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• Storing PLSQL stored-procedure values in Oracle memory caches for extended periods

  - by Ira Baxter

  I am collecting runtime profiling data from PLSQL stored procedures. The data is collected as certain stored procedures execute, but it needs to accumululate across multiple executions of those procedures. To minimize overhead, I'd like to store that profiling data in some PLSQL-accessable Oracle memory-resident storage somewhere for the duration of the data collection interval, and then dump out the accumulated values. The data collection interval might be seconds or hours; its ok not to store this data across system boots. Something like session state in web servers would do. What are my choices for storing such data? The only method I know about are contexts in dbms_sessions: procedure set_ctx (value in varchar8) as begin dbms_session.set_context ( 'Test_Ctx', 'AccumulatedValue', value, NULL, 'ProfilerSessionId' ); end set_ctx; This works, but takes some 50 milliseconds(!) per update to the accumulated value. What I'm hoping for is a way to access/store an array of values in some Oracle memory using vanilla PLSQL statements, with access times typical of array accesses made to package-local arrays.

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• Using Groovy as a scripting language...

  - by Zombies

  I prefer to use scripting languages for short tasks, anything such as a really simple http bot, bulk importing/exporting data to/from somewhere, etc etc... Basic throw-away scripts and simple stuff. The point being, that a scripting language is just an efficient tool to write quick programs with. As for my understanding of Groovy at this point... If you were to program in Groovy, and you wan't to write a quick script, wouldn't you be forced to going back to regular java syntax (and we know how that can be convoluted compared to a scripting language) in order to do anything more complicated? For example, if I want to do some http scripting, wouldn't I just be right back at using java syntax to invoke Commons HttpClient? To me, the point of a scripting language is for quickly typed and less forced constructs. And here is another thing, it doesn't seem that there is any incentive for groovy based libraries to be developed when there are already so many good java one's out there, thus making groovy appear to be a Java dependent language with minor scripting features. So right now I am wondering if I could switch to Groovy as a scripting language or continue to use a more common scripting language such as Perl, Python or Ruby.

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• Evolutionary Algorithms: Optimal Repopulation Breakdowns

  - by Brian MacKay

  It's really all in the title, but here's a breakdown for anyone who is interested in Evolutionary Algorithms: In an EA, the basic premise is that you randomly generate a certain number of organisms (which are really just sets of parameters), run them against a problem, and then let the top performers survive. You then repopulate with a combination of crossbreeds of the survivors, mutations of the survivors, and also a certain number of new random organisms. Do that several thousand times, and efficient organisms arise. Some people also do things like introduce multiple "islands" of organisms, which are seperate populations that are allowed to crossbreed once in awhile. So, my question is: what are the optimal repopulation percentages? I have been keeping the top 10% performers, and repopulating with 30% crossbreeds and 30% mutations. The remaining 30% is for new organisms. I have also tried out the multiple island theory, and I'm interested in your results on that as well. It is not lost on me that this is exactly the type of problem an EA could solve. Are you aware of anyone trying that? Thanks in advance!

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• How to serialize a Bundle?

  - by hermo

  I'd like to serialize a Bundle object, but can't seem to find a simple way of doing it. Using Parcel doesn't seem like an option, since I want to store the serialized data to file. Any ideas on ways to do this? The reason I want this is to save and restore the state of my activity, also when it's killed by the user. I already create a Bundle with the state I want to save in onSaveInstanceState. But android only keeps this Bundle when the activity is killed by the SYSTEM. When the user kills the activity, I need to store it myself. Hence i'd like to serialize and store it to file. Of course, if you have any other way of accomplishing the same thing, i'd be thankful for that too. Edit: I decided to encode my state as a JSONObject instead of a Bundle. The JSON object can then be put in a Bundle as a Serializable, or stored to file. Probably not the most efficient way, but it's simple, and it seems to work ok.

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• Securely store a password in program code?

