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  • Good practice to create extension methods that apply to System.Object?

    - by Christian
    Hello, I'm wondering whether I should create extension methods that apply on the object level or whether they should be located at a lower point in the class hierarchy. What I mean is something along the lines of: public static string SafeToString(this Object o) { if (o == null || o is System.DBNull) return ""; else { if (o is string) return (string)o; else return ""; } } public static int SafeToInt(this Object o) { if (o == null || o is System.DBNull) return 0; else { if (o.IsNumeric()) return Convert.ToInt32(o); else return 0; } } //same for double.. etc I wrote those methods since I have to deal a lot with database data (From the OleDbDataReader) that can be null (shouldn't, though) since the underlying database is unfortunately very liberal with columns that may be null. And to make my life a little easier, I came up with those extension methods. What I'd like to know is whether this is good style, acceptable style or bad style. I kinda have my worries about it since it kinda "pollutes" the Object-class. Thank you in advance & Best Regards :) Christian P.S. I didn't tag it as "subjective" intentionally.

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  • Domain model: should things like Logging, Audit, Persistence be in it

    - by hom.tanks
    I'm having a hard time convincing our architect that a Domain model should only have the essential elements of the business domain on it. Things like the fact that a class is persistable, that it needs logging and auditing and that it has a RESTful URI should not drive the domain model. They can be added later on, by using interfaces. Ours is a healthcare information management system. At the very coarse level, its a system where users login and access their healthcare information. They can share this information with others and be custodian for others' information (think Roles). But because of a few sound bytes that caught on early like "Everything should be a REST resource" the model now has a top level class called Resource that every other class extends from. I'm trying to make him see that the domain model should have well defined concepts like User Account, HealthDocument, UserRole etc which are distinct entities of the business , with specific associations between them. Clubbing everything under Resource class lets our model be inflexible besides being potentially incorrect. But he wants me to show him why its a bad idea to do it his way. I don't know how to articulate that properly but all my OO instincts tell me that its just not right. Any thoughts?

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  • I made a horrible loop.... help fix my logic please

    - by Webnet
    I know I'm doing this a bad way... but I'm having trouble seeing any alternatives. I have an array of products that I need to select 4 of randomly. $rawUpsellList is an array of all of the possible upsells based off of the items in their cart. Each value is a product object. I know this is horribly ugly code but I don't see an alternative now.... someone please put me out of my misery so this code doesn't make it to production..... $rawUpsellList = array(); foreach ($tru->global->cart->getItemList() as $item) { $product = $item->getProduct(); $rawUpsellList = array_merge($rawUpsellList, $product->getUpsellList()); } $upsellCount = count($rawUpsellList); $showItems = 4; if ($upsellCount < $showItems) { $showItems = $upsellCount; } $maxLoop = 20; $upsellList = array(); for ($x = 0; $x <= $showItems; $x++) { $key = rand(0, $upsellCount); if (!array_key_exists($key, $upsellList) && is_object($rawUpsellList[$key])) { $upsellList[$key] = $rawUpsellList[$key]; $x++; } if ($x == $maxLoop) { break; } } Posting this code was highly embarassing...

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  • Sparse (Pseudo) Infinite Grid Data Structure for Web Game

    - by Ming
    I'm considering trying to make a game that takes place on an essentially infinite grid. The grid is very sparse. Certain small regions of relatively high density. Relatively few isolated nonempty cells. The amount of the grid in use is too large to implement naively but probably smallish by "big data" standards (I'm not trying to map the Internet or anything like that) This needs to be easy to persist. Here are the operations I may want to perform (reasonably efficiently) on this grid: Ask for some small rectangular region of cells and all their contents (a player's current neighborhood) Set individual cells or blit small regions (the player is making a move) Ask for the rough shape or outline/silhouette of some larger rectangular regions (a world map or region preview) Find some regions with approximately a given density (player spawning location) Approximate shortest path through gaps of at most some small constant empty spaces per hop (it's OK to be a bad approximation often, but not OK to keep heading the wrong direction searching) Approximate convex hull for a region Here's the catch: I want to do this in a web app. That is, I would prefer to use existing data storage (perhaps in the form of a relational database) and relatively little external dependency (preferably avoiding the need for a persistent process). Guys, what advice can you give me on actually implementing this? How would you do this if the web-app restrictions weren't in place? How would you modify that if they were? Thanks a lot, everyone!

