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Articles indexed in June 2010

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  • Postgresql: Implicit lock acquisition from foreign-key constraint evaluation

    - by fennec
    So, I'm being confused about foreign key constraint handling in Postgresql. (version 8.4.4, for what it's worth). We've got a couple of tables, mildly anonymized below: device: (id, blah, blah, blah, blah, blah x 50)… primary key on id whooooole bunch of other junk device_foo: (id, device_id, left, right) Foreign key (device_id) references device(id) on delete cascade; primary key on id btree index on 'left' and 'right' So I set out with two database windows to run some queries. db1> begin; lock table device in exclusive mode; db2> begin; update device_foo set left = left + 1; The db2 connection blocks. It seems odd to me that an update of the 'left' column on device_stuff should be affected by activity on the device table. But it is. In fact, if I go back to db1: db1> select * from device_stuff for update; *** deadlock occurs *** The pgsql log has the following: blah blah blah deadlock blah. CONTEXT: SQL statement "SELECT 1 FROM ONLY "public"."device" x WHERE "id" OPERATOR(pg_catalog.=) $1 FOR SHARE OF X: update device_foo set left = left + 1; I suppose I've got two issues: the first is that I don't understand the precise mechanism by which this sort of locking occurs. I have got a couple of useful queries to query pg_locks to see what sort of locks a statement invokes, but I haven't been able to observe this particular sort of locking when I run the update device_foo command in isolation. (Perhaps I'm doing something wrong, though.) I also can't find any documentation on the lock acquisition behavior of foreign-key constraint checks. All I have is a log message. Am I to infer from this that any change to a row will acquire an update lock on all the tables which it's foreign-keyed against? The second issue is that I'd like to find some way to make it not happen like that. I'm ending up with occasional deadlocks in the actual application. I'd like to be able to run big update statements that impact all rows on device_foo without acquiring a big lock on the device table. (There's a lot of access going on in the device table, and it's kind of an expensive lock to get.)

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  • javascript location

    - by Happy
    This checks "if we are on movies.php page": if (location.href.match(/movies.php/)) { // something happens } how to add for this (like or) "if we are on music.php page"?

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  • Which are the most useful techniques for faster Bluetooth?

    - by Mike Howard
    Hi. I'm adding peer-to-peer bluetooth using GameKit to an iPhone shoot-em-up, so speed is vital. I'm sending about 40 messages a second each way, most of them with the faster GKSendDataUnreliable, all serializing with NSCoding. In testing between a 3G and 3GS, this is slowing the 3G down a lot more than I'd like. I'm wondering where I should concentrate my efforts to speed it up. How much slower is GKSendDataReliable? For the few packets that have to get there, would it be faster to send a GKSendDataUnreliable and have the peer send an acknowledgement so I can send again if I don't get the Ack within, say, 100ms? How much faster would it be to create the NSData instance using a regular C array rather than archiving with the NSCoding protocol? Is this serialization process (for about a dozen floats) just as slow as you'd expect from an object creation/deallocation overhead, or is something particularly slow happening? I heard that (for example) sending four seperate sets of data is much, much slower, than sending one piece of data four times the size. Would I make a significant saving by sending separate packets of data that wouldn't always go together in the same packet when they happen at the same time? Are there any other bluetooth performance secrets I've missed? Thanks for your help.

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  • How can I fix video tearing and pausing on Windows XP Flash videos?

    - by xvs
    I have what should be a reasonably fast PC: it's a Quadcore Intel 6600 at 2.4 GHz, 4MB of RAM, an ATI 3800 series video card and an LG L246WP monitor, which I selected particularly because it was supposed to work well with video and have no trails or other artifacts. So I should be able to play video with no problems. And I can, as long as that video isn't Flash video. With Flash, what I see is tearing, especially during pans, and pausing -- every few seconds the video pauses for about 300ms while the sound stays continuous. I tried going into the video card setup and changing vertical sync, pulldown detection, windows media video acceleration, deinterlacing and triple buffering. but no combination of settings I've tried has changed or corrected the problem in any way. I've also tried enabling and disabling hardware acceleration in the Flash settings, to no avail. This problem happens whether or not the video is streaming or has fully streamed in before playing. So, what can I do? Is this just a flash issue or is there a way to get it to work?

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  • What does the 'X' in .aspx, docx, xlsx, etc... represent?

    - by Serapth
    It's one of those things you just take for granted until one day someone asks you and you realize you can't answer it. Much like for years I never questioned the use of 1033 directories in Microsoft products for years until one day, someone asked me about it. Around the release of .NET and Office 2007, Microsoft added an x to basically all of their extensions and I frankly took it as representing XML, but that simply doesn't make sense with .aspx. So, I realize this is a very non technical question, but now that the question has been asked of me and my googling hasn't given me an answer, can anyone tell me with authority what the X represents? Is it extended? Xml? Or is there no meaning behind it?

