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• Empty Postbacks on ASP.NET pages

  - by AaronLS

  We are having a problem that seems to only be a problem when accessing our websites from internal intranet machines. When logged into the domain, and accessing our websites, postbacks are not working. Basically the page behaves as if it were refreshed and nothing was changed. When logging the GETs and POSTs with an HTTP analyzer, the post is complete empty and the ContentLength is 0. It is also very sporadic, but seems to be happening fairly often. In the case where it failed, we could see that there was an extra item in the Header for the POST, it was "Authorization" and the value was the word "Negotiate " followed by a space and then a bunch of characters and two equal symbols at the end, which looked like some kind of base64 encoded value. In a case where it succeeded, this Authorization item was no in the header, but I have logged more than one successful cases to know if that is consistent. We have seen this occur only with IE8 so far, and when it occurs it is sometimes sporadic. I can close and open the browser and it will begin working sometimes, and other times it is still broken. What might be causing the postback to be empty? This means the viewstate is not sent to the server which makes the page basically broken. It seems to certainly be a client side issue, but not sure if it's not aggravated by some server settings. Thanks in advance.

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• Permuting a binary tree without the use of lists

  - by Banang

  I need to find an algorithm for generating every possible permutation of a binary tree, and need to do so without using lists (this is because the tree itself carries semantics and restraints that cannot be translated into lists). I've found an algorithm that works for trees with the height of three or less, but whenever I get to greater hights, I loose one set of possible permutations per height added. Each node carries information about its original state, so that one node can determine if all possible permutations have been tried for that node. Also, the node carries information on weather or not it's been 'swapped', i.e. if it has seen all possible permutations of it's subtree. The tree is left-centered, meaning that the right node should always (except in some cases that I don't need to cover for this algorithm) be a leaf node, while the left node is always either a leaf or a branch. The algorithm I'm using at the moment can be described sort of like this: if the left child node has been swapped swap my right node with the left child nodes right node set the left child node as 'unswapped' if the current node is back to its original state swap my right node with the lowest left nodes' right node swap the lowest left nodes two childnodes set my left node as 'unswapped' set my left chilnode to use this as it's original state set this node as swapped return null return this; else if the left child has not been swapped if the result of trying to permute left child is null return the permutation of this node else return the permutation of the left child node if this node has a left node and a right node that are both leaves swap them set this node to be 'swapped' The desired behaviour of the algoritm would be something like this: branch / | branch 3 / | branch 2 / | 0 1 branch / | branch 3 / | branch 2 / | 1 0 <-- first swap branch / | branch 3 / | branch 1 <-- second swap / | 2 0 branch / | branch 3 / | branch 1 / | 0 2 <-- third swap branch / | branch 3 / | branch 0 <-- fourth swap / | 1 2 and so on... Sorry for the ridiculisly long and waddly explanation, would really, really apreciate any sort of help you guys could offer me. Thanks a bunch!

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• Queries within queries: Is there a better way?

  - by mririgo

  As I build bigger, more advanced web applications, I'm finding myself writing extremely long and complex queries. I tend to write queries within queries a lot because I feel making one call to the database from PHP is better than making several and correlating the data. However, anyone who knows anything about SQL knows about JOINs. Personally, I've used a JOIN or two before, but quickly stopped when I discovered using subqueries because it felt easier and quicker for me to write and maintain. Commonly, I'll do subqueries that may contain one or more subqueries from relative tables. Consider this example: SELECT (SELECT username FROM users WHERE records.user_id = user_id) AS username, (SELECT last_name||', '||first_name FROM users WHERE records.user_id = user_id) AS name, in_timestamp, out_timestamp FROM records ORDER BY in_timestamp Rarely, I'll do subqueries after the WHERE clause. Consider this example: SELECT user_id, (SELECT name FROM organizations WHERE (SELECT organization FROM locations WHERE records.location = location_id) = organization_id) AS organization_name FROM records ORDER BY in_timestamp In these two cases, would I see any sort of improvement if I decided to rewrite the queries using a JOIN? As more of a blanket question, what are the advantages/disadvantages of using subqueries or a JOIN? Is one way more correct or accepted than the other?