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  • How to avoid multiple, unused has_many associations when using multiple models for the same entity (

    - by mikep
    Hello, I'm looking for a nice, Ruby/Rails-esque solution for something. I'm trying to split up some data using multiple tables, rather than just using one gigantic table. My reasoning is pretty much to try and avoid the performance drop that would come with having a big table. So, rather than have one table called books, I have multiple tables: books1, books2, books3, etc. (I know that I could use a partition, but, for now, I've decided to go the 'multiple tables' route.) Each user has their books placed into a specific table. The actual book table is chosen when the user is created, and all of their books go into the same table. The goal is to try and keep each table pretty much even -- but that's a different issue. One thing I don't particularly want to have is a bunch of unused associations in the User class. Right now, it looks like I'd have to do the following: class User < ActiveRecord::Base has_many :books1, :books2, :books3, :books4, :books5 end class Books1 < ActiveRecord::Base belongs_to :user end class Books2 < ActiveRecord::Base belongs_to :user end First off, for each specific user, only one of the book tables would be usable/applicable, since all of a user's books are stored in the same table. So, only one of the associations would be in use at any time and any other has_many :bookX association that was loaded would be a waste. I don't really know Ruby/Rails does internally with all of those has_many associations though, so maybe it's not so bad. But right now I'm thinking that it's really wasteful, and that there may just be a better, more efficient way of doing this. Is there's some sort of special Ruby/Rails methodology that could be applied here to avoid having to have all of those has_many associations? Also, does anyone have any advice on how to abstract the fact that there's multiple book tables behind a single books model/class?

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  • Get number of posts in a topic PHP

    - by Wayne
    How do I get to display the number of posts on a topic like a forum. I used this... (how very noobish): function numberofposts($n) { $sql = "SELECT * FROM posts WHERE topic_id = '" . $n . "'"; $result = mysql_query($sql) or die(mysql_error()); $count = mysql_num_rows($result); echo number_format($count); } The while loop of listing topics: <div class="topics"> <div class="topic-name"> <p><?php echo $row['topic_title']; ?></p> </div> <div class="topic-posts"> <p><?php echo numberofposts($row['topic_id']); ?></p> </div> </div> Although it is a bad method of doing this... All I need is to know what would be the best method, don't just point me out to a website, do it here, because I'm trying to learn much. Okay? :D Thanks.

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  • Testing a Gui-heavy WPF application.

    - by Hamish Grubijan
    We (my colleagues) have a messy 12 y.o. mature app that is GUI-based, and the current plan is to add new dialogs & other GUI in WPF, as well as replace some of the older dialogs in WPF as well. At the same time we wish to be able to test that Monster - GUI automation in a maintainable way. Some challenges: The application is massive. It constantly gains new features. It is being changed around (bug fixes, patches). It has a back end, and a layer in-between. The state of it can get out of whack if you beat it to death. What we want is: Some tool that can automate testing of WPF. auto-discovery of what the inputs and the outputs of the dialog are. An old test should still work if you add a label that does nothing. It should fail, however, if you remove a necessary text field. It would be very nice if the test suite was easy to maintain, if it ran and did not break most of the time. Every new dialog should be created with testability in mind. At this point I do not know exactly what I want, so I am marking this as a community wiki. If having to test a huge GUI-based app rings the bell (even if not in WPF), then please share your good, bad and ugly experiences here.

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  • Best way to convert a Unicode URL to ASCII (UTF-8 percent-escaped) in Python?

    - by benhoyt
    I'm wondering what's the best way -- or if there's a simple way with the standard library -- to convert a URL with Unicode chars in the domain name and path to the equivalent ASCII URL, encoded with domain as IDNA and the path %-encoded, as per RFC 3986. I get from the user a URL in UTF-8. So if they've typed in http://?.ws/? I get 'http://\xe2\x9e\xa1.ws/\xe2\x99\xa5' in Python. And what I want out is the ASCII version: 'http://xn--hgi.ws/%E2%99%A5'. What I do at the moment is split the URL up into parts via a regex, and then manually IDNA-encode the domain, and separately encode the path and query string with different urllib.quote() calls. # url is UTF-8 here, eg: url = u'http://?.ws/?'.encode('utf-8') match = re.match(r'([a-z]{3,5})://(.+\.[a-z0-9]{1,6})' r'(:\d{1,5})?(/.*?)(\?.*)?$', url, flags=re.I) if not match: raise BadURLException(url) protocol, domain, port, path, query = match.groups() try: domain = unicode(domain, 'utf-8') except UnicodeDecodeError: return '' # bad UTF-8 chars in domain domain = domain.encode('idna') if port is None: port = '' path = urllib.quote(path) if query is None: query = '' else: query = urllib.quote(query, safe='=&?/') url = protocol + '://' + domain + port + path + query # url is ASCII here, eg: url = 'http://xn--hgi.ws/%E3%89%8C' Is this correct? Any better suggestions? Is there a simple standard-library function to do this?

