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• Updating a database periodically with Java

  - by MSR

  I would like to perform updates to a MySQL database using two separate classes (that do different things) -- one doing so every 10 seconds, and the second every minute. I have a few gaps in my Java knowledge and I'm wondering what the best way to achieve it is. Importantly, if connectivity to the database is lost, I need reconnection attempts to occur indefinitely, and I'm guessing the use of Prepared Statements will make queries more efficient. Should the connection to the database be left open all the time or closed between the updates being run? Maybe I also need to think about clearing objects/resources out of memory if the class instances are going to be run indefinitely.

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• How can I detect common substrings in a list of strings

  - by danio

  Given a set of strings, for example: EFgreen EFgrey EntireS1 EntireS2 J27RedP1 J27GreenP1 J27RedP2 J27GreenP2 JournalP1Black JournalP1Blue JournalP1Green JournalP1Red JournalP2Black JournalP2Blue JournalP2Green I want to be able to detect that these are three sets of files: EntireS[1,2] J27[Red,Green]P[1,2] JournalP[1,2][Red,Green,Blue] Are there any known ways of approaching this problem - any published papers I can read on this? The approach I am considering is for each string look at all other strings and find the common characters and where differing characters are, trying to find sets of strings that have the most in common, but I fear that this is not very efficient and may give false positives. Note that this is not the same as 'How do I detect groups of common strings in filenames' because that assumes that a string will always have a series of digits following it. [Edited 15/09/09 to add more sample strings]

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• Q about AbstractApplicationContext.getBeansOfType() and getBean()

  - by Paul Reiners

  We have the following legacy 2.0.7 Spring code: final Map<String, MyClass> secondaryFactories = (Map<String, MyClass>) context.getBeansOfType(MyClass.class, false, true); return (MyClass) context.getBean("myClass"); where context is an instance of org.springframework.context.support.AbstractApplicationContext Note that we ignore the return value of getBeansOfType(). This works just fine, but the problem is that the call to getBeansOfType() is time-consuming. However, even though we ignore the return value of this call, if we try to eliminate this call, then the instance of MyClass returned by getBean() is not fully initialized. (So, apparently, the call to getBeansOfType() is having some sort of side-effects that we need.) We suspect that the call to getBeansOfType() is overkill and we could do something more lightweight so that the instance of MyClass obtained by the call to getBean() would be fully initialized (but it's not null and no exception is thrown). So, is there a more efficient way of doing this?

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• Find all numbers that appear in each of a set of lists

  - by Ankur

  I have several ArrayLists of Integer objects, stored in a HashMap. I want to get a list (ArrayList) of all the numbers (Integer objects) that appear in each list. My thinking so far is: Iterate through each ArrayList and put all the values into a HashSet This will give us a "listing" of all the values in the lists, but only once Iterate through the HashSet 2.1 With each iteration perform ArrayList.contains() 2.2 If none of the ArrayLists return false for the operation add the number to a "master list" which contains all the final values. If you can come up with something faster or more efficient, funny thing is as I wrote this I came up with a reasonably good solution. But I'll still post it just in case it is useful for someone else. But of course if you have a better way please do let me know.

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• Is this the best way to get the size of a Paper via CUPS?

  - by Lawrence Johnston

  I've got a CUPS job control file. I need to get the actual dimensions of the print that was made. This is the way I've figure out to do it: Get the paper name using the media attribute. (e.g. Letter) Get the printer uri from the printer-uri attribute. (e.g. ipp://localhost/printers/MyPrinter) Get the printer name by passing the printer uri to the IPP_GET_PRINTER_ATTRIBUTES operation and getting the printer-name attribute. (e.g. MyPrinter) Get the path to the PPD passing the printer name to the the cupsGetPPD method. Open the PPD passing the path to the PPD to the ppdOpenFile method. Get the paper size by passing the PPD and paper name to the ppdPageSize method. This will work, but it seems a bit roundabout. Is there a more efficient way of getting what I need?

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• Generic Database table design

  - by Gazeth

  Just trying to figure out the best way to design my table for the following scenario: I have several areas in my system (documents, projects, groups and clients) and each of these can have comments logged against them. My question is should I have one table like this: CommentID DocumentID ProjectID GroupID ClientID etc Where only one of the ids will have data and the rest will be NULL or should I have a seperate CommentType table and have my comments table like this: CommentID CommentTypeID ResourceID (this being the id of the project/doc/client) etc My thoughts are that option 2 would be more efficient from an indexing point of view?

