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• At what point should data be sent back to server?

  - by whamsicore

  A good example would be the stackexchange "rate" button. When a post is upvoted the arrow changes color immediately. However there is a grace period for one to edit one's vote decision (oops! voted by mistake?). Is the upvote action processed immediately or does is only process after a set time period, or when the user leaves the page? How exactly is this rating processed? What is the standard for handling dynamic page edits (e.g. stackexchange rating, facebook posts?)

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• Which Revision Control Software to use for Personal Dropbox?

  - by wag2639

  I want to set up a sync repositiory that would be similar to Dropbox. Goals/Requirements: Free (Open Source very preferable) Linux host (probably Ubuntu) Windows/Mac/Linux clients Potential for multiple users with limited access (optional) Preferable easy, doesn't necessarily need to be automatic Revision control very preferable Basically, I want to be able to use multiple computers, possible with different OS's, and be able to access, use, and sync files across all of them. I also want to have a local copy of the repository for when I'm not connected to the network (as if I'm working on a laptop, I want to keep a local repository to keep revision and merge later with "master" repository). For example, I'm editing a few pictures on my laptop during the day outside of my network, but when I get home, I would like to sync the changes, including incremental changes, with my desktop at home. I would also like my roommates to be able to access and use this repository too but limit access to certain files. For example, I may want to use this to backup financial records but wouldn't want them to have access to those files. I'm a programmer and familiar with SVN but I know that wouldn't be the most appropriate since it doesn't handle binaries well and doesn't keep a local repository. I know better choices exist but I don't really know them well enough to choose the best one.

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• SQL Source Control Contest

  - by Ajarn Mark Caldwell

  If you’re a regular reader of this blog, you know that I have written several posts about how important I think it is to protect your source code, to version it, and in particular, all the aspects I like about Red Gate’s SQL Source Control product.  But for a moment, let’s take a break from my writing and I want to hear your stories.  What nightmare situation are you in, or can you imagine, where source control for your database would save the world.  Or maybe your life is not so dramatic, but you do see a challenge that, if you just had a good tool like SQL Source Control, it would go much smoother.  What’s your pain?  You have read my writings, now tell me your story, and be in the running for a free copy of SQL Source Control from Red Gate. Yes, that’s right.  Although I am just a fan of Red Gate, they have authorized me to give out a handful of licenses to blog readers who are willing to share their story by posting a comment to this blog entry.  Simply add your comment below (be sure to include a valid email address in the box that asks for that) to be entered.  The contest starts immediately and over the next few days, the best stories will win.

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• Visit our Consolidated List of Mandatory Project Costing Code and Data Fixes

  - by SherryG-Oracle

  Projects Support has a published document with a consolidated listing of mandatory code and data fixes for Project Costing.  Generic Data Fix (GDF) patches are created by development to fix data issues caused by bugs/issues in the application code.  The GDF patches are released for download via My Oracle Support which are then referenced in My Oracle Support documents and by support to provide data fixes for known code fix issues.Consolidated root cause code fix and generic data fix patches will be superceded whenever any new version is created.  These patches fix a number of critical code and data issues identified in the Project Costing flow.This document contains a consolidated list of code and data fixes for Project Costing.  The note lists the following details: Note ID Component Type (code or data) Abstract Patch Visit DocID 1538822.1 today!

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• Data Structures: What are some common examples of problems where "buffers" come into action?

  - by Dark Templar

  I was just wondering if there were some "standard" examples that everyone uses as a basis for explaining the nature of a problem that requires the use of a buffer. What are some well-known problems in the real world that can see great benefits from using a buffer? Also, a little background or explanation as to why the problem benefits from using a buffer, and how the buffer would be implemented, would be insightful for understanding the concept!

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• The Data Distribution Service for Real-Time Systems: Part 2

  Structuring and managing your data Data Distribution Service - Business - Data Distribution Service for Real-Time Systems - Databases - Data Warehousing

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• What processes would make the selling of a hard drive that previously held sensitive data justifiable? [closed]

  - by user12583188

  Possible Duplicate: Securely erasing all data from a hard drive In my personal collection are an increasing number of relatively new drives, only put on the shelf due to upgrades; in the past I have never sold hard drives with used machines for fear of having the encrypted password databases that have been stored on them compromised, but as their numbers increase I find myself more tempted to do so (due to the $$$ I know they're worth on the used market). What tools then exist to make the recovery of data from said drives difficult to the extent that selling them could be justified? Another way of saying this would be: what tools/method exist for making the attempts at recovery of any data previously stored on a certain drive impractical? I assume that it is always possible to recover data from a drive that is in working order. I assume also there are some methods for preventing recovery of data due a program called dban, and one particular feature in macOSX that deals with permanently deleting data from a disk.

