Search Results

Search found 5415 results on 217 pages for 'concurrent mark sweep'.

Page 147/217 | < Previous Page | 143 144 145 146 147 148 149 150 151 152 153 154  | Next Page >

  • What is a good motivating example for dataflow concurrency?

    - by Alex Miller
    I understand the basics of dataflow programming and have encountered it a bit in Clojure APIs, talks from Jonas Boner, GPars in Groovy, etc. I know it's prevalent in languages like Io (although I have not studied Io). What I am missing is a compelling reason to care about dataflow as a paradigm when building a concurrent program. Why would I use a dataflow model instead of a mutable state+threads+locks model (common in Java, C++, etc) or an actor model (common in Erlang or Scala) or something else? In particular, while I know of library support in the languages above (and Scala and Ruby), I don't know of a single program or library that is a poster child user of this model. Who is using it? Why do they find it better than the other models I mentioned?

    Read the article

  • Issue with SOAPUI: running test for concurrency

    - by Kangkan
    I am trying to test my web service using SOAPUI (the free version). For testing concurrency, I wished to fire concurrent threads from SOAPUI onto the service. But with the options, the thread count increases gradually (even in the burst mode). The machine where SOAPUI is installed is a WinXP machine. Can I actually do the concurrency testing? If so how? Please guide me. I am waiting for your answers and help.

    Read the article

  • NSUserDefaults loses 3 rows each time it's called

    - by Jeff Decker
    Hello Everyone! Brand new programmer here, so off-topic help/constructive criticism welcome. I am saving a default state (such as "New York") in a UIPickerView which is in a FlipSideView. It certainly saves for the first and second time I check to make sure it's the same state (I am clicking "done" and then "info" repeatedly), but on the third check the picker has moved up three states (to "New Hampshire") and then every time I check the picker progresses three more states. Here's the .h and .m files of the FlipSideViewController: #import <UIKit/UIKit.h> import "Calculator.h" @protocol FlipsideViewControllerDelegate; @interface FlipsideViewController : UIViewController { id delegate; UIPickerView *myPickerView; NSArray *pickerViewArray; } @property (nonatomic, assign) id delegate; @property (nonatomic, retain) UIPickerView *myPickerView; @property (nonatomic, retain) NSArray *pickerViewArray; (IBAction)done; @end @protocol FlipsideViewControllerDelegate - (void)flipsideViewControllerDidFinish:(FlipsideViewController *)controller; @end import "FlipsideViewController.h" @implementation FlipsideViewController @synthesize delegate; @synthesize myPickerView, pickerViewArray; -(CGRect)pickerFrameWithSize:(CGSize)size;{ CGRect screenRect = [[UIScreen mainScreen] applicationFrame]; CGRect pickerRect = CGRectMake( 0.0, screenRect.size.height - size.height, size.width, size.height); return pickerRect; } (void)viewDidLoad { [super viewDidLoad]; self.view.backgroundColor = [UIColor viewFlipsideBackgroundColor]; [self createPicker]; } -(void)viewWillAppear:(BOOL)animated;{ [super viewWillAppear:NO]; NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; [myPickerView selectRow:[defaults integerForKey:@"pickerRow"] inComponent:0 animated:NO]; } -(void)createPicker;{ pickerViewArray = [[NSArray arrayWithObjects: @"Alabama",@"Alaska", @"Arizona",@"Arkansas",@"California",@"Colorado",@"Connecticut",@"Delaware", @"District of Columbia",@"Florida",@"Georgia",@"Hawaii",@"Idaho",@"Illinois",@"Indiana",@"Iowa", @"Kansas",@"Kentucky",@"Louisiana",@"Maine",@"Maryland",@"Massachusetts",@"Michigan", @"Minnesota",@"Mississippi",@"Missouri",@"Montana",@"Nebraska",@"Nevada",@"New Hampshire",@"New Jersey", @"New Mexico",@"New York",@"North Carolina",@"North Dakota",@"Ohio",@"Oklahoma", @"Oregon",@"Pennsylvania",@"Rhode Island",@"South Carolina",@"South Dakota",@"Tennessee", @"Texas",@"Utah",@"Vermont",@"Virginia",@"Washington",@"West Virginia",@"Wisconsin",@"Wyoming", nil] retain]; myPickerView = [[UIPickerView alloc] initWithFrame:CGRectZero]; CGSize pickerSize = [myPickerView sizeThatFits:CGSizeZero]; myPickerView.frame = [self pickerFrameWithSize:pickerSize]; myPickerView.autoresizingMask = UIViewAutoresizingFlexibleWidth; myPickerView.showsSelectionIndicator = YES; myPickerView.delegate = self; myPickerView.dataSource = self; [self.view addSubview:myPickerView]; } (IBAction)done { [self.delegate flipsideViewControllerDidFinish:self]; } pragma mark - pragma mark UIPickerViewDataSource (NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component { NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; [defaults setInteger:row forKey:@"pickerRow"]; [defaults setObject:[pickerViewArray objectAtIndex:row] forKey:@"pickerString"]; return [pickerViewArray objectAtIndex:row]; } (void)pickerView:(UIPickerView *)pickerView didSelectRow:(NSInteger)row inComponent:(NSInteger)component { NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults]; [defaults setInteger:row forKey:@"pickerRow"]; [defaults setObject:[pickerViewArray objectAtIndex:row] forKey:@"pickerString"]; } (CGFloat)pickerView:(UIPickerView *)pickerView widthForComponent:(NSInteger)component { return 240.0; } (CGFloat)pickerView:(UIPickerView *)pickerView rowHeightForComponent:(NSInteger)component { return 40.0; } (NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component { return [pickerViewArray count]; } (NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView { return 1; } call me mystified! Thanks for any help. Please let me know if I can make myself more clear...

