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  • What math should all game programmers know?

    - by Tetrad
    Simple enough question: What math should all game programmers have a firm grasp of in order to be successful? I'm not specifically talking about rendering math or anything in the niche areas of game programming, more specifically just things that even game programmers should know about, and if they don't they'll probably find it useful. Note: as there is no one correct answer, this question (and its answers) is a community wiki. Also, if you would like fancy latex math equations, feel free to use http://mathurl.com/.

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  • Can I enable GZIP on Godaddy?

    - by Dave
    One of my sites lives on GoDaddy's bottom-of-the-line cheap hosting, I have the correct code in my .htaccess file, but it's not compressing because mod_deflate is not loaded. How do I enable that? The best I've found is this article which suggests I use PHP to zip everything (which is going to be more work than just changing hosting companies): " Add the following code to the very top of your Web pages above the DOCTYPE: if (substr_count($_SERVER['HTTP_ACCEPT_ENCODING'], 'gzip')) b_start("ob_gzhandler"); else ob_start();

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  • Problems building application for Ubuntu App Showdown

    - by Neil Munro
    I have managed to submit my source application to the Ubuntu build servers, however it's not building. This is the build output: https://launchpadlibrarian.net/109592385/buildlog_ubuntu-precise-i386.liberedit_12.07.20_FAILEDTOBUILD.txt.gz I know that there is a dependency on lxml for my application but I don't know how to correct that, but I can also see that it's failing to find my own python modules. I am not sure what is going on in it's entirety here, but I would greatly appreciate getting this to build so I can submit it to the Ubuntu App Showdown. Thanks, Neil

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  • ACPI _OSC control

    - by nmc
    I've noticed an error from dmesg output that ubuntu canot enable ASPM: [ 0.192722] pci0000:00: ACPI _OSC support notification failed, disabling PCIe ASPM [ 0.192728] pci0000:00: Unable to request _OSC control (_OSC support mask: 0x08) While I know that this is not a bug, I'd like to ask if there is a way to correct it and enable ASPM, the reason being that it should increase battery life (powertop shows that PCIe is always 100% on). Edit: I am running on an ASUS eee pc 1015px with the latest bios version (1401)

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  • Using polygons instead of quads on Cocos2d

    - by rraallvv
    I've been looking under the hood of Cocos2d, and I think (please correct me if I'm wrong) that although working with quads is a key feature of the engine, it should't be dificult to make it work with arrays of vertices (aka polygons) instead of quads, being the quads a special case of an array of four vertices by the way, does anyone have any code that makes cocos2d render a texture filled polygon inside a batch node? the code posted here (http://www.cocos2d-iphone.org/forum/topic/8142/page/2#post-89393) does a nice job rendering a texture filled polygon but the class doesn't work with batch nodes

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  • How to configure apache2 to just save certain POST requests without even passing them to application?

    - by Robert Grezan
    I'm running apache in front of glassfish server using BalancerMember. For performance reasons I would like that POST requests on certain endpoint are just saved to a file without passing them to application (and to return correct HTTP return code). How to configure apache to do that? EDIT: In other words, if a POST request is for path "http://example.com/upload" then the content of the post (body) should go into a file.

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  • Where and how to mention Stackoverflow participation in the résumé?

    - by Sandeepan Nath
    I think I have good enough reputation on SO now - here is my profile - http://stackoverflow.com/users/351903/sandeepan-nath. Well, this may not be that much as compared to so many other users out there but I am happy with mine. So, I was thinking of adding my profile link on my résumé. (Just the profile link and not that "I have this much reputation on SO"). Those who haven't seen, can see this question Would you put your stackoverflow profile link on your CV / Resume?. How would this look like? Forums/Blogs/Miscellaneous others No blogging as yet but active participant in Stackoverflow. My profile link - http://stackoverflow.com/users/351903/sandeepan-nath I think of putting this section after Project Details and Technical Expertise sections. Any tips/advice? Thanks Update MKO has made a very good point - "do you really want a potential employeer to be able to evaluate in detail everything you've ever written on SO". I thought of commenting but it would be too long - In my questions/answers I put a lot of statements like - "AFAIK ...", "following are my assumptions so far ...", "am I correct to conclude that... ?", "I doubt if it is possible to ..." etc. when I am not sure about something and I rarely involve in fights with other users. However I do argue on topics sometimes if I feel it is necessary and if I have a valid point. I do accept my mistakes and apologize for the same. As we all know nobody is perfect. I must have written many things which may be judged as wrong by a potential employer. But what if the same employer notices that I have improved in the quality of content by comparing old content with new one? Isn't that great? I also try to go back to older questions/answers and put corrective comments etc. when I feel I was wrong or if I can improve my post. Of course there are many employers who want you (potential employees) to be correct each and every time. They immediately remove you from consideration when you say a single incorrect thing. I have personally met such an interviewer few months back. He didn't even care to listen to any good thing I had done after he found a single wrong thing. Now the question is do you really care to work with such people? Or do you like those people who give value to the fact that you are striving to improve every day. I personally prefer the latter.