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• Associate a texture to an object (from a data-model, not graphical point of view).

  - by Raveline

  I'm writing a roguelike where objects and floor can be made of different materials. For instance, let's say we can have a wooden chair, an iron chair, a golden chair, and so on. I've got an Object class (I know, the name is terrible), which is more or less using a composite pattern, and a Material class. Material have different important properties (noise, color...). For the time being, there are 5 different instances of materials, created at the initialization of the game. How would connect an instance of Object with one of the 5 instances of materials ? I see three simple solutions : Using a pointer. Simple and brutal. Using an integer material-id, then get the materials out of a table when engine manipulates the object for various purposes (display, attack analysis, etc.). Not very beautiful, I think, and not very flexible. Using an integer material-id, then get the materials out of a std::map. A bit more flexible, but still not perfect. Do you see other possibilities ? If not, what would you choose (and why) ? Thanks in advance !

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• populate uipicker view with results from core data DB using an NSArray

  - by Chris

  I am trying to populate a UIPickerView with the results of a NSFetchRequest. The results of the NSFetchRequest are then stored in an NSArray. I am using Core Data to interact with the SQLite DB. I have a simple class file that contains a UIPickerView that is associated with a storyboard scene in my project. The header file for the class looks like the following, ViewControllerUsers.h #import <UIKit/UIKit.h> #import "AppDelegate.h" @interface ViewControllerUsers : UIViewController <NSFetchedResultsControllerDelegate, UIPickerViewDelegate, UIPickerViewDataSource> { NSArray *dictionaries; } @property (nonatomic, strong) NSFetchedResultsController *fetchedResultsController; // Core Data @property (strong, nonatomic) NSManagedObjectContext *managedObjectContext; @property (nonatomic, strong) NSArray *users; @property (strong, nonatomic) IBOutlet UIPickerView *uiPickerViewUsers; @property (weak, nonatomic) IBOutlet UIBarButtonItem *btnDone; @property (weak, nonatomic) IBOutlet UIButton *btnChangePin; // added for testing purposes @property (nonatomic, strong) NSArray *usernames; - (IBAction)dismissScene:(id)sender; - (IBAction)changePin:(id)sender; @end The implementation file looks like the following, ViewControllerUsers.m #import "ViewControllerUsers.h" @interface ViewControllerUsers () @end @implementation ViewControllerUsers // Core Data @synthesize managedObjectContext = _managedObjectContext; @synthesize uiPickerViewUsers = _uiPickerViewUsers; @synthesize usernames = _usernames; - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; if (self) { // Custom initialization } return self; } - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view. // Core Data if (_managedObjectContext == nil) { _managedObjectContext = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext]; NSLog(@"After _managedObjectContext: %@", _managedObjectContext); } NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Account"]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Account" inManagedObjectContext:_managedObjectContext]; request.resultType = NSDictionaryResultType; request.propertiesToFetch = [NSArray arrayWithObject:[[entity propertiesByName] objectForKey:@"username"]]; request.returnsDistinctResults = YES; _usernames = [_managedObjectContext executeFetchRequest:request error:nil]; NSLog (@"names: %@",_usernames); } -(NSInteger)numberOfComponentsInPickerView:(UIPickerView *)pickerView { //One column return 1; } -(NSInteger)pickerView:(UIPickerView *)pickerView numberOfRowsInComponent:(NSInteger)component { //set number of rows return _usernames.count; } -(NSString *)pickerView:(UIPickerView *)pickerView titleForRow:(NSInteger)row forComponent:(NSInteger)component { //set item per row return [_usernames objectAtIndex:row]; } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } - (void)viewDidUnload { [self setBtnDone:nil]; [self setUiPickerViewUsers:nil]; [self setBtnChangePin:nil]; [super viewDidUnload]; } - (IBAction)dismissScene:(id)sender { [self dismissModalViewControllerAnimated:YES]; } - (IBAction)changePin:(id)sender { } @end The current code is causing the app to crash, but the NSLog is show the results of the NSFetchRequest in the NSArray. I currently think that I am not formatting the results of the NSFetchRequest in the NSArray properly if I had to take a guess. The crash log looks like the following, 2013-06-26 16:49:24.219 KegCop[41233:c07] names: ( { username = blah; }, { username = chris; }, { username = root; } ) 2013-06-26 16:49:24.223 KegCop[41233:c07] -[NSKnownKeysDictionary1 isEqualToString:]: unrecognized selector sent to instance 0xe54d9a0 2013-06-26 16:49:24.223 KegCop[41233:c07] Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSKnownKeysDictionary1 isEqualToString:]: unrecognized selector sent to instance 0xe54d9a0' First throw call stack:

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• R concentrating data frame