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  • Storing arbitrary data in HTML

    - by Rob Colburn
    What is the best way to embed data in html elements for later use? As an example, let's say we have jQuery returning some JSON from the server, and we want to dump that datat out to the user as paragraphs. However, we want to be able to attach meta-data to these elements, so we can events for these later. The way I tend to handle this, is with some ugly prefixing function handle_response(data) { var html = ''; for (var i in data) { html += '<p id="prefix_' + data[i].id + '">' + data[i].message + '</p>'; } jQuery('#log').html(html).find('p').click(function(){ alert('The ID is: ' + $(this).attr('id').substr(7)); }); } Alternatively, one can build a Form in the paragraph, and store your meta-data there. But, that often feels like overkill. This has been asked before in different ways, but I do not feel it's been answered well: http://stackoverflow.com/questions/432174/how-to-store-arbitrary-data-for-some-html-tags http://stackoverflow.com/questions/209428/non-standard-attributes-on-html-tags-good-thing-bad-thing-your-thoughts

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  • C++ interpreter conceptual problem

    - by Jan Wilkins
    I've built an interpreter in C++ for a language created by me. One main problem in the design was that I had two different types in the language: number and string. So I have to pass around a struct like: class myInterpreterValue { myInterpreterType type; int intValue; string strValue; } Objects of this class are passed around million times a second during e.g.: a countdown loop in my language. Profiling pointed out: 85% of the performance is eaten by the allocation function of the string template. This is pretty clear to me: My interpreter has bad design and doesn't use pointers enough. Yet, I don't have an option: I can't use pointers in most cases as I just have to make copies. How to do something against this? Is a class like this a better idea? vector<string> strTable; vector<int> intTable; class myInterpreterValue { myInterpreterType type; int locationInTable; } So the class only knows what type it represents and the position in the table This however again has disadvantages: I'd have to add temporary values to the string/int vector table and then remove them again, this would eat a lot of performance again. Help, how do interpreters of languages like Python or Ruby do that? They somehow need a struct that represents a value in the language like something that can either be int or string.

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  • Deterministic and non uniform long string generation from seed

    - by Limonup
    I had this weird idea for an encryption that I wanted to try out, it may be bad, and it may have done before, but I'm just doing it for fun. The short version of the question is: Is it possible to generate a long, deterministic and non-uniformly distributed string/sequence of numbers from a small seed? Long(er) version: I was thinking to encrypt a text by changing encoding. The new encoding would be generated via Huffman algorithm. To work well, the Huffman algorithm would need a fairly long text with non uniform distribution. Then characters can have different bit-lengths which would be the primary strength of this encryption. The problem is that its impractical to enter in/remember a long text each time you want to decrypt the text. So I was wondering if it was possible to generate a text from password seed? It doesn't matter what the text is, as long as it has non uniform distribution of characters and that the exact same sequence can be recreated each time you give it the same seed. Preferably, are there any functions/extensions in Python that can do this? EDIT: To expand on the "strength" of varying bit length: if I have a string "test", ASCII values 116, 101, 115, 116, which gives bit values of 1110100 1100101 1110011 1110100 Then, say my Huffman algorithm generates encoding like t = 101 e = 1100111 s = 10001 The final string is 101 1100111 10001 101, if we encode this back to ASCII, we get 1011100 1111000 1101000, which is 3 entirely different characters. Obviously its impossible to perform any kind of frequency analysis or something like that on this.

