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• Database solution for 200million writes/day, monthly summarization queries

  - by sb

  Hello. I'm looking for help deciding on which database system to use. (I've been googling and reading for the past few hours; it now seems worthwhile to ask for help from someone with firsthand knowledge.) I need to log around 200 million rows (or more) per 8 hour workday to a database, then perform weekly/monthly/yearly summary queries on that data. The summary queries would be for collecting data for things like billing statements, eg. "How many transactions of type A did each user run this month?" (could be more complex, but that's the general idea). I can spread the database amongst several machines, as necessary, but I don't think I can take old data offline. I'll definitely need to be able to query a month's worth of data, maybe a year. These queries would be for my own use, and wouldn't need to be generated in real-time for an end-user (they could run overnight, if needed). Does anyone have any suggestions as to which databases would be a good fit? P.S. Cassandra looks like it would have no problem handling the writes, but what about the huge monthly table scans? Is anyone familiar with Cassandra/Hadoop MapReduce performance?

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• How To Select First Ancestor That Matches A Selector?

  - by Zach

  General: How can I select the first matching ancestor of an element in jQuery? Example: Take this HTML block <table> <tbody> <tr> <td> <a href="#" class="remove">Remove</a> </td> </tr> <tr> <td> <a href="#" class="remove">Remove</a> </td> </tr> </tbody> </table> I can remove a row in the table by clicking "Remove" using this jQuery code: $('.remove').click(function(){ $(this).parent().parent().hide(); return false; }); This works, but it's pretty fragile. If someone puts the <a> into a <div>, for example, it would break. Is there a selector syntax in jQuery that follows this logic: "Here's an element, now find the closest ancestor that matches some selection criteria and return it" Thanks

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• How do I daemonize an arbitrary script in unix?

  - by dreeves

  I'd like a daemonizer that can turn an arbitrary, generic script or command into a daemon. There are two common cases I'd like to deal with: I have a script that should run forever. If it ever dies (or on reboot), restart it. Don't let there ever be two copies running at once (detect if a copy is already running and don't launch it in that case). I have a simple script or command line command that I'd like to keep executing repeatedly forever (with a short pause between runs). Again, don't allow two copies of the script to ever be running at once. Of course it's trivial to write a "while(true)" loop around the script in case 2 and then apply a solution for case 1, but a more general solution will just solve case 2 directly since that applies to the script in case 1 as well (you may just want a shorter or no pause if the script is not intended to ever die (of course if the script really does never die then the pause doesn't actually matter)). Note that the solution should not involve, say, adding file-locking code or PID recording to the existing scripts. More specifically, I'd like a program "daemonize" that I can run like % daemonize myscript arg1 arg2 or, for example, % daemonize 'echo `date` >> /tmp/times.txt' which would keep a growing list of dates appended to times.txt. (Note that if the argument(s) to daemonize is a script that runs forever as in case 1 above, then daemonize will still do the right thing, restarting it when necessary.) I could then put a command like above in my .login and/or cron it hourly or minutely (depending on how worried I was about it dying unexpectedly). NB: The daemonize script will need to remember the command string it is daemonizing so that if the same command string is daemonized again it does not launch a second copy. Also, the solution should ideally work on both OS X and linux but solutions for one or the other are welcome. (If I'm thinking of this all wrong or there are quick-and-dirty partial solutions, I'd love to hear that too.)

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• How costly performance-wise are these actions in iPhone objective-C?

  - by Alex Gosselin

  This is really a few questions in one, I'm wondering what the performance cost is for these things, as I haven't really been following a best practice of any sort for these. The answers may also be useful to other readers, if somebody knows these. (1) If I need the core data managed object context, is it bad to use #import "myAppDelegate.h" //farther down in the code: NSManagedObjectContext *context = [(myAppDelegate.h*)[[UIApplication sharedApplication] delegate] managedObjectContext]; as opposed to leaving the warning you get if you don't cast the delegate? (2) What is the cheapest way to hard-code a string? I have been using return @"myString"; on occasion in some functions where I need to pass it to a variety of places, is it better to do it this way: static NSString *str = @"myString"; return str; (3) How costly is it to subclass an object i wrote vs. making a new one, in general? (4) When I am using core data and navigating through a hierarchy of some sort, is it necessary to turn things back into faults somehow after I read some info from them? or is this done automatically? Thanks for any help.

