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• Database Memory :: MySql Innodb how much storage memory allocation for empty field vs not empty fie

  - by Yosef

  Hi, I new in database, and dont know how and when mysql allocate memory space. In MySql Innodb how much storage memory allocation for empty field (no string inserted) vs not empty field? Other form of my question: When memory allocated space In MySql Innodb for varchar/text field in time of table creation or when data inserted inside field? Thank you, Yosef

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• Algorithm to price bulk discounts

  - by sam munkes

  Hi, i am designing a Chinese auction website. Tickets ($5, $10 & $20) are sold either individually, or via packages to receive discounts. There are various Ticket packages for example: 5-$5 tickets = receive 10% off 5-$10 tickets = receive 10% off 5-$20 tickets = receive 10% off 5-$5 tickets + 5-$10 tickets + 5-$20 tickets = receive 15% off When users add tickets to their cart, i need to figure out the cheapest package(s) to give them. the trick is that if a user adds 4-$5 tickets + 5-$10 tickets + 5-$20 tickets, it should still give him package #4 since that would be the cheapest for him. Any help in figuring out a algorithm to solve this, or any tips would be greatly appreciate it. thanks

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• Postgres user/role drop

  - by Grasper

  I am trying to drop a user: drop user testUser; I want to force this to work in a simple manner (Not a million calls)... How can I do this easily? I get this output: ERROR: role "testUser" cannot be dropped because some objects depend on it DETAIL: access to table main.tap_db_version access to table main.user_instance access to table main.target_type access to table main.status_code access to table main.state_space_profile access to table main.service_subscription access to table main.service_instance access to table main.sa_ordnance_weapon_type access to table main.operation access to table main.mission_class access to table main.map_symbol access to table main.ada_weapon_type access to table main.active_process access to table main.acft_type_00_only access to table main.abp_create_params access to table main.exercise access to table main.decl access to table main.data_set access to table main.cancellation_notice access to table main.ato_family_tree access to table main.apportionment_cat_cd access to table main.abp access to table main.alert_settings access to table main.alert_log access to table main.airspace_usage_category access to schema main access to view testUser.top_priority access to view testUser.target_ssm_msn_count access to view testUser.target_air_msn_count access to view testUser.sortie_sum access to view testUser.ref_info access to view testUser.preview_rmk_count access to view testUser.preview_pgm_las_count access to view testUser.preview_pgm_desi_count access to view testUser.preview_objective_count access to view testUser.preview_gfriend_count access to view testUser.preview_escort_msn_req access to view testUser.preview_chaff_data access to view testUser.preview_airmove_seg access to view testUser.preview_aircraft_total access to view testUser.offload_total access to view testUser.objective_count access to view testUser.fuel_planned access to view testUser.ew_data access to view testUser.dual access to view testUser.current_base_inventory access to view testUser.cell_total access to view testUser.asgn_sortie_sum access to view testUser.appor_sorties_planned access to view testUser.airmove_seg access to view testUser.aircraft_total access to view testUser.abp access to table testUser.req_msn_task access to table testUser.req_task_source_req access to table testUser.req_ssm_msn access to table testUser.req_ssm_source access to table testUser.req_msn access to table testUser.req_msn_warnings access to table testUser.req_air_msn access to table testUser.req_src_header access to table testUser.req_msn_ids access to table testUser.req_msn_comment access to table testUser.req_c2_msn access to table testUser.req_c2_source access to table testUser.req_ada_msn access to table testUser.req_ada_vertex access to table testUser.weather_forecast access to table testUser.weather_coords access to table testUser.weather_area access to table testUser.weapon_option access to table testUser.wag_activity access to table testUser.unit_remark access to table testUser.unit_location_turn access to table testUser.unit_iff access to table testUser.unit_coordination access to table testUser.unit_code access to table testUser.trace_point access to table testUser.tasking_agency access to table testUser.task_unit access to table testUser.target_type access to table testUser.tap_db_version access to table testUser.status_code access to table testUser.state_space_threat access to table testUser.state_space_profile access to table testUser.state_space access to table testUser.ssm_mission access to table testUser.spins_section_id access to table testUser.spins_codes access to table testUser.spins access to table testUser.unit_location access to table testUser.ship_target_request access to table testUser.service_subscription access to table testUser.service_instance access to table testUser.sa_ordnance_weapon_type access to table testUser.runway access to table testUser.restricted_codes access to table testUser.response_entity access to table testUser.residual_mission access to table testUser.request_objective access to table testUser.request and 194 other objects (see server log for list)