    Read the article

  • Which web Tier Framework for a public commercial website with heavy load ?

    - by Maxime ARNSTAMM
    Hello everyone, As a part of an enterprise architecture exercise, i need to find a java-based framework filling these constraints : heavy (i think) load : 5000 concurrent connections widely known : can't be too exotic, the contractors would be too high priced. relatively easy to use : developpement time must be reasonnable must be as compliant as possible with the css/html layout produced by a designer Must look like "web 2.0" from the marketing point of view. What i learned from my limited experience is : jsf : 1, don't know. 2, 3 ok. 4 not ok (at least not without huge effort) wicket : 1, not really. 2, 3 and 4 ok. gwt : 1, don't know. 2, 3 ok. 4 not ok (but more ok than jsf) others : not really "web 2.0" or not really known I'm really junior, so my ideas about those frameworks are probably wrong, that's why i come to you, stackoverflowees. Thanks for helping :)

    Read the article

  • Disk-based caching of dynamic images in IIS 7

    - by Daniel Schierbeck
    I'm writing an image server which needs to handle a relatively large number of concurrent requests (~5,000). The images being served are dynamically scaled down and cropped based on per-image specifications, which are queried from a database. The number of images is rather large, so an in-memory cache isn't viable (thrashing would most definitely occur). I'm using native caching in IIS 7 to avoid hitting the ASP.NET app which generates the images on-the-fly. I've looked around, but I couldn't find a simple way to configure IIS to store the cache on-disk -- is there such an option, or would I need to roll my own? I'd rather avoid placing the generated images in a public folder, so they can be served statically, since I would prefer to invalidate the cache entries using a query parameter (last-edit time from the database,) which doesn't seem possible to reconcile with static caching. I would love to get some feedback on this!

    Read the article

  • Named semaphores in Python?

    - by Boaz
    Hi, I have a script in python which uses a resource which can not be used by more than a certain amount of concurrent scripts running. Classically, this would be solved by a named semaphores but I can not find those in the documentation of the multiprocessing module or threading . Am I missing something or are named semaphores not implemented / exposed by Python? and more importantly, if the answer is no, what is the best way to emulate one? Thanks, Boaz PS. For reasons which are not so relevant to this question, I can not aggregate the task to a continuously running process/daemon or work with spawned processed - both of which, it seems, would have worked with the python API.

    Read the article

  • In MS SQL Server, is there a way to "atomically" increment a column being used as a counter?

    - by Dan P
    Assuming a Read Committed Snapshot transaction isolation setting, is the following statement "atomic" in the sense that you won't ever "lose" a concurrent increment? update mytable set counter = counter + 1 I would assume that in the general case, where this update statement is part of a larger transaction, that it wouldn't be. For example, I think this scenario is possible: update the counter within transaction #1 do some other stuff in transaction #1 update the counter with transaction #2 commit transaction #2 commit transaction #1 In this situation, wouldn't the counter end up only being incremented by 1? Does it make a difference if that is the only statement in a transaction? How does a site like stackoverflow handle this for its question view counter? Or is the possibility of "losing" some increments just considered acceptable?