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• What are the disadvantages of using a StringBuilder?

  - by stickman

  I know that StringBuilder is more efficient than a normal string when processing code which modifies the string value a lot because although strings act like value types, they are actually reference, which makes them immutable so every time we change it, we need to create a new reference in memory. My question is that, why doesn't .NET just use stringBuilder by default? There must be some disadvantages of it over just using String. Can anyone tell me what they are? The only thing I can think of is perhaps it is a heavier object and it takes more time to instantiate so if you aren't changing the string too much, this would override the benefits of StringBuilder

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• MySQL "IS IN" equivalent?

  - by nute

  A while ago I worked on a MS-SQL project and I remember a "IS IN" thing. I tried it on a MySQL project and it did not work. Is there an equivalent? Workaround? Here is the full query I am trying to run: SELECT * FROM product_product, product_viewhistory, product_xref WHERE ( (product_viewhistory.productId = product_xref.product_id_1 AND product_xref.product_id_2 = product_product.id) OR (product_viewhistory.productId = product_xref.product_id_2 AND product_xref.product_id_1 = product_product.id) ) AND product_product.id IS IN (SELECT DISTINCT pvh.productId FROM product_viewhistory AS pvh WHERE pvh.cookieId = :cookieId ORDER BY pvh.viewTime DESC LIMIT 10) AND product_viewhistory.cookieId = :cookieId AND product_product.outofstock='N' ORDER BY product_xref.hits DESC LIMIT 10 It's pretty big ... but the part I am interested in is: AND product_product.id IS IN (SELECT DISTINCT pvh.productId FROM product_viewhistory AS pvh WHERE pvh.cookieId = :cookieId ORDER BY pvh.viewTime DESC LIMIT 10) Which basically says I want the products to be in the "top 10" of that sub-query. How would you achieve that with MySQL (while trying to be efficient)?

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• How to find and update the next record in a linking table

  - by someoneinomaha

  I have a classifieds system I'm working on. People are able to add photos to a classified, but I only display one when displaying the list of classifieds. To do that, I have a linking table between classifieds and photos that has a "is_main" boolean field. When someone deletes one of their classified photos, I want to: 1) See if there is more than that photo tied to the classified. 2) If there is, update the next photo and set that "is_main" field to TRUE. Just trying to find out the most efficient way to do this.

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• Retrieving a single Guid in CRM 4.0

  - by user1746560

  I'm new to CRM (version 4.0) and i'm trying to return a 'yearid' guide based on a given year (which is also stored in the entity).So far i've got: public static Guid GetYearID(string yearName) { ICrmService service = CrmServiceFactory.GetCrmService(); // Create the query object. QueryExpression query = new QueryExpression("year"); ColumnSet columns = new ColumnSet(); columns.AddColumn("yearid"); query.ColumnSet = columns; FilterExpression filter = new FilterExpression(); filter.FilterOperator = LogicalOperator.And; filter.AddCondition(new ConditionExpression { AttributeName = "yearName", Operator = ConditionOperator.Equal, Values = new object[] { yearName} }); query.Criteria = filter; } But my questions are: A) What code do in addition to this to actually store the Guid? B) Is using a QueryExpression the most efficient way to do this?

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• How to implement a set ?

  - by nomemory

  I want to implement a Set in C. Is it OK to use a linked list, when creating the SET, or should I use another approach ? How do you usually implement your own set (if needed). NOTE: If I use the Linked List approach, I will probably have the following complexities for my operations: init : O(1); destroy: O(n); insert: O(n); remove: O(n); union: O(n*m); intersection: O(n*m); difference: O(n*m); ismember: O(n); issubset: O(n*m); setisequal: O(n*m); O(n*m) seems may be a little to big especially for huge data... Is there a way to implement my Set more efficient ?