  - by user1631503

  I have a data frame like this >X_com Day_1 Day_2 Day_3 Day_4 Day_5 Day_6 Day_7 Day_8 Day_9 Day_10 1 0 0 0 0 0 0 0 0 0 1 2 0 0 0 0 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 4 0 0 0 0 0 0 0 0 0 0 5 0 0 0 0 0 0 0 0 0 0 6 0 0 0 0 0 0 0 0 0 0 7 0 0 0 0 0 0 0 0 0 0 8 0 0 0 0 0 0 0 0 0 0 I need to concentrate all the values into one column and add another column with "1;" So I did this > X_new=matrix(1,8,2) > X_new[1,]=paste(X_com[1,1], X_com[1,2],X_com[1,3],X_com [1,4],X_com[1,5],X_com[1,6],X_com[1,7],X_com[1,8],X_com [1,9],X_com[1,10], sep="") > X_new[2,]=paste(X_com[2,1], X_com[2,2],X_com[2,3],X_com [2,4],X_com[2,5],X_com[2,6],X_com[2,7],X_com[2,8],X_com [2,9],X_com[2,10], sep="") > X_new[3,]=paste(X_com[3,1], X_com[3,2],X_com[3,3],X_com [3,4],X_com[3,5],X_com[3,6],X_com[3,7],X_com[3,8],X_com [3,9],X_com[3,10], sep="") > X_new[4,]=paste(X_com[4,1], X_com[4,2],X_com[4,3],X_com [4,4],X_com[4,5],X_com[4,6],X_com[4,7],X_com[4,8],X_com [4,9],X_com[4,10], sep="") > X_new[5,]=paste(X_com[5,1], X_com[5,2],X_com[5,3],X_com [5,4],X_com[5,5],X_com[5,6],X_com[5,7],X_com[5,8],X_com [5,9],X_com[5,10], sep="") > X_new[6,]=paste(X_com[6,1], X_com[6,2],X_com[6,3],X_com [6,4],X_com[6,5],X_com[6,6],X_com[6,7],X_com[6,8],X_com [6,9],X_com[6,10], sep="") > X_new[7,]=paste(X_com[7,1], X_com[7,2],X_com[7,3],X_com [7,4],X_com[7,5],X_com[7,6],X_com[7,7],X_com[7,8],X_com [7,9],X_com[7,10], sep="") > X_new[8,]=paste(X_com[8,1], X_com[8,2],X_com[8,3],X_com [8,4],X_com[8,5],X_com[8,6],X_com[8,7],X_com[8,8],X_com [8,9],X_com[8,10], sep="") > X_new[1:8,2]="1;" > as.data.frame(X_new) V1 V2 1 0000000001 1; 2 0000000000 1; 3 0000000000 1; 4 0000000000 1; 5 0000000000 1; 6 0000000000 1; 7 0000000000 1; 8 0000000000 1; I believe there's definitely a faster way of achieving this but have no clue. The other problem is, I have over a thousand of data frame like this needs to be concentrated. I'm still learning how to loop these repetitive steps but is progressing quite slowly. If the original data frames were named uniquely, does that mean I have no choice but to work on each of them individually? Thank you in advance.

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• Core Data NSPredicate for relationships.

  - by Mugunth Kumar

  My object graph is simple. I've a feedentry object that stores info about RSS feeds and a relationship called Tag that links to "TagValues" object. Both the relation (to and inverse) are to-many. i.e, a feed can have multiple tags and a tag can be associated to multiple feeds. I referred to http://stackoverflow.com/questions/844162/how-to-do-core-data-queries-through-a-relationship and created a NSFetchRequest. But when fetch data, I get an exception stating, NSInvalidArgumentException unimplemented SQL generation for predicate What should I do? I'm a newbie to core data :( I know I've done something terribly wrong... Please help... Thanks -- NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; // Edit the entity name as appropriate. NSEntityDescription *entity = [NSEntityDescription entityForName:@"FeedEntry" inManagedObjectContext:managedObjectContext]; [fetchRequest setEntity:entity]; // Edit the sort key as appropriate. NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"authorname" ascending:NO]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; NSEntityDescription *tagEntity = [NSEntityDescription entityForName:@"TagValues" inManagedObjectContext:self.managedObjectContext]; NSPredicate *tagPredicate = [NSPredicate predicateWithFormat:@"tagName LIKE[c] 'nyt'"]; NSFetchRequest *tagRequest = [[NSFetchRequest alloc] init]; [tagRequest setEntity:tagEntity]; [tagRequest setPredicate:tagPredicate]; NSError *error = nil; NSArray* predicates = [self.managedObjectContext executeFetchRequest:tagRequest error:&error]; TagValues *tv = (TagValues*) [predicates objectAtIndex:0]; NSLog(tv.tagName); // it is nyt here... NSPredicate *predicate = [NSPredicate predicateWithFormat:@"tag IN %@", predicates]; [fetchRequest setPredicate:predicate]; // Edit the section name key path and cache name if appropriate. // nil for section name key path means "no sections". NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"]; aFetchedResultsController.delegate = self; self.fetchedResultsController = aFetchedResultsController; --