    Read the article

  • WinUSB application or User-Mode Driver as a filter driver for USB Analysis/Sniffer/Trending

    - by Robert
    A question to maybe some who have worked extensively with WinUSB APIs or use mode USB drivers - Does anyone know if the WinUSB API or a user mode driver can be used as a passive observer of USB connections, capturing notification of interrupts, control requests, data transfers...etc without interfering with other applications (such as iTunes) which would obviously require concurrent access to the device at the same time my application is monitoring the connection and displaying data on it? Or do you pretty much have to write a kernel-mode filter driver and inject yourself in the USB stack in order to make that happen? In the past, there have been a few credible options (libusb-win32 and usbsnoop to be specific) though both are built around the old DDK, not the Windows Driver Foundation, and are not really supported on a regular basis any more. I'm hesitant to build something significant around them, as a result.

    Read the article

  • dynamics CRM performance question

    - by tomo
    Hello Dynamics CRM gurus :) My boss asked me to do a research on available CMSes on market because cms we are using currently is rather a mess. For me as a .NET developer it would be great to choose and implement Dynamics CRM because of extensibility and perfect integration with .NET environment and well-known tools. All marketing blahbla sounds great but I'd like to know about common DISADVANTAGES, ISSUES concerning this system. The most important is how it is performing in a company with about 150 concurrent and very active users. I heard that is't really slow comparing to competitors system. Thanks in advance Best regards, Tomasz.

    Read the article

  • Socket server stops accepting connections after a period of time

    - by Rob
    We have an async socket server written in C#. (running on Windows Web Server 2008) It works flawlessly up until it stop accepting new connections for an unknown reason. We have about 200 concurrent connections on average, however we keep a count of both connections created and connections dropped. These figures can reach as high as 10,000 or as low as only 1000 before it just stops! It can run for up to around 8 hours sometimes before it stops or it can run for about half hour, at the moment it's running for about an hour before we have another application bring it back up automatically when that can't connect (not exactly ideal). It doesn't appear like we're running out of sockets as we're closing them properly, we're also logging all errors and nothing is happening immediately before it stops. We can figure this out. Does anyone have any ideas what might be going on? I can paste code, but it generally just the same old async beginaccept/send code you see everywhere.

    Read the article

  • C#: How to remove items from the collection of a IDictionary<E, ICollection<T>> with LINQ?

    - by Rosarch
    Here is what I am trying to do: private readonly IDictionary<float, ICollection<IGameObjectController>> layers; foreach (ICollection<IGameObjectController> layerSet in layers.Values) { foreach (IGameObjectController controller in layerSet) { if (controller.Model.DefinedInVariant) { layerSet.Remove(controller); } } } Of course, this doesn't work, because it will cause a concurrent modification exception. (Is there an equivalent of Java's safe removal operation on some iterators?) How can I do this correctly, or with LINQ?

    Read the article

  • Keeping a large volume of data in Session - Suggestions / alternatives?

    - by Fishcake
    I'm developing a web app for which the client wants us to query their data as little as possible. The data will be coming from a Microsoft CRM instance. So we've agreed that data will only be queried as and when it is needed, therefore if a web user wants to see a list of contacts (for example) that list is fetched into a local DataTable. Then if a new contact is created on the website the new contact is sent to CRM and added to the local DataTable at the same time. Likewise for edits. If the user then looks at their contacts again the data will just come from the local DataTable. At the moment local data is being kept in Session but my concern is that too much memory will start being used up. However traffic is expected to be pretty small, perhaps no more than 20 concurrent users so am I worrying about nothing or is there a better way you can suggest to handle this?