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• Practice of checking 'trueness' or 'equality' of conditional statements - does it really make sense?

  - by senthilkumar1033

  I remember many years back, when I was in school, one of my computer science teachers taught us that it was better to check for 'trueness' or 'equality' of a condition and not the negative stuff like 'inequality'. Let me elaborate - If a piece of conditional code can be written by checking whether an expression is true or false, we should check the 'trueness'. Example: Finding out whether a number is odd - it can be done in two ways: if ( num % 2 != 0 ) { // Number is odd } or if ( num % 2 == 1 ) { // Number is odd } When I was beginning to code, I knew that num % 2 == 0 implies the number is even, so I just put a ! there to check if it is odd. But he was like 'Don't check NOT conditions. Have the practice of checking the 'trueness' or 'equality' of conditions whenever possible.' And he recommended that I use the second piece of code. I am not for or against either but I just wanted to know - what difference does it make? Please don't reply 'Technically the output will be the same' - we ALL know that. Is it a general programming practice or is it his own programming practice that he is preaching to others?

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• Does IE6 Really not Allow Me to set width/height from left/right/top/bottom???

  - by viatropos

  Building a site super quick and having it work on all my Mac browsers, I thought I'd take a gander on a friends old dell laptop with Windows XP and IE6. Nothing looks remotely correct. It's because I used lots of left/right/top/bottom (constraint) declarations to size elements proportionally to their parent's size (I didn't use percent sizes because the percents refer to the parent's size before margins and padding are applied, left/right/top/bottom refer to them after with position:absolute. I'm asking about that here :)). I've read lots these past few weeks on how horrible IE6 (and IE) is in general, but because of all the reasons people say to support it (large market share and the fear of installing better software), and because half the people in the company we're building a site for use IE6 (getting them to upgrade to Chrome slowly but surely), I thought if I could just get IE6 to render my constraints, that might help. So I am messing around with simple layouts here, and they work fine in my latest versions of Firefox, Safari, Chrome, and Opera, but IE6 is basically saying: If you haven't set a width or height on me, I'm assuming it's zero. But position:absolute; left:0px; right:0px; top:0px; bottom:0px; on a container that's width:1000px; height:1000px; should be the same as setting width:1000px; height:1000px on the child, no? Taking a quick look at the source for this, why won't IE6 render the constraint based absolutely positioned AND SIZED elements? (note: I will be messing around with that file for a while) Thanks

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• Learning Java and logic using debugger. Did I cheat?

  - by centr0

  After a break from coding in general, my way of thinking logically faded (as if it was there to begin with...). I'm no master programmer. Intermediate at best. I decided to see if i can write an algorithm to print out the fibonacci sequence in Java. I got really frustrated because it was something so simple, and used the debugger to see what was going on with my variables. solved it in less than a minute with the help of the debugger. Is this cheating? When I read code either from a book or someone else's, I now find that it takes me a little more time to understand. If the alghorithm is complex (to me) i end up writing notes as to whats going on in the loop. A primitive debugger if you will. When you other programmers read code, do you also need to write things down as to whats the code doing? Or are you a genius and and just retain it?

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• What is good about php/what is php good for?

  - by Roman A. Taycher

  I have often seen php bashed around the webs as a loosely typed(loose typing as in a lot of type coercion and/or easy(and perhaps common) to cast object all over not dynamic typing) language without a great compiler/interpreter/vm, with even the standard library using a number of different naming conventions. A lot of people complain about perl but many (including a lot of the complainers) also give it a lot of credit for its regexes and general flexibility and power. Other then legacy code , giant web frameworks that can do tons(drupal,ect.), and easy cheap hosting what is good about php (,also what criticism are unfair, and how is the language evolving to overcome its problems). Why would i want to learn it? why would I want to do an independent project in it? The main thing I have heard is that its php codes simplicity is sometimes easier then the over-engineered complexity you find in certain Java frameworks and applications. I'm not just trolling, i'm genuinly curious what makes php programmers use it. try to convince me to put it on my languages to dabble in and languages to learn more in depth lists.

