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• Mobile Web Applications – A guide for professional development

  - by JuergenKress

  (Tobias Bosch, Stefan Scheidt, Torsten Winterberg / Opitz Consulting Deutschland GmbH). There is a real hype around mobile solutions. Smartphones and tablets are everywhere. Frontend architecture is changing quickly to adopt cross browser technologies like HTML5 and extensive JavaScript-based development. In this book we introduce our software development process to build test-driven Single-Page JavaScript Web Applications, which will be the future next to native apps. We start with a short introduction of our RYLC showcase (know from our SOA articles), give a very short introduction to JavaScript, then talk about jQuery Mobile, Angular JS, Testing, Backend-communication and we close with deploying our RYLC-Webapp as a hybrid app using the PhoneGap (Cordova) framework. Don’t expect too much theory – it’s a practical guide explaining how RYLC Web App was built, to kickstart your own development. Currently only available in German as paperback and eBook. WebLogic Partner Community For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. BlogTwitterLinkedInMixForumWiki Technorati Tags: adf mobil

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• Turn-based Client-Server Card Game - Unicast (TCP) or Multicast (UDP)

  - by LDM91

  I am currently planning to make a card game project where the clients will communicate with the server in a turn-based and synchronous manner using messages sent over sockets. The problem I have is how to handle the following scenario: (Client takes it turn and sends its action to server) Client sends a message telling the server its move for the turn (e.g. plays the card 5 from its hand which needs to placed onto the table) Server receives messages and updates game state (server will hold all game state). Server iterates through a list of connected clients and sends a message to tell of them change in state Clients all refresh to display the state This is all based on using TCP, and looking at it now it seems a bit like the Observer pattern. The reason this seems to be an issue to me is this message doesn't seem to be point-to-point like the others as I want to send it to all the clients, and doesn't seem very efficient sending the same message in that way. I was thinking about using multicasting with UDP as then I could send the message to all the clients, however wouldn't this mean that the clients would in theory be able to message each other? There is of course the synchronous aspect as well, though this could be put on top of the UDP I guess. Basically, I would like to know what would be good practice as this project is really all about learning, and even though it won't be big enough to encounter performance issues from this I would like to consider them anyway. However, please note I am not interested in using message oriented middleware as a solution (I have experience with using MOM and I'm interested in considering other options excluding MOM if TCP sockets is a bad idea!).

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• How do references work in R?

  - by djechlin

  I'm finding R confusing because it has such a different notion of reference than I am used to in languages like C, Java, Javascript... Ruby, Python, C++, well, pretty much any language I have ever programmed in ever. So one thing I've noticed is variable names are not irrelevant when passing them to something else. The reference can be part of the data. e.g. per this tutorial a <- factor(c("A","A","B","A","B","B","C","A","C")) results <- table(a) Leads to $a showing up as an attribute as $dimnames$a. We've also witnessed that calling a function like a <- foo(alpha=1, beta=2) can create attributes in a of names alpha and beta, or it can assign or otherwise compute on 1 and 2 to properties already existing. (Not that there's a computer science distinction here - it just doesn't really happen in something like Javascript, unless you want to emulate it by passing in the object and use key=value there.) Functions like names(...) return lvalues that will affect the input of them. And the one that most got me is this. x <- c(3, 5, 1, 10, 12, 6) y = x[x <= 5] x[y] <- 0 is different from x <- c(3, 5, 1, 10, 12, 6) x[x <= 5] <- 0 Color me confused. Is there a consistent theory for what's going on here?

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• Learning good OOP design & unlearning some bad habits

  - by Nick

  I have been mostly a C programmer so far in my career with knowledge of C++. I rely on C++ mostly for the convenience STL provides and I hardly ever focus on good design practices. As I have started to look for a new job position, this bad habit of mine has come back to haunt me. During the interviews, I have been asked to design a problem (like chess, or some other scenario) using OOP and I doing really badly at that (I came to know this through feedback from one interview). I tried to google stuff and came up with so many opinions and related books that I don't know where to begin. I need a good through introduction to OOP design with which I can learn practical design, not just theory. Can you point me to any book which meets my requirements ? I prefer C++, but any other language is fine as long as I can pick-up good practices. Also, I know that books can only go so far. I would also appreciate any good practice project ideas that helped you learn and improve your OOP concepts. Thanks.