  - by Nick

  My application makes use of the RijndaelManaged class to encrypt data. As a part of this encryption, I use a SecureString object loaded with a password which get's get converted to a byte array and loaded into the RajindaelManaged object's Key at runtime. The question I have is the storage of this SecureString. A user entered password can be entered at run-time, and that can be "securely" loaded into a SecureString object, but if no user entered password is given, then I need to default to something. So ultimately the quesiton comes down to: If I have to have some known string or byte array to load into a SecureString object each time my application runs, how do I do that? The "encrypted" data ultimately gets decrypted by another application, so even if no user entered password is specified, I still need the data to be encrypted while it goes from one app to another. This means I can't have the default password be random, because the other app wouldn't be able to properly decrypt it. One possible solution I'm thinking is to create a dll which only spits out a single passphrase, then I use that passphrase and run it through a couple of different hashing/reorganizing functions at runtime before I ultimately feed it into the secureString object. Would this be secure enough?

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• How to effectively use WorkbookBeforeClose event correctly?

  - by Ahmad

  On a daily basis, a person needs to check that specific workbooks have been correctly updated with Bloomberg and Reuters market data ie. all data has pulled through and that the 'numbers look correct'. In the past, people were not checking the 'numbers' which led to inaccurate uploads to other systems etc. The idea is that 'something' needs to be developed to prevent the use from closing/saving the workbook unless he/she has checked that the updates are correct/accurate. The numbers look correct action is purely an intuitive exercise, thus will not be coded in any way. The simple solution was to prompt users prior to closing the specific workbook to verify that the data has been checked. Using VSTO SE for Excel 2007, an Add-in was created which hooks into the WorkbookBeforeClose event which is initialised in the add-in ThisAddIn_Startup private void wb_BeforeClose(Xl.Workbook wb, ref bool cancel) { //.... snip ... if (list.Contains(wb.Name)) { DailogResult result = MessageBox.Show("some message", "sometitle", MessageBoxButtons.YesNo); if (result != DialogResult.Yes) { cancel = true; // i think this prevents the whole application from closing } } } I have found the following ThisApplication.WorkbookBeforeSave vs ThisWorkbook.Application.WorkbookBeforeSave which recommends that one should use the ThisApplication.WorkbookBeforeClose event which I think is what I am doing since will span all files opened. The issue I have with the approach is that assuming that I have several files open, some of which are in my list, the event prevents Excel from closing all files sequentially. It now requires each file to be closed individually. Am I using the event correctly and is this effective & efficient use of the event? Should I use the Application level event or document level event? Is there a way to prevent the above behaviour? Any other suggestions are welcomed VS 2005 with VSTO SE

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• Simulating pass by reference for an array in Java

  - by Leif Andersen

  I was wondering, in java, is it possible to in anyway, simulate pass by reference for an array? Yes, I know the language doesn't support it, but is there anyway I can do it. Say, for example, I want to create a method that reverses the order of all the elements in an array. (I know that this code snippet isn't the best example, as there is a better algorithms to do this, but this is a good example of the type of thing I want to do for more complex problems). Currently, I need to make a class like this: public static void reverse(Object[] arr) { Object[] tmpArr = new Object[arr.length]; count = arr.length - 1; for(Object i : arr) tmpArr[count--] = i; // I would like to do arr = tmpArr, but that will only make the shallow // reference tmpArr, I would like to actually change the pointer they passed in // Not just the values in the array, so I have to do this: count = arr.length - 1; for(Object i : tmpArr) arr[count--] = i; return; } Yes, I know that I could just swap the values until I get to the middle, and it would be much more efficient, but for other, more complex purposes, is there anyway that I can manipulate the actual pointer? Again, thank you.

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• Can I write this regex in one step?

