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• Why SQL functions are faster than UDF

  - by Zerotoinfinite

  Though it's a quite subjective question but I feel it necessary to share on this forum. I have personally experienced that when I create a UDF (even if that is not complex) and use it into my SQL it drastically decrease the performance. But when I use SQL inbuild function they happen to work pretty faster. Conversion , logical & string functions are clear example of that. So, my question is "Why SQL in build functions are faster than UDF"? and it would be an advantage if someone can guide me how can I judge/manipulate function cost either mathematically or logically.

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• Selecting a value from multiple dictionaries inside an enumeration

  - by johaanfaust

  If I have an enumeration of dictionaries IEnumerable<IDictionary<string, float>> enumeration can I perform a Linq query on it so that I can select by a value from each dictionary in the enumeration using the same key? I can do this in a loop: float f; foreach (var dictionary in enumeration) { if (dictionary.TryGetValue("some key", out f)) { Console.WriteLine(f); } } (The eventual plan is to compare the performance of the query verses the equivalent nested looping statements (the enumeration itself is formed from either another query or an equivalent set of loops).)

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• How do I change the class of an object to a subclass of its current class in C++?

  - by Jared P

  I have an array of pointers to a base class, so that I can make those pointers point to (different) subclasses of the base class, but still interact with them. (really only a couple of methods which I made virtual and overloaded) I'm wondering if I can avoid using the pointers, and instead just make an array of the base class, but have some way to set the class to the subclass of my choosing. I know there must be something there specifying the class, as it needs to use that to look up the function pointer for virtual methods. By the way, the subclasses all have the same ivars and layout. Note: the design is actually based on using a template argument instead of a variable, due to performance increases, so really the abstract base class is just the interface for the subclasses, which are all the same except for their compiled code. Thanks

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• Class.Class vs Namespace.Class for top level general use class libraries?

  - by Joan Venge

  Which one is more acceptable (best-practice)?: namespace NP public static class IO public static class Xml ... // extension methods using NP; IO.GetAvailableResources (); vs public static class NP public static class IO public static class Xml ... // extension methods NP.IO.GetAvailableResources (); Also for #2, the code size is managed by having partial classes so each nested class can be in a separate file, same for extension methods (except that there is no nested class for them) I prefer #2, for a couple of reasons like being able to use type names that are already commonly used, like IO, that I don't want to replace or collide. Which one do you prefer? Any pros and cons for each? What's the best practice for this case? EDIT: Also would there be a performance difference between the two?

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• Does HTML5 only replace the video aspects of Flash/Silverlight?

  - by John

  I see a lot of talk how HTML5 video tag will kill Flash. But while video is the most widely used part of Flash/SL, it's only a small part of their technical abilities. For instance you can write a game using full 3D graphics and socket connections in Flex, and serious business applications, etc. Is the thinking that Javascript will kill those parts of Flash/Flex/SL? Because while that seems feasible now for even quite rich web-apps, what about any kind of high-performance app like real-time graphics?

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• Which are the current/emerging desktop development technologies worth looking into?

  - by heeboir

  Greetings, With all the existing development towards web development and emerging technologies in that area, I'm left wondering; what is a state of the art way to implement desktop applications in this day and age? If you were to start a new application of considerable size from scratch what technology would you invest your efforts in (focusing on cross platform portability, decent performance and interoperability with existing standards)? I've looked into the Adobe Air platform which appears quite impressive but seems rather limited to support a large application. Would something like Java/SWT still be the sensible choice? Do things like GWT fit the bill? Thanks P.S. I'm leaving my question a bit open-ended in an effort to gather diverse answers. Surely this a subjective matter and there is no right and wrong answer.

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• Is select() Ok to implemnet single socket read/write timeout ?

  - by chmike

  I have an application processing network communication with blocking calls. Each thread manages a single connection. I've added a timeout on the read and write operation by using select prior to read or write on the socket. Select is known to be inefficient when dealing with large number of sockets. But is it ok, in term of performance to use it with a single socket or are there more efficient methods to add timeout support on single sockets calls ? The benefit of select is to be portable.

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• Separate one-off code paths

  - by DeadMG

  I'm implementing an application with different code paths that shall be chosen once at startup and then fixed forevermore for that execution- for example, choosing D3D11 or D3D9 rendering path. Obviously I don't want to duplicate all my other code. Is run-time inheritance (no virtual inheritance) a fair solution? I don't want to waste a bunch of performance making virtual lookups when the type was fixed long ago. Not just that, but it makes me nervous that the functions can't be inlined and whether or not it affects RVO and NRVO and such. Am I just being over-concerned about this?