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  • Rails nested models and data separation by scope

    - by jobrahms
    I have Teacher, Student, and Parent models that all belong to User. This is so that a Teacher can create Students and Parents that can or cannot log into the app depending on the teacher's preference. Student and Parent both accept nested attributes for User so a Student and User object can be created in the same form. All four models also belong to Studio so I can do data separation by scope. The current studio is set in application_controller.rb by looking up the current subdomain. In my students controller (all of my controllers, actually) I'm using @studio.students.new instead of Student.new, etc, to scope the new student to the correct studio, and therefore the correct subdomain. However, the nested User does not pick up the studio from its parent - it gets set to nil. I was thinking that I could do something like params[:student][:user_attributes][:studio_id] = @student.studio.id in the controller, but that would require doing attr_accessible :studio_id in User, which would be bad. How can I make sure that the nested User picks up the same scope that the Student model gets when it's created? student.rb class Student < ActiveRecord::Base belongs_to :studio belongs_to :user, :dependent => :destroy attr_accessible :user_attributes accepts_nested_attributes_for :user, :reject_if => :all_blank end students_controller.rb def create @student = @studio.students.new @student.attributes = params[:student] if @student.save redirect_to @student, :notice => "Successfully created student." else render :action => 'new' end end user.rb class User < ActiveRecord::Base belongs_to :studio accepts_nested_attributes_for :studio attr_accessible :email, :password, :password_confirmation, :remember_me, :studio_attributes devise :invitable, :database_authenticatable, :recoverable, :rememberable, :trackable end

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  • COCOS2D - Animation Stops During Move

    - by maiko
    Hey guys! I am trying to run a "Walk" style animation on my main game sprite. The animations work fine, and my sprite is hooked up to my joystick all fine and dandy. However, I think where I setup the call for my walk animations are wrong. Because everytime the sprite is moving, the animation stops. I know putting the animation in such a weak if statement is probably bad, but please tell me how I could get my sprite to animate properly while it is being moved by the joystick. The sprite faces the right direction, so I can tell the action's first frame is being called, however, it doesn't animate until I stop touching my joystick. Here is How I call the action: //WALK LEFT if (joypadCap.position.x <= 69 /*&& joypadCap.position.y < && joypadCap.position.y 40 */ ) { [tjSprite runAction:walkLeft]; }; //WALK RIGHT if ( joypadCap.position.x = 71 /* && joypadCap.position.y < 100 && joypadCap.position.y 40 */) { [tjSprite runAction:walkRight]; }; THIS: is the how the joystick controls the character: CGPoint newLocation = ccp(tjSprite.position.x - distance/8 * cosf(touchAngle), tjSprite.position.y - distance/8 * sinf(touchAngle)); tjSprite.position = newLocation; Please help. Any alternative ways to call the characters walk animation would be greatly appreciated!

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  • MYOB Import "amount paid"

    - by php-b-grader
    I seem to have found an anomaly with MYOB (I've actually found many anomalies, this is just another one that is doing my head in...) I am generating a file with all invoices from the web system - no problems. If an invoice has 3 lines and the account is paid COD, I am having an problem e.g. "INV", "DATE" ... "AMOUNT", "INC TAX AMOUNT" ... "AMOUNT PAID" 8421, 12/06/2010 ... 60, 66 ... 66 8421, 12/06/2010 ... 120, 132 ... 132 8421, 12/06/2010 ... 96, 105.6 ... 105.6 8421, 12/06/2010 ... 84, 92.4 ... 92.4 When I import this file, the balance of the invoice is still outstanding and what it appears is the issue is that it is only importing the first line of "amount paid" ... so in other words, based on the above: Invoice 8421 is imported with 4 lines The total invoice amount is $396 The Amount paid (that is imported) is $66 The outstanding balance = $330 Surely the first line isn't expected to be: Inc tax Amount = $66 Amount Paid = $396 It seems completely illogical to me... am I doing something wrong or is MYOB just really bad?