  - by Marin Doric

  This is the input string "23x +y-34 x + y+21x - 3y2-3x-y+2". I want to surround every '+' and '-' character with whitespaces but only if they are not allready sourrounded from left or right side. So my input string would look like this "23x + y - 34 x + y + 21x - 3y2 - 3x - y + 2". I wrote this code that does the job: Regex reg1 = new Regex(@"\+(?! )|\-(?! )"); input = reg1.Replace(input, delegate(Match m) { return m.Value + " "; }); Regex reg2 = new Regex(@"(?<! )\+|(?<! )\-"); input = reg2.Replace(input, delegate(Match m) { return " " + m.Value; }); explanation: reg1 // Match '+' followed by any character not ' ' (whitespace) or same thing for '-' reg2 // Same thing only that I match '+' or '-' not preceding by ' '(whitespace) delegate 1 and 2 just insert " " before and after m.Value ( match value ) Question is, is there a way to create just one regex and just one delegate? i.e. do this job in one step? I am a new to regex and I want to learn efficient way.

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• Memory mapped files and "soft" page faults. Unavoidable?

  - by Robert Oschler

  I have two applications (processes) running under Windows XP that share data via a memory mapped file. Despite all my efforts to eliminate per iteration memory allocations, I still get about 10 soft page faults per data transfer. I've tried every flag there is in CreateFileMapping() and CreateFileView() and it still happens. I'm beginning to wonder if it's just the way memory mapped files work. If anyone there knows the O/S implementation details behind memory mapped files I would appreciate comments on the following theory: If two processes share a memory mapped file and one process writes to it while another reads it, then the O/S marks the pages written to as invalid. When the other process goes to read the memory areas that now belong to invalidated pages, this causes a soft page fault (by design) and the O/S knows to reload the invalidated page. Also, the number of soft page faults is therefore directly proportional to the size of the data write. My experiments seem to bear out the above theory. When I share data I write one contiguous block of data. In other words, the entire shared memory area is overwritten each time. If I make the block bigger the number of soft page faults goes up correspondingly. So, if my theory is true, there is nothing I can do to eliminate the soft page faults short of not using memory mapped files because that is how they work (using soft page faults to maintain page consistency). What is ironic is that I chose to use a memory mapped file instead of a TCP socket connection because I thought it would be more efficient. Note, if the soft page faults are harmless please note that. I've heard that at some point if the number is excessive, the system's performance can be marred. If soft page faults intrinsically are not significantly harmful then if anyone has any guidelines as to what number per second is "excessive" I'd like to hear that. Thanks.

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• So can unique_ptr be used safely in stl collections?

  - by DanDan

  I am confused with unique_ptr and rvalue move philosophy. Let's say we have two collections: std::vector<std::auto_ptr<int>> autoCollection; std::vector<std::unique_ptr<int>> uniqueCollection; Now I would expect the following to fail, as there is no telling what the algorithm is doing internally and maybe making internal pivot copies and the like, thus ripping away ownership from the auto_ptr: std::sort(autoCollection.begin(), autoCollection.end()); I get this. And the compiler rightly disallows this happening. But then I do this: std::sort(uniqueCollection.begin(), uniqueCollection.end()); And this compiles. And I do not understand why. I did not think unique_ptrs could be copied. Does this mean a pivot value cannot be taken, so the sort is less efficient? Or is this pivot actually a move, which in fact is as dangerous as the collection of auto_ptrs, and should be disallowed by the compiler? I think I am missing some crucial piece of information, so I eagerly await someone to supply me with the aha! moment.

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• F# Active Pattern List.filter or equivalent