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• What database works well with 200+GB of data?

  - by taw

  I've been using mysql (with innodb; on Amazon rds) because it's sort of universal default, but it's been ridiculously under-performing, and tweaking it only delays the inevitable. The data is mostly relatively short (<1kB of bytes each) blobs information about 100Ms of urls. There is (or should be, mysql cannot seem to handle it) very high amount of insert / update / retrieve but few complex queries - not that complex queries wouldn't be useful, but because mysql is so slow that it's far faster to get the data out, process it locally, and cache the results somewhere. I can keep tweaking mysql and throwing more hardware at it, but it seems increasingly futile. So what are the options? SQL/relational model/etc. optional - anything will do as long as it's fast, networked, and language-independent.

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• Modular Web App Network Architecture

  - by nairware

  Assuming that I am dealing with dedicated physical servers or VPSs, is it conceivable and does it make sense to have distinct servers setup with the following roles to host a web application? Reverse Proxy Web server Application server Database server Specific points of interest: I am confused how to even separate the web and application servers. My understanding was that such 3-tier architectures were feasible. It is unclear to me if the app server would reside directly between the web and database server, or if the web server could directly interact with the database as well. The app server could either do the computational heavy-lifting on behalf of the app server or it could do heavy-lifting plus control all of the business logic (as implied in the diagram above, thus denying the web server of direct database access). I am also unsure what role the reverse proxy (ex. nginx) could and should fulfill as a web server, given the above mentioned setup. I know that nginx has web server features. But I do not know if it makes sense to have the reverse proxy be its own VPS, given that the web server–in theory–would be separate from the app server.

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• 'e-Commerce' scalable database model

  - by Ruben Trancoso

  I would like to understand database scalability so I've just heard a talk about Habits of Highly Scalable Web Applications http://techportal.ibuildings.com/2010/03/02/habits-of-highly-scalable-web-applications/ On it, the presenter mainly talk about relational database scalability. I also have read something about MapReduce and Column oriented tables, big tables, hypertable etc... trying to understand which are the most up to date methods to scale web application data. But the second group, to me, is being hard to understand where it fits. It serves as transactional, reliable data store? or not, its just for large access and processing and to handle fine graned operations we will ever need to rely on RDBMSs? Could someone give a comprehensive landscape for those new technologies and how to use it?

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• Hierarchical Data in MySQL is fast to retrieve?

  - by ajsie

  i've got a list of all countries - states - cities (- subcities/villages etc) in a XML file and to retrieve for example a state's all cities it's really quick with XML (using xml parser). i wonder, if i put all this information in mysql, is retrieving a state's all cities as fast as with XML? cause XML is designed to store hierarchical data while relational databases like mysql are not. the list contains like 500 000 entities. so i wonder if its as fast as XML using either of: Adjacency list model Nested Set model And which one should i use? Cause (theoretically) there could be unlimited levels under a state. And which is fastest for this huge dataset? Thanks!

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• Player sprite moving slower on iPhone 4

  - by nvillec

  I just finished getting movement/jump animation for a player sprite in Xcode using Cocos2D. The basic movement algorithm is a timer that updates every 0.01 sec, changing the sprite position to (sprite.position.x + xVel, sprite.position.y + yVel). Each time a movement button is tapped, the appropriate velocity (initialized to 0) is changed to whatever speed I choose, then a stop movement button returns the velocity to 0. It's not an ideal solution but I'm very new at this and stoked to at least have that working with little help from the internet. So I may not have explained that perfectly, but it is in fact working to my satisfaction in Xcode's iPhone Simulator, however when I build it for my device and run it on my phone, the sprite's movement speed is noticeably slower than in Xcode. At first I thought it must have to do with the resolution of the iPhone 4, making the sprite's movement path twice as long, but I found that if I pull up the multitask bar, then return to the app the speed will sometimes jump back to normal. My second theory was that the code is just inefficient and is bogging the processes down, but I would see this reflected in the frame rate wouldn't I? It stays at 59-60 the whole time, and the spritesheet animation runs at the correct speed. Has anyone experienced this? Is this a really obvious issue that I'm completely missing? Any help (or tips for optimizing my approach to movement) would be much appreciated!