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• dynamic data - all option in paging

  - by Sharique

  I'm developing a dynamic data web app. On list.aspx page it has GridViewPager control for paging, it option in drop down list as 10,20,.. rows in a page like that, but it does not an option show all rows in a page. How I can add "All" option in it?

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• How to display data uri scheme into a C# WebBrowser Controler

  - by Emanuel

  How can I show an image base64 encoded using WebBrowser control in C#? I used the following code: <img src="data:image/gif;base64,/9j/4AAQSkZJRgABAgAAZABkAA7AAR R894ADkFkb2JlAGTAAAAAAfbAIQABAMDAwMDBAMDBAYEAwQGBwUEBAUHCAYGBw ... uhWkvoJfQO2z/rf4VpL6CX0Dts/63+FaS+gl9A7bP+tthWkvoJfQODCde4qfcg RiNWK3UyUeX9CXpHU43diOK915X5fG/reux5hUAUBftZ" /> but no image is displayed. One solution would be to save images locally and using absolute path, but this is not desirable. Any idea? Thanks.

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• Normalization of database for timesheet tool and ensure data integrity

  - by fireeyedboy

  I'm creating a timesheet application. I have the following entities (amongst others): Company Employee = an employee associated with a company Client = a client associated with a company So far I have the following (abbreviated) database setup: Company - id - name Employee - id - companyId (FK to Company.id) - name Client - id - companyId (FK to Company.id) - name Now, I want an employee to be associated with a client, but only if that client is associated with the company the employee works for. How would you guarantee this data integrity on a database level? Or should I just depend on the application to guarantee this data integrity? I thought about creating a many to many table like this: EmployeeClient - employeeId (FK to Employee.id) - companyId \ (combined FK to Client.companyId, Client.id) - clientId / Thus, when I insert a client for an employee along with the employee's company id, the database should prevent this when the client is not associated with the employee's company id. Does this make sense? Because this still doesn't guarantee the employee is associated with the company. How do you deal with these things? UPDATE The scenario is as followed: A company has multiple employees. Employees will only be linked to one company. A company has multiple clients also. Clients will only be linked to one company. (Company is a sandbox, so to speak). An employee of a company can be linked to a client of it's company, but only if the client is part of the company's clientele. In other words: The application will allow a company to create/add employees and create/add clients (hence the companyId FK in the Employee and Client tables). Next, the company will be allowed to assign certain clients to certain of it's employees (EmployeeClient table). Imagine an employee working on projects for a few clients for which s/he can write billable hours, but the employee must not be allowed to write billable hours for clients they are not assigned to by their employer (the company). So, employees will not automatically have access to all their company's clients, but only to those that the company has selected for them. Hopefully this has shed some more light on the matter.

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• Multi-property "transactions" in Core Data / NSManagedObject / NSFetchedResultsController?

  - by Martijn Thé

  Hi, Is it possible to set multiple properties of an NSManagedObject and have the NSFetchedResultsController call controllerDidChangeContent: only once? In other words, is it possible to say something like: [managedObject beginChanges]; [managedObject setPropertyA:@"Foo"]; [managedObject setPropertyB:@"Bar"]; [managedObject commitChanges]; and then have the NSFetchedResultsController call controllerDidChangeContent: (and the other methods) only one time? Thanks!

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• Need to tab out of ActiveX control in browser

  - by John Donoghue

  When tabbing through controls in an ActiveX control hosted in IE, once I get to the last control the tab key no longer does anything. I would like it to move the focus outside the ActiveX control to the next html control. This works fine when the ActiveX control is hosted in a WinForms app, does anybody know how to make this work in the browser? It may also be relevant that the ActiveX control is a simple wrapper around a WPF control.

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• Getting the data out of the data Formview

  - by QEDDave

  I have an ASP pg with a formview list control on it that hooks up to a sql database customer table I want to access the customer name outside the form. How do I: A) access the bound text box in the form view template? Something like Text1.text=formview1.customername.text (that doesn't work but that's the kinda thing) B) access the database field in the table that the sqlsource connects to to feed the formview Really appreciate the help. I bet it's easy to do but I'm just not getting there.

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• Do You Develop Your PL/SQL Directly in the Database?