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  • Blackberry application works in simulator but not device

    - by Kai
    I read some of the similar posts on this site that deal with what seems to be the same issue and the responses didn't really seem to clarify things for me. My application works fine in the simulator. I believe I'm on Bold 9000 with OS 4.6. The app is signed. My app makes an HTTP call via 3G to fetch an XML result. type is application/xhtml+xml. In the device, it gives no error. it makes no visual sign of error. I tell the try catch to print the results to the screen and I get nothing. HttpConnection was taken right out of the demos and works fine in sim. Since it gives no error, I begin to reflect back on things I recall reading back when the project began. deviceside=true? Something like that? My request is simply HttpConnection connection = (HttpConnection)Connector.open(url); where url is just a standard url, no get vars. Based on the amount of time I see the connection arrows in the corner of the screen, I assume the app is launching the initial communication to my server, then either getting a bad result, or it gets results and the persistent store is not functioning as expected. I have no idea where to begin with this. Posting code would be ridiculous since it would be basically my whole app. I guess my question is if anyone knows of any major differences with device versus simulator that could cause something like http connection or persistent store to fail? A build setting? An OS restriction? Any standard procedure I may have just not known about that everyone should do before beginning device testing? Thanks

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  • Why does adding Crossover to my Genetic Algorithm give me worse results?

    - by MahlerFive
    I have implemented a Genetic Algorithm to solve the Traveling Salesman Problem (TSP). When I use only mutation, I find better solutions than when I add in crossover. I know that normal crossover methods do not work for TSP, so I implemented both the Ordered Crossover and the PMX Crossover methods, and both suffer from bad results. Here are the other parameters I'm using: Mutation: Single Swap Mutation or Inverted Subsequence Mutation (as described by Tiendil here) with mutation rates tested between 1% and 25%. Selection: Roulette Wheel Selection Fitness function: 1 / distance of tour Population size: Tested 100, 200, 500, I also run the GA 5 times so that I have a variety of starting populations. Stop Condition: 2500 generations With the same dataset of 26 points, I usually get results of about 500-600 distance using purely mutation with high mutation rates. When adding crossover my results are usually in the 800 distance range. The other confusing thing is that I have also implemented a very simple Hill-Climbing algorithm to solve the problem and when I run that 1000 times (faster than running the GA 5 times) I get results around 410-450 distance, and I would expect to get better results using a GA. Any ideas as to why my GA performing worse when I add crossover? And why is it performing much worse than a simple Hill-Climb algorithm which should get stuck on local maxima as it has no way of exploring once it finds a local max?

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  • ASP.NET MVC2 and Browser Caching

    - by Dan
    Hi I have a web application that fetches a lot of content via ajax. For example when a user edits some data, the browser will send the changes using an ajax post and then do an ajax get to get fresh content and replace an existing div on the page with that content. This was working just find with MVC1, but in MVC2 I would get inconsistent results. I've found that MVC1 by default included an Expires item in the response headers set to the current time, but in MVC2 the Expires header is missing. This is a problem with some browsers (IE8) actually using the cached version of the ajax get instead of the fresh version. To deal with the problem I created a simple ActionFilterAttribute that sets the reponse cache to NoCache (see below), which works, but it seems kind of sillly to decorate every controller with this attribute. Is there a global way to set this for every controller? Is this a bug in MVC2 and it really should be setting the expires on every ActionResult/view/page? Don't most MVC programs deal with data entry where stale data is a very bad thing? Thanks Dan public class ResponseNoCachingAttribute : ActionFilterAttribute { public override void OnResultExecuted(ResultExecutedContext filterContext) { base.OnResultExecuted(filterContext); filterContext.HttpContext.Response.Cache.SetCacheability(System.Web.HttpCacheability.NoCache); } }

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  • Is private members hacking a defined behaviour ?

    - by ereOn
    Hi, Lets say I have the following class: class BritneySpears { public: int getValue() { return m_value; }; private: int m_value; }; Which is an external library (that I can't change). I obviously can't change the value of m_value, only read it. Even subclassing BritneySpears won't work. What if I define the following class: class AshtonKutcher { public: int getValue() { return m_value; }; public: int m_value; }; And then do: BritneySpears b; // Here comes the ugly hack AshtonKutcher* a = reinterpret_cast<AshtonKutcher*>(&b); a->m_value = 17; // Print out the value std::cout << b.getValue() << std::endl; I know this is a bad practice. But just for curiosity: is this guaranted to work ? Is it a defined behaviour ? Bonus question: Have you ever had to use such an ugly hack ? Thanks !

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  • Simulated Annealing and Yahtzee!