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• Turn Based Event Algorithm

  - by GamersIncoming

  I'm currently working on a small roguelike in XNA, which sees the player in a randomly generated series of dungeons fending off creeps, as you might expect. As with most roguelikes, the player makes a move, and then each of the creeps currently active on screen will make a move in turns, until all creeps have updated, and it return's to the player's go. On paper, the simple algorithm is straightforward: Player takes turn Turn Number increments For each active creep, update Position Once all active creeps have updated, allow player to take next turn However, when it comes to actually writing this in more detail, the concept becomes a bit more tricky for me. So my question comes as this: what is the best way to handle events taking turns to trigger, where the completion of each last event triggers the next, when dealing with a large number of creeps (probably stored as an array of an enemy object), and is there an easier way to create some kind of engine that just takes all objects that need updating and chains them together so their updates follow suit? I'm not asking for code, just algorithms and theory in the direction of objects triggering updates one after the other, in a turn based manner. Thanks in advance. Edited: Here's the code I currently have that is horrible :/ if (player.getTurnOver() && updateWait == 0) { if (creep[creepToUpdate].getActive()) { creep[creepToUpdate].moveObject(player, map1); updateWait = 10; } if (creepToUpdate < creep.Length -1) { creepToUpdate++; } else { creepToUpdate = 0; player.setTurnOver(false); } } if (updateWait > 0) { updateWait--; }

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• Dealing w/ Sqlite Join results in a cursor

  - by Bill

  I have a one-many relationship in my local Sqlite db. Pretty basic stuff. When I do my left outer join I get back results that look like this: the resulting cursor has multiple rows that look like this: A1.id | A1.column1 | A1.column2 | B1.a_id_fk | B1.column1 | B1.column2 A1.id | A1.column1 | A1.column2 | B2.a_id_fk | B2.column1 | B2.column2 and so on... Is there a standard practice or method of dealing with results like this ? Clearly there is only A1, but it has many B-n relationships. I am coming close to using multiple queries instead of the "relational db way". Hopefully I am just not aware of the better way to do things. I intend to expose this query via a content provider and I would hate for all of the consumers to have to write the same aggregation logic.

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• Hierarchical Data in MySQL is as fast as XML to retrieve?

  - by ajsie

  i've got a list of all countries - states - cities (- subcities/villages etc) in a XML file and to retrieve for example a state's all cities it's really quick with XML (using xml parser). i wonder, if i put all this information in mysql, is retrieving a state's all cities as fast as with XML? cause XML is designed to store hierarchical data while relational databases like mysql are not. the list contains like 500 000 entities. so i wonder if its as fast as XML using either of: Adjacency list model Nested Set model And which one should i use? Cause (theoretically) there could be unlimited levels under a state (i heard that adjacency isn't good for unlimited child-levels). And which is fastest for this huge dataset? Thanks!

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• MySQL dual license behavior

  - by jromero

  Hi SO, I'm running a commercial(closed source) Web App development for the first time. Initially I considered MySQL the most feasible option for a DB, until I get quite confused about its dual license behavior. If I want a commercial application do I still can use the GPL version of MySQL or I must get a license? The same question in a different way: If I use MySQL's GPL version does that force me to license the whole app under GPL? Either case I would go with PostgreSQL, I just want to make really really sure about this. Even in SO I've seen related("duplicates") questions but never a clear answer... All other tools I'm gonna use to code the project are licensed under BSD or MIT. Just in case, the role of MySQL in the project is merely as relational DB to store persistent data and query it. I'd really appreciate if someone can clarify this for me. Regards, thanks in advanced.

