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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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• 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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• 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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• 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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• How to draw an E-R diagram?

  - by Appy

  I am learning DBMS in my college. Recently I was given an assignment to draw a E-R Model of a Bus Reservation system which handles Reservations, Ticketing and cancellations. I understand the theory about E-R model when I study from a book, but it gets confusing when I try to draw one from scratch. How should one proceed? There seem to be a lot of ways to model a E-R diagram for a particular requirement. It's really confusing. Can anyone explain taking Bus reservation System as an example? Here is the model I made (But I am not confident with it because at every step, I could think of many more alternatives!) - Entity_Set Passenger(passengerID,name,age,gender) Entity_Set Ticket(ticketID,status) //Status is either WaitingList , Confirmed or Cancelled Entity_Set Bus (busID,MaxSeats,Type) //Type is Ac or Non-AC Entity_Set Route(routeID,ArrivalTime,DepartureTime,Source,Destination) And a Ternary relationship between Passenger, Ticket and Bus with attributes as passengerID, ticketID, busID . Binary relationship between Bus and Route with attributes as busID, routeID . I have few doubts regarding - 1 . Should we take Time as a composite attribute with Arrival and Departure as its attributes (What's the difference if we take that way?) 2 . The same with Source and Destination. Should they be made into a composite attribute "Place" or something like "Location"? 3. Are there any weak entity sets here? Can you please 'create' a weak entity set and explain? Because I have no idea at all what to take as a Weak entity set?

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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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• 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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• Which opcodes are faster at the CPU level?

  - by Geotarget

  In every programming language there are sets of opcodes that are recommended over others. I've tried to list them here, in order of speed. Bitwise Integer Addition / Subtraction Integer Multiplication / Division Comparison Control flow Float Addition / Subtraction Float Multiplication / Division Where you need high-performance code, C++ can be hand optimized in assembly, to use SIMD instructions or more efficient control flow, data types, etc. So I'm trying to understand if the data type (int32 / float32 / float64) or the operation used (*, +, &) affects performance at the CPU level. Is a single multiply slower on the CPU than an addition? In MCU theory you learn that speed of opcodes is determined by the number of CPU cycles it takes to execute. So does it mean that multiply takes 4 cycles and add takes 2? Exactly what are the speed characteristics of the basic math and control flow opcodes? If two opcodes take the same number of cycles to execute, then both can be used interchangeably without any performance gain / loss? Any other technical details you can share regarding x86 CPU performance is appreciated

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• Need theoretical help, how to comprehend an if-else dependency net

  - by macbie

  I am going to face a following issue: I'm writing a program that manages some properties, some of them are general and some are specific. Each property is a pair of key and value, and for example: if it is given a general property and other specific property with exactly the same key and value has been existed before then the general property will swap the specific one in the register. If there are two the same general properties - both will remain in the register. And so on; it is like a net of dependencies. In my case I can handle with it intuitively and foresee all cases, but only because the system is not too vast. What if it would? I have met such problems a few times in many different programs and languages (i.e working with C semaphores) and my question is: How to approach this kind of problem? Is this connected with finite state machine, graph theory or something similar? How to be sure that I have considered the whole system and each possible case? Could you recommend some resources (books, sites) to learn from?

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• Should I use Perl or PHP or something else for this project?

  - by Clinton

  I'm about to embark on a project that will need to: Process XML Heavy text parsing of non-xml documents Insertion of data from xml and non-xml documents into a relational DB. Present processed data to user from db using webpages. The website will be subject to short periods of very heavy loads to pages (300+ visitors a minute for several minutes), but most of the time will be idle (a dozen or so visitors a minute). The ability to cache or scale to load will be very nice. I have a very strong background in Java and web services, but I do not want to use Java for this project as I'd like to diversify my skill set. Which language would you recommend and what are some pros and cons that you might recognize from your own experiences?

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• What JavaScript framework to choose? JQuery+JQueryUI, Dojo or ExtJS?

  - by Ivan

  I am choosing a JavaScript Framework to master and use extensively in all my future projects (mostly working with relational DATA, web services via AJAX and implementing complex rich client UIs). Now I am choosing between JQuery+JQueryUI, Dojo and ExtJS. What should I choose? 1st priority is power and functionality, 2nd priority is beauty and maintainability of code and ease of use, 3rd priority is flexibility and modularity, 4th priority is speed and size. IE compatibility hardly matters, I'd like it to be modern, legacy-free and standard-conformant.

