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  • Why are joins bad when considering scalability?

    - by acidzombie24
    Why are joins bad or 'slow'. I know i heard this more then once. I found this quote The problem is joins are relatively slow, especially over very large data sets, and if they are slow your website is slow. It takes a long time to get all those separate bits of information off disk and put them all together again. source I always thought they were fast especially when looking up a PK. Why are they 'slow'?

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  • MySQL LIMIT 1 but query 15 rows?

    - by Ian
    Basically what I'm trying to do is compare the ID's of rows against 15 results in MySQL, eliminating all but 1 (using NOT IN) and then pull that result. Now normally this would be fine by itself, however the order of the 15 rows I'm doing the SQL query for are constantly changing based on a ranking, so there is a possibility that between the time the ranking updates, and the ajax request (which I submit the ID's for NOT IN) more than just one ID has changed, which would of course bring back more than one row which I do not want. So in short, is there a way in which I can query 15 rows, but only return one? Without having to run two separate queries. Any help is appreciated, thank you. EXAMPLE: Say I have 7 items in my database, and I'm displaying 5 on the page to the user. These are what are being displayed to the user: Apple Orange Kiwi Banana Grape But in the database I also have Peach Blackberry Now what I want to do is if the user deletes an item from their list, it will add another item (based on a ranking they have) Now the issue is, in order to know what they have on their list at the moment I send the remaining items to the database (say they deleted Kiwi, I would send Apple, Orange, Banana, and Grape) So now I select the highest ranked 5 items from are remaining six items, make sure they are not the ones already displayed on the page, and then add the new one to list (either Peach or Blackberry) All good and well, except that if both peach and blackberry now outrank grape, then I will be returning two results instead of just one. Because it would've searched... Apple Orange Banana Peach Blackberry and excluded... Apple Orange Banana Grape Which leaves us with both Peach and Blackberry, instead of just Peach or Blackberry

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  • C# & SQL Server Authentication

    - by Peter
    Hello, I'm currently developing a C# app with an SQL Server DB back-end. I'm approaching the point of deployment and hitting a problem. The applicaiton will be deployed within an active directory network. As far as SQL authentication goes, I understand that I have 2 options - Windows Authenticaiton or Server Authenticaiton. If I use Server Authentication, I'm concerned that the username and password for the account will be stored in plain text in the app.config file, and therefore leave the database vulnerable. Using Windows Authenticaiton will avoid this issue, however it would mean giving every member of staff within our organisation read/write access to the database in order to run the app correctly. Whilst this is ok, it also means that they can easily connect to the database themselves via other means and directly alter the data outside of the app. I'm guessing there is someting really obvious I'm missing here, but I've been googling all evening to no avail. Any advice/guidance would be much appreciated! Peter Addition - my project is Windows Form based not ASP.NET - is encrypting the app.config file still the right answer? If it is, does anyone have any examples that are not ASP.NET based?

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  • how we can save a file as temporary basis

    - by SunilRai86
    how we can save a file as temporary basis i have a xml file it is in encrypted mode i want to decrypt it .but i want it doesn't save on disk rather it save on flash memory. after decryption i have to read values and then it should destroy(decrypted xml file).

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  • NSFetchedResultsController on secondary UITableView - how to query data?

    - by Jason
    I am creating a core-data based Navigation iPhone app with multiple screens. Let's say it is a flash-card application. The data model is very simple, with only two entities: Language, and CardSet. There is a one-to-many relationship between the Language entity and the CardSet entities, so each Language may contain multiple CardSets. In other words, Language has a one-to-many relationship Language.cardSets which points to the list of CardSets, and CardSet has a relationship CardSet.language which points to the Language. There are two screens: (1) An initial TableView screen, which displays the list of languages; and (2) a secondary TableView screen, which displays the list of CardSets in the Language. In the initial screen, which lists the languages, I am using NSFetchedResultsController to keep the list of languages up-to-date. The screen passes the Language selected to the secondary screen. On the secondary screen, I am trying to figure out whether I should again use an NSFetchedResultsController to maintain the list of CardSets, or if I should work through Language.cardSets to simply pull the list out of the object model. The latter makes the most sense programatically because I already have the Language - but then it would not automatically be updated on changes. I have looked at the NSFetchedResultsController documentation, and it seems like I can easily create predicates based on attributes - but not relationships. I.e., I can create the following NSFetchedResultsController: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name LIKE[c] 'Chuck Norris'"]; How can I access my data through the direct relationship - Language.cardSets - and also have the table auto-update using NSFetchedResultsController? Is this possible?