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• Need advice on cron job'ing a very large process

  - by Arms

  I have a PHP script that grabs data from an external service and saves data to my database. I need this script to run once every minute for every user in the system (of which I expect to be thousands). My question is, what's the most efficient way to run this per user, per minute? At first I thought I would have a function that grabs all the user Ids from my database, iterate over the ids and perform the task for each one, but I think that as the number of users grow, this will take longer, and no longer fall within 1 minute intervals. Perhaps I should queue the user Ids, and perform the task individually for each one? In which case, I'm actually unsure of how to proceed. Thanks in advance for any advice.

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• group by country with ActiveRecords in Rails

  - by Adnan

  Hello, I have a table with users: name | country | .. | UK | .. | US | .. | US | .. | UK | .. | FR | .. | FR | .. | UK | .. | UK | .. | DE | .. | DE | .. | UK | .. | CA | . . What is the most efficient way with ActiveRecords to get the list of countries in my view and for each country how many users are from, so: US 123 UK 54 DE 33 . . .

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• Most optimal way to detect if black (or any color pixels) exist in an image file?

  - by Zando

  What's the best and most flexible algorithm to detect any black (or colored pixel) in a given image file? Say I'm given an image file that could, say, have a blue background. And any non blue pixel, including a white pixel, is counted as a "mark". The function returns true if there are X number of pixels that deviate from each other at a certain threshold. I thought it'd be fastest to just simply iterate through every pixel and see if its color matches the last. But if it's the case that pixel (0,0) is deviant, and every other pixel is the same color (and I want to allow at least a couple deviated pixels before considering an image to be "marked), this won't work or be terribly efficient.

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• Explanation of NSMutableURLRequest : setHTTPMethod

  - by kkmoslehpour

  I am new to objective c programming. I am currently trying to insert data into mysql database. I have read a couple links on this and could not find the exact answer I am looking for. Here is what I am trying to do: I have my app that user inputs a name in a text field and once the press the add button, it makes a connection to my php file and my php file does the rest of the work (using POST method) and adds the name to the mysql dataase. I have seen a lot of people use NSMutableURLRequest : setHTTPMethod :POST`` in their code (in my case my php file does that and I don't haveNSMutableURLRequest` included in my code and it works perfectly fine.) My questions are: Are there any benefits of including NSMutableURLRequest in your code when you can just call your php code to take care of the POST for you? What does NSMutableURLRequest exactly do and which way is more efficient?

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• C# remove duplicates from List<List<int>>

  - by marseilles84

  I'm having trouble coming up with the most efficient algorithm to remove duplicates from List<List<int>>, for example (I know this looks like a list of int[], but just doing it that way for visual purposes: my_list[0]= {1, 2, 3}; my_list[1]= {1, 2, 3}; my_list[2]= {9, 10, 11}; my_list[3]= {1, 2, 3}; So the output would just be new_list[0]= {1, 2, 3}; new_list[1]= {9, 10, 11}; Let me know if you have any ideas. I would really appreciate it.

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• Best approach to synchronising properties across threads

  - by user290796

  Hi, I'm looking for some advice on the best approach to synchronising access to properties of an object in C++. The application has an internal cache of objects which have 10 properties. These objects are to be requested in sets which can then have their properties modified and be re-saved. They can be accessed by 2-4 threads at any given time but access is not intense so my options are: Lock the property accessors for each object using a critical section. This means lots of critical sections - one for each object. Return copies of the objects when requested and have an update function which locks a single critical section to update the object properties when appropriate. I think option 2 seems the most efficient but I just want to see if I'm missing a hidden 3rd option which would be more appropriate. Thanks, J

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• Correct way to take absolute value of INT_MIN

  - by aka.nice

  I want to perform some arithmetic in unsigned, and need to take absolute value of negative int, something like do_some_arithmetic_in_unsigned_mode(int some_signed_value) { unsigned int magnitude; int negative; if(some_signed_value<0) { magnitude = 0 - some_signed_value; negative = 1; } else { magnitude = some_signed_value; negative = 0; } ...snip... } But INT_MIN might be problematic, 0 - INT_MIN is UB if performed in signed arithmetic. What is a standard/robust/safe/efficient way to do this in C?

