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• SQL vs MySQL: Rules about aggregate operations and GROUP BY

  - by Phazyck

  In this book I'm currently reading while following a course on databases, the following example of an illegal query using an aggregate operator is given: Find the name and age of the oldest sailor. Consider the following attempt to answer this query: SELECT S.name, S.age FROM Sailors.S The intent is for this query to return not only the maximum age but also the name of the sailors having that age. However, this query is illegal in SQL--if the SELECT clause uses an aggregate operation, then it must use only aggregate operations unless the query contains a GROUP BY clause! Some time later while doing an exercise using MySQL, I faced a similar problem, and made a mistake similar to the one mentioned. However, MySQL didn't complain and just spit out some tables which later turned out not be what I needed. Is the query above really illegal in SQL, but legal in MySQL, and if so, why is that? In what situation would one need to make such a query?

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• I/O Asynchronous Completion

  - by lockedscope

  In the following, it is said that an I/O handle must be associated with the thread pool but i could not find where in the given example an handle is associated with the thread. Which function or code helps to bind the file handle in that example? Using asynchronous I/O completion events, a thread from the thread pool processes data only when the data is received, and once the data has been processed, the thread returns to the thread pool. To make an asynchronous I/O call, an operating-system I/O handle must be associated with the thread pool and a callback method must be specified. When the I/O operation completes, a thread from the thread pool invokes the callback method. http://msdn.microsoft.com/en-us/library/aa720215(VS.71).aspx

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• Timeout LinqToSql inserting millions of records

  - by Bas

  I'm inserting approximently 3 million records in a database using this solution. Eventually when the application has been inserting records for a while (my last run lasted around 4 hours), it gives a timeout with the following SqlException: "SqlExcepetion: Timeout expired. The timeoutperiod elapsed prior to completion of the operation or the server is not responding." What's the best way to handle this exception? Is there a way to prevent this from happening or should I catch the exception? Thanks in advance!

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• java methods and race condition in a jsp/servlets application.

  - by A.S al-shammari

  Hi. Suppose that I have a method called doSomething() and I want to use this method in a multithreaded application (each servlet inherits from HttpServlet).I'm wondering if it is possible that a race condition will occur in the following cases: doSomething() is not staic method and it writes values to a database. doSomething() is static method but it does not write values to a database. what I have noticed that many methods in my application may lead to a race condition or dirty read/write. for example , I have a Poll System , and for each voting operation, a certain method will change a single cell value for that poll as the following: [poll_id | poll_data ] [1 | {choice_1 : 10, choice_2 : 20}] will the JSP/Servlets app solve these issues by itself, or I have to solve all that by myself? Thanks..

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• To Show a Continuous ProgressBar using ExtJS

  - by UIDreamer

  Hi, Problem:- I need to embed a progressbar that will run continuously until the completion of the operation. ExtJS provides a Progressbar Ext.Progressbar which will:- a) Run Continuously using wait method b) Run after updating the updateProgress method. In both the cases output of the progressbar will be The solution that i am trying for is:- Step 1 : Step 2 : Step 3 : Kindly suggest me a solution or a approach. The JavaScript library that i am using is ExtJS. Thanks in Advance. Links Referred for the example:- http://dev.sencha.com/deploy/dev/examples/simple-widgets/progress-bar.html

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• Repeating a List in Scala

  - by Ralph

  I am a Scala noob. I have decided to write a spider solitaire solver as a first exercise to learn the language and functional programming in general. I would like to generate a randomly shuffled deck of cards containing 1, 2, or 4 suits. Here is what I came up with: val numberOfSuits = 1 (List["clubs", "diamonds", "hearts", "spades"].take(numberOfSuits) * 4).take(4) which should return List["clubs", "clubs", "clubs", "clubs"] List["clubs", "diamonds", "clubs", "diamonds"] List["clubs", "diamonds", "hearts", "spades"] depending on the value of numberOfSuits, except there is no List "multiply" operation that I can find. Did I miss it? Is there a better way to generate the complete deck before shuffling? BTW, I plan on using an Enumeration for the suits, but it was easier to type my question with strings. I will take the List generated above and using a for comprehension, iterate over the suits and a similar List of card "ranks" to generate a complete deck.

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• How to test for secure SMTP mail service on a mail server

  - by Vinay S Shenoy

  I'm working on a project to auto-configure a user's email server settings in Java. I am extracting the mail server from his email address and looking up the MX records of that mail server using the DirContext class with com.sun.jndi.dns.DnsContextFactory. Then I'm opening a Socket to each server and testing them using a HELO command and checking the responses. My problem is that this works only when I test it with the unsecure SMTP port 25. How can I use it with the secure port 465? I tried using Secure Sockets by using SSLSocketFactory sslsocketfactory = (SSLSocketFactory)SSLSocketFactory.getDefault(); SSLSocket socket = (SSLSocket)sslsocketfactory.createSocket(mailserver, STANDARD_SMTP_PORT); But all connections get a timeout exception as follows alt1.gmail-smtp-in.l.google.com. java.net.ConnectException: Operation timed out Please help.