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• Is anyone familiar with SDPT.clsSDPT?

  - by David Stratton

  Normally I wouldn't ask this kind of question here, but I'm desperate at this point. I'm attempting to support a classic ASP app written by a predecessor who is no longer available. Keeping it short, several applications use a dll to perform encryption of sensitive data. This dll is named SDPT.dll, and the line of code used to create an object is set objSDPT = server.CreateObject("SDPT.clsSDPT") At this point, I am getting errors in a critical app on one of my servers, and I've actually hit a dead end. The error is a standard "Server.CreateObject Failed" message, which I know how to troubleshoot in most cases. However, in this case, all of my normal tries, plus several hours of Google searches are coming up with nothing that works. At this point, I'm not so much looking for help in troubleshooting the issue as I am in finding any sort of reference on this third party component. Even finding that is proving to be difficult, so I'm resorting to asking any of the seasoned developers that hang out here if they are familiar with this product, who it was developed by, and if any documentation on it exists anywhere.

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• Error in merging two sequences of timestamps to yield strings

  - by AruniRC

  The code sorts two input sequences - seq01 and seq02 - on the basis of their timestamp values and returns a sequence that denotes which sequence is to be read for the values to be in order. For cases where seq02's timestamp value is lesser than seq01's timestamp value we yield a "2" to the sequence being returned, else a "1". These denote whether at that point seq01 is to be taken or seq02 is to be taken for the data to be in order (by timestamp value). let mergeSeq (seq01:seq<_>) (seq02:seq<_>) = seq { use iter01 = seq01.GetEnumerator() use iter02 = seq02.GetEnumerator() while iter01.MoveNext() do let _,_,time01 = iter01.Current let _,_,time02 = iter02.Current while time02 < time01 && iter02.MoveNext() do yield "2" yield "1" } To test it in the FSI created two sequences a and b, a={1;3;5;...} and b={0;2;4;...}. So the expected values for let c = mergeSeq a b would have been {"2","1","2","1"...}. However I am getting this error: error FS0001: The type ''a * 'b * 'c' does not match the type 'int' EDIT After correcting: let mergeSeq (seq01:seq<_>) (seq02:seq<_>) = seq { use iter01 = seq01.GetEnumerator() use iter02 = seq02.GetEnumerator() while iter01.MoveNext() do let time01 = iter01.Current let time02 = iter02.Current while time02 < time01 && iter02.MoveNext() do yield "2" yield "1" } After running this, there's another error: call MoveNext. Somehow the iteration is not being performed.

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• Sharing same vector control between different places

  - by Alexander K

  Hi everyone, I'm trying to implement the following: I have an Items Manager, that has an Item class inside. Item class can store two possible visual representations of it - BitmapImage(bitmap) and UserControl(vector). Then later, in the game, I need to share the same image or vector control between all possible places it takes place. For example, consider 10 trees on the map, and all point to the same vector control. Or in some cases this can be bitmap image source. So, the problem is that BitmapImage source can be easily shared in the application by multiple UIElements. However, when I try to share vector control, it fails, and says Child Element is already a Child element of another control. I want to know how to organize this in the best way. For example replace UserControl with other type of control, or storage, however I need to be sure it supports Storyboard animations inside. The code looks like this: if (bi.item.BitmapSource != null) { Image previewImage = new Image(); previewImage.Source = bi.item.BitmapSource; itemPane.ItemPreviewCanvas.Children.Add(previewImage); } else if (bi.item.VectorSource != null) { UserControl previewControl = bi.item.VectorSource; itemPane.ItemPreviewCanvas.Children.Add(previewControl); } Thanks in advance

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• How Can I Find a List of All Exceptions That a Given Library Function Throws in Python?