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• What is the best (Windows) program launcher?

  - by AR

  One of the biggest general productivity boosters I've used is a good program launcher. I was a long-time user of SlickRun, and I've tried a few others. My current favorite is Executor - by far the best I've used. Other options: Executor: My current favorite Vista Start Menu: Pretty good, actually, but Executor is similar (binds to Win+Z) and much more flexible. Quicksilver: For Macs only, but it seems to be the gold standard against which most other launchers are measured. Google Desktop: Press Ctrl+Ctrl and it's a quick launcher! AutoHotKey: Much,much more than just a launcher - more than I need, really. SlickRun: simple and unobtrusive Launchy: Seems to be the launcher of choice for many StackOverflow users :) Colibri: "Type Ahead - Information at the tip of your wings". Quite a cool concept. Many, many others. Scott Hanselman outlines some more here. I realize that everyone will have their own preferences, but the question is: is there anything that really stands out in terms of speed, features, and especially productivity increase?

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• Finding the Largest and Smallest Integers In A Set- Basic

  - by Ka112324

  I'm kind of on the right track, however my output is not quite right. The program asks for the number of integers you have and then it asks for those numbers. For an example is says please enter the number of integers, you can put 3. And then you enter 3 numbers. I can't use arrays because I am a beginner student and we have not learned those yet. Using count is the only way that allows me to input integers. What do I need to add to my program? Again I am a general computer science student so I can't use anything advanced. I used include iostream, namespace int main and all that you just cant see it int data; int num; int count=0; int max=0; do { cout<<"Enter the number of intergers"<<endl; cin>>num; while (count<num) { cout<<"Please enter a number"<<endl; cin>>data; count++; if (data<min) { min=data; } if (data>max) { max=data; } } cout<<"Smallest integer:"<<min<<endl; cout<<"Largest integer:"<<max<<endl; cout<<"Would you like to continue?"<<endl; cin>>ans; } while ((ans=='y')||(ans=='Y')); return 0; }

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• C++: Conceptual problem in designing an intepreter

  - by sub

  I'm programming an interpreter for an experimental programming language (educational, fun,...) So far, everything went well (Tokenizer & Parser), but I'm getting a huge problem with some of the data structures in the part that actually runs the tokenized and parsed code. My programming language basically has only two types, int and string, and they are represented as C++ strings (std class) and ints Here is a short version of the data structure that I use to pass values around: enum DataType { Null, Int, String } class Symbol { public: string identifier; DataType type; string stringValue; int intValue; } I can't use union because string doesn't allow me to. This structure above is beginning to give me a headache. I have to scatter code like this everywhere in order to make it work, it is beginning to grow unmaintainable: if( mySymbol.type == Int ) { mySymbol.intValue = 1234; } else { mySymbol.stringValue = "abcde"; } I use the Symbol data structure for variables, return values for functions and general representation of values in the programming language. Is there any better way to solve this? I hope so!

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• Database PK-FK design for future-effective-date entries?

