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• Profiling statements inside a User-Defined Function

  - by Craig Walker

  I'm trying to use SQL Server Profiler (2005) to track down some application performance problems. One of the calls being made is to a table-valued user-defined function. This function wraps a select that joins several tables together. In SQL Server Profiler, the call to the UDF is logged. However, the select that underlies the UDF isn't being logged at all. Because of this, I'm not getting useful data on which tables & indexes are being hit. I'd like to feed this info into the Database Tuning Advisor for some indexing advice. Is there any way (short of unwrapping the queries themselves) to log the tables called by UDFs in Profiler?

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• Implementing ma? osx loop device driver.

  - by Inso Reiges

  Hello, I am aware that there is a native implementation of loop device system on osx, the hdiutil/hdix driver. But due to a number of reasons i need to roll out my own custom loop driver. Since hdix is closed-source can anyone give some starting pointers, links, advises, etc. on the subject? I had expirience implementing loop drivers on linux and windows but i don't really have a clue where to start from on osx. The basic functionality i need to implement is the same: given any file on disk, simulate a virtual block device interface for it. I also would like my loop driver to use all the native partition filter stacking available for real and hdix virtual block devices on osx.

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• Is writing to a socket an arbitrary limitation of the sendfile() syscall?

  - by Sufian

  Prelude sendfile() is an extremely useful syscall for two reasons: First, it's less code than a read()/write() (or recv()/send() if you prefer that jive) loop. Second, it's faster (less syscalls, implementation may copy between devices without buffer, etc...) than the aforementioned methods. Less code. More efficient. Awesome. In UNIX, everything is (mostly) a file. This is the ugly territory from the collision of platonic theory and real-world practice. I understand that sockets are fundamentally different than files residing on some device. I haven't dug through the sources of Linux/*BSD/Darwin/whatever OS implements sendfile() to know why this specific syscall is restricted to writing to sockets (specifically, streaming sockets). I just want to know... Question What is limiting sendfile() from allowing the destination file descriptor to be something besides a socket (like a disk file, or a pipe)?

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• [java] 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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• ASP.NET: Moving ViewState to bottom of page

  - by Seb Nilsson

  What are the latest and greatest ways to move ViewState to bottom of the page Can this be done in a IHttpHandler that can be specified in the web.config to intercept requests to "*.aspx"? <httpHandlers> <add verb="*" path="*.aspx" type="MyApp.OptimizedPageHandler" /> <httpHandlers> Other options is that this could be done in a IHttpModule, but that is not as performant, as it will intercept all requests. Also it could be done in an a class deriving from the Page or MasterPage-class, but this is not as modular. Are there any performance penalties to this?

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• Variable as numeric sent to stored procedure (SQL Server 2005)

  - by TimCarrett

  I see that with SQL Server 2005 you can pass a parameter as numeric e.g. create procedure dbo.TestSP @Param1 numeric as But what does this equate to? E.g. Numeric(10,0), Numeric(9,2), etc? We have some Developers here who are using this instead of the correct definition for the field that this parameter is going to be used against e.g. instead of using Numeric(10, 0) for the parameter @Param1. Also are there any underlying performance issues with using Numeric instead of the data type defined against the field in the table? Many thanks.

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• Generate HTML To PDF Control for the .NET application

  - by Karan

  Has anyone used any open source or paid .NET Control which does the conversion job from html to pdf file? At the moment, i am using Winnovative convertor control. But it has a performance limitation during the generation of bulk pages (like more than 1000) in the pdf. The limitation comes when we use bigger images in the html content. From last 4 months i've been working on the winnovative control and found plenty of major bugs in it. For a small application and usage. winnovative is good but not for the level where application will be used by thousands of clients. Please suggest.

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• Displaying thumbnails of images (present at different locations in the sdcard) in a listview

  - by frieza

  Hi all, I have several images present in different folders in my sdcard. I would like to display a list of thumbnails. So what I have done is while rendering any row in the list I read the file in an input stream, get the byte array, decode it to obtain a bitmap and set it in an imageview. So far so good. But when I scroll the list, the list scrolls in jerks. I believe this is because decoding a bitmap from byte array takes some time. What I would like to know is that, is there any optimization which I can do to improve the performance, or better still is there any better method to achieve what I want ?