  - by thatjeffsmith

  I know this sounds like a REALLY weird question for many of you. Let me make one thing clear right away though, I am NOT talking about creating and replacing PLSQL objects directly into a production environment. Do we really need to talk about developers in production again? No, what I am talking about is a developer doing their work from start to finish in a development database. These are generally available to a development team for building the next and greatest version of your databases and database applications. And of course you are using a third party source control system, right? Last week I was in Tampa, FL presenting at the monthly Suncoast Oracle User’s Group meeting. Had a wonderful time, great questions and back-and-forth. My favorite heckler was there, @oraclenered, AKA Chet Justice.  I was in the middle of talking about how it’s better to do your PLSQL work in the Procedure Editor when Chet pipes up - Don’t do it that way, that’s wrong Just press play to edit the PLSQL directly in the database Or something along those lines. I didn’t get what the heck he was talking about. I had been showing how the Procedure Editor gives you much better feedback and support when working with PLSQL. After a few back-and-forths I got to what Chet’s main objection was, and again I’m going to paraphrase: You should develop offline in your SQL worksheet. Don’t do anything in the database until it’s done. I didn’t understand. Were developers expected to be able to internalize and mentally model the PL/SQL engine, see where their errors were, etc in these offline scripts? No, please give Chet more credit than that. What is the ideal Oracle Development Environment? If I were back in the ‘real world’ of database development, I would do all of my development outside of the ‘dev’ instance. My development process looks a little something like this: Do I have a program that already does something like this – copy and paste Has some smart person already written something like this – copy and paste Start typing in the white-screen-of-panic and bungle along until I get something that half-works Tweek, debug, test until I have fooled my subconscious into thinking that it’s ‘good’ As you might understand, I don’t want my co-workers to see the evolution of my code. It would seriously freak them out and I probably wouldn’t have a job anymore (don’t remind me that I already worked myself out of development.) So here’s what I like to do: Run a Local Instance of Oracle on my Machine and Develop My Code Privately I take a copy of development – that’s what source control is for afterall – and run it where no one else can see it. I now get to be my own DBA. If I need a trace – no problem. If I want to run an ASH report, no worries. If I need to create a directory or run some DataPump jobs, that’s all on me. Now when I get my code ‘up to snuff,’ then I will check it into source control and compile it into the official development instance. So my teammates suddenly go from seeing no program, to a mostly complete program. Is this right? If not, it doesn’t seem wrong to me. And after talking to Chet in the car on the way to the local cigar bar, it seems that he’s of the same opinion. So what’s so wrong with coding directly into a development instance? I think ‘wrong’ is a bit strong here. But there are a few pitfalls that you might want to look out for. A few come to mind – and I’m sure Chet could add many more as my memory fails me at the moment. But here goes: Development instance isn’t properly backed up – would hate to lose that work Development is wiped once a week and copied over from Prod – don’t laugh Someone clobbers your code You accidentally on purpose clobber someone else’s code The more developers you have in a single fish pond, the greater chance something ‘bad’ will happen This Isn’t One of Those Posts Where I Tell You What You Should Be Doing I realize many shops won’t be open to allowing developers to stage their own local copies of Oracle. But I would at least be aware that many of your developers are probably doing this anyway – with or without your tacit approval. SQL Developer can do local file tracking, but you should be using Source Control too! I will say that I think it’s imperative that you control your source code outside the database, even if your development team is comprised of a single developer. Store your source code in a file, and control that file in something like Subversion. You would be shocked at the number of teams that do not use a source control system. I know I continue to be shocked no matter how many times I meet another team running by the seat-of-their-pants. I’d love to hear how your development process works. And of course I want to know how SQL Developer and the rest of our tools can better support your processes. And one last thing, if you want a fun and interactive presentation experience, be sure to have Chet in the room

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• SQL Server Table Polling by Multiple Subscribers