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• VMware Kernel Module Updater hangs on Ubuntu 13.04

  VMware Player has a nice auto-detection of kernel changes, and requests the user to compile the required modules in order to load them. This happens from time to time after a regular update of your system. Usually, the dialog of VMware Kernel Module Updater pops up, asks for root access authentication, and completes the compilation. VMware Player or Workstation checks if modules for the active kernel are available. In theory this is supposed to work flawlessly but in reality there are pitfalls occassionally. With the recent upgrade to Ubuntu 13.04 Raring Ringtail and the latest kernel 3.8.0-21 the actual VMware Kernel Module Updater simply disappeared and the application wouldn't start as expected. When you launch VMware Player as super user (root) the dialog would stall like so: VMware Kernel Module Updater stalls while stopping the services Prior to version 5.x of VMware Player or version 7.x of VMware Workstation you would run a command like: $ sudo vmware-config.pl to resolve the module version conflict but this doesn't work anyway. Solution Instead, you have to execute the following line in a terminal or console window: $ sudo vmware-modconfig --console --install-all Those switches are (as of writing this article) not documented in the output of the --help switch. But VMware already documented this procedure in their knowledge base: VMware Workstation stops functioning after updating the kernel on a Linux host (1002411). Update As of today I had the first kernel upgrade to version 3.8.0-22 in Ubuntu 13.04. Don't even try it without vmware-modconfig...

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• Tools for game script / storyboard

  - by Pietro Polsinelli

  I am searching for a tool that will help in writing a game script. By "script" I mean the text core of a storyboard - without the drawing drafts, which may or may not be there (yet). What I'm thinking of will let write a piece of text of the script, define a simplified workflow from that step, and then define the text of next steps, and so on. Searching online, I found Inform http://inform7.com/ ("A Design System for Interactive Fiction Based on Natural Language") which in theory is exactly what I am searching for, but trying to use it it has this model of a space (a dungeon, a library) where you are picking up objects and exploring them. In my case I am designing more a Sims like game, the flow is entirely different. Considering non specific software, mind mapping tools miss the linearity of the process. What I am writing is a directed graph - simply a work-flow, but the way I want to design it is more text based than work-flow based. SO what I'm doing now is using a text editor, which I'll transform directly in code. Any suggestions?

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• What are good hosting companies for PHP 5.3 Mysql / CouchDb / MongoDB Dev ( Lithium / CakePHP Framew

  - by Abba Bryant

  I am looking for a quality reliable host for some lithium development. I don't mind a shared platform as long as I have some ssh access. I require php 5.3.x, Mysql 5.x, and the usual imageMagick etc. Non-relational DB support up front would be nice but if they let me set one up myself I would be okay with doing it. I don't need a lot in the way of control panel tools. Good ones are appreciated but bad ones I would prefer not to even deal with. I don't anticipate needing much in the way of email but mail support would be nice to have. Cost isn't a big issue. I don't want to pay an arm and a leg but don't mind paying for what I need. Good support and decent uptime would be nice but I don't need an SLO or anything.

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• Strategy in storing ad-hoc numbers/constants?

  - by Jiho Han

  I have a need to store a number of ad-hoc figures and constants for calculation. These numbers change periodically but they are different type of values. One might be a balance, a money amount, another might be an interest rate, and yet another might be a ratio of some kind. These numbers are then used in a calculation that involve other more structured figures. I'm not certain what the best way to store these in a relational DB is - that's the choice of storage for the app. One way, I've done before, is to create a very generic table that stores the values as text. I might store the data type along with it but the consumer knows what type it is so, in situations I didn't even need to store the data type. This kind of works fine but I am not very fond of the solution. Should I break down each of the numbers into specific categories and create tables that way? For example, create Rates table, and Balances table, etc.?

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• Are long methods always bad?

