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• Using * in SELECT Query

  - by libregeek

  I am currently porting an application written in MySQL3 and PHP4 to MySQL5 and PHP5. On analysis I found several SQL queries which uses "select * from tablename" even if only one column(field) is processed in PHP. The table has almost 60 columns and it has a primary key. In most cases, the only column used is id which is the primary key. Will there be any performance boost if I use queries in which the column names are explicitly mentioned instead of * ? (In this application there is only one method which we need all the columns and all other methods return only a subset of the columns)

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• Using memtables in sql. When is it reasonable and is it safe?

  - by Spiros

  I was just reading an update from a friend's project, mentioning the use of memtables to store data temporatily and then flush to a table on disk. Up to now, I have never faced a situation where I would use a memtable, or a situation where I would think the use of a mem table would be beneficial; so I wonder, when would someone use mem tables? what makes a memtable (appart from access speed) a reasonable choice? and how safe is it, even for temp data? there is always the limitation of available physical memory.

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• Guaranteed COM object release?

  - by Jurily

  I wrote the following code under the assumption that Excel will die with Monkey: class ExcelMonkey { private static Excel.Application xl = new Excel.Application(); public static bool parse(string filename) { if (filename.Contains("foo")) { var workbook = xl.Workbooks.Open(filename); var sheet = workbook.Worksheets.get_Item(1); // do stuff return true; } return false; } } How do I make sure it does? Do I need to release workbook and sheet separately? I want to have Excel around for the lifetime of the program, it's a huge performance improvement.

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• Java bytecode compiler benchmarks

  - by Dave Jarvis

  Q.1. What free compiler produces the fastest executable Java bytecode? Q.2. What free virtual machine executes Java bytecode the fastest (on 64-bit multi-core CPUs)? Q.3. What other (currently active) compiler projects are missing from this list: http://www.ibm.com/developerworks/java/jdk/ http://gcc.gnu.org/java/ http://openjdk.java.net/groups/compiler/ http://java.sun.com/javase/downloads/ http://download.eclipse.org/eclipse/downloads/ Q.4. What performance improvements can compilers do that JITs cannot (or do not)? Q.5. Where are some recent benchmarks, comparisons, or shoot-outs (for Q1 or Q2)? Thank you!

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• Logging from multiple apps/processes to a single log file

  - by Andrew

  Our app servers (weblogic) all use log4j to log to the same file on a network share. On top of this we have all web apps in a managed server logging errors to a common error.log. I can't imagine this is a good idea but wanted to hear from some pros. I know that each web app has its own classloader, so any thread synchronization only occurs within the app. So what happens when multiple processes start converging on a single log file? Can we expect interspersed log statements? Performance problems? What about multiple web apps logging to a common log file? The environment is Solaris.

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• Oracle: '= ANY()' vs. 'IN ()'

  - by eidylon

  Hi all, I just stumbled upon something in ORACLE SQL (not sure if it's in others), that I am curious about. I am asking here as a wiki, since it's hard to try to search symbols in google... I just found that when checking a value against a set of values you can do WHERE x = ANY (a, b, c) As opposed to the usual WHERE x IN (a, b, c) So I'm curious, what is the reasoning for these two syntaxes? Is one standard and one some oddball Oracle syntax? Or are they both standard? And is there a preference of one over the other for performance reasons, or ? Just curious what anyone can tell me about that '= ANY' syntax. CheerZ!

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• Efficiency of while(true) ServerSocket Listen

  - by Submerged

  I am wondering if a typical while(true) ServerSocket listen loop takes an entire core to wait and accept a client connection (Even when implementing runnable and using Thread .start()) I am implementing a type of distributed computing cluster and each computer needs every core it has for computation. A Master node needs to communicate with these computers (invoking static methods that modify the algorithm's functioning). The reason I need to use sockets is due to the cross platform / cross language capabilities. In some cases, PHP will be invoking these java static methods. I used a java profiler (YourKit) and I can see my running ServerSocket listen thread and it never sleeps and it's always running. Is there a better approach to do what I want? Or, will the performance hit be negligible? Please, feel free to offer any suggestion if you can think of a better way (I've tried RMI, but it isn't supported cross-language. Thanks everyone

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• How do I return an empty result set from a procedure using T-SQL?

