looking for information about a given ip address mapping api's information about books, movies, music information about places, businesses, attractions meteorological, financial or other scientific data shopping, products I would appreciate any suggestions you may have about interesting data freely available through the web. thanks

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• Data Usage Checker Tools

  - by Lucifer

  Hey All, I am about to begin a project for a new client, and am worried about a few things concerning data usage on their internet plan. We're in an area where most of the major networks don't cover the area, and the ones that do, have very expensive plans, with very low data allowance per month. I need to develop an app, but part of the problem lies with checking database values every 30 seconds. It's pretty important that this check is happening every 30 seconds, as the database is actually updated all day everyday, approx. every 5seconds (apparently). Each row in the database consists of about a page full of text if you were to paste it into MS Word. So, are there any logical ways of minimizing data usage in my case, and also how am I able to see exactly how much data is used just to establish a connection to the database? Are there any tools for this kind of info? Thanks :)

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• How to store data using core data in iphone?

  - by Warrior

  I am new to iphone development.I want to show a form a and store the contents in to a core data database after clicking the submit button.I have created a form.xcdatamodel and class events.h and events.m with reference to the apple docs.In some Sample codes the values are stored statically in the delegate class and they use core data delegate methods. But in my case the form view come after passing 2 views. I want to store the data entered here .How can i achieve it.Please help me out.Thanks.

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• What kind of data structure shall i use for handling huge data

  - by Rachel

  I am parsing huge xhtml files and am trying to play around with the content in it. Basically the words in it, their positions etc. I tried using the HashMap, ArayList etc. All of them give OutOfMemory issue after loading 130347 data. What is the kind of data structure that can be used to hold huge data in JAVA.

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• Does java have class for complex number?

  - by Rambo

  Does java have class for complex number?

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• data ownership and performance

  - by Ami

  We're designing a new application and we ran into some architectural question when thinking about data ownership. we broke down the system into components, for example Customer and Order. each of this component/module is responsible for a specific business domain, i.e. Customer deals with CRUD of customers and business process centered around customers (Register a n new customer, block customer account, etc.). each module is the owner of a set of database tables, and only that module may access them. if another module needs data that is owned by another module, it retrieves it by requesting it from that module. so far so good, the question is how to deal with scenarios such as a report that needs to show all the customers and for each customer all his orders? in such a case we need to get all the customers from the Customer module, iterate over them and for each one get all the data from the Order module. performance won't be good...obviously it would be much better to have a stored proc join customers table and orders table, but that would also mean direct access to the data that is owned by another module, creating coupling and dependencies that we wish to avoid. this is a simplified example, we're dealing with an enterprise application with a lot of business entities and relationships, and my goal is to keep it clean and as loosely coupled as possible. I foresee in the future many changes to the data scheme, and possibly splitting the system into several completely separate systems. I wish to have a design that would allow this to be done in a relatively easy way. Thanks!

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• Retrieving Data From formData in Rails jquery-file-upload

  - by CanCeylan

  I am trying to add additional form data by using https://github.com/blueimp/jQuery-File-Upload/wiki/How-to-submit-additional-form-data this tutorial for jQuery-File-Upload plugin in my Rails app. I'm following the instructions for Setting formData on upload start for each individual file upload. My problem is, after saving the files with their titles as explained in tutorial, I cannot show them in the final table, because I don't know how to reach the formData's values. How should I reach the data inside data.formData = inputs.serializeArray(); and post them next to each item ? Thanks.

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• Accessing data feed

  - by racket99

  I have a Java program on my desktop which displays financial data gleaned from the web. It is a 3rd party application. What I would like to do is intercept the data before it goes to the Java application and record it into a flat file for the purpose of later data analysis. Is this at all possible? I imagine the data are available and are entering my computer through some port which the Java app picks up and then displays. Help appreciated. Thanks

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• .NET security mechanism to restrict access between two Types in the same Website project?

  - by jdk

  Question: Is there a mechanism in the .NET Framework to hide one custom Type from another without using separate projects/assemblies? I'm using C# with ASP.NET in a Website project (Note: Not a Web Application). Obviously there's not a way to enforce this restriction using language-specific OO keywords so I am looking for something else, for example: maybe a permission framework or code access mechanism, maybe something that uses meta data like Attributes. I'm unsure. I don't really care whether the solution actually hides classes from each other or just makes them inaccessible, etc. A runtime or design time answer will suffice. Looking for something easy to implement otherwise it's not worth the effort ... Background: I'm working in an ASP.NET Website project and the team has decided not to use separate project assemblies for different software layers. Therefore I'm looking for a way to have, for example, a DataAccess/ folder of which I disallow its classes to access other Types in the ASP.NET Website project.