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• Restricting deletion with NHibernate

  - by FrontSvin

  I'm using NHibernate (fluent) to access an old third-party database with a bunch of tables, that are not related in any explicit way. That is a child tables does have parentID columns which contains the primary key of the parent table, but there are no foreign key relations ensuring these relations. Ideally I would like to add some foreign keys, but cannot touch the database schema. My application works fine, but I would really like impose a referential integrity rule that would prohibit deletion of parent objects if they have children, e.i. something similar 'ON DELETE RESTRICT' but maintained by NHibernate. Any ideas on how to approach this would be appreciated. Should I look into the OnDelete() method on the IInterceptor interface, or are there other ways to solve this? Of course any solution will come with a performance penalty, but I can live with that.

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• Using pthread condition variable with rwlock

  - by Doomsday

  Hello, I'm looking for a way to use pthread rwlock structure with conditions routines in C++. I have two questions: First: How is it possible and if we can't, why ? Second: Why current POSIX pthread have not implemented this behaviour ? To understand my purpose, I explain what will be my use: I've a producer-consumer model dealing with one shared array. The consumer will cond_wait when the array is empty, but rdlock when reading some elems. The producer will wrlock when adding(+signal) or removing elems from the array. The benefit of using rdlock instead of mutex_lock is to improve performance: when using mutex_lock, several readers would block, whereas using rdlock several readers would not block.

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• Looking for a source code management system with a good GUI client

  - by Anders Öhrt

  We are currently using CS-RCS Pro for source code management, and are looking for to replace this due to performance issues. It is based on client side file access with no own protocol, which makes it painfully slow to use over a slow VPN line since it always rewrites the whole history of a file. It does however have a GUI client which is very simple and gives a great overview. We have three main requirements in a SCM: Fast. It must have a server side service or some other smart way so working with files with a large history is fast. A good Windows GUI client (not Explorer shell integration, not VS or Eclipse IDE integration), so working with files and branches is easy. The possibility to have several branches checked out at once in different directories. Does anyone have a recommendation of a SCM which fulfills there requirements?

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• Forced to use too many hidden fields; looking for an alternative approach

  - by harisri786

  I am looking for a better approach to do this. I have around 70 to 80 hidden fields in my page. This hidden fields are initialized at the server side and then used at the client side for validations, calculations, etc,. using java script. I wanted to know if there is any other alternative approach to using hidden fields in asp.net. I guess, these many hidden fields are increasing the page size and hence affecting the performance of my web page and I want to do away with it. FYI: I am working on an asp.net web application.

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• Objective-C style question: do "release" or "nil" properties in dealloc?

  - by Piotr Czapla

  Hi, Apple usually release ivars in dealloc but is there anything wrong with nilling the properties in dealloc? I mean instead of this: - (void) dealoc(){ [myRetainedProperty release]; [super dealloc]; } write code like this: - (void) dealoc(){ self.myRetainedProperty = nil; [super dealloc]; } I know that it is one additional method call but on the other hand it is safer as it doesn't crashes when you change your property form retain to assign and forget to amend dealloc. What do you think? Can you think about any other reason to use release instead of setting nil besides performance?

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• Capture IP packets on Dialup connection - Windows 7

  - by Assaf Levy

  Our product utilizes (the wonderful) Winpcap to capture ip packets from all devices with an IP address and analyze them in real time. Unfortunately, we discovered that it does NOT capture any packets on dialup (e.g. PPP) connections on Windows 7, and that there are no near-term plans for enabling this (1). So we need something else. Microsoft Network Monitor and Windows Packet Filter are two options that surfaced during a bit of googling, but before delving into research I wanted to ask the experienced: what are out options, given the following requirements: Capture all in/outbound IP packets on the machine. Complete background processing - no UI should be involved. Support Windows Vista / 7. Performance (user should not feel the difference). Thanks in advance.

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• Oracle spatial search within distance

  - by KA_lin

  I have the following table Cities: ID(int),City(char),latitude(float),longitude(float). Now based on a user`s longitude(ex:44.8) and latitude(ex:46.3) I want to search for all the cities near him within 100 miles/KM. I have found some examples but don`t know how to adapt them to my case select * from GEO.Cities a where SDO_WITHIN_DISTANCE([I don`t know], MDSYS.SDO_GEOMETRY(2001, 8307, MDSYS.SDO_POINT_TYPE(44.8,46.3, NULL) ,NULL, NULL), 'distance = 1000') = 'TRUE'; Any help would be appreciated. P.S: If it is possible to have the distance and to be sorted P.P.S: I want to do it in this way due to performance issues, I have done this in this way http://www.scribd.com/doc/2569355/Geo-Distance-Search-with-MySQL but it takes too long...

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• C# asp.net MVC: When to update LastActivityDate?

  - by Oskar Kjellin

  I'm using asp.net mvc and creating a public website. I need to keep track of users that are online. I see that the standard way in asp.net of doing this is to keep track of LastActivityDate. My question is when should I update this? If I update it every time the users clicks somewhere, I will feel a performance draw back. However if I do not do that, people that only surf arround will be listed as offline. What is the best way to do this in asp.net MVC?