  - by akaphenom

  I have a records of types type tradeLeg = { id : int ; tradeId : int ; legActivity : LegActivityType ; actedOn : DateTime ; estimates : legComponents ; entryType : ShareOrDollarBased ; confirmedPrice: DollarsPerShare option; actuals : legComponents option ; type trade = { id : int ; securityId : int ; ricCode : string ; tradeActivity : TradeType ; enteredOn : DateTime ; closedOn : DateTime ; tradeLegs : tradeLeg list ; } Obviously the tradeLegs are a type off of a trade. A leg may be settled or unsettled (or unsettled but price confirmed) - thus I have defined the active pattern: let (|LegIsSettled|LegIsConfirmed|LegIsUnsettled|) (l: tradeLeg) = if Helper.exists l.actuals then LegIsSettled elif Helper.exists l.confirmedPrice then LegIsConfirmed else LegIsUnsettled and then to determine if a trade is settled (based on all legs matching LegIsSettled pattern: let (|TradeIsSettled|TradeIsUnsettled|) (t: trade) = if List.exists ( fun l -> match l with | LegIsSettled -> false | _ -> true) t.tradeLegs then TradeIsSettled else TradeIsUnsettled I can see some advantages of this use of active patterns, however i would think there is a more efficient way to see if any item of a list either matches (or doesn't) an actie pattern without having to write a lambda expression specifically for it, and using List.exist. Question is two fold: is there a more concise way to express this? is there a way to abstract the functionality / expression (fun l - match l with | LegIsSettled - false | _ - true) Such that let itemMatchesPattern pattern item = match item with | pattern -> true | _ -> false such I could write (as I am reusing this design-pattern): let curriedItemMatchesPattern = itemMatchesPattern LegIsSettled if List.exists curriedItemMatchesPattern t.tradeLegs then TradeIsSettled else TradeIsUnsettled Thoughts?

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• SQL (mySQL) update some value in all records processed by a select

  - by jdmuys

  I am using mySQL from their C API, but that shouldn't be relevant. My code must process records from a table that match some criteria, and then update the said records to flag them as processed. The lines in the table are modified/inserted/deleted by another process I don't control. I am afraid in the following, the UPDATE might flag some records erroneously since the set of records matching might have changed between step 1 and step 3. SELECT * FROM myTable WHERE <CONDITION>; # step 1 <iterate over the selected set of lines. This may take some time.> # step 2 UPDATE myTable SET processed=1 WHERE <CONDITION> # step 3 What's the smart way to ensure that the UPDATE updates all the lines processed, and only them? A transaction doesn't seem to fit the bill as it doesn't provide isolation of that sort: a recently modified record not in the originally selected set might still be targeted by the UPDATE statement. For the same reason, SELECT ... FOR UPDATE doesn't seem to help, though it sounds promising :-) The only way I can see is to use a temporary table to memorize the set of rows to be processed, doing something like: CREATE TEMPORARY TABLE workOrder (jobId INT(11)); INSERT INTO workOrder SELECT myID as jobId FROM myTable WHERE <CONDITION>; SELECT * FROM myTable WHERE myID IN (SELECT * FROM workOrder); <iterate over the selected set of lines. This may take some time.> UPDATE myTable SET processed=1 WHERE myID IN (SELECT * FROM workOrder); DROP TABLE workOrder; But this seems wasteful and not very efficient. Is there anything smarter? Many thanks from a SQL newbie.

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• How to organize the work when project needs to be re-implemented due to poor code quality?

  - by Dmitriy Nagirnyak

  Hi, I have joined a very small where one main developer has been buiding the web app (.NET 4.0) during ~6 months. The project should be delivered within next 2 months. After first look at the code I can say that I would never allow it to go to production (things like catch { }, not tests at all with WebForms etc). So the code quality is incredibly low. My task is to improve that and still deliver the solution. So I plan to start with unit testing and MVC2 reimplementing most of the functionality (though using some of the existing code). I estimate that I will need about 6 weeks to catch up with the current progress and be on te same functionality level as the application will be in 6 months. The problem is that the main developer who has been working on the project does not seem to be very 'professional' and skillful (he seems to be really starting in IT and many basic things are unknown to him). It will take significant amount of time and effort to educate him how to do the proper testing, development and apply some patterns. I am ready to take responsibility for the reimplemnting the application but at the same time I don't want the main developer to be on idle but as he won't be able to significantly contribute to the better-world project at this stage I am not sure what would the best way to keep productivity high for both of us. Currently I think following solution is good enough: He proceeds doing what he does until I will catch up with him and then start working on a new project together. The problem is that of course this approach is not very productive as one developer will do better-world project while the other will proceed with what he did, effectively doing similar tasks. Can you suggest how we could better organise the work together in order to be most efficient for the overall project? Thanks, Dmitriy.