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  • Responsive Design: Media query fix for IE10 on Windows Phone 8

    - by ihaynes
    Originally posted on: http://geekswithblogs.net/ihaynes/archive/2013/07/01/responsive-design-media-query-fix-for-ie10-on--windows.aspxThe version of IE10 on Windows Phone 8 apparently has a bug which results in media queries not seeing the correct device width.This post from Devhammer explains all.http://devhammer.net/responsive-design-fix-for-windows-phone-8-device-adaptationI'd not noticed this on the WP8 Emulator which proves yet again that testing on real devices is essential.

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  • The C++ web stack, is there one?

    - by NimChimpsky
    Java would be jsps and servlets (or a framework such as Spring) running on the JVM and tomcat (or glassfish etc). C# would be asp and C# running on dot.net framework and IIS ? (I have no experience with this please correct and improve my terminology) Is there an equivalent for C++ ? I could happily call some C++ from a java servlet/controller but was wondering if there are existing frameworks and libraries out there specifically for creating business logic in C++ with a web front end.

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  • Is this possible to re-duplicate the hardware signal on Linux?

    - by Ted Wong
    Since that every things is a file on the UNIX system. If I have a hardware, for example, a mouse, move from left corner to right corner, it should produce some kinds of file to communicate with the system. So, if my assumption is correct, is this possible to do following things: Capture the raw data, which is about moving mouse cursor from left corner to right corner? Reduplicate the raw data, using a program, same producing speed, and data, in order to "redo" moving mouse cursor from left corner to right corner

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  • When reversing a Google Analytics e-commerce transaction is the per-unit price positive or negative?

    - by Michael Glenn
    Google's own instructions for reversing an e-commerce transaction seem to contradict themselves regarding the unit price. In the instructions it states The item field has a positive per-unit price and a negative quantity. yet, the code sample has a negative per-unit price and negative quantity. _gaq.push(['_addItem', '1234', // order ID - necessary to associate item with transaction 'DD44', // SKU/code - required 'T-Shirt', // product name 'Olive Medium', // category or variation '-11.99', // unit price - required '-1' // quantity - required ]); Which is correct?

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  • Wine 1.5 %ProgramFiles% error

    - by elclanrs
    I'm trying to install d3dx9 with winetricks on wine 1.5 from ppa and I keep getting an error. I tried: WINEARCH=win32 WINEPREFIX=~/.win32 winecfg sudo WINEARCH=win32 WINEPREFIX=~/.win32 winetricks And still get this error: wine cmd.exe /c echo '%ProgramFiles%' returned empty string If I type wine cmd.exe /c echo '%ProgramFiles%' into the terminal I get C:\Program Files so the path seems correct but not when I run winetricks. I also tried this regedit fix with no luck. Any ideas?

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  • Solving Inbound Refinery PDF Conversion Issues, Part 1