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• Should class IOException in Java have been an unchecked RuntimeException?

  - by Derek Mahar

  Do you agree that the designers of Java class java.io.IOException should have made it an unchecked run-time exception derived from java.lang.RuntimeException instead of a checked exception derived only from java.lang.Exception? I think that class IOException should have been an unchecked exception because there is little that an application can do to resolve problems like file system errors. However, in When You Can't Throw An Exception, Elliotte Rusty Harold claims that most I/O errors are transient and so you can retry an I/O operation several times before giving up: For instance, an IOComparator might not take an I/O error lying down, but — because many I/O problems are transient — you can retry a few times, as shown in Listing 7: Is this generally the case? Can a Java application correct I/O errors or wait for the system to recover? If so, then it is reasonable for IOException to be checked, but if it is not the case, then IOException should be unchecked so that business logic can delegate handling of this exception to a separate system error handler.

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• split double in c wihout any libary

  - by DoomStone

  Hello I have a question for a c programmer out there, we have a tast at school to create a soft real time system in an operation system made by our teacher. Well that is all fine and dandy, we have chosen to create a system that calcuate how many unites of medicine a diabetic need based on his or hers blood sugar. It does not need to be correct just that we have the idea of a real time system :D But we have hit a little snag our formula for calculating the units of medicine is [blood sugar] * 1.2 But the only way we can send messages between processes is via a structure that contains 8 longs, but here is where my knowledge of c ends, we need for some way to split this double into 2 longs, example: the whole number in long 0 and the decimals in long 1 and then assemble it on the other side. But I have no idea who to do this, and therefore need a little help. We have tried but we do not have access to c standard libraries

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• Using Apache Velocity with StringBuilders/CharSequences

  - by mindas

  We are using Apache Velocity for dynamic templates. At the moment Velocity has following methods for evaluation/replacing: public static boolean evaluate(Context context, Writer writer, String logTag, Reader reader) public static boolean evaluate(Context context, Writer out, String logTag, String instring) We use these methods by providing StringWriter to write evaluation results. Our incoming data is coming in StringBuilder format so we use StringBuilder.toString and feed it as instring. The problem is that our templates are fairly large (can be megabytes, tens of Ms on rare cases), replacements occur very frequently and each replacement operation triples the amount of required memory (incoming data + StringBuilder.toString() which creates a new copy + outgoing data). I was wondering if there is a way to improve this. E.g. if I could find a way to provide a Reader and Writer on top of same StringBuilder instance that only uses extra memory for in/out differences, would that be a good approach? Has anybody done anything similar and could share any source for such a class? Or maybe there any better solutions to given problem?

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• How to synchronize threads in python?

  - by Eric

  I have two threads in python (2.7). I start them at the beginning of my program. While they execute, my program reaches the end and exits, killing both of my threads before waiting for resolution. I'm trying to figure out how to wait for both threads to finish before exiting. def connect_cam(ip, execute_lock): try: conn = TelnetConnection.TelnetClient(ip) execute_lock.acquire() ExecuteUpdate(conn, ip) execute_lock.release() except ValueError: pass execute_lock = thread.allocate_lock() thread.start_new_thread(connect_cam, ( headset_ip, execute_lock ) ) thread.start_new_thread(connect_cam, ( handcam_ip, execute_lock ) ) In .NET I would use something like WaitAll() but I haven't found the equivalent in python. In my scenario, TelnetClient is a long operation which may result in a failure after a timeout.

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• Consuming Third Party web services through Spring WebServiceTemplate

  I'm trying to consume a Third Party web service, through a wsdl file provided. I would load the file locally from a Spring-J2EE based project underneath WEB-INF folder. The wsdl might have more than one operation exposed. So I need a way to be able to choose the method to be called. I would also need to make use of a JaxbMarshaller. Can anyone help with a code snippet for the same? Thanks for the help.