    - by Jasie
    I've picked up Programming Challenges and found a Yahtzee! problem which I will simplify: There are 13 scoring categories There are 13 rolls by a player (comprising a play) Each roll must fit in a distinct category The goal is to find the maximum score for a play (the optimal placement of rolls in categories); score(play) returns the score for a play Brute-forcing to find the maximum play score requires 13! (= 6,227,020,800) score() calls. I choose simulated annealing to find something close to the highest score, faster. Though not deterministic, it's good enough. I have a list of 13 rolls of 5 die, like: ((1,2,3,4,5) #1 (1,2,6,3,4),#2 ... (1,4,3,2,2) #13 ) And a play (1,5,6,7,2,3,4,8,9,10,13,12,11) passed into score() returns a score for that play's permutation. How do I choose a good "neighboring state"? For random-restart, I can simply choose a random permutation of nos. 1-13, put them in a vector, and score them. In the traveling salesman problem, here's an example of a good neighboring state: "The neighbours of some particular permutation are the permutations that are produced for example by interchanging a pair of adjacent cities." I have a bad feeling about simply swapping two random vector positions, like so: (1,5,6,7, 2 , 3,4,8,9,10, 13, 12,11) # switch 2 and 13 (1,5,6,7, 13, 3,4,8,9,10, 2 , 12,11) # now score this one But I have no evidence and don't know how to select a good neighboring state. Anyone have any ideas on how to pick good neighboring states?

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  • The Implications of Modern Day Software Development Abstractions

    - by Andreas Grech
    I am currently doing a dissertation about the implications or dangers that today's software development practices or teachings may have on the long term effects of programming. Just to make it clear: I am not attacking the use abstractions in programming. Every programmer knows that abstractions are the bases for modularity. What I want to investigate with this dissertation are the positive and negative effects abstractions can have in software development. As regards the positive, I am sure that I can find many sources that can confirm this. But what about the negative effects of abstractions? Do you have any stories to share that talk about when certain abstractions failed on you? The main concern is that many programmers today are programming against abstractions without having the faintest idea of what the abstraction is doing under-the-covers. This may very well lead to bugs and bad design. So, in you're opinion, how important is it that programmers actually know what is going below the abstractions? Taking a simple example from Joel's Back to Basics, C's strcat: void strcat( char* dest, char* src ) { while (*dest) dest++; while (*dest++ = *src++); } The above function hosts the issue that if you are doing string concatenation, the function is always starting from the beginning of the dest pointer to find the null terminator character, whereas if you write the function as follows, you will return a pointer to where the concatenated string is, which in turn allows you to pass this new pointer to the concatenation function as the *dest parameter: char* mystrcat( char* dest, char* src ) { while (*dest) dest++; while (*dest++ = *src++); return --dest; } Now this is obviously a very simple as regards abstractions, but it is the same concept I shall be investigating. Finally, what do you think about the issue that schools are preferring to teach Java instead of C and Lisp ? Can you please give your opinions and your says as regards this subject? Thank you for your time and I appreciate every comment.

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  • How does a client find the port number of a server?

    - by Jonathan
    Hello all, I am currently learning about basic networking in java. I have been playing around with the server and client relationship between two of my computers. However, I cannot figure out how distributed programs (say, a videogame), can not only find the 'host' computer, but also the port number on which the server is running in order to create a Socket between the two computers. The only way I really see to create a Socket is with an already known IP Address, and with a known port number. How do you search a LAN network for another computer (host) searching for clients? How do you determine what port the server is located on without 'pinging' all available ports for a response (which, I understand, is bad form... Something about 'server attack'...)? In such a situation as a video game, there can be any number of computers on the same network, and any number of them might be attempting to host, or otherwise running the application. Any other important information, or perhaps reference to a more detailed tutorial than the one I am using, regarding making connections on so very little information on the client side would be appreciated. Many thanks, Jonathan

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  • [MySQL/PHP] Avoid using RAND()

    - by Andrew Ellis
    So... I have never had a need to do a random SELECT on a MySQL DB until this project I'm working on. After researching it seems the general populous says that using RAND() is a bad idea. I found an article that explains how to do another type of random select. Basically, if I want to select 5 random elements, I should do the following (I'm using the Kohana framework here)? If not, what is a better solution? Thanks, Andrew <?php final class Offers extends Model { /** * Loads a random set of offers. * * @param integer $limit * @return array */ public function random_offers($limit = 5) { // Find the highest offer_id $sql = ' SELECT MAX(offer_id) AS max_offer_id FROM offers '; $max_offer_id = DB::query(Database::SELECT, $sql) ->execute($this->_db) ->get('max_offer_id'); // Check to make sure we're not trying to load more offers // than there really is... if ($max_offer_id < $limit) { $limit = $max_offer_id; } $used = array(); $ids = ''; for ($i = 0; $i < $limit; ) { $rand = mt_rand(1, $max_offer_id); if (!isset($used[$rand])) { // Flag the ID as used $used[$rand] = TRUE; // Set the ID if ($i > 0) $ids .= ','; $ids .= $rand; ++$i; } } $sql = ' SELECT offer_id, offer_name FROM offers WHERE offer_id IN(:ids) '; $offers = DB::query(Database::SELECT, $sql) ->param(':ids', $ids) ->as_object(); ->execute($this->_db); return $offers; } }