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• Choosing between ExtJS and YUI based on application parameters.

  - by Kabeer

  Hello. I need help in taking call to choose between Ext JS and YUI libraries. Here are the key factors I have derived from my application requirements & development process: Complex, windows forms like controls Widgets, Layouts, Utilities Inter widget communication Easy to extend Easy to learn Intuitive & concise coding Strong exception handling Active support / community To update with upcoming technologies (HTML5, etc.) Skins & Themes to be easy to change Skins & Themes to support variety (a text box for different context to appear differently) Support & Utilities for standard protocols (XmlHttp, JSON) Good performance (responsive) Cost is not crucial, but I don't mind saving :)

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• Infinispan equivalent to ehcache's copyOnRead and copyOnWrite

  - by waxwing

  Hi, I am planning to implement a cache solution into an existing web app. Nothing complicated: basically a concurrent map that supports overflowing to disk and automatic eviction. Clustering the cache could be requirement in the future, but not now. I like ehcache's copyOnRead and copyOnWrite features, because it means that I don't have to manually clone things before modifying something I take out of the cache. Now I have started to look at Infinispan, but I have not found anything equivalent there. Does it exist? I.e., the following unit tests should pass: @Test public void testCopyOnWrite() { Date date = new Date(0); cache.put(0, date); date.setTime(1000); date = cache.get(0); assertEquals(0, date.getTime()); } @Test public void testCopyOnRead() { Date date = new Date(0); cache.put(0, date); assertNotSame(cache.get(0), cache.get(0)); }

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• Why would you want a case sensitive database?

  - by Khorkrak

  What are some reasons for choosing a case sensitive collation over a case insensitive one? I can see perhaps a modest performance gain for the DB engine in doing string comparisons. Is that it? If your data is set to all lower or uppercase then case sensitive could be reasonable but it's a disaster if you store mixed case data and then try to query it. You have then apply a lower() function on the column so that it'll match the corresponding lower case string literal. This prevents index usage in every dbms. So wondering why anyone would use such an option.

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• Optimizing for speed - 4 dimensional array lookup in C

  - by Tiago

  I have a fitness function that is scoring the values on an int array based on data that lies on a 4D array. The profiler says this function is using 80% of CPU time (it needs to be called several million times). I can't seem to optimize it further (if it's even possible). Here is the function: unsigned int lookup_array[26][26][26][26]; /* lookup_array is a global variable */ unsigned int get_i_score(unsigned int *input) { register unsigned int i, score = 0; for(i = len - 3; i--; ) score += lookup_array[input[i]][input[i + 1]][input[i + 2]][input[i + 3]]; return(score) } I've tried to flatten the array to a single dimension but there was no improvement in performance. This is running on an IA32 CPU. Any CPU specific optimizations are also helpful. Thanks

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• Best way for programmers to edit XAML

  - by JessicaB

  I was wondering how programmers chose to edit XAML. Most of the programmers I speak to seem to edit the raw XML, but that seems nuts to me since it is such a natural thing for a more visual editor (of course you often have to get down to the raw code ultimately, but isn't there a better way to lay out a grid, or edit a template, or add non c# triggers or manage commands? The one that really set me off was editing a menu -- Visual Studio 1.0 had a better menu editor for C++ than the raw XAML editing experience.) When I edit .aspx files I use a visual editor much of the time, and then for the raw stuff I get into the html code. I am aware of Expression Blend, but that seems far more focused on artistic types and GUI experts rather than programmers. Does anyone have recommendations for a better editor for XAML than VS? Especially so since VS seems to have real nasty problems with XAML editing too, like bugginess and poor performance? Appreciate your helping this XAML newbie.