  - by b14ck

  Sorry for the long title, but it seems most descriptive for my question. Basically, I'm having a difficult time finding exception information in the official python documentation. For example, in one program I'm currently writing, I'm using the shutil libary's move function: from shutil import move move('somefile.txt', '/tmp/somefile.txt') That works fine, as long as I have write access to /tmp/, there is enough diskspace, and if all other requirements are satisfied. However, when writing generic code, it is often difficult to guarantee those factors, so one usually uses exceptions: from shutil import move try: move('somefile.txt', '/tmp/somefile.txt') except: print 'Move failed for some reason.' I'd like to actually catch the appropriate exceptions thrown instead of just catching everything, but I simply can't find a list of exceptions thrown for most python modules. Is there a way for me to see which exceptions a given function can throw, and why? This way I can make appropriate cases for each exception, eg: from shutil import move try: move('somefile.txt', '/tmp/somefile.txt') except PermissionDenied: print 'No permission.' except DestinationDoesNotExist: print "/tmp/ doesn't exist" except NoDiskSpace: print 'No diskspace available.' Answer points go to whoever can either link me to some relevant documentation that I've somehow overlooked in the official docs, or provide a sure-fire way to figure out exactly which exceptions are thrown by which functions, and why. Thanks!

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• Going "behind Hibernate's back" to update foreign key values without an associated entity

  - by Alex Cruise

  Updated: I wound up "solving" the problem by doing the opposite! I now have the entity reference field set as read-only (insertable=false updatable=false), and the foreign key field read-write. This means I need to take special care when saving new entities, but on querying, the entity properties get resolved for me. I have a bidirectional one-to-many association in my domain model, where I'm using JPA annotations and Hibernate as the persistence provider. It's pretty much your bog-standard parent/child configuration, with one difference being that I want to expose the parent's foreign key as a separate property of the child alongside the reference to a parent instance, like so: @Entity public class Child { @Id @GeneratedValue Long id; @Column(name="parent_id", insertable=false, updatable=false) private Long parentId; @ManyToOne(cascade=CascadeType.ALL) @JoinColumn(name="parent_id") private Parent parent; private long timestamp; } @Entity public class Parent { @Id @GeneratedValue Long id; @OrderBy("timestamp") @OneToMany(mappedBy="parent", cascade=CascadeType.ALL, fetch=FetchType.LAZY) private List<Child> children; } This works just fine most of the time, but there are many (legacy) cases when I'd like to put an invalid value in the parent_id column without having to create a bogus Parent first. Unfortunately, Hibernate won't save values assigned to the parentId field due to insertable=false, updatable=false, which it requires when the same column is mapped to multiple properties. Is there any nice way to "go behind Hibernate's back" and sneak values into that field without having to drop down to JDBC or implement an interceptor? Thanks!

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• Java Generics Class Type Parameter Inference

  - by Pindatjuh

  Given the interface: public interface BasedOnOther<T, U extends BasedList<T>> { public T getOther(); public void staticStatisfied(final U list); } The BasedOnOther<T, U extends BasedList<T>> looks very ugly in my use-cases. It is because the T type parameter is already defined in the BasedList<T> part, so the "uglyness" comes from that T needs to be typed twice. Problem: is it possible to let the Java compiler infer the generic T type from BasedList<T> in a generic class/interface definition? Ultimately, I'd like to use the interface like: class X extends BasedOnOther<BasedList<SomeType>> { public SomeType getOther() { ... } public void staticStatisfied(final BasedList<SomeType> list) { ... } } Instead: class X extends BasedOnOther<SomeType, BasedList<SomeType>> { public SomeType getOther() { ... } public void staticStatisfied(final BasedList<SomeType> list) { ... } }