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  • ASP.NET CacheDependency out of ThreadPool

    - by Stephen
    In an async http handler, we add items to the ASP.NET cache, with dependencies on some files. If the async method executes on a thread from the ThreadPool, all is fine: AsyncResult result = new AsyncResult(context, cb, extraData); ThreadPool.QueueUserWorkItem(new WaitCallBack(DoProcessRequest), result); But as soon as we try to execute on a thread out of the ThreadPool: AsyncResult result = new AsyncResult(context, cb, extraData); Runner runner = new Runner(result); Thread thread = new Thread(new ThreadStart(runner.Run()); ... where Runner.Run just invokes DoProcessRequest, The dependencies do trigger right after the thread exits. I.e. the items are immediately removed from the cache, the reason being the dependencies. We want to use an out-of-pool thread because the processing might take a long time. So obviously something's missing when we create the thread. We might need to propagate the call context, the http context... Has anybody already encountered that issue? Note: off-the-shelf custom threadpools probably solve this. Writing our own threadpool is probably a bad idea (think NIH syndrom). Yet I'd like to understand this in details, though.

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  • Is this the right way to organize my database tables?

    - by Moss
    So I'm making a website that allows users to build contact lists. So their are users, the users have lists, and the lists have contacts. It seems to me that I need 3 tables for this but I just want to make sure. There would be a User table of course, and then a "List of Lists" table that has the username, and listname, as primary key along with whatever other info we want to attach to the lists as a whole. Finally, for lack of a better word, the List table which would again have the username/listname p.k., then the contact ID and notes and such that the user attaches to that contact on that specific list. I hope that is a clear explanation. For some reason I feel unsure about this arrangement. For one thing if the website becomes popular the List table could swell to billions of rows. And it also feels a little weird that everybody's list info is all jumbled up in the same table. I suppose I could create separate tables for each user and even for each list but that seems like a bad idea for other reasons. My db explanation assumes I can use foreign keys on my tables which at the moment isn't actually an option. If I can't get InnoDB tables enabled I will probably use ID's for the lists instead of depending on a compound key. Maybe I should do this anyway?

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  • ORA- 01157 / Cant connect to database

    - by Tom
    Hi everyone, this is a follow up from this question. Let me start by saying that i am NOT a DBA, so i'm really really lost with this. A few weeks ago, we lost contact with one of our SID'S. All the other services are working, but this one in particular is not. What we got was this message when trying to connect ORA-01033: ORACLE initialization or shutdown in progress An attempt to alter database open ended up in ORA-01157: cannot identify/lock data file 6 - see DBWR trace file ORA-01110: data file 6: '/u01/app/oracle/oradata/xxx/xxx_data.dbf' I tried to shutdown / restart the database, but got this message. Total System Global Area 566231040 bytes Fixed Size 1220604 bytes Variable Size 117440516 bytes Database Buffers 444596224 bytes Redo Buffers 2973696 bytes Database mounted. ORA-01157: cannot identify/lock data file 6 - see DBWR trace file ORA-01110: data file 6: '/u01/app/oracle/oradata/xxx/xxx_data.dbf' When all continued the same, I erased the dbf files (rm xxx_data.dbf xxx_index.dbf), and recreated them using touch xxx_data.dbf. I also tried to recreate the tablespaces using `CREATE TABLESPACE DATA DATAFILE XXX_DATA.DBF` and got Database not open As I said, i don't know how bad this is, or how far i'm from gaining access to my database (well, to this SID at least, the others are working). I would imagine that a last resource would be to throw everything away, and recreating it, but I don't know how to, and I was hoping there's a less destructive solution. Any help will be greatly appreciated . Thanks in advance.

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