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• Implement dictionary using java

  - by ahmad

  Task Dictionary ADT The dictionary ADT models a searchable collection of key-element entries Multiple items with the same key are allowed Applications: word-definition pairs Dictionary ADT methods: find(k): if the dictionary has an entry with key k, returns it, else, returns null findAll(k): returns an iterator of all entries with key k insert(k, o): inserts and returns the entry (k, o) remove(e): remove the entry e from the dictionary size(), isEmpty() Operation Output Dictionary insert(5,A) (5,A) (5,A) insert(7,B) (7,B) (5,A),(7,B) insert(2,C) (2,C) (5,A),(7,B),(2,C) insert(8,D) (8,D) (5,A),(7,B),(2,C),(8,D) insert(2,E) (2,E) (5,A),(7,B),(2,C),(8,D),(2,E) find(7) (7,B) (5,A),(7,B),(2,C),(8,D),(2,E) find(4) null (5,A),(7,B),(2,C),(8,D),(2,E) find(2) (2,C) (5,A),(7,B),(2,C),(8,D),(2,E) findAll(2) (2,C),(2,E) (5,A),(7,B),(2,C),(8,D),(2,E) size() 5 (5,A),(7,B),(2,C),(8,D),(2,E) remove(find(5)) (5,A) (7,B),(2,C),(8,D),(2,E) find(5) null (7,B),(2,C),(8,D),(2,E) Detailed explanation: NO Specific requirements: please Get it done i need HELP !!!

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• Postgres : Post statement (or insert) asynchronous, non-blocking processing.

  - by Hassan Syed

  I'm wondering if it is possible, that after a collection of rows is inserted, to initiate an operation that is executed asynchronously, is non-blocking, and doesn't need to inform the originator of the request - of the result. I am working with large amounts of events and I can guarantee that the post-insert logic will not fail -- I just want to have a single insert thread in my event-sources, and I want this thread to keep flying without blocking, and without being responsible for any post-delivery book-keeping. I can tell you that I would potentially have a 100 of these jobs executing concurrently and each job might operate on 5 tables with anywhere between 200-1000 inserts on each of these tables. A hint in the right direction should be enough.

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• iPhone: One Object, One Thread

  - by GingerBreadMane

  On the iPhone, I would like to do some operations on an image in a separate thread. Rather than dealing with semiphores, locking, etc., I'd like to use the 'One Object, One Thread' method of safely writing this concurrent operation. I'm not sure what is the correct way to copy my object into a new thread so that the object is not accessed in the main thread. Do I use the 'copy' method? If so, do I do this before the thread or inside the thread? ... -(void)someMethod{ UIImage *myImage; [NSThread detachNewThreadSelector:@selector(getRotatedImage:) toTarget:self withObject:myImage]; } -(void)getRotatedImage:(UIImage *)image{ ... ... UIImage *copiedImage = [image copy]; ... ... }

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• Force line-buffering of stdout when piping to tee

  - by houbysoft

  Usually, stdout is line-buffered. In other words, as long as your printf argument ends with a newline, you can expect the line to be printed instantly. This does not appear to hold when using a pipe to redirect to tee. I have a C++ program, a, that outputs strings, always \n-terminated, to stdout. When it is run by itself (./a), everything prints correctly and at the right time, as expected. However, if I pipe it to tee (./a | tee output.txt), it doesn't print anything until it quits, which defeats the purpose of using tee. I know that I could fix it by adding a fflush(stdout) after each printing operation in the C++ program. But is there a cleaner, easier way? Is there a command I can run, for example, that would force stdout to be line-buffered, even when using a pipe?

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• Php variable in several files including jquery

  - by vipinsahu

  i created two variable and these two variable are using everywhere . i don't want to store these variable in to database e.g ( $username ,$password and there are 3 files using these variable load.php,index.php and add.php , i am also using jquery to load the add.php as in ajax (to add the user in JSON) $.ajax({ type: "POST", url: "add.php", data: "twitter="+encodeURIComponent(twitter), /* Sending the filled in twitter name */ success: function(msg){ /* PHP returns 1 on success, and 0 on error */ var status = parseInt(msg); if(status) { $('#response').html('Thank you '); $('#twitterName').val(''); } else $('#response').html('<span style="color:red">There is no user.</span>'); } }); how can i use these two variable in a single file to perform the whole operation Thanks

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• error -4861 - I do a BULK INSERT the contents of a csv file into a table through stored procedure

  - by Chandru

  Hi, Could you please help me,I have an application, in which I do a BULK INSERT the contents of a csv file into a table through stored procedure, the stored Procedure uses BULK INSERT (SQL Server 2005). This Works fine in a standalone system. However when I use the same in a multitier (Web server, Application Server and DB Server) architecture it is throwing 4861 error. Could you please help? The Files are stored in the Web Server. The Translated error message below: " Error – 2147217900:4861: Since it can not be opened for the file \Servername\c$\Folder1\Folder2\Folder3\file.csv, It can not be loaded with large capacity. Operation system error code is 5 (error not ……….) " Thanks Regards, Chandru

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• Get the tags of a document in Subversion

  - by Onno

  I was wondering if there is a way to easily see the tags of a specific file in Subversion using the command line and/or TortoiseSVN. Most version control system allow you to see easily access the tags/labels of a file. When using TortoiseSVN I can do this when I access the "Revision Graph". This however is a operation that takes around 44 minutes. I consider this very hard work just to know what tags have been created for the file. Is there another way to do it? Or is there no way to instantaneously access tag information. Thanks, Onno

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• Google Visualization Annotated Time Line, removing data points.

