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• Django complex queries

  - by Josh K

  I need to craft a filter for an object that checks date ranges. Right now I'm performing a very inefficient loop which checks all the objects. I would like to simplify this to a database call. The logic is you have a start and an end date objects. I need to check if the start OR the end is within the range of an appointment. if (start >= appointment.start && start < appointment.end) || (end > appointment.start && end <= appointment.end) I could do this in SQL, but I'm not as familiar with the Django model structure for more complex queries.

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• Style of if: to nest or not to nest

  - by Marco

  A colleague of mine and me had a discussion about the following best-practice issue. Most functions/methods start with some parameter checking. I advocate the following style, which avoids nesting. if (parameter one is ugly) return ERROR; if (parameter two is nonsense || it is raining) return ERROR; // do the useful stuff return result; He, who comes from a more functional/logic programming background, prefers the following, because it reduces the number of exit points from the function. if (parameter one is ok) { if (parameter two is ok && the sun is shining) { // do the useful stuff return result } } return ERROR; Which one would you prefer and why?

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• For what programs are Objective C and Ruby ideal on the Mac?

  - by Kurt

  Hi, as a Mac outsider it seems that two popular programming languages on the Mac appear to be Objective C and Ruby. From what I understand the main API Cocoa seems to be written in and optimized for Objective C, but it is also possible to use Ruby for that. Are there different areas where each language is ideal, for example, I could imagine Objective C could be ideal for a GUI layer, or standalone desktop app, and Ruby could be good for web services etc. What about classic business logic, or data access layers? What language would be a good choice for a library of services for example? Can we write a library in one language and link to it from a main program written in the other language? If I wanted to write a layered enterprise application using domain driven design and dependency injection which languages could support each concerns? Are things like DDD and DI common amongst Mac devs? Just a curious outsider.

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• Issues with taglibs while using jasmine-maven-plugin to test dojo widgets with templates

  - by user2880454

  I am using jasmine-maven-plugin to run javascript unit tests for my dojo widgets. One of my dojo widgets refers to a html template jsp file with taglibs. When I initialize my dojo widgets, I get the following error: Error: Invalid template: <%@ taglib uri="http://www.springframework.org/security/tags" prefix="sec"% The plugin uses jetty to deploy the scripts to test. I tried including jstl jar into the WEB-INF folder but it doesn't work. I am assuming it's just not DOJO and this taglib issue can occur even with simple js file. I am looking for some clue on why taglibs are not recognized here. If I remove the taglib entries, my tests just work fine.

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• How to join nearly identical several queries into one?

  - by Devyn

  Hi, Assume I have an order_dummy table where order_dummy_id, order_id, user_id, book_id, author_id are stored. You may complain the logic of my table but I somehow need to do it that way. I want to execute following queries. SELECT * FROM order_dummy WHERE order_id = 1 AND user_id = 1 AND book_id = 1 ORDER BY `order_dummy_id` DESC LIMIT 1 SELECT * FROM order_dummy WHERE order_id = 1 AND user_id = 1 AND book_id = 2 ORDER BY `order_dummy_id` DESC LIMIT 1 SELECT * FROM order_dummy WHERE order_id = 1 AND user_id = 1 AND book_id = 3 ORDER BY `order_dummy_id` DESC LIMIT 1 Please keep in mind that several numbers of same book is included in one order. Therefore, I list order_dummy_id by descending and limit 1 so only LATEST ORDER of A BOOK is shown. But my goal is to show other books in that way in one table. I used group by like this ... SELECT * FROM order_dummy WHERE order_id = 1 AND user_id = 1 GROUP BY book_id but it only shows order_dummy_id with ascending result. I have no idea anymore. Looking forward your kindness help!

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• long running process in asp.net C#

  - by user339323

  Hello All, I have a web application that has a long running (resource intensive) process in the code behind and the end output is a pdf file (images to pdf conversion tool) It runs fine..and since I am on a dedicated server, it is not at all a problem with respect to resources right now. However, I wonder that the system would reach its resource limits if, there are more than 20 users processing at a time. I have seen services online where the user enters their email and the processes are, I suppose, queued in the background and the results emailed with the 1st in 1st out method. Can someone please give me a start on how to implement this kind of logic in asp.net applications using C#? Thanks a lot in advance, Prasad.