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• Space partitioning algorithm

  - by Karol Kolenda

  I have a set of points which are contained within the rectangle. I'd like to split the rectangles into subrectangles based on point density (giving a number of subrectangles or desired density, whichever is easiest). The partitioning doesn't have to be exact (almost any approximation better than regular grid would do), but the algorithm have to cope with the large number of points - approx. 200 millions. The desired number of subrectangles however is substantially lower (around 1000). Does anyone knows any algorithm which may help me with this particular task?

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• Merge method in MergeSort Algorithm .

  - by Tony

  I've seen many mergeSort implementations .Here is the version in Data Structures and Algorithms in Java (2nd Edition) by Robert Lafore : private void recMergeSort(long[] workSpace, int lowerBound,int upperBound) { if(lowerBound == upperBound) // if range is 1, return; // no use sorting else { // find midpoint int mid = (lowerBound+upperBound) / 2; // sort low half recMergeSort(workSpace, lowerBound, mid); // sort high half recMergeSort(workSpace, mid+1, upperBound); // merge them merge(workSpace, lowerBound, mid+1, upperBound); } // end else } // end recMergeSort() private void merge(long[] workSpace, int lowPtr, int highPtr, int upperBound) { int j = 0; // workspace index int lowerBound = lowPtr; int mid = highPtr-1; int n = upperBound-lowerBound+1; // # of items while(lowPtr <= mid && highPtr <= upperBound) if( theArray[lowPtr] < theArray[highPtr] ) workSpace[j++] = theArray[lowPtr++]; else workSpace[j++] = theArray[highPtr++]; while(lowPtr <= mid) workSpace[j++] = theArray[lowPtr++]; while(highPtr <= upperBound) workSpace[j++] = theArray[highPtr++]; for(j=0; j<n; j++) theArray[lowerBound+j] = workSpace[j]; } // end merge() One interesting thing about merge method is that , almost all the implementations didn't pass the lowerBound parameter to merge method . lowerBound is calculated in the merge . This is strange , since lowerPtr = mid + 1 ; lowerBound = lowerPtr -1 ; that means lowerBound = mid ; Why the author didn't pass mid to merge like merge(workSpace, lowerBound,mid, mid+1, upperBound); ? I think there must be a reason , otherwise I can't understand why an algorithm older than half a center ,and have all coincident in the such little detail.

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• Suggested GA operators for a TSP problem?

  - by Mark

  I'm building a genetic algorithm to tackle the traveling salesman problem. Unfortunately, I hit peaks that can sustain for over a thousand generations before mutating out of them and getting better results. What crossover and mutation operators generally do well in this case?

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• Suggestion on algorithm to distribute objects of different value

  - by Unknown

  Hello, I have the following problem: Given N objects of different values (N < 30, and the values are multiple of a "k" constant, i.e. k, 2k, 3k, 4k, 6k, 8k, 12k, 16k, 24k and 32k), I need an algorithm that will distribute all items to M players (M <= 6) in such a way that the total value of the objects each player gets is as even as possible (in other words, I want to distribute all objects to all players in the fairest way possible). I don't need (pseudo)code to solve this (also, this is not a homework :) ), but I'll appreciate any ideas or links to algorithms that could solve this. Thanks!

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• Singleton pattern in web applications

  - by ryudice

  I'm using a singleton pattern for the datacontext in my web application so that I dont have to instantiate it every time, however I'm not sure how web applications work, does IIS open a thread for every user connected? if so, what would happend if my singleton is not thread safe? Also, is it OK to use a singleton pattern for the datacontext? Thanks.