    - by Kevin Smith
    Working with Inbound Refinery (IBR)  and PDF Conversion can be very frustrating. When everything is working smoothly you kind of forgot it is even there. Documents are cheeked into WebCenter Content (WCC), sent to IBR for conversion, converted to PDF, returned to WCC, and viola your Office documents have a nice PDF rendition available for viewing. Then a user checks in a bunch of password protected Word files, the conversions fail, your IBR queue starts backing up, users start calling asking why their document have not been released yet, and your spend a frustrating afternoon trying to recover and get things back running properly again. Password protected documents are one cause of PDF conversion failures, and I will cover those in a future blog post, but there are many other problems that can cause conversions to fail, especially when working with the WinNativeConverter and using the native applications, e.g. Word, to convert a document to PDF. There are other conversion options like PDFExportConverter which uses Oracle OutsideIn to convert documents directly to PDF without the need for the native applications. However, to get the best fidelity to the original document the native applications must be used. Many customers have tried PDFExportConverter, but have stayed with the native applications for conversion since the conversion results from PDFExportConverter were not as good as when the native applications are used. One problem I ran into recently, that at least has a easy solution, are Word documents that display a Show Repairs dialog when the document is opened. If you open the problem document yourself you will see this dialog. This will cause the conversion to time out. Any time the native application displays a dialog that requires user input the conversion will time out. The solution is to set add a setting for BulletProofOnCorruption to the registry for the user running Word on the IBR server. See this support note from Microsoft for details. The support note says to set the registry key under HKEY_CURRENT_USER, but since we are running IBR as a service the correct location is under HKEY_USERS\.DEFAULT. Also since in our environment we were using Office 2007, the correct registry key to use was: HKEY_USERS\.DEFAULT\Software\Microsoft\Office\11.0\Word\Options Once you have done this restart the IBR managed server and resubmit your problem document. It should now be converted successfully. For more details on IBR see the Oracle® WebCenter Content Administrator's Guide for Conversion.

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  • How to select display to record in recordmydesktop

    - by Tom
    I have a dual monitor setup and wish to only record the 1st monitor with recordmydesktop, but I am unsure of the settings when doing it via the command line, so far I have this: recordmydesktop --display=1 --width=1920 height=1080 --fps=15 --no-sound --delay=10 But I get this error message: Cannot connect to X server 1 How do I find the right X server to connect to and are the rest of my settings correct? I'm using 11.04, cheers.

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  • Azure Service Bus - Authorization failure

    - by Michael Stephenson
    I fell into this trap earlier in the week with a mistake I made when configuring a service to send and listen on the azure service bus and I thought it would be worth a little note for future reference as I didnt find anything online about it.  After configuring everything when I ran my code sample I was getting the below error. WebHost failed to process a request.Sender Information: System.ServiceModel.ServiceHostingEnvironment+HostingManager/28316044Exception: System.ServiceModel.ServiceActivationException: The service '/-------/BrokeredMessageService.svc' cannot be activated due to an exception during compilation.  The exception message is: Generic: There was an authorization failure. Make sure you have specified the correct SharedSecret, SimpleWebToken or Saml transport client credentials.. ---> Microsoft.ServiceBus.AuthorizationFailedException: Generic: There was an authorization failure. Make sure you have specified the correct SharedSecret, SimpleWebToken or Saml transport client credentials.   at Microsoft.ServiceBus.RelayedOnewayTcpClient.ConnectRequestReplyContext.Send(Message message, TimeSpan timeout, IDuplexChannel& channel)   at Microsoft.ServiceBus.RelayedOnewayTcpListener.RelayedOnewayTcpListenerClient.Connect(TimeSpan timeout)   at Microsoft.ServiceBus.RelayedOnewayTcpClient.EnsureConnected(TimeSpan timeout)   at Microsoft.ServiceBus.Channels.CommunicationObject.Open(TimeSpan timeout)   at Microsoft.ServiceBus.Channels.RefcountedCommunicationObject.Open(TimeSpan timeout)   at Microsoft.ServiceBus.RelayedOnewayChannelListener.OnOpen(TimeSpan timeout)   at Microsoft.ServiceBus.Channels.CommunicationObject.Open(TimeSpan timeout)   at System.ServiceModel.Dispatcher.ChannelDispatcher.OnOpen(TimeSpan timeout)   at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)   at System.ServiceModel.ServiceHostBase.OnOpen(TimeSpan timeout)   at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)   at Microsoft.ServiceBus.SocketConnectionTransportManager.OnOpen(TimeSpan timeout)   at Microsoft.ServiceBus.Channels.TransportManager.Open(TimeSpan timeout, TransportChannelListener channelListener)   at Microsoft.ServiceBus.Channels.TransportManagerContainer.Open(TimeSpan timeout, SelectTransportManagersCallback selectTransportManagerCallback)   at Microsoft.ServiceBus.SocketConnectionChannelListener`2.OnOpen(TimeSpan timeout)   at Microsoft.ServiceBus.Channels.CommunicationObject.Open(TimeSpan timeout)   at Microsoft.ServiceBus.Channels.CommunicationObject.Open(TimeSpan timeout)   at System.ServiceModel.Dispatcher.ChannelDispatcher.OnOpen(TimeSpan timeout)   at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)   at System.ServiceModel.ServiceHostBase.OnOpen(TimeSpan timeout)   at System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.ActivateService(String normalizedVirtualPath)   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath)   --- End of inner exception stack trace ---   at System.ServiceModel.ServiceHostingEnvironment.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath)   at System.ServiceModel.ServiceHostingEnvironment.EnsureServiceAvailableFast(String relativeVirtualPath)Process Name: w3wpProcess ID: 8056As recommended by the error message I checked everything about the application configuration and also the keys and eventually I found the problem.When I set the permissions in the ACS rule group I had copied and pasted the claim name for net.windows.servicebus.action from the Azure portal and hadnt spotted the <space> character on the end of it like you sometimes pick up when copying text in the browser.  This meant that the listen and send permissions were not setup correctly which is why (as you would expect) my two applications could not connect to the service bus.So lesson learnt here, if you do copy and paste into the ACS rules just be careful you dont leave a space on the end of anything otherwise it will be difficult to spot that its configured incorrectly