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• Uva's 3n+1 problem

  - by dmindreader

  I'm solving Uva's 3n+1 problem and I don't get why the judge is rejecting my answer. The time limit hasn't been exceeded and the all test cases I've tried have run correctly so far. import java.io.*; public class NewClass{ /** * @param args the command line arguments */ public static void main(String[] args) throws IOException { int maxCounter= 0; int input; int lowerBound; int upperBound; int counter; int numberOfCycles; int maxCycles= 0; int lowerInt; BufferedReader consoleInput = new BufferedReader(new InputStreamReader(System.in)); String line = consoleInput.readLine(); String [] splitted = line.split(" "); lowerBound = Integer.parseInt(splitted[0]); upperBound = Integer.parseInt(splitted[1]); int [] recentlyused = new int[1000001]; if (lowerBound > upperBound ) { int h = upperBound; upperBound = lowerBound; lowerBound = h; } lowerInt = lowerBound; while (lowerBound <= upperBound) { counter = lowerBound; numberOfCycles = 0; if (recentlyused[counter] == 0) { while ( counter != 1 ) { if (recentlyused[counter] != 0) { numberOfCycles = recentlyused[counter] + numberOfCycles; counter = 1; } else { if (counter % 2 == 0) { counter = counter /2; } else { counter = 3*counter + 1; } numberOfCycles++; } } } else { numberOfCycles = recentlyused[counter] + numberOfCycles; counter = 1; } recentlyused[lowerBound] = numberOfCycles; if (numberOfCycles > maxCycles) { maxCycles = numberOfCycles; } lowerBound++; } System.out.println(lowerInt +" "+ upperBound+ " "+ (maxCycles+1)); } }

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• How to control virtual memory management in linux?

  - by chmike

  I'm writing a program that uses an mmap file to hold a huge buffer organized as an array of 64 MB blocks. The blocks are used to aggregate data received from different hosts through the network. As a consequence the total data size written in each block is not known in advance. Most of the time it is only 2MB but in some cases it can be up to 20MB or more. The data doesn't stay long in the buffer. 90% is deleted after less than a second and the rest is transmitted to another host. I would like to know if there is a way to tell the virtual memory manager that ram pages are not dirty anymore when data is deleted. Should I use mmap and munmap when a block is used and released to control the virtual memory ? What would be the overhead of doing this ? Also, some colleagues expressed concerns about the performance impact of allocating such a big mmap space. I expect it to behave like a swap file so that only dirty pages are to be considered.

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• How do I avoid having JSONP returns cached in an HTML5 offline application?

  - by Kent Brewster

  I had good luck with cached offline apps until I tried including data from JSONP endpoints. Here's a tiny example, which loads a single movie from the new Netflix widget API: <!DOCTYPE html> <html manifest="main.manifest"> <head> <title>Testing!</title> </head> <body> <p>Attempting to recover a title from Netflix now...</p> <script type="text/javascript"> function ping(r) { alert('API reply: ' + r.catalog_title.title.regular); } var cb = new Date().getTime(); var s = document.createElement('SCRIPT'); s.src = 'http://movi.es/7Soq?v=2.0&output=json&expand=widget&callback=ping&cacheBuster=' + cb; alert('SCRIPT src: ' + s.src); s.type = 'text/javascript'; document.getElementsByTagName('BODY')[0].appendChild(s); </script> </body> </html> ... and here's the contents of my manifest, main.manifest, which contains no files and is only there so my browser knows to cache the calling HTML file. CACHE MANIFEST Yes, I've confirmed that my server is sending the manifest down with the correct content type, text/cache-manifest. The app works fine--meaning both alerts show--the first time I run it, but subsequent runs, even with the attempt at cache-busting in line 10, seem to be attempting to load the script from cache no matter what the query string is. I see the alert showing the script source, but the callback never fires. If I remove the manifest link from line 2 and reset my browser--being Safari and the iPhone Simulator--to clear cache, it works every time. I've also tried alerting the number of SCRIPT tags in the page, and it's definitely seeing both the existing and dynamically-created tag in all cases.