  - by Kivin

  I'm interested in returning an empty result set from SQL Server stored procedures in certain events. The intended behaviour is that a L2SQL DataContext.SPName().SingleOrDefault() will result in CLR null value. I'm presently using the following solution, but I'm unsure whether it would be considered bad practice, a performance hazard (I could not find one by reading the execution plan), or if there is simply a better way: SELECT * FROM [dbo].[TableName] WHERE 0 = 1; The execution plan is a constant scan with a trivial cost associated with it. The reason I am asking this instead of simply not running any SELECTs is because I'm concerned previous SELECT @scalar or SELECT INTO statements could cause unintended result sets to be served back to L2SQL. Am I worrying over nothing?

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• How do I watch a file for changes using Python?

  - by Jon Cage

  I have a log file being written by another process which I want to watch for changes. Each time a change occurrs I'd like to read the new data in to do some processing on it. What's the best way to do this? I was hoping there'd be some sort of hook from the PyWin32 library. I've found the win32file.FindNextChangeNotification function but have no idea how to ask it to watch a specific file. If anyone's done anything like this I'd be really grateful to hear how... [Edit] I should have mentioned that I was after a solution that doesn't require polling. [Edit] Curses! It seems this doesn't work over a mapped network drive. I'm guessing windows doesn't 'hear' any updates to the file the way it does on a local disk.

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• Why No NSAttributedString on the iPhone?

  - by Jasarien

  Hey guys, Does anyone know what made Apple leave out NSAttributedString when turning AppKit into UIKit? The reason I ask is that I would really like to use it in my iPhone app, and there appears to be no replacement or alternative than doing it myself... It is possible to have mixed font attributes on a string - it's just a hell of a lot of work to to achieve something similar that was possible with a few lines of code with NSAttributedString. Also, doing all this extra drawing code myself makes my table view cells really heavy, and really hurts performance. Anyone got any ideas? Any genius's working on an opensource alternative to NSAttributedString?

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• How to use Event notification in Solaris 10 when a directory change

  - by user357594

  I read the following page: Robert Benson's article on ECF developers.sun.com/solaris/articles/event_completion.html I also read the Solaris man pages but they are not very clear of how to use event notifications for directories. For example, If I add a new file into a directory, I would like to get some notification of that event. I found this link: blogs.sun.com/praks/entry/file_events_notification Which has what I need but it is for Solaris 11 ( which is not in the market yet). Based on the link below, I don't want to use poll because I want to get the performance advantage of events. blogs.sun.com/dap/entry/event_ports_and_performance Any suggestion is highly appreciated! -Armando.

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• Order hybrid mixed mysql search result in one query?

  - by Fredrik

  This problem is easy fixed clientside. But for performance I want to do it directly to the database. LIST a +------+-------+-------+ | name | score | cre | +------+-------+-------+ | Abe | 3 | 1 | | Zoe | 5 | 2 | | Mye | 1 | 3 | | Joe | 3 | 4 | Want to retrieve a joined hybrid result without duplications. Zoe (1st higest score) Joe (1st last submitted) Abe (2nd highest score) Mye (2nd last submitted) ... Clientside i take each search by itself and step though them. but on 100.000+ its getting awkward. To be able to use the LIMIT function would ease things up a lot! SELECT name FROM a ORDER BY score DESC, cre DESC; SELECT name FROM a ORDER BY cre DESC, score DESC;

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• Backup Active Directory only

  - by MainMa

  Hi, I have a server with Windows Server 2008. I want to install a new Windows Server 2008 R2 on a new hard disk but on a same machine. What is the way to backup/migrate only Active Directory? I found that migration must be done with Microsoft Active Directory Migration Tool, but it requires both source and target domains running at the same time. Any other suggests are to use an ordinary system backup/restore, but this will restore all other roles, whereas I need only Active Directory role on the new server.