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  • Where and how to mention Stackoverflow participation in the résumé?

    - by Sandeepan Nath
    I think I have good enough reputation on SO now - here is my profile - http://stackoverflow.com/users/351903/sandeepan-nath. Well, this may not be that much as compared to so many other users out there but I am happy with mine. So, I was thinking of adding my profile link on my résumé. (Just the profile link and not that "I have this much reputation on SO"). Those who haven't seen, can see this question Would you put your stackoverflow profile link on your CV / Resume?. How would this look like? Forums/Blogs/Miscellaneous others No blogging as yet but active participant in Stackoverflow. My profile link - http://stackoverflow.com/users/351903/sandeepan-nath I think of putting this section after Project Details and Technical Expertise sections. Any tips/advice? Thanks Update MKO has made a very good point - "do you really want a potential employeer to be able to evaluate in detail everything you've ever written on SO". I thought of commenting but it would be too long - In my questions/answers I put a lot of statements like - "AFAIK ...", "following are my assumptions so far ...", "am I correct to conclude that... ?", "I doubt if it is possible to ..." etc. when I am not sure about something and I rarely involve in fights with other users. However I do argue on topics sometimes if I feel it is necessary and if I have a valid point. I do accept my mistakes and apologize for the same. As we all know nobody is perfect. I must have written many things which may be judged as wrong by a potential employer. But what if the same employer notices that I have improved in the quality of content by comparing old content with new one? Isn't that great? I also try to go back to older questions/answers and put corrective comments etc. when I feel I was wrong or if I can improve my post. Of course there are many employers who want you (potential employees) to be correct each and every time. They immediately remove you from consideration when you say a single incorrect thing. I have personally met such an interviewer few months back. He didn't even care to listen to any good thing I had done after he found a single wrong thing. Now the question is do you really care to work with such people? Or do you like those people who give value to the fact that you are striving to improve every day. I personally prefer the latter.

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  • 3 SEO Secrets to Rocket Above the Competition in Just 10 Days!

    Correct Title Tags - That's right, the original and best way to outrank the website above you is to tweak the title tags on every single page on your website, and make sure they 100% different! Another great tip - don't just use one keyword, but: 'Keyword 1 & Keyword 2' on each of the pages, and note the pipe separator in the middle, not the comma or dots.

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  • How do you calculate UVW coordinates?

    - by Jenko
    I'm working on a 3d engine and I'm calculating UVT coordinates, where U and V represent pixels on the texture measured in 0-1, and T is: T = perspective / Z But I'm trying to use this perspective-correct triangle rasteriser, which requires a W, per vertex. How do I calculate the W for each vertex for the drawPerspectiveTexturedPolygon() function? Hint: The code comments refer to W as the "homogenous coordinate" ... does that mean anything?

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  • Demantra Engine Failure Hanging Error Not Starting Debugging INstall and Configuration Checklist

    - by user702295
    There is a new Demantra engine configuration checklist to ensure that your enginge setup and configuration is correct.  These are the questions that development will ask should your issue turn into a bug.   See the following MyOracleSupport note: Demantra Engine on Linux or Unix Failure Hanging Error Not Starting Debugging Install and Configuration Checklist Note ID 1086704.1

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  • Scrum - real life example?