    Read the article

  • handling Concurrency in SQL SERVER 2005

    - by sameer
    Hi, I have one question for you, if you can answer and refer resource it will be great help. I have a scenario where i need to create a appointment slot and a serial no for each slot memberwise. ex: Member Id |App Slot # 1|1 1|2 2|1 2|2 1|3 what im doing is take the Max slot number,increamenting it and insert it memberwise. but the problem is concurrent user can create a slot when i take the max slot after that if any other user insert the slot the value that im working with is no more valid, how to over come this problem Thanks & Regards, Sameer

    Read the article

  • java tool for debugging

    - by user269723
    Hi experts, Currently we are studying the java based tool which is primararily Reporting tool.It was developed in 2000/2001 period and uses many open source libraries like Apache Avalon/Mx4J.Adaptor/edu.Oswego(java concurrent package) etc. Tool uses jdk 1.3.1 and goal is to upgrade to jdk 1.5.We have also been asked to remove these 'outdated' packages and replace by standard java packages if possible. Unfortunately we have the code available for study but lacks any documentation and really difficult to track the flow(Total number of classes written might be more than 1000) during debugging. Whats the best way to understand this kind of tool? any Graphical tool to see the relationship between the classes? Thanks SR

    Read the article

  • Server-side technology for a game

    - by Soonts
    We’re creating a massively-multiplayer social game. We expect up to 1 million concurrent users. The game is not real-time, instead it’s turn-based. We need reliable messaging between our clients and the server, preferably over HTTP protocol. Besides the multiplayer functionality, we’ll also need a content delivery service. Could you please recommend a server-side technology for us, so we’ll start searching for the right people to hire? Is it correct assumption that no single server will hold that amount of load so it must scale horizontally? Will Windows Azure do the job? Thanks in advance.

    Read the article

  • How to generate a good random seed to pass to srand()?

    - by zr
    Hi, I am writing a C++ program which needs to create a temporary file for its internal usage. I would like to allow concurrent executions of the program by running multiple proccesses, so the temporary file name needs to be randomized, that way each spawned process will generate a unique temporary file name for its own use. I am using rand() to generate random characters for part of the file name, so i need to initialize the random number generator's seed using srand(). What options are there for passing a good argument to srand() such that two processes will not be initialized with the same seed value? My code needs to work both on Windows and pn Linux TIA.

    Read the article

  • Service injection into Controller (Spring MVC)

    - by ThaSaleni
    Hi I have a Spring web application, I have built it up to the controller stage and I could inject my Daos, into my Services fine. Now when I want to inject my Service into my controller i get an error for dependency with the Dao and further down the sessionFactory. I don't want to inject these again cause this will ultimately lead me to eventually create a data source but I have my Daos for data access and they already know about sessionFactory. Am I missing something here? here's the sample code snippets My Service: @Service("productService") @Transactional public class ProductServiceImpl implements ProductService { private ProductDao productDao; @Autowired public void setDao(ProductDao productDao) { this.productDao = productDao; } My Controller @Controller @WebServlet(name="controllerServlet", loadOnStartup= urlPatterns=...}) public class ControllerServlet extends HttpServlet { boolean isUserLogedIn =false; @Autowired private ProductService productService; public void setProductService(ProductService productService){ this.productService = productService; } Servlet-context Stack trace javax.servlet.ServletException: Servlet.init() for servlet mvcServlet threw exception org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472) org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98) org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927) org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407) org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:999) org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java: 565) org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:1812) java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) java.lang.Thread.run(Thread.java:662) root cause org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'controllerServlet': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.phumzile.acme.services.ProductService com.phumzile.acme.client.web.controller.ControllerServlet.productService; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [com.phumzile.acme.services.ProductService] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)} org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.p ostProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:287) org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1106) org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:517) org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456) org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294) org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225) SERVLET-CONTEXT <context:component-scan base-package="com.phumzile.acme.client" /> <!-- Enables the Spring MVC @Controller programming model --> <mvc:annotation-driven /> </beans> APP-CONFIG <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="locations"> <list> <value>configuration.properties</value> </list> </property> </bean> <context:annotation-config/> <context:component-scan base-package="com.phumzile.acme" /> <import resource="db-config.xml" /> </beans> DB-CONFIG <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close"> <property name="idleConnectionTestPeriod" value="10800"/> <property name="maxIdleTime" value="21600"/> <property name="driverClass"> <value>${jdbc.driver.className}</value> </property> <property name="jdbcUrl"> <value>${jdbc.url}</value> </property> <property name="user"> <value>${jdbc.username}</value> </property> <property name="password"> <value>${jdbc.password}</value> </property> </bean> <bean id="sessionFactory" class="org.springframework.orm.hibernate3.a nnotation.AnnotationSessionFactoryBean"> <property name="dataSource"> <ref bean="dataSource" /> </property> <property name="annotatedClasses"> <list> <!-- Entities --> <value>com.phumzile.acme.model.User</value> <value>com.phumzile.acme.model.Person</value> <value>com.phumzile.acme.model.Company</value> <value>com.phumzile.acme.model.Product</value> <value>com.phumzile.acme.model.Game</value> <value>com.phumzile.acme.model.Book</value> <!-- Entities --> </list> </property> <property name="packagesToScan" value="com.phumzile.acme" /> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect">${jdbc.hibernate.dialect </prop> <prop key="hibernate.hbm2ddl.auto">validate</prop> <prop key="hibernate.show_sql">true</prop> </props> </property> </bean> <bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager"> <property name="sessionFactory"> <ref bean="sessionFactory" /> </property> </bean> <tx:annotation-driven /> </beans> CONFIGURATION.PROPERTIES jdbc.driver.className=com.mysql.jdbc.Driver jdbc.url=jdbc:mysql://localhost:3306/mydb jdbc.username=root jdbc.password=root jdbc.hibernate.dialect=org.hibernate.dialect.MySQLDialect