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• Extend base type and automatically update audit information on Entity

  - by Nix

  I have an entity model that has audit information on every table (50+ tables) CreateDate CreateUser UpdateDate UpdateUser Currently we are programatically updating audit information. Ex: if(changed){ entity.UpdatedOn = DateTime.Now; entity.UpdatedBy = Environment.UserName; context.SaveChanges(); } But I am looking for a more automated solution. During save changes, if an entity is created/updated I would like to automatically update these fields before sending them to the database for storage. Any suggestion on how i could do this? I would prefer to not do any reflection, so using a text template is not out of the question. A solution has been proposed to override SaveChanges and do it there, but in order to achieve this i would either have to use reflection (in which I don't want to do ) or derive a base class. Assuming i go down this route how would I achieve this? For example EXAMPLE_DB_TABLE CODE NAME --Audit Tables CREATE_DATE CREATE_USER UPDATE_DATE UPDATE_USER And if i create a base class public abstract class IUpdatable{ public virtual DateTime CreateDate {set;} public virtual string CreateUser { set;} public virtual DateTime UpdateDate { set;} public virtual string UpdateUser { set;} } The end goal is to be able to do something like... public overrride void SaveChanges(){ //Go through state manager and update audit infromation //FOREACH changed entity in state manager if(entity is IUpdatable){ //If state is created... update create audit. //if state is updated... update update audit } } But I am not sure how I go about generating the code that would extend the interface.

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• Simulating pass by reference for an array reference (i.e. a reference to a reference) in Java

  - by Leif Andersen

  I was wondering, in java, is it possible to in anyway, simulate pass by reference for an array? Yes, I know the language doesn't support it, but is there anyway I can do it. Say, for example, I want to create a method that reverses the order of all the elements in an array. (I know that this code snippet isn't the best example, as there is a better algorithms to do this, but this is a good example of the type of thing I want to do for more complex problems). Currently, I need to make a class like this: public static void reverse(Object[] arr) { Object[] tmpArr = new Object[arr.length]; count = arr.length - 1; for(Object i : arr) tmpArr[count--] = i; // I would like to do arr = tmpArr, but that will only make the shallow // reference tmpArr, I would like to actually change the pointer they passed in // Not just the values in the array, so I have to do this: count = arr.length - 1; for(Object i : tmpArr) arr[count--] = i; return; } Yes, I know that I could just swap the values until I get to the middle, and it would be much more efficient, but for other, more complex purposes, is there anyway that I can manipulate the actual pointer? Again, thank you.

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• Cocoa Core data: cannot save Created Items in NSTableview

  - by Paul Rostorp

  Hello, I'm am a beginner in mac os x development and am trying to get started with all this. Here is my problem : I've create a non-document based cocoa app using core data as storage. I've added an entity and attributes to the xdatamodel. In IB i've created an NSArrayController and linked it properly. I've created an nstableview binded to the nsarraycontroller. Next I added a button linked to nsarraycontroller with the " add: " method. When I try it out, I can add and edit the items in the table. Here comes the problem: Core data is supposed to save everything automatically, but to make sure i linked the "save" button in the menu to the appdelegate and to the " file's owner" , first responder, application... everything possible ( with both " save :" and " saveaction:" methods ). And still it doesn't save when clicking save: when I restart the cell created ( and renamed ) are gone. And also, I didn't even edit the source code yet; core data for such simple tasks is supposed to only need Interface builder. Please help me for this, I haven't found any threads resolving this problem. Thank you in advance.

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• PHP, We have sessions, and cookies....I love cookies, but they are blowing my mind right now.