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• Zend without Database

  - by dbemerlin

  Hi, i googled for an hour now but maybe my Google-Fu is just too weak, i couldn't find a solution. I want to create an application that queries a service via JSON requests (all data and backend/business logic is stored in the service). With plain PHP it's simple enough since i just make a curl request, json_decode the result and get what i need. This already works quite well. A request might look like this: Call http://service-host/userlist with body: {"logintoken": "123456-1234-5678-901234"} Get Result: { "status": "Ok", "userlist":[ {"name": "foo", "id": 1}, {"name": "bar", "id": 2} ] } Now we want to get that into the Zend Framework since it's a hobby project and we want to learn about Zend. The problem is that all information i could find use a Database. Is there even a way to create a Zend Project that does not use a Database? And how can i write a model that represents the actions instead of objects and object-relations?

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• is this a simple monad example?

  - by zcaudate

  This is my attempt to grok monadic functions after watching http://channel9.msdn.com/Shows/Going+Deep/Brian-Beckman-Dont-fear-the-Monads. h uses bind to compose together two arbitrary functions f and g. What is the unit operator in this case? ;; f :: int - [str] ;; g :: str = [keyword] ;; bind :: [str] - (str - [keyword]) - [keyword] ;; h :: int - [keyword] (defn f [v] (map str (range v))) (defn g [s] (map keyword (repeat 4 s))) (defn bind [l f] (flatten (map f l))) (f 8) ;; = (0 1 2 3 4 5 6 7) (g "s") ;; = (:s :s :s :s) (defn h [v] (bind (f v) g)) (h 9) ;; = (:0 :0 :0 :0 :1 :1 :1 :1 :2 :2 :2 :2 :3 :3 :3 :3 :4 :4 :4 :4 :5 :5 :5 :5)

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• Implementing simple business model in Haskell

  - by elmes

  Supose we have a very simple model: Station has at least one Train Train has at least two Stations The model has to allow to check what stations any given train visits and to check what trains visit a particular station. How to model it in Haskell? I am a Haskell newbie, so please correct me: once an object is created, you cannot modify it - you can only make a new object based on that one (~immutability). Am I right? If so, I'll have to create a lot of temporary variables with semi-initialized objects (during deserialization or even in unit tests). Basically what I need is an example of modeling domain classes in Haskell - after reading "Learn you a haskell.." I still have no idea how to use this language.

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• Basic Conditional Checking for IF statements in C

  - by ZaZu

  Hi there, Can someone please explain what really goes on in this code ? If I put the AND statement, the message wont show if values are less than 0 or greater than 10 ... I think I must use 1 0 logic to work this out right ? I just need someone to briefly explain it please. #include<stdio.h> main(){ puts("enter number"); scanf("%d",num); if(num<0 || num >10) puts("yay"); } How is that IF statement different when AND is put : #include<stdio.h> main(){ puts("enter number"); scanf("%d",num); if(num<0 && num >10) puts("yay"); } Thanks !!

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• How to send reminder notifications to subscribers for renewal from SQL Server 2005?

  - by codemonkie

  I have a table in SQL DB, namely dbo.subscribers, it contains following columns: -SubscriberID -JoinDateTime The business logic says a subscription last for 2 weeks and a reminder should be sent after 7 days from the JoinDateTime. The way that the system was designed to send reminders are via a URL call, e.g. http://xxx.xxx.xxx.xxx/renew_userid=SubscriberID/ and that can only be called from our webserver which is the only whitelisted IP machines given. Currently there is a windows service written to query the DB once a day at midnight to grab all expiring subscribers and send them reminders, however this batch approach only sends reminders to the nearest date, well, I could have set the interval down from 1 day to 1 hour such that the service can send notifications out closer to the exact JoinDateTime + 7 days requirements. I have heard a stored procedure can be written and perform task like this to a nearly real-time manner, if yes, please give me some hints on how to do it. Another question is - is SSRS bit of an overkill to perform things like this? Please advice. TIA

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• Is there a free code coverage tool suitable for use with .NET 4 and NUnit?

  - by Damian Powell

  Is there a free code coverage tool suitable for use with .NET 4 and NUnit that runs from the command line (and is thus suitable for use on a build server)? Please note that any tools that require editions of Visual Studio higher than Professional are not appropriate in this case. I am asking this question because I can't get NCover 1.5.8 to work with NUnit 2.5.5 on a .NET 4 C# app. I can run the unit tests, and I can generate a Coverage.Xml file, but it is empty - it contains no sequence points. After a lot of research, I have concluded that this is because NCover 1.5.8 simply doesn't work with .NET 4. However, if you know better, please feel free to answer this question from another user.