    - by Camilo
    I'm starting with scrum and saw many partial examples on books and tutorials, but when try to use scrum in the real life, it's not easy to write the user stories and create the product backlog. I want to see a real project with user stories, product backlog and sprint backlogs to see if I'm doing it in the correct way. Is there any open source project with a public product backlog ? Is there any shared complete user stories and product backlog from a real project?

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  • Webpage loading with wrong content-type after setting up CloudFlare

    - by Daniel Little
    I recently migrated my blog to the Ghost service, I've also setup an alias DNS record with CloudFlare. While showing the blog to a colleague I discovered one of the posts wasn't loading properly and would instead prompt to be downloaded with an application/octet-stream content-type. I can view all the pages without any issues and I believe we're both on the same network as well. Has anyone received a wrong content type like application/octet-stream using CloudFlare, or know what I can do to correct this?

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  • Installed Sun Java 6 - configuration problem when running as sudo

    - by HorusKol
    I have install Sun Java 6 on an Ubuntu server and set an environment variable in the default profile as per the instructions at http://www.edugate.ie/workshop-guides/shibboleth-2-identity-provider-installation-linux-debian-or-ubuntu I then try to run an installer for a Java servlet - but when I run it as myself, it cannot create the required directory in /opt. When I run it as sudo, I am told that JAVA_HOME is not correct and it doesn't even start the installer - shouldn't this be coming from /etc/profile like it is for my normal user?

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  • Max ram for computer 16GB or 8GB

    - by Laptop memory question
    Manufacturer's specifications for my notebook say memory can be extended from 4GB to 8GB. Whereas, running sudo dmidecode suggests the computer can use 16GB as below: Handle 0x0037, DMI type 16, 15 bytes Physical Memory Array Location: System Board Or Motherboard Use: System Memory Error Correction Type: None Maximum Capacity: 16 GB Error Information Handle: Not Provided Number Of Devices: 4 Which one is correct?