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• Using Oracle ADF Data Visualization Tools (DVT) Line Graphs to Display Weather Information

  - by Christian David Straub

  OverviewA guest post by Jeanne Waldman.I have a simple JDeveloper Fusion application that retrieves weather data. I wanted to compare the week's temperatures of different locations in a graph. I decided to check out the dvt:lineGraph component, and it took me a few minutes to add it to my jspx page and supply it with data.Drag and Drop the dvt:lineGraph onto your pageI opened my .jspx page in design modeIn the Component Palette, I selected ADF Data Visualization.Then I dragged 'Line' onto my page.A dialog popped up giving me options of the type of line graph. I chose the default.A lineGraph displayed with some default data. Hook up your weather dataNow I wanted to hook up my own data. I browsed the tagdoc, and I found the tabularData attribute.Attribute: tabularDataType: java.util.ListTagDoc:Specifies a list of data that the graph uses to create a grid and populate itself. The List consists of a three-member Object array for each data value to be passed to the graph. The members of each array must be organized as follows: The first member (index 0) is the column label, in the grid, of the data value. This is generally a String. If the graph has a time axis, then this should be a Java Date. Column labels typically identify groups in the graph. The second member (index 1) is the row label, in the grid, of the data value. This is generally a String. Row labels appear as series labels in the graph (usually in the legend). The third member (index 2) is the data value, which is usually a Double.The first member is the column label of the data value. This would be the day of the week.The second member is the row label of the data value. This would be the location name.The third member is the data value, usually a Double. This would be the temperature. I already had all this information, I just needed to put it in a List with a three-member Object array for each data value.   /**    * This is used for the lineGraph to show the data for each location.    */   public List<Object[]> getTabularData()   {      List<Object[]> tabularData = new ArrayList<Object []>();      List<WeatherForecast> weatherForecastList = getWeatherForecastList();      // loop through the list and build up the tabular data. Then cache it.      for(WeatherForecast wf : weatherForecastList)      {        List<ForecastDay> forecastDayList = wf.getForecastDayList();        String location = wf.getLocation();        for (ForecastDay fday : forecastDayList)        {          String day = fday.getPrettyDate();          String highTemp = fday.getHighF();          tabularData.add(new Object[]{day, location, Double.valueOf(highTemp)});        }             }      return tabularData;    }  Now I bound the lineGraph to this method by setting tabularData to#{weatherForAllLocationsBean.tabularData}weatherForAllLocationsBean is my bean that is defined in faces-config.xml. Adding a barGraphIn about 30 seconds, I added a barGraph with the same data. I dragged and dropped a bar graph onto the page, used the same tabularData as I did in the line graph. The page looks like this:  ConclusionI was very happy how fast it was to hook up my weather data to these graphs. They look great, and they have built in functionality. For instance, I can hide/show a location by clicking on the name of the location in the legend.

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• SQL SERVER – CXPACKET – Parallelism – Usual Solution – Wait Type – Day 6 of 28