  - by Daniel Hester

  Background Designing Stored Procedures that are safe for multiple subscribers (to call simultaneously) can be challenging.  For example let’s say that you want multiple worker processes to poll a shared work queue that’s encapsulated as a SQL Table. This is a common scenario and through experience you’ll find that you want to use Table Hints to prevent unwanted locking when performing simultaneous queries on the same table. There are three table hints to consider: NOLOCK, READPAST and UPDLOCK. Both NOLOCK and READPAST table hints allow you to SELECT from a table without placing a LOCK on that table. However, SELECTs with the READPAST hint will ignore any records that are locked due to being updated/inserted (or otherwise “dirty”), whereas a SELECT with NOLOCK ignores all locks including dirty reads. For the initial update of the flag (that marks the record as available for subscription) I don’t use the NOLOCK Table Hint because I want to be sensitive to the “active” records in the table and I want to exclude them.  I use an Update Lock (UPDLOCK) in conjunction with a WHERE clause that uses a sub-select with a READPAST Table Hint in order to explicitly lock the records I’m updating (UPDLOCK) but not place a lock on the table when selecting the records that I’m going to update (READPAST). UPDATES should be allowed to lock the rows affected because we’re probably changing a flag on a record so that it is not included in a SELECT from another subscriber. On the UPDATE statement we should explicitly use the UPDLOCK to guard against lock escalation. A SELECT to check for the next record(s) to process can result in a shared read lock being held by more than one subscriber polling the shared work queue (SQL table). It is expected that more than one worker process (or server) might try to process the same new record(s) at the same time. When each process then tries to obtain the update lock, none of them can because another process has a shared read lock in place. Thus without the UPDLOCK hint the result would be a lock escalation deadlock; however with the UPDLOCK hint this condition is mitigated against. Note that using the READPAST table hint requires that you also set the ISOLATION LEVEL of the transaction to be READ COMMITTED (rather than the default of SERIALIZABLE). Guidance In the Stored Procedure that returns records to the multiple subscribers: Perform the UPDATE first. Change the flag that makes the record available to subscribers.  Additionally, you may want to update a LastUpdated datetime field in order to be able to check for records that “got stuck” in an intermediate state or for other auditing purposes. In the UPDATE statement use the (UPDLOCK) Table Hint on the UPDATE statement to prevent lock escalation. In the UPDATE statement also use a WHERE Clause that uses a sub-select with a (READPAST) Table Hint to select the records that you’re going to update. In the UPDATE statement use the OUTPUT clause in conjunction with a Temporary Table to isolate the record(s) that you’ve just updated and intend to return to the subscriber. This is the fastest way to update the record(s) and to get the records’ identifiers within the same operation. Finally do a set-based SELECT on the main Table (using the Temporary Table to identify the records in the set) with either a READPAST or NOLOCK table hint.  Use NOLOCK if there are other processes (besides the multiple subscribers) that might be changing the data that you want to return to the multiple subscribers; or use READPAST if you're sure there are no other processes (besides the multiple subscribers) that might be updating column data in the table for other purposes (e.g. changes to a person’s last name).  NOLOCK is generally the better fit in this part of the scenario. See the following as an example: CREATE PROCEDURE [dbo].[usp_NewCustomersSelect] AS BEGIN -- OVERRIDE THE DEFAULT ISOLATION LEVEL SET TRANSACTION ISOLATION LEVEL READ COMMITTED -- SET NOCOUNT ON SET NOCOUNT ON -- DECLARE TEMP TABLE -- Note that this example uses CustomerId as an identifier; -- you could just use the Identity column Id if that’s all you need. DECLARE @CustomersTempTable TABLE ( CustomerId NVARCHAR(255) ) -- PERFORM UPDATE FIRST -- [Customers] is the name of the table -- [Id] is the Identity Column on the table -- [CustomerId] is the business document key used to identify the -- record globally, i.e. in other systems or across SQL tables -- [Status] is INT or BIT field (if the status is a binary state) -- [LastUpdated] is a datetime field used to record the time of the -- last update UPDATE [Customers] WITH (UPDLOCK) SET [Status] = 1, [LastUpdated] = GETDATE() OUTPUT [INSERTED].[CustomerId] INTO @CustomersTempTable WHERE ([Id] = (SELECT TOP 100 [Id] FROM [Customers] WITH (READPAST) WHERE ([Status] = 0) ORDER BY [Id] ASC)) -- PERFORM SELECT FROM ENTITY TABLE SELECT [C].[CustomerId], [C].[FirstName], [C].[LastName], [C].[Address1], [C].[Address2], [C].[City], [C].[State], [C].[Zip], [C].[ShippingMethod], [C].[Id] FROM [Customers] AS [C] WITH (NOLOCK), @CustomersTempTable AS [TEMP] WHERE ([C].[CustomerId] = [TEMP].[CustomerId]) END In a system that has been designed to have multiple status values for records that need to be processed in the Work Queue it is necessary to have a “Watch Dog” process by which “stale” records in intermediate states (such as “In Progress”) are detected, i.e. a [Status] of 0 = New or Unprocessed; a [Status] of 1 = In Progress; a [Status] of 2 = Processed; etc.. Thus, if you have a business rule that states that the application should only process new records if all of the old records have been processed successfully (or marked as an error), then it will be necessary to build a monitoring process to detect stalled or stale records in the Work Queue, hence the use of the LastUpdated column in the example above. The Status field along with the LastUpdated field can be used as the criteria to detect stalled / stale records. It is possible to put this watchdog logic into the stored procedure above, but I would recommend making it a separate monitoring function. In writing the stored procedure that checks for stale records I would recommend using the same kind of lock semantics as suggested above. The example below looks for records that have been in the “In Progress” state ([Status] = 1) for greater than 60 seconds: CREATE PROCEDURE [dbo].[usp_NewCustomersWatchDog] AS BEGIN -- TO OVERRIDE THE DEFAULT ISOLATION LEVEL SET TRANSACTION ISOLATION LEVEL READ COMMITTED -- SET NOCOUNT ON SET NOCOUNT ON DECLARE @MaxWait int; SET @MaxWait = 60 IF EXISTS (SELECT 1 FROM [dbo].[Customers] WITH (READPAST) WHERE ([Status] = 1) AND (DATEDIFF(s, [LastUpdated], GETDATE()) > @MaxWait)) BEGIN SELECT 1 AS [IsWatchDogError] END ELSE BEGIN SELECT 0 AS [IsWatchDogError] END END Downloads The zip file below contains two SQL scripts: one to create a sample database with the above stored procedures and one to populate the sample database with 10,000 sample records.  I am very grateful to Red-Gate software for their excellent SQL Data Generator tool which enabled me to create these sample records in no time at all. References http://msdn.microsoft.com/en-us/library/ms187373.aspx http://www.techrepublic.com/article/using-nolock-and-readpast-table-hints-in-sql-server/6185492 http://geekswithblogs.net/gwiele/archive/2004/11/25/15974.aspx http://grounding.co.za/blogs/romiko/archive/2009/03/09/biztalk-sql-receive-location-deadlocks-dirty-reads-and-isolation-levels.aspx