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• node.js UDP data lost at high package rates

  - by koleto

  I am observing a significant data-lost on a UDP connection with node.js 0.6.18 and 0.8.0 . It appears at high packet rates about 1200 packet per second with frames about 1500 byte limit. Each data packages has a incrementing number so it easy to track the number of lost packages. var server = dgram.createSocket("udp4"); server.on("message", function (message, rinfo) { //~processData(message); //~ writeData(message, null, 5000); }).bind(10001); On the receiving callback I tested two cases I first saved 5000 packages in a file. The result ware no dropped packages. After I have included a data processing routine and got about 50% drop rate. What I expected was that the process data routine should be completely asynchronous and should not introduce dead time to the system, since it is a simple parser to process binary data in the package and to emits events to a further processing routine. It seems that the parsing routine introduce dead time in which the event handler is unable to handle each packets. At the low package rates (< 1200 packages/sec) there are no data lost observed! Is this a bug or I am doing something wrong?

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• What good open source programs exist for fuzzing popular image file types?

  - by JohnnySoftware

  I am looking for a free, open source, portable fuzzing tool for popular image file types that is written in either Java, Python, or Jython. Ideally, it would accept specifications for the fuzzable fields using some kind of declarative constraints. Non-procedural grammar for specifying constraints are greatly preferred. Otherwise, might as well write them all in Python or whatever. Just specifying ranges of valid values or expressions for them. Ideally, it would support some kind of generative programming to export the fuzzer into various programming languages to suit cases where more customization was required. If it supported a direct-manipulation GUI for controlling parameter values and ranges, that would be nice too. The file formats that should be supported are: GIF JPEG PNG So basically, it should be sort of a toolkit consisting of ready-to-run utility, a framework or library, and be capable of generating the fuzzed files directly as well as from programs it generates. It needs to be simple so that test images can be created quickly. It should have a batch capability for creating a series of images. Creating just one at a time would be too painful. I do not want a hacking tool, just a QA tool. Basically, I just want to address concerns that it is taking too long to get commonplace image rendering/parsing libraries stable and trustworthy.

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• In Visual Studio (2008) is there a way to have a custom dependent file on another custom file?

  - by rball

  Instead of a *.cs code behind or beside I'd like to have a *.js file. I'm developing a MVC application an have no need for a code beside because I have controllers, but in certain cases it'd be nice to have a JavaScript code beside or some way to associate the file to the page it's being used on. I suppose I could just name them similarly, but I'm wanting to show the association if possible so there's no question about what the file is for. Typically what I'm talking about is within Visual Studio now under your Global.asax file you will have a plus sign to the left: + Global.asax Once you expand it you'll get - Global.asax Global.asax.cs I'd like the same thing to happen: + Home.spark - Home.spark Home.spark.js Updated: My existing csproj file has a path to the actual file, not sure if that's screwing it up. I've currently got: <ItemGroup> <Content Include="Views\User\Profile.spark.js"> <DependentUpon>Views\User\Profile.spark</DependentUpon> </Content> </ItemGroup> <ItemGroup> <Content Include="Views\User\Profile.spark" /> </ItemGroup> and it's simply just showing the files besides each other.

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• How to determine the width of content or size a container to content

  - by ISVK

  My goal is to display the entire contents of a FlowDocument (that is, without paginating) in a column layout. It would have a fixed height, but the width would depend on the contents of the FlowDocument. My problem is: FlowDocumentReader does not automatically resize to the contents of the FlowDocument. As you see in my XAML below, FlowDocumentReader.Width is 5000 units (just a large number that can accommodate most documents) -- when I make it Auto, it just clips to the width of the ScrollViewer and paginates my stuff! Is there a proper way of solving this problem? I also made a screenshot of what this looks like now, but the ScrollViewer scrolls past the end of the document in most cases: http://i.imgur.com/3FSRl.png <ScrollViewer x:Name="scrollViewer" HorizontalScrollBarVisibility="Visible" VerticalScrollBarVisibility="Disabled" > <FlowDocumentReader x:Name="flowDocReader" ClipToBounds="False" Width="5000" > <FlowDocument x:Name="flowDoc" Foreground="#FF404040" ColumnRuleWidth="2" ColumnGap="40" ColumnRuleBrush="#FF404040" IsHyphenationEnabled="True" IsOptimalParagraphEnabled="True" ColumnWidth="150"> <Paragraph> Lorem ipsum dolor sit amet, ...etc... </Paragraph> <Paragraph> Lorem ipsum dolor sit amet, ...etc... </Paragraph> <Paragraph> Lorem ipsum dolor sit amet, ...etc... </Paragraph> </FlowDocument> </FlowDocumentReader> </ScrollViewer>