  - by pinaldave

  CXPACKET has to be most popular one of all wait stats. I have commonly seen this wait stat as one of the top 5 wait stats in most of the systems with more than one CPU. Books On-Line: Occurs when trying to synchronize the query processor exchange iterator. You may consider lowering the degree of parallelism if contention on this wait type becomes a problem. CXPACKET Explanation: When a parallel operation is created for SQL Query, there are multiple threads for a single query. Each query deals with a different set of the data (or rows). Due to some reasons, one or more of the threads lag behind, creating the CXPACKET Wait Stat. There is an organizer/coordinator thread (thread 0), which takes waits for all the threads to complete and gathers result together to present on the client’s side. The organizer thread has to wait for the all the threads to finish before it can move ahead. The Wait by this organizer thread for slow threads to complete is called CXPACKET wait. Note that not all the CXPACKET wait types are bad. You might experience a case when it totally makes sense. There might also be cases when this is unavoidable. If you remove this particular wait type for any query, then that query may run slower because the parallel operations are disabled for the query. Reducing CXPACKET wait: We cannot discuss about reducing the CXPACKET wait without talking about the server workload type. OLTP: On Pure OLTP system, where the transactions are smaller and queries are not long but very quick usually, set the “Maximum Degree of Parallelism” to 1 (one). This way it makes sure that the query never goes for parallelism and does not incur more engine overhead. EXEC sys.sp_configure N'cost threshold for parallelism', N'1' GO RECONFIGURE WITH OVERRIDE GO Data-warehousing / Reporting server: As queries will be running for long time, it is advised to set the “Maximum Degree of Parallelism” to 0 (zero). This way most of the queries will utilize the parallel processor, and long running queries get a boost in their performance due to multiple processors. EXEC sys.sp_configure N'cost threshold for parallelism', N'0' GO RECONFIGURE WITH OVERRIDE GO Mixed System (OLTP & OLAP): Here is the challenge. The right balance has to be found. I have taken a very simple approach. I set the “Maximum Degree of Parallelism” to 2, which means the query still uses parallelism but only on 2 CPUs. However, I keep the “Cost Threshold for Parallelism” very high. This way, not all the queries will qualify for parallelism but only the query with higher cost will go for parallelism. I have found this to work best for a system that has OLTP queries and also where the reporting server is set up. Here, I am setting ‘Cost Threshold for Parallelism’ to 25 values (which is just for illustration); you can choose any value, and you can find it out by experimenting with the system only. In the following script, I am setting the ‘Max Degree of Parallelism’ to 2, which indicates that the query that will have a higher cost (here, more than 25) will qualify for parallel query to run on 2 CPUs. This implies that regardless of the number of CPUs, the query will select any two CPUs to execute itself. EXEC sys.sp_configure N'cost threshold for parallelism', N'25' GO EXEC sys.sp_configure N'max degree of parallelism', N'2' GO RECONFIGURE WITH OVERRIDE GO Read all the post in the Wait Types and Queue series. Additionally a must read comment of Jonathan Kehayias. Note: The information presented here is from my experience and I no way claim it to be accurate. I suggest you all to read the online book for further clarification. All the discussion of Wait Stats over here is generic and it varies from system to system. It is recommended that you test this on the development server before implementing on the production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: DMV, Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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• As a game developer, which data structure use for develop the game? [duplicate]

  - by Rizwanabbasi

  This question already has an answer here: When should vector/list be used? 5 answers We are developing a game for bank robbery. The game plots a bank robbery. Lots of people witness that robbery. Our game will load the lists of suspected offenders while the players (witnesses) will have to identify the offenders of this robbery. Game should load list of offenders to identify the one as quickly as possible. Admin can add/remove offenders in the lists and two or more lists of offenders can also be merged into one (to show it to the player). As a game developer, which data structure we should use for develop the game? Justify your selection with solid arguments. Remember the most critical requirement is that the list should load super fast.

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• How to find data usage of a user on my website?

  - by Dharmik

  I have a website (project) where users get logged in, do their work and then they log out. I need to build a report that displays how much each person has used of data. (bandwidth, how much was downloaded in Kb, etc) So the process may be like counting start of usage from user login to user logout. I have seen a little about Webalizer and AWStats for something like this, But I am not sure how they work. I have tried Content-Length but some pages don't send content-length.I have also seen mod_bandwidth but still I am little confused. This process is needed for my site because now, our company is thinking of charging per usage and also bandwidth allocation for each users (according to their membership). I haven't worked with this type of tools, I am newbie in this matter. I have done only simple websites not any setting like this in Apache or Linux. My project is in Codeigniter.

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• Configuration data: single-row table vs. name-value-pair table

  - by Heinzi

  Let's say you write an application that can be configured by the user. For storing this "configuration data" into a database, two patterns are commonly used. The single-row table CompanyName | StartFullScreen | RefreshSeconds | ... ---------------+-------------------+------------------+-------- ACME Inc. | true | 20 | ... The name-value-pair table ConfigOption | Value -----------------+------------- CompanyName | ACME Inc. StartFullScreen | true (or 1, or Y, ...) RefreshSeconds | 20 ... | ... I've seen both options in the wild, and both have obvious advantages and disadvantages, for example: The single-row tables limits the number of configuration options you can have (since the number of columns in a row is usually limited). Every additional configuration option requires a DB schema change. In a name-value-pair table everything is "stringly typed" (you have to encode/decode your Boolean/Date/etc. parameters). (many more) Is there some consensus within the development community about which option is preferable?

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