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• Multiple Socket Connections

  - by BSchlinker

  I need to write a server which accepts connections from multiple client machines, maintains track of connected clients and sends individual clients data as necessary. Sometimes, all clients may be contacted at once with the same message, other times, it may be one individual client or a group of clients. Since I need confirmation that the clients received the information and don't want to build an ACK structure for a UDP connection, I decided to use a TCP streaming method. However, I've been struggling to understand how to maintain multiple connections and keep them idle. I seem to have three options. Use a fork for each incoming connection to create a separate child process, use pthread_create to create an entire new thread for each process, or use select() to wait on all open socket IDs for a connection. Recommendations as to how to attack this? I've begun working with pthreads but since performance will likely not be an issue, multicore processing is not necessary and perhaps there is a simpler way.

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• Init modules in apache2

  - by user306963

  Hello, I used to write apache modules in apache 1.3, but these days I am willing to pass to apache2. The module that I am writing at the moment has is own binary data, not a database, for performance purposes. I need to load this data in shared memory, so every child can access it without making his own copy, and it would be practical to load/create the binary data at startup, as I was used to do with apache 1.3. Problem is that I don't find an init event in apache2, in 1.3 in the module struct, immediatly after STANDARD_MODULE_STUFF you find a place for a /** module initializer */, in which you can put a function that will be executed early. Body of the function I used to write is something like: if ( getppid == 1 ) { // Load global data here // this is the parent process void* data = loadGlobalData( someFilePath ); setGlobalData( config, data ); } else { // this is the init of a child process // do nothing } I am looking for a place in apache2 in where I can put a similar function. Can you help? Thanks Benvenuto

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• ASP.NET Download All Files as Zip

  - by Ronnie Overby

  I have a folder on my web server that has hundreds of mp3 files in it. I would like to provide the option for a user to download a zipped archive of every mp3 in the directory from a web page. I want to compress the files programmatically only when needed. Because the zip file will be quite large, I am thinking that I will need to send the zip file to the response stream as it is being zipped, for performance reasons. Is this possible? How can I do it?

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• Is adding indexes to a SQL Server ever a bad idea?

  - by Aerik

  We have a mid-size SQL Server based application that has no indexes defined. Not even on the the identity columns. I suggested to our moderately expensive application consultant that perhaps we might get better performance (particularly as our database grows) by creating some indexes on appropriate fields, and he said: "Indexes will significantly impact other areas of the application and customers should not create them under any circumstances." Anybody ever heard of anything like this? Are there ever circumstances where one should not create any indexes? I can see nothing special about this app - it's got int identity columns, then lots of string columns, bunch of relational tables but nothing special or weird that I can see. Thanks!

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• ./configure : /bin/sh^M : bad interpreter

  - by Vineeth

  Hello there, I've been trying to install lpng142 on my fed 12 system. Seems like a problem to me. I get this error [root@localhost lpng142]# ./configure bash: ./configure: /bin/sh^M: bad interpreter: No such file or directory [root@localhost lpng142]# How do I fix this? and for more details, I shall include the /etc/fstub file details here # # /etc/fstab # Created by anaconda on Wed May 26 18:12:05 2010 # # Accessible filesystems, by reference, are maintained under '/dev/disk' # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info # /dev/mapper/VolGroup-lv_root / ext4 defaults 1 1 UUID=ce67cf79-22c3-45d4-8374-bd0075617cc8 /boot ext4 defaults 1 2 /dev/mapper/VolGroup-lv_swap swap swap defaults 0 0 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 [root@localhost etc]# Help, please

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• New to AVL tree implementation.

  - by nn

  I am writing a sliding window compression algorithm (LZ77) that searches for phrases in a "moving" dictionary. So far I have written a BST where each node is stored in an array and it's index in the array is also the value of the starting position in the window itself. I am now looking at transforming the BST to an AVL tree. I am a little confused at the sample implementations I have seen. Some only appear to store the balance factors whereas others store the height of each tree. Are there any performance advantage/disadvantages of storing the height and/or balance factor for each node? Apologies if this is a very simple question, but I'm still not visualizing how I want to restructure my BST to implement height balancing. Thanks.

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• Remove first 'n' elements from list without itterating

  - by Eldhose M Babu

  I need an efficient way of removing items from list. If some condition happens, I need to remove first 'n' elements from a list. Can some one suggest the best way to do this? Please keep in mind: performance is a factor for me, so I need a faster way than itterating. Thanks. I'm thinking of a way through which the 'n'th item can be made as the starting of the list so that the 0-n items will get garbage collected. Is it possible?