  - by Matt

  I am not sure how to go about accessing the variable I need to set on a cookie... I was thinking about using the $_POST global but I dont know how based on my design if it will work. I am using a master page type design seperating index.php from my function includes and database information and individual pages (that will be returned to an include in index.php based on a $_GET) Okay so back to my question. What is the most efficient way to set a cookie on a design that has a main page that everything will branch from. How would I pull the value. Is $_POST a good enough way to go about it? Also...by saying it must be the first thing sent...does that mean I cannot run any serverside scripts before that? I could definately utilize a login query I think but I dont want to write code just to be dissapointed based on my lack of time and knowledge. I did search for answers...I know this most likely feels like a generic question that could be answered in a difference place...but I know I will get an accurate and professional answer here...so I dont want to bet on the half answers I found otherwise. Of course I will sanitize everything and not store any sensitive information (passwords,address,phone,or anything really for that matter besides some kind of session ID and the username) If this is confusing I am sorry but I am on a gov computer...and they lock these tighter than ft knox...so getting my code on here will be a chore until I get back to my room. Thanks, Matt

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• Programmer Puzzle: Encoding a chess board state throughout a game

  - by Andrew Rollings

  Not strictly a question, more of a puzzle... Over the years, I've been involved in a few technical interviews of new employees. Other than asking the standard "do you know X technology" questions, I've also tried to get a feel for how they approach problems. Typically, I'd send them the question by email the day before the interview, and expect them to come up with a solution by the following day. Often the results would be quite interesting - wrong, but interesting - and the person would still get my recommendation if they could explain why they took a particular approach. So I thought I'd throw one of my questions out there for the Stack Overflow audience. Question: What is the most space-efficient way you can think of to encode the state of a chess game (or subset thereof)? That is, given a chess board with the pieces arranged legally, encode both this initial state and all subsequent legal moves taken by the players in the game. No code required for the answer, just a description of the algorithm you would use. EDIT: As one of the posters has pointed out, I didn't consider the time interval between moves. Feel free to account for that too as an optional extra :) EDIT2: Just for additional clarification... Remember, the encoder/decoder is rule-aware. The only things that really need to be stored are the player's choices - anything else can be assumed to be known by the encoder/decoder. EDIT3: It's going to be difficult to pick a winner here :) Lots of great answers!

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• asp.net mvc - How to create fake test objects quickly and efficiently

  - by Simon G

  Hi, I'm currently testing the controller in my mvc app and I'm creating a fake repository for testing. However I seem to be writing more code and spending more time for the fakes than I do on the actual repositories. Is this right? The code I have is as follows: Controller public partial class SomeController : Controller { IRepository repository; public SomeController(IRepository rep) { repository = rep; } public virtaul ActionResult Index() { // Some logic var model = repository.GetSomething(); return View(model); } } IRepository public interface IRepository { Something GetSomething(); } Fake Repository public class FakeRepository : IRepository { private List<Something> somethingList; public FakeRepository(List<Something> somethings) { somthingList = somthings; } public Something GetSomething() { return somethingList; } } Fake Data class FakeSomethingData { public static List<Something> CreateSomethingData() { var somethings = new List<Something>(); for (int i = 0; i < 100; i++) { somethings.Add(new Something { value1 = String.Format("value{0}", i), value2 = String.Format("value{0}", i), value3 = String.Format("value{0}", i) }); } return somethings; } } Actual Test [TestClass] public class SomethingControllerTest { SomethingController CreateSomethingController() { var testData = FakeSomethingData.CreateSomethingData(); var repository = new FakeSomethingRepository(testData); SomethingController controller = new SomethingController(repository); return controller; } [TestMethod] public void SomeTest() { // Arrange var controller = CreateSomethingController(); // Act // Some test here // Arrange } } All this seems to be a lot of extra code, especially as I have more than one repository. Is there a more efficient way of doing this? Maybe using mocks? Thanks