  - by wobbily_col

  So looking around earlier I noticed some comments about long methods being bad practice. I am not sure I always agree that long methods are bad (and would like opinions from others). For example I have some Django views that do a bit of processing of the objects before sending them to the view, a long method being 350 lines of code. I have my code written so that it deals with the paramaters - sorting / filtering the queryset, then bit by bit does some processing on the objects my query has returned. So the processing is mainly conditional aggregation, that has complex enough rules it can't easily be done in the database, so I have some variables declared outside the main loop then get altered during the loop. varaible_1 = 0 variable_2 = 0 for object in queryset : if object.condition_condition_a and variable_2 > 0 : variable 1+= 1 ..... ... . more conditions to alter the variables return queryset, and context So according to the theory I should factor out all the code into smaller methods, so That I have the view method as being maximum one page long. However having worked on various code bases in the past, I sometimes find it makes the code less readable, when you need to constantly jump from one method to the next figuring out all the parts of it, while keeping the outermost method in your head. I find that having a long method that is well formatted, you can see the logic more easily, as it isn't getting hidden away in inner methods. I could factor out the code into smaller methods, but often there is is an inner loop being used for two or three things, so it would result in more complex code, or methods that don't do one thing but two or three (alternatively I could repeat inner loops for each task, but then there will be a performance hit). So is there a case that long methods are not always bad? Is there always a case for writing methods, when they will only be used in one place?

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• A simple example of movement prediction

  - by Daniel

  I've seen lots of examples of theory about the reason for client-side prediction, but I'm having a hard time converting it into code. I was wondering if someone knows of some specific examples that share some of the code, or can share their knowledge to shed some light into my situation. I'm trying to run some tests to get a the movement going (smoothly) between multiple clients. I'm using mouse input to initiate movement. I'm using AS3 and C# on a local Player.IO server. Right now I'm trying to get the Client side working, as I'm only forwarding position info with the client. I have 2 timers, one is an onEnterFrame and the other is a 100ms Timer, and one on mouseClick listener. When I click anywhere with a mouse, I update my player class to give it a destination point On every enterFrame Event for the player, it moves towards the destination point At every 100ms it sends a message to the server with the position of where it should be in a 100ms. The distance traveled is calculated by taking the distance (in Pixels) that the player can travel in one second, and dividing it by the framerate for the onEnterFrame handler, and by the update frequency (1/0.100s) for the server update. For the other Players, the location is interpolated and animated on every frame based on the new location. Is this the right way of doing it?

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• Cannot use second display with 12.04 and Intel 2000/3000

  - by Carolyn Marenger

  I am unable to get anything to display on my second monitor, or even get the system to recognize that there is a second screen. I am running Ubuntu 12.04 on a Gigabyte GA-H61M-S2PV, revision 2.0 box. The integrated chipset is an Intel 2000/3000, and there are both a D-Dub and a DVI-D display ports on the MB. This is the first operating system I have installed on this system. I have a second monitor plugged into the DVI-D port via a DVI-D to D-Sub adapter. I cannot verify that the motherboard or adapter were/are working, short of installing windows to test the theory. When I go into the "System Settings - Displays" control window, it shows one display. I have rebooted with the second monitor attached, and I have perused the BIOS settings in case it might have been disabled. So far, I have had no indication that the second monitor is recognized, not even a flicker at power on. If I swap monitors and cables between the DVI-D and D-Dub ports, the other monitor lights up, so I know the monitor and video cable are not the issue. Any suggestions would be appreciated. Thanks, Carolyn

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• PHP or C# script to parse CSV table values to fill in one-to-many table

  - by Yaaqov

  I'm looking for an example of how to split-out comma-delimited data in a field of one table, and fill in a second table with those individual elements, in order to make a one-to-many relational database schema. This is probably really simple, but let me give an example: I'll start with everything in one table, Widgets, which has a "state" field to contain states that have that widget: Table: WIDGET =============================== | id | unit | states | =============================== |1 | abc | AL,AK,CA | ------------------------------- |2 | lmn | VA,NC,SC,GA,FL | ------------------------------- |3 | xyz | KY | =============================== Now, what I'd like to create via code is a second table to be joined to WIDGET called *Widget_ST* that has widget id, widget state id, and widget state name fields, for example Table: WIDGET_ST ============================== | w_id | w_st_id | w_st_name | ------------------------------ |1 | 1 | AL | |1 | 2 | AK | |1 | 3 | CA | |2 | 1 | VA | |2 | 2 | NC | |2 | 1 | SC | |2 | 2 | GA | |2 | 1 | FL | |3 | 1 | KY | ============================== I am learning C# and PHP, so responses in either language would be great. Thanks.