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• Good book for THINKING in terms of algorithms?

  - by chrisgoyal

  Before you mark this is a duplicate, let me explain why this is different. Most of the books on algorithms are more of a reference. You basically have a list of algorithms at your disposal. But what happens when you need to create a new algorithm for something? These books don't teach how to think in terms of algorithms. So I'm looking for books that will teach me the thinking-process of creating algorithms. Any good suggestions?

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• How Jason Santa Maria and David DeSandro blog?

  - by Gabe

  That's the question. How do they create their unique blog posts, like this: http://desandro.com/articles/why-art/ ? What would I need to learn (languages, skills, etc) to be able to do something like it?

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• Orkut.com -- architecture and technology behind it

  - by Vadi

  I am looking for the architecture and technology behind orkut.com, since it is one of the largest asp.net based application. I am able to get Facebook related details but not Orkut.com as I am looking for windows-based solution for such type of application. Any details are greatly appreciated ..

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• Help with a compiler warning: Initialization from distinct Objective-C type when types match

  - by Alex Gosselin

  Here is the function where I get the compiler warning, I can't seem to figure out what is causing it. Any help is appreciated. -(void)displaySelector{ //warning on the following line: InstanceSelectorViewController *controller = [[InstanceSelectorViewController alloc] initWithCreator:self]; [self.navController pushViewController:controller animated:YES]; [controller release]; } Interface and implementation for the initWithCreator: method -(InstanceSelectorViewController*)initWithCreator:(InstanceCreator*)creator; -(InstanceSelectorViewController*)initWithCreator:(InstanceCreator*)crt{ if (self = [self initWithNibName:@"InstanceSelectorViewController" bundle:nil]) { creator = crt; } return self; }

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• jQuery plugin for Event Driven Architecture?

  - by leeand00

  Are there any Event Driven Architecture jQuery plugins? Step 1: Subscribing The subscribers subscribe to the event handler in the middle, and pass in a callback method, as well as the name of the event they are listening for... i.e. The two green subscribers will be listening for p0 events. And the blue subscriber will be listening for p1 events. Step 2: The p0 event is fired by another component to the Event Handler A p0 event is fired to the Event Handler The event handler notifies it's subscribers of the event, calling the callback methods they specified when they subscribed in Step 1: Subscribing. Note that the blue subscriber is not notified because it was not listening for p0 events. Step 3: The p1 event is fired a component to the Event Handler The p1 event is fired by another component Just as before except that now the blue subscriber receives the event through its callback and the other two green subscribers do not receive the event. Images by leeand00, on Flickr I can't seem to find one, but my guess is that they just call it something else in Javascript/jquery Also is there a name for this pattern? Because it isn't just a basic publisher/subscriber, it has to be called something else I would think.

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• [Principles] Concrete Type or Interface for method return type?

  - by SDReyes

  In general terms, whats the better election for a method's return type: a concrete type or an interface? In most cases, I tend to use concrete types as the return type for methods. because I believe that an concrete type is more flexible for further use and exposes more functionality. The dark side of this: Coupling. The angelic one: A concrete type contains per-se the interface you would going to return initially, and extra functionality. What's your thumb's rule? Is there any programming principle for this? BONUS: This is an example of what I mean http://stackoverflow.com/questions/491375/readonlycollection-or-ienumerable-for-exposing-member-collections

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• How to handle payment types with varying properties in the most elegant way.