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  • MAC : How to check if the file is still being copied in cpp?

    - by Peda Pola
    In my current project, we had a requirement to check if the file is still copying. We have already developed a library which will give us OS notification like file_added , file_removed , file_modified, file_renamed on a particular folder along with the corresponding file path. The problem here is that, lets say if you add 1 GB file, it is giving multiple notification such as file_added , file_modified, file_modified as the file is being copied. Now i decided to surpass these notifications by checking if the file is copying or not. Based on that i will ignore events. I have written below code which tells if the file is being copied or not which takes file path as input parameter. Details:- In Mac, while file is being copied the creation date is set as some date less than 1970. Once it is copied the date is set to current date. Am using this technique. Based on this am deciding that file is being copied. Problem:- when we copy file in the terminal it is failing. Please advice me any approach. bool isBeingCopied(const boost::filesystem::path &filePath) { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; bool isBeingCopied = false; if([[[[NSFileManager defaultManager] attributesOfItemAtPath:[NSString stringWithUTF8String:filePath.string().c_str()] error:nil] fileCreationDate] timeIntervalSince1970] < 0) { isBeingCopied = true; } [pool release]; return isBeingCopied; }

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  • Java ArrayList remove dupes without sets

    - by Kieran
    I'm having problems removing duplicates from an ArrayList. It's for an assignment for college. Here's the code I have already: public int numberOfDiffWords() { ArrayList<String> list = new ArrayList<>(); for(int i=0; i<words.size()-1; i++) { for(int j=i+1; j<words.size(); j++) { if(words.get(i).equals(words.get(j))) { // do nothing } else { list.add(words.get(i)); } } } return list.size(); } The problem is in the numberOfDiffWords() method. The populate list method is working correctly, as my instructor has given me a sample string (containing 4465 words) to analyse - printing words.size() gives the correct result. I want to return the size of the new ArrayList with all duplicates removed. words is an ArrayList class attribute. UPDATE: I should have mentioned I'm only allowed to use dynamic indexed-based storage for this part of the assignment, which means no hash-based storage.

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  • iPhone -trouble with a loading data from webservice into a tableview

    - by medampudi
    I am using a Window based application and then loading up my initial navigationview based controller. After loading it if the user is not registered/ does not have a credentials present then it takes the user to a login view controller . loginViewController *sampleView = [[loginViewController alloc] initWithNibName:@"loginViewController" bundle:nil]; [self.navigationController presentModalViewController:sampleView animated:YES]; [sampleView release]; then right after that i try to load the table with data that i get from a webservice using asiHTTP .. for this question lets say it takes 3 seconds time to get the data and then deserialize it . now... my question is it works out okey in the later runs as I store the username and password in a seure location... but in the first instance.... i am not able to get the data to laod to the tableview... I have tried a lot of things... 1. Initially the data fetch methods was in a diffrent methods.. so i thought that might be the problem as then moved it the same place as the tbleviewController(navigationController) 2. I event put in the Reload data at the end of the functionality for the data parsing and deserialization... nothing happens. 3. i did not understand the concept of @property and alll.... 4. The screen is black screen with nothing displayed on it for a good 5 seconds in the consecutive launches of the app.... so could we have something like a MBPorgressHUD implemented for the same. could any one please help for these scenarios and guidance as to what paths to take from here...

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  • Read/Write Excel Files Directly To/From Memory

    - by Corey O.
    Several people have asked, in a roundabout way, but I have yet to see a workable solution. Is there any way to open an excel file from directly memory (like a byte[]) ? Likewise is there a way to write a file directly to memory? I am looking for solutions that will not involve the hard disk or juggling temporary files. Thanks in advance for any suggestions.