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• Pros and cons of sorting data in DB?

  - by Roman

  Let's assume I have a table with field of type VARCHAR. And I need to get data from that table sorted alphabetically by that field. What is the best way (for performance): add sort by field to the SQL-query or sort the data when it's already fetched? I'm using Java (with Hibernate), but I can't tell anything about DB engine. It could be any popular relational database (like MySQL or MS Sql Server or Oracle or HSQL DB or any other). The amount of records in table can vary greatly but let's assume there are 5k records.

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• Confusion with floats converted into ints during collision detection

  - by TheBroodian

  So in designing a 2D platformer, I decided that I should be using a Vector2 to track the world location of my world objects to retain some sub-pixel precision for slow-moving objects and other such subtle nuances, yet representing their bodies with Rectangles, because as far as collision detection and resolution is concerned, I don't need sub-pixel precision. I thought that the following line of thought would work smoothly... Vector2 wrldLocation; Point WorldLocation; Rectangle collisionRectangle; public void Update(GameTime gameTime) { Vector2 moveAmount = velocity * (float)gameTime.ElapsedGameTime.TotalSeconds wrldLocation += moveAmount; WorldLocation = new Point((int)wrldLocation.X, (int)wrldLocation.Y); collisionRectangle = new Rectangle(WorldLocation.X, WorldLocation.Y, genericWidth, genericHeight); } and I guess in theory it sort of works, until I try to use it in conjunction with my collision detection, which works by using Rectangle.Offset() to project where collisionRectangle would supposedly end up after applying moveAmount to it, and if a collision is found, finding the intersection and subtracting the difference between the two intersecting sides to the given moveAmount, which would theoretically give a corrected moveAmount to apply to the object's world location that would prevent it from passing through walls and such. The issue here is that Rectangle.Offset() only accepts ints, and so I'm not really receiving an accurate adjustment to moveAmount for a Vector2. If I leave out wrldLocation from my previous example, and just use WorldLocation to keep track of my object's location, everything works smoothly, but then obviously if my object is being given velocities less than 1 pixel per update, then the velocity value may as well be 0, which I feel further down the line I may regret. Does anybody have any suggestions about how I might go about resolving this?

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• What goes between SQL Server and Client?

  - by worlds-apart89

  This question is an updated version of a previous question I have asked on here. I am new to client-server model with SQL Server as the relational database. I have read that public access to SQL Server is not secure. If direct access to the database is not a good practice, then what kind of layer should be placed between the server and the client? Note that I have a desktop application that will serve as the client and a remote SQL Server database that will provide data to the client. The client will input their username and password in order to see their data. I have heard of terms like VPN, ISA, TMG, Terminal Services, proxy server, and so on. I need a fast and secure n-tier architecture. P.S. I have heard of web services in front of the database. Can I use WCF to retrieve, update, insert data? Would it be a good approach in terms of security and performance?

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• What is the most efficient way to store a mapping "key -> event stream"?

  - by jkff

  Suppose there are ~10,000's of keys, where each key corresponds to a stream of events. I'd like to support the following operations: push(key, timestamp, event) - pushes event to the event queue for key, marked with the given timestamp. It is guaranteed that event timestamps for a particular key are pushed in sorted or almost sorted order. tail(key, timestamp) - get all events for key since the given timestamp. Usually the timestamp requests for a given key are almost monotonically increasing, almost synchronously with pushes for the same key. This stuff has to be persistent (although it is not absolutely necessary to persist pushes immediately and to keep tails with pushes strictly in sync), so I'm going to use some kind of database. What is the optimal kind of database structure for this task? Would it be better to use a relational database, a key-value storage, or something else?

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