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  • Black Screen on Startup even after running chkdsk

    - by phwd
    I started an old (Dell Inspiron 2200) the startup goes all the way to Microsoft Windows XP Logo then I get a black screen. I am still able to move the cursor but that is about it. I tried running Recovery console (from CD) with chkdsk command. First time it said they were errors. I decided to do a fixboot and see if the errors went away. They did. Restarted and still no luck. If there are commands that I can call either from recovery console or elsewhere to further describe the problem please tell me and I will re-edit the question. srvtag:7XNSG81 Also what are my full range of options before wiping the hard-drive (if that is even the problem) I want to exhaust all options before replacing hardware.

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  • Can I load lots of data only once and use it on each request?

    - by eikes
    Is there a way to load a big data object into the memory, which usually has to be loaded at each request, only once? In Java you can instantiate an object in a servlet when this servlet is loaded, but once it's there you can use it in any request. Example is below. Can this be done in PHP? public class SampleServlet extends HttpServlet { private static HugeGraphObject hgo; public void init() { hgo = HugeGraphObjectFactory.get(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String param = request.getParameter("q"); response.getWriter().write(hgo.getSomeThing(param)); } }

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  • C++: Keep track of times function is called.

    - by Brundle
    Keeping track of how many times a function is called is easy when passing the counter as an argument into the function. It's also easy when returning a one from the called function. But, I do not want to go that route. The reason behind this is because it seems like bad programming (letting the function know too much information). Is there a better way to keep track of how many times this function has been called? I'm just looking for concepts that I could study. Providing code examples is not neccessary, but might be helpful.

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  • How to simulate an unhandled exception in Java

    - by Martin Wiboe
    Hi, I am creating some multi-threaded code, and I have created a JobDispatcher class that creates threads. I want this object to handle any unhandled exceptions in the worker threads, and so I am using Thread.setUncaughtExceptionHandler(this); Now, I would like to test this functionality - how can I generate an unhandled exception in the run() method of my worker object? Thanks, Martin

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  • subqueries linq

    - by user297378
    Hey all I am trying to do a subquery in linq but the subquery is a value and it seems to not be working, can anyone help out? I am using the entit frame work I keep getting and int to string error not sure why. from lrp in remit.log_record_product join lr in remit.log_record on lrp.log_record_id equals lr.log_record_id where (lrp.que_submit_date >= RadDatePickerStartDate.SelectedDate) && (lrp.que_submit_date <= RadDatePickerEndDate.SelectedDate) select new { lrp.que_submit_date, lr.officer_name, lr.c_fname, lr.c_lname, lrp.price_sold, lrp.product_cost, gap_account_number = (from gap in remit.gap_contracts where gap.log_record_product_id == lrp.log_record_product_id select gap.account_number), iui_account_number = (from iui in remit.iui_contracts where iui.log_record_product_id == lrp.log_record_product_id select iui.account_number), dp_account_number = (from dp in remit.dp_contracts where dp.log_record_product_id == lrp.log_record_product_id select dp.account_number), mpd_account_number = (from mpd in remit.mbp_contracts where mpd.log_record_product_id == lrp.log_record_product_id select mpd.product_account_number) }

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  • How to transfer Eclipse workspace and project from Windows to Linux and Mac

    - by Li Ma
    We have a a product developed on Windows for years. The product is composed of one Eclipse workspace and about 20 projects. On Windows, we ask every developer check out projects into d:\dev\product folder, and copy a unified Workspace to d:\dev\prod_workspace. This way, whenever a new machine is set, we simply copy files to the same folder, and we can start working immediately. No We need to move our development environment to Linux and Mac. But there's no D:\ on Unix. And home folder for Linux is mostly like /home/username and /Users/username for Mac. We found Eclipse keeps absolute path in workspace when referring to projects, so simply copy workspace over does not work anymore. Even when we manually create/configure workspace on a Linux machine, it still cannot be copied over to another user, because the absolute path is changed. I guess our goal is to allow easy setup of development environment. Do you have any suggestion to move eclipse workspace around? Thanks! Li

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  • How to use accessors within the same class in Objective C?

    - by Azeworai
    Hi, I have a few properties defined in my header file like so @property (assign) bool connectivity_N; @property (assign) bool isConnected_N; In my implementation file I have an init and the synthesized properties like so @implementation Map @synthesize connectivity_N; @synthesize isConnected_N; a init to set the initial values like so -(id) init { if( (self=[super init]) ) { //initialise default properties self.connectivity_N=NO; self.isConnected_N=NO; } return self; } I'm running into an error that states Error: accessing unknown 'connectivity_N' class method. In this public method within the class +(bool) isConnectable:(directions) theDirection{ bool isTheDirectionConnectable= NO; switch (theDirection) { case north: isTheDirectionConnectable= self.connectivity_N; break; I'm not sure why is this so as I'm trying to grab the value of the property. According to the apple developer documentation "The default names for the getter and setter methods associated with a property are propertyName and setPropertyName: respectively—for example, given a property “foo”, the accessors would be foo and setFoo:" That has given me a clue that I've done something wrong here, I'm fairly new to objective C so would appreciate anyone who spends the time to explain this to me. Thanks!