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• Postgres : Post statement (or insert) asynchronous, non-blocking processing.

  - by Hassan Syed

  I'm wondering if it is possible, that after a collection of rows is inserted, to initiate an operation that is executed asynchronously, is non-blocking, and doesn't need to inform the originator of the request - of the result. I am working with large amounts of events and I can guarantee that the post-insert logic will not fail -- I just want to have a single insert thread in my event-sources, and I want this thread to keep flying without blocking, and without being responsible for any post-delivery book-keeping. I can tell you that I would potentially have a 100 of these jobs executing concurrently and each job might operate on 5 tables with anywhere between 200-1000 inserts on each of these tables. A hint in the right direction should be enough.

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• Updating or inserting high scores in SQL

  - by Roger Gilbrat

  I've been racking my brain over this for the past few days and I'm not sure it's possible, but figured I ask here. Is it possible for a single SQL statement to update a high score if your score is greater or insert it if your first score? My Score table has a UserID, Level and Score columns and I like it to follow the following logic: If your new score is greater than your last score for this Level, then replace it. If you don't have a score for this Level then add it. If your score for this Level is less than your highest score for this Level then do nothing. Is this possible in a single SQL statement or do I have to use two, one to see if you have a new high score and if so, replace it? Each UserID would have only one score in the table for each Level. I'm using MySQL.

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• Proper abstraction of the database tier in a 3 tier system?

  - by Earlz

  Hello, I am creating a 3 tier application. Basically it goes Client - (through optional server to be a thin-client) - Business Logic - Database Layer And basically making it so that there is never any skipping around. As such, I want for all of the SQL queries and such to be in the Database Layer. Well, now I'm a bit confused. I made a few static classes to start off the database tier but what should I do for the database connections? Should I just create a new database connection anytime I enter the Database Layer or would that be wasteful? Does Connection.Open() take time whenever you have a ConnectionPool? To me, it just feels wrong for the Business tier to have to pass in a IdbConnection object to the Database tier. It seems like the Database tier should handle all of that DB-specific code. What do you think? How can I do it the proper way while staying practical?

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• Performance Overhead of Perf Event Subsystem in Linux Kernel

  - by Bo Xiao

  Performance counters for Linux are a new kernel-based subsystem that provide a framework for all things performance analysis. It covers hardware level (CPU/PMU, Performance Monitoring Unit) features and software features (software counters, tracepoints) as well. Since 2.6.33, the kernel provide 'perf_event_create_kernel_counter' kernel api for developers to create kernel counter to collect system runtime information. What I concern most is the performance impact on overall system when tracepoint/ftrace is enabled. There are no docs I can find about them. I was once told that ftrace was implemented by dynamically patching code, will it slow the system dramatically?

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• Better method for flipping multidimensional array?

  - by sudowned

  I've retrieved some data from the database, which is in the following structure: [0] [item_id] = 197 [dice_chat_css] = "foo" [dice_image] = "bar.png" [1] [item_id] = 128 [dice_chat_css] = "foo" [dice_image] = "bar.png" The most convenient and computationally inexpensive way for me to pass this data to the rest of my (PHP) application is with item_id as the index, because it saves having to loop over the array to look up values. If this was a flat array, I could accomplish this trivially with array_flip, but since it isn't, it's my pick of using either the multidimensional array_flip listed in the comments on PHP.net, or roll my own logic: for ($i = 0; $i < sizeOf($r); $i++){ $s[$r[$i]['item_id']]['dice_image'] = $r[$i]['dice_image']; $s[$r[$i]['item_id']]['dice_chat_css'] = $r[$i]['dice_chat_css']; } I know it's simple, but it feels like I'm reinventing the wheel here. Is there an accepted, more optimized method available or am I being weird about this?

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• Trouble rendering a view inside a generic class

  - by Horace Loeb

  I'm trying to encapsulate the logic for generating my sitemap in a separate class so I can use Delayed::Job to generate it out of band: class ViewCacher include ActionController::UrlWriter def initialize @av = ActionView::Base.new(Rails::Configuration.new.view_path) @av.class_eval do include ApplicationHelper end end def cache_sitemap songs = Song.all sitemap = @av.render 'sitemap/sitemap', :songs => songs Rails.cache.write('sitemap', sitemap) end end But whenever I try ViewCacher.new.cache_sitemap I get this error: ActionView::TemplateError: ActionView::TemplateError (You have a nil object when you didn't expect it! The error occurred while evaluating nil.url_for) on line #5 of app/views/sitemap/_sitemap.builder: I assume this means that ActionController::UrlWriter is not included in the right place, but I really don't know

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• Should class IOException in Java have been an unchecked RuntimeException?