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  • has anyone produced an in-memory GIT repository?

    - by Andrew Matthews
    I would like to be able to take advantage of the benefits of GIT (and its workflows), but without the cost of disk access - I just would like to leverage the distributed revision control capabilities of GIT to produce something like a hybrid of memcached and GIT. (preferably in .NET) Is there such a beast out there?

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  • encapsulation in python list (want to use " instead of ')

    - by Codehai
    I have a list of users users["pirates"] and they're stored in the format ['pirate1','pirate2']. If I hand the list over to a def and query for it in MongoDB, it returns data based on the first index (e.g. pirate1) only. If I hand over a list in the format ["pirate1","pirate"], it returns data based on all the elements in the list. So I think there's something wrong with the encapsulation of the elements in the list. My question: can I change the encapsulation from ' to " without replacing every ' on every element with a loop manually? Short Example: aList = list() # get pirate Stuff # users["pirates"] is a list returned by a former query # so e.g. users["pirates"][0] may be peter without any quotes for pirate in users["pirates"]: aList.append(pirate) aVar = pirateDef(aList) print(aVar) the definition: def pirateDef(inputList = list()): # prepare query col = mongoConnect().MYCOL # query for pirates Arrrr pirates = col.find({ "_id" : {"$in" : inputList}} ).sort("_id",1).limit(50) # loop over users userList = list() for person in pirates: # do stuff that has nothing to do with the problem # append user to userlist userList.append(person) return userList If the given list has ' encapsulation it returns: 'pirates': [{'pirate': 'Arrr', '_id': 'blabla'}] If capsulated with " it returns: 'pirates' : [{'_id': 'blabla', 'pirate' : 'Arrr'}, {'_id': 'blabla2', 'pirate' : 'cheers'}] EDIT: I tried figuring out, that the problem has to be in the MongoDB query. The list is handed over to the Def correctly, but after querying pirates only consists of 1 element... Thanks for helping me Codehai

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  • Ideal HTTP cache control headers for different types of resources

    - by chris_l
    I want to find a minimal set of headers, that work with "all" caches and browsers (also when using HTTPS!) On my (GWT-based) web site, I'll have three kinds of resources: 1. Forever cacheable (public / equal for all users) These files don't ever change, and they get a filename based on the MD5 of their contents (this is GWT's approach). They should get cached as much as possible, even when using HTTPS (so I assume, I should set Cache-Control: public, especially for Firefox?) 2. Changing for every new version of the site (public / equal for all users) These files can be cached, but probably need to be revalidated every time. 3. Individual for each request (private / user specific) These resources (e. g. JSON responses) should never be cached unencrypted to disk under no circumstances. (Maybe I'll have a few specific requests that could be cached.) I have a general idea on which headers I would probably use for each type, but there's always something I could be missing.

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  • Read files via php

    - by Koka
    You all know about restrictions that exist in shared environment, so with that in mind, please suggest me a php function or something with the help of which I could stream my videos and other files. I have a lot of videos on the server, unlimited bandwidth and disk space, but I am limited in ram and cpu.

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  • Can i change the identity of the logged in user in ASP.net?

    - by Rising Star
    I have an ASP.net application I'm developing authentication for. I am using an existing cookie-based log on system to log users in to the system. The application runs as an anonymous account and then checks the cookie when the user wants to do something restricted. This is working fine. However, there is one caveat: I've been told that for each page that connects to our SQL server, I need to make it so that the user connects using an Active Directory account. because the system I'm using is cookie based, the user isn't logged in to Active Directory. Therefore, I use impersonation to connect to the server as a specific account. However, the powers that be here don't like impersonation; they say that it clutters up the code. I agree, but I've found no way around this. It seems that the only way that a user can be logged in to an ASP.net application is by either connecting with Internet Explorer from a machine where the user is logged in with their Active Directory account or by typing an Active Directory username and password. Neither of these two are workable in my application. I think it would be nice if I could make it so that when a user logs in and receives the cookie (which actually comes from a separate log on application, by the way), there could be some code run which tells the application to perform all network operations as the user's Active Directory account, just as if they had typed an Active Directory username and password. It seems like this ought to be possible somehow, but the solution evades me. How can I make this work?