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• Reinstall TeamCity when Tomcat becomes corrupt

  - by dodegaard

  I've got a TeamCity 4 installation where tomcat has bit the dust with the following error "The APR Based Apache Tomcat Native library which allows for optimal performance in production environments was not found in java.library path". It appears this started happening once the JDK was installed on the server to allow for a compile. The JDK has been removed and the JRE reinstalled but still no go. My question is should I reinstall TeamCity completely or is there a way to simply reinstall tomcat so I don't hose the configuration? Your help is greatly appreciated.

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• Fastest Java web templating language

  - by CaptainAwesomePants

  I'm about to start in on a new Spring MVC project, and I'm examining the various options for the view. I've never been a fan of JSP, and I've run into JSP-related performance problems in the past, so I was looking through the other options. I'm hoping that somewhere somebody's taken a census of the various options (maybe it'll have to be me) and pronounced which ones are quick, or at least which options there are. Here are the choices I've thought of, ordered from obvious to bizarre: JSP, JSTL Velocity FreeMarker GSP (Groovy JSP) ERB powered by IronRuby or some such craziness Tea Any suggestions, personal preferences, or other good options for the list?

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• Does the .NET CLR Really Optimize for the Current Processor

  - by dewald

  When I read about the performance of JITted languages like C# or Java, authors usually say that they should/could theoretically outperform many native-compiled applications. The theory being that native applications are usually just compiled for a processor family (like x86), so the compiler cannot make certain optimizations as they may not truly be optimizations on all processors. On the other hand, the CLR can make processor-specific optimizations during the JIT process. Does anyone know if Microsoft's (or Mono's) CLR actually performs processor-specific optimizations during the JIT process? If so, what kind of optimizations?

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• Need help converting apache .htaccess code to lighttpd url_rewrite code

  - by miCRoSCoPiC_eaRthLinG

  Hi All, I have this custom written CMS built on XAMPP. I'm trying to test the same on lighttpd to benchmark the so-called performance gains... but am stuck at the rewrite rules. I use the default rewrite rules of WordPress in my .htaccess which hands all url parsing over to my script as long as there aren't any files or directories same as the URL structure. Here's the code: RewriteBase /somedir/ # Let the Script handle all pretty URLs RewriteCond %{SCRIPT_FILENAME} !-d RewriteCond %{SCRIPT_FILENAME} !-f RewriteRule .* index.php [L] Can anyone please help me translate the same to the lighttpd format? I could only (partially) figure out the last line myself going through the lighty docs ... i.e. url.rewrite-once = ( ".*" => "index.php" ) But that of course won't suffice... All my CMS is doing is giving me 404's. Thanks, miCRoSCoPiC^eaRthLinG

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• Improving the efficiency of Kinect for Windows DTWGestureRecognition Application

  - by Ray

  Currently I am using the DTWGestureRecognition open source tool for Kinect SDK v1.5. I have recorded a few gestures and use them to navigate through Windows 7. I also have implemented voice control for simple things such as opening PowerPoint, Chrome, etc. My main issue is that the application uses quite a bit of my CPU power which causes it to become slow. During gestures and voice commands, the CPU usage sometimes spikes to 80-90%, which causes the application to be unresponsive for a few seconds. I am running it on a 64 bit Windows 7 machine with an i5 processor and 8 GB of RAM. I was wondering if anyone with any experience using this tool or Kinect in general has made it more efficient and less performance hogging. Right now I removed sections which display the RGB video and the Depth video but even doing that did not make a big impact. Any help is appreciated, thanks!

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• Can I use UIPerformance grails plugin and host my static resources in another domain?

  - by fabien7474

  The UIPerfomance plugin is an easy way to speed up your web pages by applying some of the best practices rules from Yahoo performance team (like minifying, setting a far-future expires header, versioned images...) Unfortunately I didn't find a way to store the static resources in a location outside of the webapplication which has his own advantages ( smaller WAR sizes, better optimize cookieless server, static resources served faster by a highly optimized native httpd, no need to redeploy WAR when updating static resources..). So my question is: is it possible to use this great plugin with static resoures stored outside the web application? And if yes, how?