  - by Vitaly Babiy

  I am trying to build a graph that will change resolution depending on how far you are zoomed in. Here is what it looks like when you are complete zoomed out. So this looks good so when I zoom in I get a higher resolution data and my graph looks like this: The problem is when I zoom out the higher resolution data does not get cleared out of the graph: The tables below the graphs are table display what is in the DataTable. This is what drawing code looks like. var g_graph = new google.visualization.AnnotatedTimeLine(document.getElementById('graph_div_json')); var table = new google.visualization.Table(document.getElementById('table_div_json')); function handleQueryResponse(response){ log("Drawing graph") var data = response.getDataTable() g_graph.draw(data, {allowRedraw:true, thickness:2, fill:50, scaleType:'maximized'}) table.draw(data, {allowRedraw:true}) } I am try to find a way for it to only displaying the data that is in the DataTable. I have tried removing the allowRedraw flag but then it breaks the zooming operation. Any help would be greatly appreciated. Thanks

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• what is the pattern for modifying a collection in C#

  - by macias

  What is the pattern (best practice) for such problem -- modifying elements (values) in collection? Conditions: size of the collection is not changed (no element is deleted or added) modification is in-place In C++ it was easy and nice, I just iterated trough a collection and changed the elements. But in C# iterating (using enumerator) is read-only operation (speaking in terms of C++, only const_iterator is available). So, how to do this in C#? Example: having sequence of "1,2,3,4" modification is changing it to "1, 2, 8, 9" but not "1, 2, 3" or "1, 2, 3, 4, 5".

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• [Cocoa] NSImage transparency

  - by ndg

  I'm trying to set a custom drag icon for use in an NSTableView. Everything seems to work but I've run into a problem due to my inexperience with Quartz. - (NSImage *)dragImageForRowsWithIndexes:(NSIndexSet *)dragRows tableColumns:(NSArray *)tableColumns event:(NSEvent *)dragEvent offset:(NSPointPointer)dragImageOffset { NSImage *dragImage = [NSImage imageNamed:@"icon.png"]; NSString *count = [NSString stringWithFormat:@"%d", [dragRows count]]; [dragImage lockFocus]; [dragImage compositeToPoint:NSZeroPoint fromRect:NSZeroRect operation:NSCompositeSourceOver fraction:0.5]; [count drawAtPoint:NSZeroPoint withAttributes:nil]; [dragImage unlockFocus]; return dragImage; } Essentially what I'm looking to do is render my icon.png file with 50% opacity along with an NSString which shows the number of rows currently being dragged. The issue I'm seeing is that my NSString renders with a low opacity, but not my icon.

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• How to use a 3rd party control inside the viewmodel?

  - by Sander

  I have a 3rd party control which among other things performs loading of some data. I want my viewmodel to keep track of this load operation and adjust its own state accordingly. If it were up to me, I'd do the data loading far away from the view, but it is not. So, I seem to be in the situation where my viewmodel depends on my view. How do I best handle this? I feel rather dirty making the view publish events to the viewmodel but I don't see any other reasonable way to get this info into the viewmodel. A similar situation might crop up with standard controls, too - imagine if your viewmodel depends on the events coming from a MediaElement - how do you properly model this? Do you put the MediaElement into the viewmodel? That doesn't sound right. If publishing the events to the viewmodel is indeed the most reasonable way, is there some common pattern used for this? How do you do it?

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• what is the use of creating proxy for an webservice

  - by prince23

  hi, i have an webserivce written where i do an insertion opertion to DB. path :http://localhost:1838/Ajax/WebService.asmx?wsdl.name of the webservice is localhost i have added webservice for the project now on button click event i try to call this webserice like this localhost obj= new localhost(); obj.insert(); now i am able to do the insertion operation fine. but i wanted to create an proxy for the webservice so wat is the use of it doing like tat? when i run this command in my command prompt in vs wsdl /out:myProxyClass.cs http://localhost:1838/Ajax/WebService.asmx?WSDL i get an error unable to connect the remote server. no connection would be made because the target machine actively refused it looking forward for an solution any help would great thank you

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• Using CreateFileMapping between two programs - C

  - by Jamie Keeling

  Hello, I have two window form applications written in C, one holds a struct consisting of two integers, another will receive it using the CreateFileMapping. Although not directly related I want to have three events in place so each of the processes can "speak" to each other, one saying that the first program has something to pass to the second, one saying the first one has closed and another saying the second one has closed. What would be the best way about doing this exactly? I've looked at the MSDN entry for the CreateFileMapping operation but I'm still not sure as to how it should be done. I didn't want to start implementing it without having some sort of clear idea as to what I need to do. Thanks for your time.

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