  - by Scott Balmos

  Ultimately I'm going to convert this into a Hibernate/JPA design. But I wanted to start out from purely a database perspective. We have various tables containing data that is future-effective-dated. Take an employee table with the following pseudo-definition: employee id INT AUTO_INCREMENT ... data fields ... effectiveFrom DATE effectiveTo DATE employee_reviews id INT AUTO_INCREMENT employee_id INT FK employee.id Very simplistic. But let's say Employee A has id = 1, effectiveFrom = 1/1/2011, effectiveTo = 1/1/2099. That employee is going to be changing jobs in the future, which would in theory create a new row, id = 2 with effectiveFrom = 7/1/2011, effectiveTo = 1/1/2099, and id = 1's effectiveTo updated to 6/30/2011. But now, my program would have to go through any table that has a FK relationship to employee every night, and update those FK to reference the newly-effective employee entry. I have seen various postings in both pure SQL and Hibernate forums that I should have a separate employee_versions table, which is where I would have all effective-dated data stored, resulting in the updated pseudo-definition below: employee id INT AUTO_INCREMENT employee_versions id INT AUTO_INCREMENT employee_id INT FK employee.id ... data fields ... effectiveFrom DATE effectiveTo DATE employee_reviews id INT AUTO_INCREMENT employee_id INT FK employee.id Then to get any actual data, one would have to actually select from employee_versions with the proper employee_id and date range. This feels rather unnatural to have this secondary "versions" table for each versioned entity. Anyone have any opinions, suggestions from your own prior work, etc? Like I said, I'm taking this purely from a general SQL design standpoint first before layering in Hibernate on top. Thanks!

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• Is method reference caching a good idea in Java 8?

  - by gexicide

  Consider I have code like the following: class Foo { Y func(X x) {...} void doSomethingWithAFunc(Function<X,Y> f){...} void hotFunction(){ doSomethingWithAFunc(this::func); } } Consider that hotFunction is called very often. Would it then be advisable to cache this::func, maybe like this: class Foo { Function<X,Y> f = this::func; ... void hotFunction(){ doSomethingWithAFunc(f); } } As far as my understanding of java method references goes, the Virtual Machine creates an object of an anonymous class when a method reference is used. Thus, caching the reference would create that object only once while the first approach creates it on each function call. Is this correct? Should method references that appear at hot positions in the code be cached or is the VM able to optimize this and make the caching superfluous? Is there a general best practice about this or is this highly VM-implemenation specific whether such caching is of any use?

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• Most effecient way to create a "slider" timeline in HTML, CSS, and JavaScript?

  - by ZapChance

  Alright, so here's my dilemma. I've got these two "slides" lined up, one ready to be passed into view. I have it working and all, but I can scroll over to the right to see the second slide! How could I have it you can only view the one slide? JavaScript used: function validate(form) { var user = form.username.value; var pass = form.password.value; if(user === "test") { if(pass === "pass") { var hideoptions = {"direction" : "left", "mode" : "hide"}; var showoptions = {"direction" : "left", "mode" : "show"}; /*$("#loginView").toggle("slide", hideoptions, 1000, function() { $("#loginView").css("margin-left", "100%"); }); $("#mainView").toggle("slide", showoptions, 1000, function() { $("#mainView").css("margin-left", 0); });*/ $("#loginView").animate({ marginLeft: "-100%" }, 1000); $("#mainView").animate({ marginLeft: "0" }, 1000); } else { alert("nope"); } } else { alert("nope 2"); } } As you can see here @ http://jsfiddle.net/D7Va3/1/ (JSFiddle), once you enter "test" and "pass", then click enter, the tiles slide. But. If you reload, you can see that you can scroll to the right of the screen and view the second slide prematurely, which is just not going to work for me. I still need to achieve the same seamless transition, but you must only be able to view one slide at a time. Also, I plan to expand with more slides, so if you're feeling lucky today, I'd really love to see an example of how I could support multiple frames. I'm very new to JavaScript (yet I know syntax rules, and general coding knowledge from other languages), so the better you explain, the more knowledgeable I can be, and I'd be very grateful for that. Thanks in advance!