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  • Fun with Aggregates

    - by Paul White
    There are interesting things to be learned from even the simplest queries.  For example, imagine you are given the task of writing a query to list AdventureWorks product names where the product has at least one entry in the transaction history table, but fewer than ten. One possible query to meet that specification is: SELECT p.Name FROM Production.Product AS p JOIN Production.TransactionHistory AS th ON p.ProductID = th.ProductID GROUP BY p.ProductID, p.Name HAVING COUNT_BIG(*) < 10; That query correctly returns 23 rows (execution plan and data sample shown below): The execution plan looks a bit different from the written form of the query: the base tables are accessed in reverse order, and the aggregation is performed before the join.  The general idea is to read all rows from the history table, compute the count of rows grouped by ProductID, merge join the results to the Product table on ProductID, and finally filter to only return rows where the count is less than ten. This ‘fully-optimized’ plan has an estimated cost of around 0.33 units.  The reason for the quote marks there is that this plan is not quite as optimal as it could be – surely it would make sense to push the Filter down past the join too?  To answer that, let’s look at some other ways to formulate this query.  This being SQL, there are any number of ways to write logically-equivalent query specifications, so we’ll just look at a couple of interesting ones.  The first query is an attempt to reverse-engineer T-SQL from the optimized query plan shown above.  It joins the result of pre-aggregating the history table to the Product table before filtering: SELECT p.Name FROM ( SELECT th.ProductID, cnt = COUNT_BIG(*) FROM Production.TransactionHistory AS th GROUP BY th.ProductID ) AS q1 JOIN Production.Product AS p ON p.ProductID = q1.ProductID WHERE q1.cnt < 10; Perhaps a little surprisingly, we get a slightly different execution plan: The results are the same (23 rows) but this time the Filter is pushed below the join!  The optimizer chooses nested loops for the join, because the cardinality estimate for rows passing the Filter is a bit low (estimate 1 versus 23 actual), though you can force a merge join with a hint and the Filter still appears below the join.  In yet another variation, the < 10 predicate can be ‘manually pushed’ by specifying it in a HAVING clause in the “q1” sub-query instead of in the WHERE clause as written above. The reason this predicate can be pushed past the join in this query form, but not in the original formulation is simply an optimizer limitation – it does make efforts (primarily during the simplification phase) to encourage logically-equivalent query specifications to produce the same execution plan, but the implementation is not completely comprehensive. Moving on to a second example, the following query specification results from phrasing the requirement as “list the products where there exists fewer than ten correlated rows in the history table”: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) < 10 ); Unfortunately, this query produces an incorrect result (86 rows): The problem is that it lists products with no history rows, though the reasons are interesting.  The COUNT_BIG(*) in the EXISTS clause is a scalar aggregate (meaning there is no GROUP BY clause) and scalar aggregates always produce a value, even when the input is an empty set.  In the case of the COUNT aggregate, the result of aggregating the empty set is zero (the other standard aggregates produce a NULL).  To make the point really clear, let’s look at product 709, which happens to be one for which no history rows exist: -- Scalar aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709;   -- Vector aggregate SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = 709 GROUP BY th.ProductID; The estimated execution plans for these two statements are almost identical: You might expect the Stream Aggregate to have a Group By for the second statement, but this is not the case.  The query includes an equality comparison to a constant value (709), so all qualified rows are guaranteed to have the same value for ProductID and the Group By is optimized away. In fact there are some minor differences between the two plans (the first is auto-parameterized and qualifies for trivial plan, whereas the second is not auto-parameterized and requires cost-based optimization), but there is nothing to indicate that one is a scalar aggregate and the other is a vector aggregate.  This is something I would like to see exposed in show plan so I suggested it on Connect.  Anyway, the results of running the two queries show the difference at runtime: The scalar aggregate (no GROUP BY) returns a result of zero, whereas the vector aggregate (with a GROUP BY clause) returns nothing at all.  Returning to our EXISTS query, we could ‘fix’ it by changing the HAVING clause to reject rows where the scalar aggregate returns zero: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID HAVING COUNT_BIG(*) BETWEEN 1 AND 9 ); The query now returns the correct 23 rows: Unfortunately, the execution plan is less efficient now – it has an estimated cost of 0.78 compared to 0.33 for the earlier plans.  Let’s try adding a redundant GROUP BY instead of changing the HAVING clause: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY th.ProductID HAVING COUNT_BIG(*) < 10 ); Not only do we now get correct results (23 rows), this is the execution plan: I like to compare that plan to quantum physics: if you don’t find it shocking, you haven’t understood it properly :)  The simple addition of a redundant GROUP BY has resulted in the EXISTS form of the query being transformed into exactly the same optimal plan we found earlier.  What’s more, in SQL Server 2008 and later, we can replace the odd-looking GROUP BY with an explicit GROUP BY on the empty set: SELECT p.Name FROM Production.Product AS p WHERE EXISTS ( SELECT * FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ); I offer that as an alternative because some people find it more intuitive (and it perhaps has more geek value too).  Whichever way you prefer, it’s rather satisfying to note that the result of the sub-query does not exist for a particular correlated value where a vector aggregate is used (the scalar COUNT aggregate always returns a value, even if zero, so it always ‘EXISTS’ regardless which ProductID is logically being evaluated). The following query forms also produce the optimal plan and correct results, so long as a vector aggregate is used (you can probably find more equivalent query forms): WHERE Clause SELECT p.Name FROM Production.Product AS p WHERE ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) < 10; APPLY SELECT p.Name FROM Production.Product AS p CROSS APPLY ( SELECT NULL FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () HAVING COUNT_BIG(*) < 10 ) AS ca (dummy); FROM Clause SELECT q1.Name FROM ( SELECT p.Name, cnt = ( SELECT COUNT_BIG(*) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID GROUP BY () ) FROM Production.Product AS p ) AS q1 WHERE q1.cnt < 10; This last example uses SUM(1) instead of COUNT and does not require a vector aggregate…you should be able to work out why :) SELECT q.Name FROM ( SELECT p.Name, cnt = ( SELECT SUM(1) FROM Production.TransactionHistory AS th WHERE th.ProductID = p.ProductID ) FROM Production.Product AS p ) AS q WHERE q.cnt < 10; The semantics of SQL aggregates are rather odd in places.  It definitely pays to get to know the rules, and to be careful to check whether your queries are using scalar or vector aggregates.  As we have seen, query plans do not show in which ‘mode’ an aggregate is running and getting it wrong can cause poor performance, wrong results, or both. © 2012 Paul White Twitter: @SQL_Kiwi email: [email protected]

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