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• writing a fast parser in python

  - by panzi

  I've written a hands-on recursive pure python parser for a some file format (ARFF) we use in one lecture. Now running my exercise submission is awfully slow. Turns out by far the most time is spent in my parser. It's consuming a lot of CPU time, the HD is not the bottleneck. I wonder what performant ways are there to write a parser in python? I'd rather not rewrite it in C. I tried to use jython, but that decreased performance a lot! The files I parse are partially huge ( 150 MB) with very long lines. My current parser only needs a look-ahead of one character. I'd post the source here but I don't know if that's such a good idea. After all the submission deadline has not jet ended. But then, the focus in this exercise is not the parser. You can choose whatever language you want to use and there already is a parser for Java.

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• Looking for the most painless non-RDBMS storage method in C#

  - by NateD

  I'm writing a simple program that will run entirely client-side. (Desktop programming? do people still do that?) and I need a simple way to store trivial amounts of data in a structured form, but really don't see any need to use a database system. What's more, some of the data needs to be serialized and passed around to different users, like some kind of "file" or perhaps a "document". (has anyone ever done that before?) So, I've looked at using .Net DataSets, LINQ, direct XML manipulation, and they all seem like they would get the job done, but I would like to know before I dive into any of them if there's one method that is generally regarded as easier to code than others. As I said, the amount of data to be stored is trivial, even if one hundred people all used the same machine we're not talking about more than 10 MB, so performance is not as large a concern as is codeability/maintainability. Thank you all in advance!

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• Using one sqlconnection/sqlcommand through 2 DB-bound methods

  - by dotnetdev

  I have a class with a method which gets data from a database through a SELECT stored proc. This method uses a SqlDbReader by returning ExecuteReader() on a SqlCommand. The connection and everything is made in this method, with fields (such as connection string) set as class level fields. I now need to populate an array based on the results of this query (so the columns of each row will go into the array with its own index). However, this query will not select all of the data from one table which is involved. I can write the queries to get what I need, but how can I use one connection throughout the class? If I instantiate the connection object and call Open() in the constructor, I get an exception @ runtime. I'm hoping for something like this: // At class level: sqlconn.Open(); // sqlcommand set up Method() { // Fire stored proc // Insert results in a collection } Method2() { // Pass same collection in (use same one), // Add new row columns into same collection } How can I do this with strict performance in mind? Thanks

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• How to improve INSERT INTO ... SELECT locking behavior

  - by Artem

  In our production database, we ran the following pseudo-code SQL batch query running every hour: INSERT INTO TemporaryTable (SELECT FROM HighlyContentiousTableInInnoDb WHERE allKindsOfComplexConditions are true) Now this query itself does not need to be fast, but I noticed it was locking up HighlyContentiousTableInInnoDb, even though it was just reading from it. Which was making some other very simple queries take ~25 seconds (that's how long that other query takes). Then I discovered that InnoDB tables in such a case are actually locked by a SELECT! http://www.mysqlperformanceblog.com/2006/07/12/insert-into-select-performance-with-innodb-tables/ But I don't really like the solution in the article of selecting into an OUTFILE, it seems like a hack (temporary files on filesystem seem sucky). Any other ideas? Is there a way to make a full copy of an InnoDB table without locking it in this way during the copy. Then I could just copy the HighlyContentiousTable to another table and do the query there.

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• Best way to store large dataset in SQL Server?

  - by gary

  I have a dataset which contains a string key field and up to 50 keywords associated with that information. Once the data has been inserted into the database there will be very few writes (INSERTS) but mostly queries for one or more keywords. I have read "Tagsystems: performance tests" which is MySQL based and it seems 2NF appears to be a good method for implementing this, however I was wondering if anyone had experience with doing this with SQL Server 2008 and very large datasets. I am likely to initially have 1 million key fields which could have up to 50 keywords each. Would a structure of keyfield, keyword1, keyword2, ... , keyword50 be the best solution or two tables keyid keyfield | 1 | | M keyid keyword Be a better idea if my queries are mostly going to be looking for results that have one or more keywords?

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