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• How should I properly format this code?

  - by ct2k7

  Hi, I've a small issue here. I am using an if statement with UIAlertView and I have two situations, both result in UIAlertViews. However, in one situation, I want to dismiss just the UIAlertView, the other, I want the UIAlertView to be dismissed and view to return to root view. This code describes is: if([serverOutput isEqualToString:@"login.true"]){ [Alert dismissWithClickedButtonIndex:0 animated:YES]; [UIApplication sharedApplication].networkActivityIndicatorVisible = NO; UIAlertView *success = [[UIAlertView alloc] initWithTitle:@"Success" message:@"The transaction was a success!" delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil]; [success show]; [success release]; } else { UIAlertView *failure = [[UIAlertView alloc] initWithTitle:@"Failure" message:@"The transaction failed. Contact sales operator!" delegate:self cancelButtonTitle:@"Ok" otherButtonTitles:nil, nil]; [failure show]; [failure release]; } } -(void)alertView: (UIAlertView *)success clickedButtonAtIndex: (NSInteger)buttonIndex{ switch(buttonIndex) { case 0: { [self.navigationController popToRootViewControllerAnimated:YES]; } } } So, in both cases, they follow the above action, but obviously, that's not what I want. Any ideas on what I do here?

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• Using function arguments to dynamically generate a query

  - by Varun

  I am working on an issue management system, developed in PHP/MySQL. It requires search functionality, where the user will mention the search parameters and based on these parameters the system will return the result set. To solve this I am trying to write a function and all the user selected parameters are passed as arguments. Based on the arguments I will dynamically generate the query. Sample Query: select * from tickets inner join ticket_assigned_to on tickets.id=ticket_assigned_to.ticket_id where tickets.project_id= in ('') and tickets.status in ('') and ticket_assigned_to.user_id in ('') and tickets.reporter_user_id='' and tickets.operator_user_id in ('') and tickets.due_date between '' and '' and tickets.ts_created between '' and ''; I also need to handle cases where the arguments can be ORed or ANDed in the query. For example: select * from tickets inner join ticket_assigned_to on tickets.id=ticket_assigned_to.ticket_id where tickets.project_id= in ('') and tickets.status in ('') or tickets.due_date = '' or tickets.ts_created between '' and ''; I am also planning to use the same function at other places in the project also. Like to display all the tickets of a user or all tickets created between given dates and so on... How to handle this situation? Should I go with a single function which handles all this or numerous small functions? Need guidance here.

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• Read Cookies using Javascript

  - by Ajith

  I want to create a cookie using php,an also i need to read it using javascript.ie, by using setcookie('mycookie','hello',time()+34000) in php i am creating a cookie in my system.Now,i need to read it using javascript.Is it possible?If anybody knows please give me some idea.Please....help me.I am using javscript as follows ` function Get_Cookie( check_name ) { // first we'll split this cookie up into name/value pairs // note: document.cookie only returns name=value, not the other components var a_all_cookies = document.cookie.split( ';' ); var a_temp_cookie = ''; var cookie_name = ''; var cookie_value = ''; var b_cookie_found = false; // set boolean t/f default f for ( i = 0; i < a_all_cookies.length; i++ ) { // now we'll split apart each name=value pair a_temp_cookie = a_all_cookies[i].split( '=' ); // and trim left/right whitespace while we're at it cookie_name = a_temp_cookie[0].replace(/^\s+|\s+$/g, ''); // if the extracted name matches passed check_name if ( cookie_name == check_name ) { b_cookie_found = true; // we need to handle case where cookie has no value but exists (no = sign, that is): if ( a_temp_cookie.length > 1 ) { cookie_value = unescape( a_temp_cookie[1].replace(/^\s+|\s+$/g, '') ); } // note that in cases where cookie is initialized but no value, null is returned return cookie_value; break; } a_temp_cookie = null; cookie_name = ''; } if ( !b_cookie_found ) { return null; } } if (Get_Cookie('__gsb')) { alert('Found'); } `