  - by Byron Sommardahl

  I'm using ASP.NET MVC 2. Keeping it simple, I have three payment types: credit card, e-check, or "bill me later". I want to: choose one payment type display some fields for one payment type in my view run some logic using those fields (specific to the type) display a confirmation view run some more logic using those fields (specific to the type) display a receipt view Each payment type has fields specific to the type... maybe 2 fields, maybe more. For now, I know how many and what fields, but more could be added. I believe the best thing for my views is to have a partial view per payment type to handle the different fields and let the controller decide which partial to render (if you have a better option, I'm open). My real problem comes from the logic that happens in the controller between views. Each payment type has a variable number of fields. I'd like to keep everything strongly typed, but it feels like some sort of dictionary is the only option. Add to that specific logic that runs depending on the payment type. In an effort to keep things strongly typed, I've created a class for each payment type. No interface or inherited type since the fields are different per payment type. Then, I've got a Submit() method for each payment type. Then, while the controller is deciding which partial view to display, it also assigns the target of the submit action. This is not elegant solution and feels very wrong. I'm reaching out for a hand. How would you do this?

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• google reader like architecture

  - by islam

  dear i want to make architect for application like google reader that save users feeds(rss,atoms) in database what is the best architecture i can do to make something like this ineed to know a good db desgin if i have to save something on files (xml or something) need to archive .etc hope to find some hints

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• Database theory - relationship between two tables

  - by iansinke

  I have a database with two tables - let's call them Foo and Bar. Each foo may be related to any number of bars, and each bar may be related to any number of foos. I want to be able to retrieve, with one query, the foos that are associated with a certain bar, and the bars that are associated with a certain foo. My question is, what is the best way of recording these relationships? Should I have a separate table with records of each relationship (e.g. two columns, foo and bar)? Should the foo table have a column for a list of bars, and vice versa? Is there another option that I'm overlooking? I'm using SQL Server, if that makes a difference.

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• C#: How to resolve this circular dependency?

  - by Rosarch

  I have a circular dependency in my code, and I'm not sure how to resolve it. I am developing a game. A NPC has three components, responsible for thinking, sensing, and acting. These components need access to the NPC controller to get access to its model, but the controller needs these components to do anything. Thus, both take each other as arguments in their constructors. ISenseNPC sense = new DefaultSenseNPC(controller, worldQueryEngine); IThinkNPC think = new DefaultThinkNPC(sense); IActNPC act = new DefaultActNPC(combatEngine, sense, controller); controller = new ControllerNPC(act, think); (The above example has the parameter simplified a bit.) Without act and think, controller can't do anything, so I don't want to allow it to be initialized without them. The reverse is basically true as well. What should I do? ControllerNPC using think and act to update its state in the world: public class ControllerNPC { // ... public override void Update(long tick) { // ... act.UpdateFromBehavior(CurrentBehavior, tick); CurrentBehavior = think.TransitionState(CurrentBehavior, tick); } // ... } DefaultSenseNPC using controller to determine if it's colliding with anything: public class DefaultSenseNPC { // ... public bool IsCollidingWithTarget() { return worldQuery.IsColliding(controller, model.Target); } // ... }

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• which language to use for building web application?

  - by harshit

  Hi I already have experience in developing websites using java technologies ... Now i have a task to develop another website and i have the liberty to select technology to built. I dont want to built using Java/J2ee standard technology as i want to learn new language. The specification about website i can give is that: 1) its a real estate based site. 2) so it will have a db of real estate data around million records 3) website will have more than 1000 hits /day and will have various functionality like search, add , delete,generate reports etc. So i mean UI should be good and fast. Technologies i have in mind .NEt( i have already worked on it but it licensed so may not go for it) , Groovy, Ruby on rails ,Play, GWT etc ... I am a college student and the website is again of a student(non techie guy) so i have 5-6 mnths to bring the website up I have read about them but all have adv and disadv but would like to hear from people who have used it and can tell me what they felt about the languages and problems while developing it.. Please feel free to drop any opinion you feel . Thanks

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• RPG Game loop and class structure (cocos2D for iPhone)

  - by mac_55

  I'm looking to make an RPG with Cocos2D on the iPhone. I've done a fair bit of research, and I really like the model Cocos2D uses for scenes. I can instantiate a scene, set up my characters etc. and it all works really nicely... what I have problems with is structuring a game loop and separating the code from the scenes. For example, where do I put my code that will maintain the state of the game across multiple scenes? and do I put the code for events that get fired in a scene in that scene's class? or do I have some other class that separates the init code from the logic? Also, I've read a lot of tutorials that mention changing scenes, but I've read none that talk about updating a scene - taking input from the user and updating the display based on that. Does that happen in the scene object, or in a separate display engine type class. Thanks in advance!