    Read the article

  • net c# lock statement in data access layer

    - by Pedro Rivera
    I saw a code where they have the data access layer like this: public class CustomerDA{ private static readonly object _sync = new object(); private static readonly CustomerDA _mutex = new CustomerDA(); private CustomerDA(){ } public CustomerDA GetInstance(){ lock(_sync){ return _mutex; } } public DataSet GetCustomers(){ //database SELECT //return a DataSet } public int UpdateCustomer(some parameters){ //update some user } } public class CustomerBO{ public DataSet GetCustomers(){ //some bussiness logic return CustomerDA.GetInstance().GetCustomers(); } } I was using it, but start thinking... "and what if had to build a facebook like application where there are hundreds of thousands of concurrent users? would I be blocking each user from doing his things until the previous user ends his database stuff? and for the Update method, is it useful to LOCK THREADS in the app when database engines already manage concurrency at database server level?" Then I started to think about moving the lock to the GetCustomers and UpdateCustomer methods, but think again: "is it useful at all?"

    Read the article

  • For single-producer, single-consumer should I use a BlockingCollection or a ConcurrentQueue?

    - by Jonathan Allen
    For single-producer, single-consumer should I use a BlockingCollection or a ConcurrentQueue? Concerns: * My goal is to pull up to 100 items at a time and send them as a batch to the next step. * If I use a ConcurrentQueue, I have to manually cause it to go asleep when there is no work to be done. Otherwise I waste CPU cycles on spinning. * If I use a BlockingQueue and I only have 99 work items, it could indefinitely block until there the 100th item arrives. http://msdn.microsoft.com/en-us/library/system.collections.concurrent.aspx

    Read the article

  • how to store dynamically generated pages in html?

    - by Dharmik Bhandari
    I'm working on ASP.net MVC3 Web application that is facing scalability issue. For improving performance I want to store dynamically generated pages in html and serve them from generated html directly rather then querying database for each page request. I'm sure this will dramatically increase performance. Can any one share any hint / example / tutorial on how to do it? And what are challenges? I would also like to know how others are handling performance issue for large e-commerce sites with at-least thousand categories and 200k products with at least 200-500 concurrent visitors? What are the best approaches? Thanks in advance.

    Read the article

  • What is the best way to make a schedule in MFC

    - by Vanwaril
    I have a list of items that are each associated with a start and end time and date. What I want to do is, given a time and date range, display only the items that fall within that window, even partially. What I'm doing is creating a CListCtrl with all the items in it and the CListCtrl is sorted by start time by default. But given a time range, I don't know how to search for the first item that is within the range. Another problem with the list control is it displays as a list, whereas it would be nice if there was a control that could also show things that are concurrent side by side. I'm doing this within a dialog application.

    Read the article

  • PHP Launch Execute Files Concurrently

    - by Ozzy
    Hi all. Basically, I was doing some testing using apache bench. The file i was testing takes 2 seconds to execute (its optimised, it connects to an external server hence the slowdown) Basically I found that the more concurrent useres i emulated, the more executions of the file i could do per second. Is there anyway that i can do something like this in php? : <?php execute_file('file.php'); execute_file('file.php'); execute_file('file.php'); execute_file('file.php'); execute_file('file.php'); ?> That would execute the file 5 times but would NOT wait for the files to finish downloading so the above example would quickly call the 5 functions then exit. Im assuming somesort of timeout would be used?