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• SQL queries to determine all values that would satisfy an arbitrary query

  - by jasterm007

  I'm trying to figure out how to efficiently run a set of queries that will provide a new table of all values that would return results for an arbitrary query. Say my table has a schema like: id name age city What is an efficient way to list all values that would return results for an arbitrary query, say "NOT city=X AND age BETWEEN Y and Z"? My naive approach for this would be to use a script and recurse through all possible combinations of {city, age, age} and see which SELECTs return more than 0 results, but that seems incredibly inefficient. I've also tried building large joins on {city, age, age} as well and basically using that table as an argument list to the query, but that quickly becomes an impossibility for queries on many columns. For simple conjunctive equality queries, i.e. "name=X and age=Y", this is much simpler, as I can do something like SELECT name, age, count(*) AS count FROM main GROUP BY name, age HAVING count > 0 But I'm having difficulty coming up with a general approach for anything more complicated than that. Any pointers in the right direction would be most helpful, thanks.

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• Elegent methods for caching search results from RESTful service?

  - by Paul

  I have a RESTful web service which I access from the browser using JavaScript. As an example, say that this web service returns a list of all the Message resources assigned to me when I send a GET request to /messages/me. For performance reasons, I'd like to cache this response so that I don't have to re-fetch it every time I visit my Manage Messages web page. The cached response would expire after 5 minutes. If a Message resource is created "behind my back", say by the system admin, it's possible that I won't know about it for up to 5 minutes, until the cached search response expires and is re-fetched. This is acceptable, because it creates no confusion for me. However if I create a new Message resource which I know should be part of the search response, it becomes confusing when it doesn't appear on my Manage Messages page immediately. In general, when I knowingly create/delete/update a resource that invalidates a cached search response, I need that cached response to be expired/flushed immediately. The core problem which I can't figure out: I see no simple way of connecting the task of creating/deleting/updating a resource with the task of expiring the appropriate cached responses. In this example it seems simple, I could manually expire the cached search response whenever I create/delete/update a(ny) Message resource. But in a more complex system, keeping track of which search responses to expire under what circumstances will get clumsy quickly. If someone could suggest a simple solution or some clarifying thoughts, I'd appreciate it.

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• Common block usage in Fortran

  - by Crystal

  I'm new to Fortran and just doing some simple things for work. And as a new programmer in general, not sure exactly how this works, so excuse me if my explanation or notation is not the best. At the top of the .F file there are common declarations. The person explaining it to me said think of it like a struct in C, and that they are global. Also in that same .F file, they have it declared with what type. So it's something like: COMMON SOMEVAR INTEGER*2 SOMEVAR And then when I actually see it being used in some other file, they declare local variables, (e.g. SOMEVAR_LOCAL) and depending on the condition, they set SOMEVAR_LOCAL = 1 or 0. Then there is another conditional later down the line that will say something like IF (SOMEVAR_LOCAL. eq. 1) SOMEVAR(PARAM) = 1; (Again I apologize if this is not proper Fortran, but I don't have access to the code right now). So it seems to me that there is a "struct" like variable called SOMEVAR that is of some length (2 bytes of data?), then there is a local variable that is used as a flag so that later down the line, the global struct SOMEVAR can be set to that value. But because there is (PARAM), it's like an array for that particular instance? Thanks. Sorry for my bad explanation, but hopefully you will understand what I am asking.

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• Why can't these generic type parameters be inferred?

  - by Jon M

  Given the following interfaces/classes: public interface IRequest<TResponse> { } public interface IHandler<TRequest, TResponse> where TRequest : IRequest<TResponse> { TResponse Handle(TRequest request); } public class HandlingService { public TResponse Handle<TRequest, TResponse>(TRequest request) where TRequest : IRequest<TResponse> { var handler = container.GetInstance<IHandler<TRequest, TResponse>>(); return handler.Handle(request); } } public class CustomerResponse { public Customer Customer { get; set; } } public class GetCustomerByIdRequest : IRequest<CustomerResponse> { public int CustomerId { get; set; } } Why can't the compiler infer the correct types, if I try and write something like the following: var service = new HandlingService(); var request = new GetCustomerByIdRequest { CustomerId = 1234 }; var response = service.Handle(request); // Shouldn't this know that response is going to be CustomerResponse? I just get the 'type arguments cannot be inferred' message. Is this a limitation with generic type inference in general, or is there a way to make this work?