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• Speeding up CakePHP

  - by DavidYell

  I've been a keen fan and user of CakePHP for about 2.5 years now, but the main bugbear that most fellow developers level at the framework is that it's slow, and the dispatch cycle takes too long to make it a viable solution for production environments. I'm hoping that this question will inspire people to share their tips, tricks and hacks for speeding up CakePHP performance. The blog post I most often refer to is here, http://www.pseudocoder.com/archives/8-ways-to-speed-up-cakephp-apps Which has great tips, but there must be more out there! So please feel free to share your thoughts on making this excellent framework that much more nimble!

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• Multiple Broadcast Messages with Less Data or Less Broadcast Messages with More Data?

  - by niko

  Hi, I am developing an application which is communicating with the server. Tha application can perform log-in and get different parameters from server. The application consists of a RESTful client (custom class for making requests), Communication Service (the service which runs in the background) and the main activity. For now I created multiple broadcast messages and multiple broadcast receivers in the main activity so when the application performs login operation a receiver (loginBroadcastReceiver) in the main activity receives a message and when another parameter is received from the server different message is broadcasted and another receiver handles the message. This way however the application performance is poor but I am not sure whether it is due to multiple broadcast receivers. Does anyone know what is the best way to exchange data between service and main activity - is it better to create a single broadcast receiver and retrieve all parameters from message or is it better to initialize multiple broadcast receivers for multiple parameters? I would appreciate if you could provide any useful resource about the topic because I'm writing the thesis and it would be good if the solution could be explained.

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• C# Button Text Unicode characters.

  - by Fossaw

  C# doesn't want to put Unicode characters on buttons. If I put \u2129 in the Text attribute of the button, the button displays the \u2129, not the Unicode character, (example - I chose 2129 because I could see it in the font currently active on the machine). I saw this question before, link text, but the question isn't really answered, just got around. I am working on applications which are going all over the world, and don't want to install all the fonts, more then "don't want", there are that many that I doubt the machine I am working on has sufficient disk space. Our overseas sales agents supply the Unicode character "numbers". Is there another way forward with this? As an aside, (curiosity), why does it not work?

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• Can games be considered real-time systems?

  - by harry

  I've been reading up on real-time systems and how they work etc. I was looking at the wikipedia article as well that said a game of Chess with a timer per move can be considered a real-time system because the program MUST compute a move in that time. What about other games? As we know, games generally try and run at 25+ FPS, could it be considered a soft real-time system since if it falls under 25 (I'm using 25 as a pre-defined threshold btw) it's not the end of the world, just a hit to the performance that we wanted? Also - games have events they must handle as well. The user uses the keyboard/mouse and the system must answer those events accordingly within (again) a pre-defined time, before the game is considered to have "failed". Oh, and I'm talking single-player for now to keep things simple. It sounds like games fit the soft real-time system criteria, but I'd like to know if I'm missing anything... thanks.

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• How to estimate the thread context switching overhead?

  - by Ignas Limanauskas

  I am trying to improve the performance of the threaded application with real-time deadlines. It is running on Windows Mobile and written in C / C++. I have a suspicion that high frequency of thread switching might be causing tangible overhead, but can neither prove it or disprove it. As everybody knows, lack of proof is not a proof of opposite :). Thus my question is twofold: If exists at all, where can I find any actual measurements of the cost of switching thread context? Without spending time writing a test application, what are the ways to estimate the thread switching overhead in the existing application? Does anyone know a way to find out the number of context switches (on / off) for a given thread?

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• High Throughput and Windows Workflow Foundation

  - by SometimesUseful

  Can WWF handle high throughput scenarios where several dozen records are 'actively' being processed in parallel at any one time? We want to build a workflow process which handles a few thousand records per hour. Each record takes up to a minute to process, because it makes external web service calls. We are testing Windows Workflow Foundation to do this. But our demo programs show processing of each record appear to be running in sequence not in parallel, when we use parallel activities to process several records at once within one workflow instance. Should we use multiple workflow instances or parallel activities? Are there any known patterns for high performance WWF processing?

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