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• Doctrine2 ArrayCollection

  - by boosis

  Ok, I have a User entity as follows <?php class User { /** * @var integer * @Id * @Column(type="integer") * @GeneratedValue */ protected $id; /** * @var \Application\Entity\Url[] * @OneToMany(targetEntity="Url", mappedBy="user", cascade={"persist", "remove"}) */ protected $urls; public function __construct() { $this->urls = new \Doctrine\Common\Collections\ArrayCollection(); } public function addUrl($url) { // This is where I have a problem } } Now, what I want to do is check if the User has already the $url in the $urls ArrayCollection before persisting the $url. Now some of the examples I found says we should do something like if (!$this->getUrls()->contains($url)) { // add url } but this doesn't work as this compares the element values. As the $url doesn't have id value yet, this will always fail and $url will be dublicated. So I'd really appreciate if someone could explain how I can add an element to the ArrayCollection without persisting it and avoiding the duplication? Edit I have managed to achive this via $p = function ($key, $element) use ($url) { if ($element->getUrlHash() == $url->getUrlHash()) { return true; } else { return false; } }; But doesn't this still load all urls and then performs the check? I don't think this is efficient as there might be thousands of urls per user.

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• Bash Templating: How to build configuration files from templates with Bash?

  - by FractalizeR

  Hello. I'm writting a script to automate creating configuration files for Apache and PHP for my own webserver. I don't want to use any GUIs like CPanel or ISPConfig. I have some templates of Apache and PHP configuration files. Bash script needs to read templates, make variable substitution and output parsed templates into some folder. What is the best way to do that? I can think of several ways. Which one is the best or may be there are some better ways to do that? I want to do that in pure Bash (it's easy in PHP for example) 1)http://stackoverflow.com/questions/415677/how-to-repace-variables-in-a-nix-text-file template.txt: the number is ${i} the word is ${word} script.sh: #!/bin/sh #set variables i=1 word="dog" #read in template one line at the time, and replace variables #(more natural (and efficient) way, thanks to Jonathan Leffler) while read line do eval echo "$line" done < "./template.txt" BTW, how do I redirect output to external file here? Do I need to escape something if variables contain, say, quotes? 2) Using cat & sed for replacing each variable with it's value: Given template.txt: The number is ${i} The word is ${word} Command: cat template.txt | sed -e "s/\${i}/1/" | sed -e "s/\${word}/dog/" Seems bad to me because of the need to escape many different symbols and with many variables the line will be tooooo long. Can you think of some other elegant and safe solution?

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• SQL Server - Multi-Column substring matching

  - by hamlin11

  One of my clients is hooked on multi-column substring matching. I understand that Contains and FreeText search for words (and at least in the case of Contains, word prefixes). However, based upon my understanding of this MSDN book, neither of these nor their variants are capable of searching substrings. I have used LIKE rather extensively (Select * from A where A.B Like '%substr%') Sample table A: ID | Col1 | Col2 | Col3 | ------------------------------------- 1 | oklahoma | colorado | Utah | 2 | arkansas | colorado | oklahoma | 3 | florida | michigan | florida | ------------------------------------- The following code will give us row 1 and row 2: select * from A where Col1 like '%klah%' or Col2 like '%klah%' or Col3 like '%klah%' This is rather ugly, probably slow, and I just don't like it very much. Probably because the implementations that I'm dealing with have 10+ columns that need searched. The following may be a slight improvement as code readability goes, but as far as performance, we're still in the same ball park. select * from A where (Col1 + ' ' + Col2 + ' ' + Col3) like '%klah%' I have thought about simply adding insert, update, and delete triggers that simply add the concatenated version of the above columns into a separate table that shadows this table. Sample Shadow_Table: ID | searchtext | --------------------------------- 1 | oklahoma colorado Utah | 2 | arkansas colorado oklahoma | 3 | florida michigan florida | --------------------------------- This would allow us to perform the following query to search for '%klah%' select * from Shadow_Table where searchtext like '%klah%' I really don't like having to remember that this shadow table exists and that I'm supposed to use it when I am performing multi-column substring matching, but it probably yields pretty quick reads at the expense of write and storage space. My gut feeling tells me there there is an existing solution built into SQL Server 2008. However, I don't seem to be able to find anything other than research papers on the subject. Any help would be appreciated.