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• How do you work around memcached's key/value limitations?

  - by mjy

  Memcached has length limitations for keys (250?) and values (roughtly 1MB), as well as some (to my knowledge) not very well defined character restrictions for keys. What is the best way to work around those in your opinion? I use the Perl API Cache::Memcached. What I do currently is store a special string for the main key's value if the original value was too big ("parts:<number") and in that case, I store <number parts with keys named 1+<main key, 2+<main key etc.. This seems "OK" (but messy) for some cases, not so good for others and it has the intrinsic problem that some of the parts might be missing at any time (so space is wasted for keeping the others and time is wasted reading them). As for the key limitations, one could probably implement hashing and store the full key (to work around collisions) in the value, but I haven't needed to do this yet. Has anyone come up with a more elegant way, or even a Perl API that handles arbitrary data sizes (and key values) transparently? Has anyone hacked the memcached server to support arbitrary keys/values?

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• Insert or Update using Oracle and PL/SQL

  - by Shane

  I have a PL/SQL function that performs an update/insert on an Oracle database that maintains a target total and returns the difference between the existing value and the new value. Here is the code I have so far: FUNCTION calcTargetTotal(accountId varchar2, newTotal numeric ) RETURN number is oldTotal numeric(20,6); difference numeric(20,6); begin difference := 0; begin select value into oldTotal from target_total WHERE account_id = accountId for update of value; if (oldTotal != newTotal) then update target_total set value = newTotal WHERE account_id = accountId difference := newTotal - oldTotal; end if; exception when NO_DATA_FOUND then begin difference := newTotal; insert into target_total ( account_id, value ) values ( accountId, newTotal ); -- sometimes a race condition occurs and this stmt fails -- in those cases try to update again exception when DUP_VAL_ON_INDEX then begin difference := 0; select value into oldTotal from target_total WHERE account_id = accountId for update of value; if (oldTotal != newTotal) then update target_total set value = newTotal WHERE account_id = accountId difference := newTotal - oldTotal; end if; end; end; end; return difference end calcTargetTotal; This works as expected in unit tests with multiple threads never failing. However when loaded on a live system we have seen this fail with a stack trace looking like this: ORA-01403: no data found ORA-00001: unique constraint () violated ORA-01403: no data found The line numbers (which I have removed since they are meaningless out of context) verify that the first update fails due to no data, the insert fail due to uniqueness, and the 2nd update is failing with no data, which should be impossible. From what I have read on other thread a MERGE statement is also not atomic and could suffer similar problems. Does anyone have any ideas how to prevent this from occurring?

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• Why do .NET developers offer 32-bit/64-bit versions of .NET assemblies?

  - by Tyler

  Evey now and then I see both x86 and x64 versions of a .NET assembly. Consider the following web part for SharePoint. Why wouldn't the developer just offer a single version and have let the JIT compiler sort out the rest? When I see these kinds offering is it just that the developer decided to create a native image using a tool like ngen in order to avoid a JIT? Someone please help me out here, I feel like I'm missing something of note. Updated From what I got below, both x86 and x64 builds are offered because one or more of the following reasons: The developer wanted to avoid JITing and created a native image of his code, targeting a given architecture using a tool like ngen.exe. The assembly contains platform specific COM calls and so it makes no point to build it as AnyCPU. In these cases builds that target different platforms may contain different code. The assembly may contain Win32 calls using pinvoke which won't get remapped by a JIT and so the build should target the platform it is bound to.