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• Validating a phone number in Android PreferenceScreen

  - by djechelon

  I have a PreferenceScreen in which the user is capable, if system can't autodetect it, to enter the device's phone number. I'm still learning this part of Android but I managed to understand a bit of PreferenceScreens by examples provided by Android SDK itself and a few tutorials. What I want is that the user can save the phone number only if null or valid, where by "valid" I mean running a generic validation logic (ie. an anonymous method that returns true or false, that can be reused in any possible situation*) or better, just to simplify things, ^(\+39)?3[0-9]{9}$ For now I have the following XML snip <EditTextPreference android:inputType="phone" android:key="@string/preference_phoneNo" android:selectAllOnFocus="true" android:singleLine="true" android:summary="@string/pref_phoneNumber_description" android:title="@string/pref_phoneNumber" /> and following code by courtesy of Eclipse New Activity wizard: private void setupSimplePreferencesScreen() { if (!isSimplePreferences(this)) { return; } addPreferencesFromResource(R.xml.pref_general); bindPreferenceSummaryToValue(findPreference(getString(R.string.preference_phoneNo))); } addPreferenceFromResource is supposed to load the XML node and add the preference to the screen, while binPreferenceSummaryToValue is supposed to make description text change when preference is updated. Just for sake of completeness for those who don't like code courtesy of the IDE, the second method is provided by Eclipse who also provides a private class in the code file that is /** * A preference value change listener that updates the preference's summary * to reflect its new value. */ In the general case, what should I do to perform validation logic before the preference gets saved when I click OK on the preference editor? Where is the validation logic to be put in a PreferenceScreen? *Aren't we all here to learn?

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• Tips on refactoring an Android prototype

  - by Brad

  I have an Android project I've inherited from another developer. The original code was hacked together using a single View and a single Activity. The view class has a State variable that is switched on during input and rendering. Each "screen" is a single bitmap rendered directly onto the screen. There are no layouts used at all. To make things even worse each variable in both the View and Activity classes were all declared public static and would access each other frequently. I've reworked the code so it is now somewhat manageable, but it's still in those original two classes. This is my first decently sized Android app so I'm not completely sure where to go next. From the looks of things, each "screen" should have its own View and Activity. Is this the general practice? If so I need some way to share data between the separate Activities. I've read suggestions to use a Singleton class that holds generic data. Is there any other ways that are more built into the Android framework? Thanks in advance.

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• Access to SQL Server 2005 from a non-domain machine using Windows authentication

  - by user304582

  Hi, I have a Windows domain within which a machine is running SQL Server 2005 and which is configured to support only Windows authentication. I would like to run a C# client application on a machine on the same network, but which is NOT on the domain, and access a database on the SQL Server 2005 instance. I thought that it would be a simple matter of doing something like this: string connectionString = "Data Source=server;Initial Catalog=database;User Id=domain\user;Password=password"; SqlConnection connection = new SqlConnection(connectionString); connection.Open(); However, this fails: the client-side error is: System.Data.SqlClient.SqlException: Login failed for user 'domain\user' and the server-side error is: Error 18456, Severity 14, State 5 I have tried various things including setting integrated security to true and false, and \ instead of \ in the User Id, but without success. In general, I know that it possible to connect to the SQL Server 2005 instance from a non-domain machine (for example, I am working with a Linux-based application which happily does this), but I don't seem to be able to work out how to do it from a Windows machine. Help would be appreciated! Thanks, Martin

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• Is there such a thing as a MemberExpression that handles a many-to-many relationship?

  - by Jaxidian

  We're trying to make it easy to write strongly-typed code in all areas of our system, so rather than setting var sortColumn = "FirstName" we'd like to say sortOption = (p => p.FirstName). This works great if the sortOption is of type Expression<Func<Person, object>> (we actually use generics in our code but that doesn't matter). However, we run into problems for many-to-many relationships because this notation breaks down. Consider this simple code: internal class Business { public IQueryable<Address> Addresses { get; set; } public string Name { get; set; } } internal class Address { public State MyState { get; set; } } internal class State { public string Abbreviation { get; set; } public int StateID { get; set; } } Is it possible to have this sort of MemberExpression to identify the StateID column off of a business? Again, the purpose of using this is not to return a StateID object, it's to just identify that property off of that entity (for sorting, filtering, and other purposes). It SEEMS to me that there should be some way to do this, even if it's not quite as pretty as foo = business.Addresses.SomeExtension(a => a.State.StateID);. Is this really possible? If more background is needed, take a look at this old question of mine. We've since updated the code significantly, but this should give you the general detailed idea of the context behind this question.