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  • Acquiring drive names (as opposed to drive letters) in Java

    - by Mattijs
    Hi, On my Windows machine, my main hard drive has the letter C: and the name "Local disk". To list the drive letters in Java on Windows, the File object has the static listRoots() method. But I can't find a way to acquire the drive names (as opposed to the drive letters) on Windows. Has anyone tried this before? Thanks, Mattijs

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  • i read that for RESTful websites. it is not good to use $_SESSION. Why is it not good? how then do i

    - by keisimone
    I read that it is not good to use $_SESSION. http://www.recessframework.org/page/towards-restful-php-5-basic-tips I am creating a WEBSITE, not web service in PHP. and i am trying to make it more RESTful. at least in spirit. right now i am rewriting all the action to use Form tags POST and add in a hidden value called _method which would be "delete" for deleting action and "put" for updating action. however, i am not sure why it is recommended NOT to use $_SESSION. i would like to know why and what can i do to improve. To allow easy authorization checking, what i did was to after logging in the user, the username is stored in the $_SESSION. Everytime the user navigates to a page, the page would check if the username is stored inside $_SESSION and then based on the $_SESSION retrieves all the info including privileges from the database and then evaluates the authorization to access the page based on the info retrieved. Is the way I am implementing bad? not RESTful? how do i improve performance and security? Thank you.

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  • PHP what is faster to use

    - by user1631500
    What is faster / better to use? To put html into variables and print them later, or to just html print / echo print the content based on condition? EXAMPLE 1:(html into variables) if(!isset($_SESSION['daddy'])) { $var = "<span class='something'>Go here:<a href='#'>Click</a></span> <span class='something'>Go here:<a href='#'>Click</a></span>" } else { $one=$_SESSION["one"]; $two=$_SESSION["two"]; $three=$_SESSION["three"]; $var = You are cool enough to view the content; } echo $var; EXAMPLE 2:(print based on condition) if(!isset($_SESSION['daddy'])) { $var = 1; } else { $one=$_SESSION["one"]; $two=$_SESSION["two"]; $three=$_SESSION["three"]; $var = 0; } if ($var==1) { ?> <span class='something'>Go here:<a href='#'>Click</a></span> <span class='something'>Go here:<a href='#'>Click</a></span <?php } else { ?> You are cool enough to view the content. <?php } ?>

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  • Load image from string

    - by zaf
    Given a string containing jpeg image data, is it possible to load this directly in pygame? I've tried using StringIO but failed and I don't completely understand the 'file-like' object concept. Currently, as a workaround, I'm saving to disk and then loading an image the standard way: # imagestring contains a jpeg f=open('test.jpg','wb') f.write(imagestring) f.close() image=pygame.image.load('test.jpg') Any suggestions on improving this so that we avoid creating a temp file?

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  • odp.net SQL query retrieve set of rows from two input arrays.

    - by Karl Trumstedt
    I have a table with a primary key consisting of two columns. I want to retrieve a set of rows based on two input arrays, each corresponding to one primary key column. select pkt1.id, pkt1.id2, ... from PrimaryKeyTable pkt1, table(:1) t1, table(:2) t2 where pkt1.id = t1.column_value and pkt1.id2 = t2.column_value I then bind the values with two int[] in odp.net. This returns all different combinations of my resulting rows. So if I am expecting 13 rows I receive 169 rows (13*13). The problem is that each value in t1 and t2 should be linked. Value t1[4] should be used with t2[4] and not all the different values in t2. Using distinct solves my problem, but I'm wondering if my approach is wrong. Anyone have any pointers on how to solve this the best way? One way might be to use a for-loop accessing each index in t1 and t2 sequentially, but I wonder what will be more efficient. Edit: actually distinct won't solve my problem, it just did it based on my input-values (all values in t2 = 0)

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