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• Java: immutability, overuse of stack -- better data structure?

  - by HH

  I overused hashSets but it was slow, then changed to Stacks, speed boost-up. Poly's reply uses Collections.emptyList() as immutable list, cutting out excess null-checkers. No Collections.emptyStack(). Combining the words stack and immutability, from the last experiences, gets "immutable stack" (probably not related to functional prog). Java Api 5 for list interface shows that Stack is an implementing class for list and arraylist, here. The java.coccurrent pkg does not have any immutable Stack data structure. The first hinted of misusing stack. The lack of immutabily in the last and poly's book recommendation leads way to list. Something very primitive, fast, no extra layers, with methods like emptyThing(). Overuse of stack and where I use it DataFile.java: public Stack<DataFile> files; FileObject.java: public Stack<String> printViews = new Stack<String>(); FileObject.java:// private static Stack<Object> getFormat(File f){return (new Format(f)).getFormat();} Format.java: private Stack<Object> getLine(File[] fs,String s){return wF;} Format.java: private Stack<Object> getFormat(){return format;} Positions.java: public static Stack<Integer[]> getPrintPoss(String s,File f,Integer maxViewPerF) Positions.java: Stack<File> possPrint = new Stack<File>(); Positions.java: Stack<Integer> positions=new Stack<Integer>(); Record.java: private String getFormatLine(Stack<Object> st) Record.java: Stack<String> lines=new Stack<String>(); SearchToUser.java: public static final Stack<File> allFiles = findf.getFs(); SearchToUser.java: public static final Stack<File> allDirs = findf.getDs(); SearchToUser.java: private Stack<Integer[]> positionsPrint=new Stack<Integer[]>(); SearchToUser.java: public Stack<String> getSearchResults(String s, Integer countPerFile, Integer resCount) SearchToUser.java: Stack<File> filesToS=Fs2Word.getFs2W(s,50); SearchToUser.java: Stack<String> rs=new Stack<String>(); View.java: public Stack<Integer[]> poss = new Stack<Integer[4]>(); View.java: public static Stack<String> getPrintViewsFileWise(String s,Object[] df,Integer maxViewsPerF) View.java: Stack<String> substrings = new Stack<String>(); View.java: private Stack<String> printViews=new Stack<String>(); View.java: MatchView(Stack<Integer> pss,File f,Integer maxViews) View.java: Stack<String> formatFile; View.java: private Stack<Search> files; View.java: private Stack<File> matchingFiles; View.java: private Stack<String> matchViews; View.java: private Stack<String> searchMatches; View.java: private Stack<String> getSearchResults(Integer numbResults) Easier with List: AllDirs and AllFs, now looping with push, but list has more pow. methods such as addAll [OLD] From Stack to some immutable data structure How to get immutable Stack data structure? Can I box it with list? Should I switch my current implementatios from stacks to Lists to get immutable? Which immutable data structure is Very fast with about similar exec time as Stack? No immutability to Stack with Final import java.io.*; import java.util.*; public class TestStack{ public static void main(String[] args) { final Stack<Integer> test = new Stack<Integer>(); Stack<Integer> test2 = new Stack<Integer>(); test.push(37707); test2.push(80437707); //WHY is there not an error to remove an elment // from FINAL stack? System.out.println(test.pop()); System.out.println(test2.pop()); } }

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• Difference Between WCF WCF Ria, and Data Service

  - by Asim Sajjad

  What is the defference between the WCF Service , WCF Ria Services and the data servics.