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• Java - How to find the redirected url of a url?

  - by Yatendra Goel

  I am accessing web pages through java as follows: URLConnection con = url.openConnection(); But in some cases, a url redirects to another url. So I want to know the url to which the previous url redirected. Below are the header fields that I got as a response: null-->[HTTP/1.1 200 OK] Cache-control-->[public,max-age=3600] last-modified-->[Sat, 17 Apr 2010 13:45:35 GMT] Transfer-Encoding-->[chunked] Date-->[Sat, 17 Apr 2010 13:45:35 GMT] Vary-->[Accept-Encoding] Expires-->[Sat, 17 Apr 2010 14:45:35 GMT] Set-Cookie-->[cl_def_hp=copenhagen; domain=.craigslist.org; path=/; expires=Sun, 17 Apr 2011 13:45:35 GMT, cl_def_lang=en; domain=.craigslist.org; path=/; expires=Sun, 17 Apr 2011 13:45:35 GMT] Connection-->[close] Content-Type-->[text/html; charset=iso-8859-1;] Server-->[Apache] So at present, I am constructing the redirected url from the value of the Set-Cookie header field. In the above case, the redirected url is copenhagen.craigslist.org Is there any standard way through which I can determine which url the particular url is going to redirect. I know that when a url redirects to other url, the server sends an intermediate response containing a header field that tells the url which it is going to redirect but I am not receiving that intermediate response through the url.openConnection(); method.

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• Need a better way to execute console commands from python and log the results

  - by Wim Coenen

  I have a python script which needs to execute several command line utilities. The stdout output is sometimes used for further processing. In all cases, I want to log the results and raise an exception if an error is detected. I use the following function to achieve this: def execute(cmd, logsink): logsink.log("executing: %s\n" % cmd) popen_obj = subprocess.Popen(\ cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE) (stdout, stderr) = popen_obj.communicate() returncode = popen_obj.returncode if (returncode <> 0): logsink.log(" RETURN CODE: %s\n" % str(returncode)) if (len(stdout.strip()) > 0): logsink.log(" STDOUT:\n%s\n" % stdout) if (len(stderr.strip()) > 0): logsink.log(" STDERR:\n%s\n" % stderr) if (returncode <> 0): raise Exception, "execute failed with error output:\n%s" % stderr return stdout "logsink" can be any python object with a log method. I typically use this to forward the logging data to a specific file, or echo it to the console, or both, or something else... This works pretty good, except for three problems where I need more fine-grained control than the communicate() method provides: stdout and stderr output can be interleaved on the console, but the above function logs them separately. This can complicate the interpretation of the log. How do I log stdout and stderr lines interleaved, in the same order as they were output? The above function will only log the command output once the command has completed. This complicates diagnosis of issues when commands get stuck in an infinite loop or take a very long time for some other reason. How do I get the log in real-time, while the command is still executing? If the logs are large, it can get hard to interpret which command generated which output. Is there a way to prefix each line with something (e.g. the first word of the cmd string followed by :).

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• Algorithm for assigning a unique series of bits for each user?

  - by Mark

  The problem seems simple at first: just assign an id and represent that in binary. The issue arises because the user is capable of changing as many 0 bits to a 1 bit. To clarify, the hash could go from 0011 to 0111 or 1111 but never 1010. Each bit has an equal chance of being changed and is independent of other changes. What would you have to store in order to go from hash - user assuming a low percentage of bit tampering by the user? I also assume failure in some cases so the correct solution should have an acceptable error rate. I would an estimate the maximum number of bits tampered with would be about 30% of the total set. I guess the acceptable error rate would depend on the number of hashes needed and the number of bits being set per hash. I'm worried with enough manipulation the id can not be reconstructed from the hash. The question I am asking I guess is what safe guards or unique positioning systems can I use to ensure this happens.

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