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• High-quality ERD generator for PostgresQL under Linux?

  - by Dave Jarvis

  Background MySQL Workbench can produce appealing and high-quality ERDs such as: Research I have not found a tool that even comes close for PostgreSQL. Tools I have found: dbVisualizer - Yellow squares. AquaFold - Yellow squares. SQL Developer - Coloured squares. Dia - Coloured squares. SchemaBank - Can't export to PNG; looks okay, nothing stellar. SchemaSpy - XML export makes it possible to write an XSL skin... Gliffy - Incompatible Flash version. Druid - No. pgAdmin3 - Not applicable? phpPgAdmin - Couldn't login without a 30-minute configuration battle. Requirements Looking for an ERD tool: Visually stunning by default Can reverse-engineer a PostgreSQL (or JDBC-compliant) database Runs on Linux (or under WINE) Export high-resolution PNG (or SVG) FOSS

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• How do you draw like a Crayon?

  - by Simucal

  Crayon Physics Deluxe is a commercial game that came out recently. Watch the video on the main link to get an idea of what I'm talking about. It allows you to draw shapes and have them react with proper physics. The goal is to move a ball to a star across the screen using contraptions and shapes you build. While the game is basically a wrapper for the popular Box2D Physics Engine, it does have one feature that I'm curious about how it is implemented. Its drawing looks very much like a Crayon. You can see the texture of the crayon and as it draws it varies in thickness and darkness just like an actual crayon drawing would look like. The background texture is freely available here. Close up of crayon drawing - Note the varying darkness What kind of algorithm would be used to render those lines in a way that looks like a Crayon? Is it a simple texture applied with a random thickness and darkness or is there something more going on?

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• how many index per database table?

  - by sam

  Hi, How many indexes is preferred for one table in MYSQL?? I have a company table where I search mostly for ID,state and category? Thansk

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• MVVM Madness: Commands

  - by JP

  I like MVVM. I don't love it, but like it. Most of it makes sense. But, I keep reading articles that encourage you to write a lot of code so that you can write XAML and don't have to write any code in the code-behind. Let me give you an example. Recently I wanted to hookup a command in my ViewModel to a ListView MouseDoubleClickEvent. I wasn't quite sure how to do this. Fortunately, Google has answers for everything. I found the following articles: http://blog.functionalfun.net/2008/09/hooking-up-commands-to-events-in-wpf.html http://joyfulwpf.blogspot.com/2009/05/mvvm-invoking-command-on-attached-event.html http://sachabarber.net/?p=514 http://geekswithblogs.net/HouseOfBilz/archive/2009/08/27/adventures-in-mvvm-ndash-binding-commands-to-any-event.aspx http://marlongrech.wordpress.com/2008/12/13/attachedcommandbehavior-v2-aka-acb/ While the solutions were helpful in my understanding of commands, there were problems. Some of the aforementioned solutions rendered the WPF designer unusable because of a common hack of appending "Internal" after a dependency property; the WPF designer can't find it, but the CLR can. Some of the solutions didn't allow multiple commands to the same control. Some of the solutions didn't allow parameters. After experimenting for a few hours I just decided to do this: private void ListView_MouseDoubleClick(object sender, MouseButtonEventArgs e) { ListView lv = sender as ListView; MyViewModel vm = this.DataContext as MyViewModel; vm.DoSomethingCommand.Execute(lv.SelectedItem); } So, MVVM purists, please tell me what's wrong with this? I can still Unit test my command. This seems very practical, but seems to violate the guideline of "ZOMG... you have code in your code-behind!!!!" Please share your thoughts. Thanks in advance.

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• char take 1 byte in database?

  - by 5YrsLaterDBA

  does a char take 1 byte in database?

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