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• Accessing two sides of a user-user relationship in rails

  - by Lowgain

  Basically, I have a users model in my rails app, and a fanship model, to facilitate the ability for users to become 'fans' of each other. In my user model, I have: has_many :fanships has_many :fanofs, :through => :fanships In my fanship model, I have: belongs_to :user belongs_to :fanof, :class_name => "User", :foreign_key => "fanof_id" My fanship table basically consists of :id, :user_id and :fanof_id. This all works fine, and I can see what users a specific user is a fan of like: <% @user.fanofs.each do |fan| %> #things <% end %> My question is, how can I get a list of the users that are a fan of this specific user? I'd like it if I could just have something like @user.fans, but if that isn't possible what is the most efficient way of going about this? Thanks!

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• How to correctly migrate urls from custom asp.net solution to Wordpress?

  - by Marek

  I have a web site built using asp.net with ugly URLs like /DisplayContent.aspx?id=789564. I know how to migrate the database, but the Wordpress urls will be (naturally) different. Can I simply write some mapping or do I have to include a rewrite rule for each subpage (300 pages) in .htaccess? Should I provide a rewrite rule for each existing page that would transform a full old url to the known new url, like for example: /DisplayContent.aspx?id=789798 -> /2010-5-10/Title-Of-The-Post Even if I manage to migrate the URLs, the structure of the HTML for the new content will naturally be different. How does this affect SEO? Should I run asp.net and wordpress side by side and issue the redirects from the asp.net application? What is the most efficient solution to this kind of migration of URLs without doing PHP programming?

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• hunting maven dependencies

  - by Tom

  I want to start using maven in code I distribute but I can't find an efficient way to work with dependencies. Every new dependency takes me far too long to add. As a simple example, I need to add Tomcat for compilation. Do I really have to manually trawl the repo in my browser to find the group-id, artifact-id and version number? In every case it seems easier to find the non-maven downloads. I hope I've missed something obvious.

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• delete all records except the id I have in a python list

  - by jay_t

  Hi all, I want to delete all records in a mysql db except the record id's I have in a list. The length of that list can vary and could easily contain 2000+ id's, ... Currently I convert my list to a string so it fits in something like this: cursor.execute("""delete from table where id not in (%s)""",(list)) Which doesn't feel right and I have no idea how long list is allowed to be, .... What's the most efficient way of doing this from python? Altering the structure of table with an extra field to mark/unmark records for deletion would be great but not an option. Having a dedicated table storing the id's would indeed be helpful then this can just be done through a sql query... but I would really like to avoid these options if possible. Thanks,

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• enumerate all combinations in c++

  - by BCS

  My question is similar to this combinations question but in my case I have N (N 4) small sets (1-2 items per set for now might go to 3 maybe 4) and want to generate each combination of one item from each set. The current solution looks somethinging along the lines of this for(T:: iterator a = setA.begin(); a != setA.end(); ++a) for(T:: iterator b = setB.begin(); b != setB.end(); ++b) for(T:: iterator c = setC.begin(); c != setC.end(); ++c) for(T:: iterator d = setD.begin(); d != setD.end(); ++d) for(T:: iterator e = setE.begin(); e != setE.end(); ++e) something(*a,*b,*c,*d,*e); Simple, effective, probably reasonably efficient, but ugly and not very extensible. Does anyone know of a better/cleaner way to do this?

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• To use an api or store a large dataset in a rails app?

  - by Dave

  Hi all- I am working on a site that has the potential to need a LOT of space. Basically we hope to have every video game every created stored in a database along with an image of the cover. There are some api's out there that might be able to help, like GiantBomb's (www.giantbomb.com). We are trying to decide whether to store the data locally and if so where to find that comprehensive a list, or make calls to the api on demand. The problem with the latter is likely latency and also downtime problems. Assuming we want to store it locally here are the questions: 1) Where can we find this kind of data (yes, I looked on google, and no I couldnt find anything:)) 2) What is the most efficient way to encode and store the images? Thanks!

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• Creating a page selector with JSP/JSTL

  - by zakSyed

  I am working on a project where I am required to build a page somewhat similar to the one you see when you visit a website like blockbuster. When you click on browse more you are taken to a page with a bar on top with different page numbers and a drop down to select the number of pages you want to view on that page. I want to include a feature like that on my page but I am not sure where to start. In my page I have list of 200 items which I want to display page by page. I was suggested to use custom tags, but is there a more simpler or efficient way to create that functionality. My web application uses Spring MVC framework and is coded entirely in Java. Any suggestions will be appreciated.

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