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• PHP Fix Warning: Cannot modify header information - headers already sent...

  - by Storm Kiernan

  Warning: Cannot modify header information - headers already sent by (output started at /home/blocexco/public_html/homepage.php:73) in /home/blocexco/public_html/classes/mysql/mysql.security.php on line 99 This error is repeated a second time for mysql.security.php on line 100. homepage:73 <div class="login"> <?php require_once 'login.php'; ?> </div> mysql.security.php: 99-100 setcookie('username', "", time() - (60 * 60 * 24 * 365)); setcookie('password', "", time() - (60 * 60 * 24 * 365)); I know this isn't a "BOM" issue as I've read about. There is output before and after my calls to header() and setcookie() functions - this is necessary since the homepage includes a php file which then injects the right login or logout form. I've heard about using ob_start() at the beginning of content, but that's not a very specific instruction...I tried placing it at the beginning of homepage.php (just before the html tag) and that didn't fix anything. I'm new to PHP (a few days in, and new to web-app dev in general). To be honest, it blows my mind that I can't just change which page I am on, via php without bending over backwards...

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• What guarantees are there on the run-time complexity (Big-O) of LINQ methods?

  - by tzaman

  I've recently started using LINQ quite a bit, and I haven't really seen any mention of run-time complexity for any of the LINQ methods. Obviously, there are many factors at play here, so let's restrict the discussion to the plain IEnumerable LINQ-to-Objects provider. Further, let's assume that any Func passed in as a selector / mutator / etc. is a cheap O(1) operation. It seems obvious that all the single-pass operations (Select, Where, Count, Take/Skip, Any/All, etc.) will be O(n), since they only need to walk the sequence once; although even this is subject to laziness. Things are murkier for the more complex operations; the set-like operators (Union, Distinct, Except, etc.) work using GetHashCode by default (afaik), so it seems reasonable to assume they're using a hash-table internally, making these operations O(n) as well, in general. What about the versions that use an IEqualityComparer? OrderBy would need a sort, so most likely we're looking at O(n log n). What if it's already sorted? How about if I say OrderBy().ThenBy() and provide the same key to both? I could see GroupBy (and Join) using either sorting, or hashing. Which is it? Contains would be O(n) on a List, but O(1) on a HashSet - does LINQ check the underlying container to see if it can speed things up? And the real question - so far, I've been taking it on faith that the operations are performant. However, can I bank on that? STL containers, for example, clearly specify the complexity of every operation. Are there any similar guarantees on LINQ performance in the .NET library specification?

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• VB.Net Memory Issue

  - by Skulmuk

  We have an application that has some interesting memory usage issues. When it first opens, the program uses aroun 50-60MB of memory. This stays consistent on 32-bit machines. On 64-bit machines, however, re-activating the form in any way (clicking, dragging, alt-tabbing, etc.) adds around another 50MB to it's memory usage. It repeats this process several times before resetting back to around 45MB, at which point the cycle begins again. I've done some research and a lot of people have said that VB in general has pretty poor garbage collection, which could be affecting the software in some way. However, I've yet to find a solution. There are no events fired when the application is activated (as shown by 32-bit usage) - the applications is merely sitting awaiting the user's actions. At load, the system pulls some data into a tree view, but that's the only external connection, and it only re-fires the routine when the user makes a change to something and saves the change. Has anyone else experienced anything this strange, and if so, does anyone know of what might fix it? It seems strange that it only occurs under x64 systems. Thanks

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