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• iPhone - Core Data crash on migration

  - by Sergey Zenchenko

  I have problems, when i install app from Xcode all works but if I build app and install it from iTunes I have an error with the database at launch. This happens only than i have changes in the core data model and need to migrate to a new version. At first launch at crashes with message: Thread 0: 0 libSystem.B.dylib 0x00034588 pwrite + 20 1 libsqlite3.dylib 0x000505ec _sqlite3_purgeEligiblePagerCacheMemory + 2808 2 libsqlite3.dylib 0x000243d8 sqlite3_backup_init + 7712 3 libsqlite3.dylib 0x000244ac sqlite3_backup_init + 7924 4 libsqlite3.dylib 0x0000d418 sqlite3_file_control + 4028 5 libsqlite3.dylib 0x000228b4 sqlite3_backup_init + 764 6 libsqlite3.dylib 0x00022dd0 sqlite3_backup_init + 2072 7 libsqlite3.dylib 0x000249a8 sqlite3_backup_init + 9200 8 libsqlite3.dylib 0x00029800 sqlite3_open16 + 11360 9 libsqlite3.dylib 0x0002a200 sqlite3_open16 + 13920 10 libsqlite3.dylib 0x0002ab84 sqlite3_open16 + 16356 11 libsqlite3.dylib 0x00049418 sqlite3_prepare16 + 54056 12 libsqlite3.dylib 0x00002940 sqlite3_step + 44 13 CoreData 0x00011958 _execute + 44 14 CoreData 0x000113e0 -[NSSQLiteConnection execute] + 696 15 CoreData 0x000994be -[NSSQLConnection prepareAndExecuteSQLStatement:] + 26 16 CoreData 0x000be14c -[_NSSQLiteStoreMigrator performMigration:] + 244 17 CoreData 0x000b6c60 -[NSSQLiteInPlaceMigrationManager migrateStoreFromURL:type:options:withMappingModel:toDestinationURL:destinationType:destinationOptions:error:] + 1040 18 CoreData 0x000aceb0 -[NSStoreMigrationPolicy(InternalMethods) migrateStoreAtURL:toURL:storeType:options:withManager:error:] + 92 19 CoreData 0x000ad6f0 -[NSStoreMigrationPolicy migrateStoreAtURL:withManager:metadata:options:error:] + 72 20 CoreData 0x000ac9ee -[NSStoreMigrationPolicy(InternalMethods) _gatherDataAndPerformMigration:] + 880 21 CoreData 0x0000965c -[NSPersistentStoreCoordinator addPersistentStoreWithType:configuration:URL:options:error:] + 1328 At next launches app doesn't loads data from database.

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• WCF Data Service Exception

  - by Ravi

  Hi, I am working on C#.Net with ADO.NET Dataservice WCF Data Services. I try to update one record to relational table, when I reach context.SetLink() I am getting exception("The context is not currently tracking the entity"). I don't know how to solve this problem. My code is specified below. LogNote dbLogNote =logNote; LogSubSession dbLogSubSession = (from p in context.LogSubSession where p.UID == logNote.SubSessionId select p).First<LogSubSession>() as LogSubSession; context.AddToLogNote(dbLogNote); dbLogNote.LogSubSession = dbLogSubSession; context.SetLink(dbLogNote, "LogSubSession", dbLogSubSession); context.SaveChanges(); Here LogSubSession is a primary table and LogNote is a foreign table. I am updating data into foreign table based on primary key table. Thanks

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• C# System.Data.SQLite Designer Code

  - by Nathan

  I've been messing around with the SQLite Designer in Visual Studio 2008 and I have noticed that when I use the generated Insert/Update statements they run extremely slow. Example: I have a data table with four columns and 5700 rows it took ~5 mins to insert the data into the database table However, I wrote my own database connection and insert methods using parameters and a single transaction and the same 5700 rows were inserted in under 1 second. Why is the generated code so slow and what is benefit to even using it? Thanks. Nathan

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• Core Data Error "Fetch Request must have an entity"

  - by Graeme

  Hi, I've attempted to add the TopSongs parser and Core Data files into my application, and it now builds succesfully, with no errors or warning messages. However, as soon as the app loads, it crashes, giving the following reason: *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'executeFetchRequest:error: A fetch request must have an entity.' I have renamed all files, including the .xcdatamodel file. Could this be the problem (the renaming of the .xcdatamodel)? I'm assuming this error means that no data can be found. Thanks.

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