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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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• 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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• 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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• 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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• Are there any e-commerce websites that use NoSQL databases

  - by Saif Bechan

  I have read a lot lately about 'NoSQL' databases such as CouchDB, MongoDB etc. Most of the websites I have seen using this are mainly text based websites such as The New York Times and Source forge. I was wondering if you could apply this to websites where payment is a huge issue. I am thinking of the following issues: How well can you secure the data Do these system provide an easy backup/restore machanism How are transactions handled commit/rollback I have read the following articles that cover some aspects: Can I do transactions and locks in CouchDB? Pros/Cons of document based database vs relational database In these posts the aspect of transactions if covered. However the questions of security and backups is not covered. Can someone shed some light on this subject? And if possible, does anyone know of some e-commerce websites that have successfully implemented the document based database.

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• What format do I use to store a relatively small amount of user data

  - by wcm

  I am writing a small program for our local high school (pro bono). The program has an interface allows the user to enter school holidays. This is a simple stand alone Windows app. What format should I use to store the data? A big relational data is obviously overkill. My initial plan was to store the data in an XML file. Co-workers have been suggesting that I use JSON files, Access Databases, SQL Lite, and SQL Server Express. There was even a suggestion of old school INI files.

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• Why job postings always looking for "rockstars?"

  - by Xepoch

  I have noticed a recent trend in requesting programmers who are rockstars. I get it, they're looking for someone who is really good at what they do. But why (pray) make the reference to a rockstar? Do these companies really want these traits as a real rockstar? Party all night and wake up to take care of quick business in the morning? Substance abuse, Narcissism with celebrity, Compensation well exceeding their management, Excellent at putting on a short-lived show, Entertainment instead of value, 1 hit (project) wonders or single-genre performers, Et cetera What is wrong with Senior or Principal Software Engineer who has an established and proven passion for the business? Rather do we mean quite the opposite, someone who: rolls up the sleeves and gets to work, takes appropriate direction and helps influence teams, programs in lessons' learned and proper practices, provides timely communication to the whole team, can code and understand multiple languages, understands the science and theory behind computation, Is there a trend to diversify the software engineering ranks? How many software rockstars can you hire before your band starts breaking up? Sure, there are lots of folks doing this stuff on their own, maybe even a rare few who do coding for show, but I wager the majority is for business. I don't see ads for rockstar accountants, or rockstar machinists, or rockstart CFOs. What makes the software programmer and their hiring departments lean towards this kind of job title?

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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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• What's a better choice for SQL-backed number crunching - Ruby 1.9, Python 2, Python 3, or PHP 5.3?

  - by Ivan

  Crterias of 'better': fast im math and simple (little of fields, many records) db transactions, convenient to develop/read/extend, flexible, connectible. The task is to use a common web development scripting language to process and calculate long time series and multidimensional surfaces (mostly selectint/inserting sets of floats and dong maths with rhem). The choice is Ruby 1.9, Python 2, Python 3, PHP 5.3, Perl 5.12, JavaScript (node.js). All the data is to be stored in a relational database (due to its heavily multidimensional nature), all the communication with outer world is to be done by means of web services.

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• Java: JPA classes, refactoring from Date to DateTime

  - by bguiz

  With a table created using this SQL Create Table X ( ID varchar(4) Not Null, XDATE date ); and an entity class defined like so @Entity @Table(name = "X") public class X implements Serializable { @Id @Basic(optional = false) @Column(name = "ID", nullable = false, length = 4) private String id; @Column(name = "XDATE") @Temporal(TemporalType.DATE) private Date xDate; //java.util.Date ... } With the above, I can use JPA to achieve object relational mapping. However, the xDate attribute can only store dates, e.g. dd/MM/yyyy. How do I refactor the above to store a full date object using just one field, i.e. dd/MM/yyyy HH24:mm?

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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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• 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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• Remove a certain value from string which keeps on changing

  - by user2971375

  I m trying to make a utility to generate a Insert script of sql tables along with relational table. I got all the values in c#. Now I want to remove the one column name and its value from the script.most probably the identity column. Eg. The string I have (which keeps on changing with table name and varies) INSERT Core.Customers ([customerId],[customername],[customeradress],[ordernumber]) Values(123,N'Rahul',N'244 LIZ MORN',2334) NOW I know I have to remove CustomerId. (sometimes need to be replaces with @somevariable) Please give me an efficient way how to retrieve customerId value and Deleting column name and value . Conditions: insert script length and columns names keep changing. Method should return the deleted value. At some point of time customer id can be same as order id. In that case my string.remove method fails.

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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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