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  • PNG composition using GD and PHP

    - by Dominic
    I am trying to take a rectangular png and add depth using GD by duplicating the background and moving it down 1 pixel and right 1 pixel. I am trying to preserve a transparent background as well. I am having a bunch of trouble with preserving the transparency. Any help would be greatly appreciated. Thanks! $obj = imagecreatefrompng('rectangle.png'); $depth = 5; $obj_width = imagesx($obj); $obj_height = imagesy($obj); imagesavealpha($obj, true); for($i=1;$i<=$depth;$i++){ $layer = imagecreatefrompng('rectangle.png'); imagealphablending( $layer, false ); imagesavealpha($layer, true); $new_obj = imagecreatetruecolor($obj_width+$i,$obj_height+$i); $new_obj_width = imagesx($new_obj); $new_obj_height = imagesy($new_obj); imagealphablending( $new_obj, false ); imagesavealpha($new_obj, true); $trans_color = imagecolorallocatealpha($new_obj, 0, 0, 0, 127); imagefill($new_obj, 0, 0, $trans_color); imagecopyresampled($new_obj, $layer, $i, $i, 0, 0, $obj_width, $obj_height, $obj_width, $obj_height); //imagesavealpha($new_obj, true); //imagesavealpha($obj, true); } header ("Content-type: image/png"); imagepng($new_obj); imagedestroy($new_obj);

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  • Securely store a password in program code?

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

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  • How to assign a numbering scheme to TreeNodes based on position

    - by TChristian
    I have a TreeView control in a Windows Forms application that is displaying my own subclass of TreeNode. I need to display a number along with each node's text indicating its position in the tree, like 1 for the root, 1.1 for its first child, 1.2 for its second child, etc. I'm using C# with .NET 2.0 The best that I can come up with is, after the tree is built, go to each node, recursively find the parent and append the parent's sibling number to the front of the node's text until you reach the root.

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  • Regex AND operator

    - by user366735
    Based on this answer http://stackoverflow.com/questions/469913/regular-expressions-is-there-an-and-operator I tried the following on http://regexpal.com/ but was unable to get it to work. What am missing? Does javascript not support it? Regex: (?=foo)(?=baz) String: foo,bar,baz

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  • Unable to attach "AdventureWorks2008" Sample Database to a named Instance in SQL Server 2008

    - by uzorick
    First of all "Northwind" and "AdventureWorksDW2008" databases attached without problem, but "AdventureWorks2008" fails with the following error. // Msg 5120, Level 16, State 105, Line 1 Unable to open the physical file "C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\Documents". Operating system error 2: "2(The system cannot find the file specified.)". Msg 5105, Level 16, State 14, Line 1 A file activation error occurred. The physical file name 'C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\Documents' may be incorrect. Diagnose and correct additional errors, and retry the operation. Msg 1813, Level 16, State 2, Line 1 Could not open new database 'AdventureWorks2008'. CREATE DATABASE is aborted. // PS: I did not use the default database instance "MSSQLSERVER" during install, so Where is it finding this path "C:...\MSSQL10.MSSQLSERVER...\Documents"?

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  • What does /*!*/ mean in C#?

    - by Tristan
    I'm new to C# and am reading code with /*!*/ in what seem like strange places. For instance class methods defined as: protected override OptionsParser/*!*/ CreateOptionsParser() protected override void ParseHostOptions(string/*!*/[]/*!*/ args) Unfortunately /*!*/ is not googleable. What does it mean?

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  • Troubleshooting Errors When Embedding Type Information (Doug Rothaus)

    Visual Studio 2010 has a new feature, Embed Interop Types, that can simplify application deployment and solve those pesky issues that can arise when using COM Interop and Primary Interop Assemblies (PIAs). If you’ve ever had to ship multiple versions of an application that automates Microsoft Office where the only difference between your published versions is the version of the PIA (to match different Office versions), then this feature is for you. You enable type embedding when you reference...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Best/Preferred software for photography.

    - by chills42
    I am just getting into photography as a hobby, and am looking for some good tools for image uploading/browsing/editing. I am currently using the Canon EOS utility that came with the camera for uploading, Picasa for browsing, and GIMP for editing. Pros: The files are stored using the standard file system (no proprietary library like iPhoto) Great photo editing possibilities Free (except the Canon Utility, but that was bundled) Cons: Multiple programs Hard to view the Exif Data (I like the way that iPhoto displays the data) Over-simplified editing tools in Picasa What other tools should I look into? Also, I occasionally shoot in RAW, and would prefer Mac support (better monitor), but I also have windows and linux machines.

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  • Backup windows image to thumb drive?

    - by Dean
    I recently bought a new netbook from Malasia. It doesn't have a brand name, or officially supporting drivers. It came with a version of windows, and working drivers for all the hardware - but I want to install Ubuntu on here. Being a netbook, it has no CD/DVD drive. I want some free easy to use software to image the entire drive onto a thumb drive, which I could later use to boot up a recovery program to reinstall windows, should I fail to get all the hardware supported on Linux. I have already done some research and found driver backup/restore software in this thread, and will probably use that failing a more all-encompasing solution.

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