  - by Derek Mahar

  Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling of this exception to a separate system error handler.

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• Oracle SQL Update query takes days to update

  - by B Senthil Kumar

  I am trying to update a record in the target table based on the record coming in from source. For instance, if the incoming record is present in the target table I would update them in the target else I would simply insert. I have over one million records in my source while my target has 46 million records. The target table is partitioned based on calendar key. I implement this whole logic using Informatica. I find that the Informatica code is perfectly fine looking at the Informatica session log but its in the update it takes long time (more than 5 days to update one million records). Any suggestions as to what can be done on the scenario to improve the performance?

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• Use where condition with unjoined table

  - by Dragos D

  I have the following problem: I am trying to retreive a sum value based on one condition. Problem is that I can't join the conditional value since my tables aren't joined. Here is my syntax: SELECT SUM(value) FROM value v join day d on v.day_id = d.day_id join budget b on d.budget_id = b.budget_id join unit u on v.unit_id = u.unit_id where #output.class = (SELECT distinct s.class FROM sale s where s.id = #output.sale_id) AND u.unit_name in ('electronics') With this sybtax I get no error but neither values. Can you please tell me where I do wrong?

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• Python Game using pyGame with Window Menu elements

  - by Zoja

  Here's the deal. I'm trying to write an arkanoid clone game and the thing is that I need a window menu like you get in pyGTK. For example File-(Open/Save/Exit) .. something like that and opening an "about" context where the author should be written. I'm already using pyGame for writting the game logic. I've tried pgu to write the GUI but that doesn't help me, altough it has those menu elements I'm taking about, you can't include the screen of the game in it's container. Does anybody know how to include such window menus with the usage of pyGame ?

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• How does Maven find a Artifact in a remote repository?

  - by Thomas

  I'm trying to create a maven plugin to generate a file with the URL to all the dependencies in a project. I have been able to get the dependencies and their artifact, but I'm having trouble getting the download URL. Using ArtifactResolver and ArticateMetadataSource I get some of the artifact information. However I fail to get all the information for all the dependencies. I haven't been able to find documentation on the resolution logic, so that I can call it form my plugin. I can use an ArtifactResolver to download the artifact, but what I really wanted was just the URL. The Maven Artifact API has a a method called getDownloadURL (see http://maven.apache.org/ref/2.0.4/maven-artifact/apidocs/org/apache/maven/artifact/Artifact.html). However I cant seem to find a way to get a real value into it. I always get a null value. Is there a way to have it resolved (downloading or not) and get the URL for where the file came from?

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• How to find scrollable elements in DOM using XPath?

  - by ak.

  Basically I need to find all elements on the page that have a scrollbar (vertical or horizontal) How to tell if an element has a scrollbar and can actually be scrolled? I found this code snippet on jsperf. Is it possible to capture the logic behind the code into and XPath expression? Or are there any other ways to check for scrollbars? Added: Just to explain what I'm trying to do: I'm developing extension for Firefox. Basically it introduces Vim-style mouseless shortcuts (I know there is Vimperator and Pentadactyl...). One of the features I'd like to implement is to allow the use to select the container that's scrolled with j/k keys. That's why I need to discover all scrollable elements on any given random page.

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• ASP.net MVC How to run multiple instances of the same app at the same time in different subdomains?

  - by basilmir

  ASP.net MVC How to run multiple instances of the same app at the same time in different subdomains? I have a dozen or so subdomains. sub1.website.com sub2.website.com and the folder structure like this \website\sub1 \website\sub2 If i need to run the same app for all of the subdomains, what would be the best appoach? Host is in the root \website\ and have it figure out where to look based on the "user"? (i imagine i need to implement de logic in the code) OR Just copy the app in each of the subdomains, and have the app "not knowing" that it is actually an instance? (this would mean that when i update the app, i have to copy it everywhere) What other approaches are there to this kind of issue? Each app will use a different database name so that will need to we coded in somekind of external file.

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