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• An implementation of Sharir's or Aurenhammer's deterministic algorithm for calculating the intersect

  - by RGrey

  The problem of finding the intersection/union of 'N' discs/circles on a flat plane was first proposed by M. I. Shamos in his 1978 thesis: Shamos, M. I. “Computational Geometry” Ph.D. thesis, Yale Univ., New Haven, CT 1978. Since then, in 1985, Micha Sharir presented an O(n log2n) time and O(n) space deterministic algorithm for the disc intersection/union problem (based on modified Voronoi diagrams): Sharir, M. Intersection and closest-pair problems for a set of planar discs. SIAM .J Comput. 14 (1985), pp. 448-468. In 1988, Franz Aurenhammer presented a more efficient O(n log n) time and O(n) space algorithm for circle intersection/union using power diagrams (generalizations of Voronoi diagrams): Aurenhammer, F. Improved algorithms for discs and balls using power diagrams. Journal of Algorithms 9 (1985), pp. 151-161. Earlier in 1983, Paul G. Spirakis also presented an O(n^2) time deterministic algorithm, and an O(n) probabilistic algorithm: Spirakis, P.G. Very Fast Algorithms for the Area of the Union of Many Circles. Rep. 98, Dept. Comput. Sci., Courant Institute, New York University, 1983. I've been searching for any implementations of the algorithms above, focusing on computational geometry packages, and I haven't found anything yet. As neither appear trivial to put into practice, it would be really neat if someone could point me in the right direction!

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• Determining failing sectors on portable flash memory

  - by Faxwell Mingleton

  I'm trying to write a program that will detect signs of failure for portable flash memory devices (thumb drives, etc). I have seen tools in the past that are able to detect failing sectors and other kinds of trouble on conventional mechanical hard drives, but I fear that flash memory does not have the same kind of predictable low-level access to the hardware due to the internal workings of the storage. Things like wear-leveling and other block-remapping techniques (to skip over 'dead' sectors?) lead me to believe that determining if a flash drive is failing will be difficult at best, if not impossible (short of having constant read failures and device unmounts). Flash drives at their end-of-life should be easy to detect (constant CRC discrepancies during reads and all-out failure). But what about drives that might be failing early? Are there any tell-tale signs like slower throughput speeds that might indicate a flash drive is going to fail much sooner than normal? Along the lines of detecting potentially bad blocks, I had considered attempting random reads/writes to a file close to or exactly the size of the entire volume, but even then is it possible that the drive might report sizes under its maximum capacity to account for 'dead' blocks? In short, is there any way to circumvent or at least detect (algorithmically or otherwise) the use of block-remapping or other life extension techniques for flash memory? Let me end this question by expressing my uncertainty as to whether or not this belongs on serverfault.com . This is definitely a hardware-related question, but I also desire a software solution - preferably one that I can program myself. If this question is misplaced, I will be happy to migrate it to serverfault - but I do need a programming solution. Please let me know if you need clarification :) Thanks!

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• Finding Common Phrases in SQL Server TEXT Column

  - by regex

  Short Desc: I'm curious to see if I can use SQL Analysis services or some other SQL Server service to mine some data for me that will show commonalities between SQL TEXT fields in a dataset. Long Desc I am looking at a subset of data that consists of about 10,000 rows of TEXT blobs which are used as a notes column in a issue tracking (ticketing) software. I would like to use something out of the box (without having to build something) that might be able to parse through all of the rows and find commonly used byte sequences in the "Notes" column. In other words, I want to find commonly used phrases (two to three word phrases, so 9 - 20 character sections of the TEXT blob). This will help me better determine if associate's notes contain similar phrases (troubleshooting techniques) that we could standardize in our troubleshooting process flow. Closing Note I'd really rather not build an application to do this as my method will probably not be the most efficient way to do it. Hopefully all this makes sense. Please let me know in the comments if anything needs clarification.

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