    Read the article

  • MySQL and INT auto_increment fields

    - by PHPguy
    Hello folks, I'm developing in LAMP (Linux+Apache+MySQL+PHP) since I remember myself. But one question was bugging me for years now. I hope you can help me to find an answer and point me into the right direction. Here is my challenge: Say, we are creating a community website, where we allow our users to register. The MySQL table where we store all users would look then like this: CREATE TABLE `users` ( `uid` int(2) unsigned NOT NULL auto_increment COMMENT 'User ID', `name` varchar(20) NOT NULL, `password` varchar(32) NOT NULL COMMENT 'Password is saved as a 32-bytes hash, never in plain text', `email` varchar(64) NOT NULL, `created` int(11) unsigned NOT NULL default '0' COMMENT 'Timestamp of registration', `updated` int(11) unsigned NOT NULL default '0' COMMENT 'Timestamp of profile update, e.g. change of email', PRIMARY KEY (`uid`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; So, from this snippet you can see that we have a unique and automatically incrementing for every new user 'uid' field. As on every good and loyal community website we need to provide users with possibility to completely delete their profile if they want to cancel their participation in our community. Here comes my problem. Let's say we have 3 registered users: Alice (uid = 1), Bob (uid = 2) and Chris (uid = 3). Now Bob want to delete his profile and stop using our community. If we delete Bob's profile from the 'users' table then his missing 'uid' will create a gap which will be never filled again. In my opinion it's a huge waste of uid's. I see 3 possible solutions here: 1) Increase the capacity of the 'uid' field in our table from SMALLINT (int(2)) to, for example, BIGINT (int(8)) and ignore the fact that some of the uid's will be wasted. 2) introduce the new field 'is_deleted', which will be used to mark deleted profiles (but keep them in the table, instead of deleting them) to re-utilize their uid's for newly registered users. The table will look then like this: CREATE TABLE `users` ( `uid` int(2) unsigned NOT NULL auto_increment COMMENT 'User ID', `name` varchar(20) NOT NULL, `password` varchar(32) NOT NULL COMMENT 'Password is saved as a 32-bytes hash, never in plain text', `email` varchar(64) NOT NULL, `is_deleted` int(1) unsigned NOT NULL default '0' COMMENT 'If equal to "1" then the profile has been deleted and will be re-used for new registrations', `created` int(11) unsigned NOT NULL default '0' COMMENT 'Timestamp of registration', `updated` int(11) unsigned NOT NULL default '0' COMMENT 'Timestamp of profile update, e.g. change of email', PRIMARY KEY (`uid`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; 3) Write a script to shift all following user records once a previous record has been deleted. E.g. in our case when Bob (uid = 2) decides to remove his profile, we would replace his record with the record of Chris (uid = 3), so that uid of Chris becomes qual to 2 and mark (is_deleted = '1') the old record of Chris as vacant for the new users. In this case we keep the chronological order of uid's according to the registration time, so that the older users have lower uid's. Please, advice me now which way is the right way to handle the gaps in the auto_increment fields. This is just one example with users, but such cases occur very often in my programming experience. Thanks in advance!

    Read the article

  • Why avoid pessimistic locking in a version control system?

    - by raven
    Based on a few posts I've read concerning version control, it seems people think pessimistic locking in a version control system is a bad thing. Why? I understand that it prevents one developer from submitting a change while another has the file checked out, but so what? If your code files are so big that you constantly have more than one person working on them at the same time, I submit that you should reorganize your code. Break it up into smaller functional units. Integration of concurrent code changes is a tedious and error-prone process even with the tools a good version control system provides to make it easier. I think it should be avoided if at all possible. So, why is pessimistic locking discouraged?

    Read the article

  • How to maintain a pool of names ?

    - by Jacques René Mesrine
    I need to maintain a list of userids (proxy accounts) which will be dished out to multithreaded clients. Basically the clients will use the userids to perform actions; but for this question, it is not important what these actions are. When a client gets hold of a userid, it is not available to other clients until the action is completed. I'm trying to think of a concurrent data structure to maintain this pool of userids. Any ideas ? Would a ConcurrentQueue do the job ? Clients will dequeue a userid, and add back the userid when they are finished with it.

    Read the article

< Previous Page | 143 144 145 146 147 148 149 150 151 152 153 154  | Next Page >