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• Django: common template subsections

  - by Parand

  What's a good way to handle commonly occurring subsections of templates? For example, there is a sub-header section that's used across 4 different pages. The pages are different enough to not work well with template inheritance (ie. "extends" doesn't fit well). Is "include" the recommended method here? It feels a bit heavyweight, requiring each subsection or snippet to be in its own file. Are there any performance issues in using include or is it smart about forming template from the subsections (ie. if I make extensive use of it, do I pay any penalties)? I think what I'm looking for is something like template tags, but without the programming - a simple way to create a library of html template tags I can sprinkle in other templates.

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• Can I replicate some of the optimisations done by the JVM by hand?

  - by Subb

  I'm working on a Sudoku solver at school and we're having a little performance contest. Right now, my algorithm is pretty fast on the first run (about 2.5ms), but even faster when I solve the same puzzle 10 000 times (about 0.5ms for each run). Those timing are, of course, depend of the puzzle being solved. I know the JVM do some optimization when a method is called multiple time, and this is what I suspect is happening. I don't think I can further optimize the algorithm itself (though I'll keep looking), so I was wondering if I could replicate some of the optimizations done by the JVM. Note : compiling to native code is not an option Thanks!

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• SQL Server, fetching data from multiple joined tables. Why is slow?

  - by user562192

  I have problem with performance when retrieving data from SQL Server. My sql query looks something like this: SELECT table_1.id, table_1.value, table_2.id, table_2.value,..., table_20.id, table_20.value From table_1 INNER JOIN table_2 ON table_1.id = table_2.table_1_id INNER JOIN table_3 ON table_2.id = table_3.table_2_id... WHERE table_1.row_number BETWEEN 1 AND 20 So, I am fetching 20 results. This query takes about 5 seconds to execute. When I select only table_1.id, it returns results instantly. Because of that, I guess that problem is not in JOINs, it is in retrieving data from multiple tables. Any suggestions how I would speed up this query?

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• Worried about spiders repeatedly hitting high-demand page

  - by Matt Thrower

  Due to some rather bizarre architectural considerations I've had to set up something that really ought to run as a console application as a web page. It does the job of writing a large variety of text files and xml feeds from our site data for various other services to pick up so obviously it takes a little while to run and is pretty processor intensive. However, before I deploy it I'm rather worried that it might get hit repeatedly by spiders and the like. It's fine for the data to be re-written but continual hits on this page are going to trigger performance issues for obvious reasons. Is this something I ought to worry about? Or in reality is spider traffic unlikely to be intensive enough to cause problems?

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• C#. Struct design. Why 16 byte is recommended size?

  - by maxima120

  I read Cwalina book (recommendations on development and design of .NET apps). He says that good designed struct has to be less than 16 bytes in size (for performance purpose). My questions is - why exactly is this? And (more important) can I have larger struct with same efficiency if I run my .NET 3.5 (soon to be .NET 4.0) 64-bit application on i7 under Win7 x64 (is this limitation CPU / OS based)? Just to stress again - I need as efficient struct as it is possible. I try to keep it in stack all the time, the application is heavily multi-threaded and runs on sub-millisecond intervals, the current size of the struct is 64 byte.

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• The case of the mysterious MySQL caching across restarts

  - by shanusmagnus

  I found a very slow MySQL query in my web app. The weird thing is that the query is only slow the first time it's executed, despite the fact that the query_cache is set to its default (query_cache_size 0) like so: mysql> show variables like 'query%'; +------------------------------+---------+ | Variable_name | Value | +------------------------------+---------+ | query_alloc_block_size | 8192 | | query_cache_limit | 1048576 | | query_cache_min_res_unit | 4096 | | query_cache_size | 0 | | query_cache_type | ON | | query_cache_wlock_invalidate | OFF | | query_prealloc_size | 8192 | +------------------------------+---------+ The even weirder thing is that this speedup persists even after the MySQL server has been stopped and restarted (I'm using OSX, and perform this restart using the system preferences pane.) The only way I can re-create the poor performance of the initial query is by rebooting the system. So my question is: how is this happening? Obviously some sort of caching at work, but where? And how does it persist across database restarts? This query is mediated through our web app, which comes via PHP/Apache, but there are no extra bells and whistles, and the curious caching also persists across Apache restarts. Help?

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• Go, AppEngine: How to structure templates for application

  - by laslowh

  How are people handling the use of templates in their Go-based AppEngine applications? Specifically, I'm looking for a project structure that affords the following: Hierarchical (directory) structure of templates and partial templates Allow me to use HTML tools/editors on my templates (embedding template text in xxx.go files makes this difficult) Automatic reload of template text when on dev server Potential stumbling blocks are: template.ParseGlob() will not traverse recursively. For performance reasons it has been recommended not to upload your templates as raw text files (because those text files reside on different servers than executing code). Please note that I am not looking for a tutorial/examples of the use of the template package. This is more of an app structure question. That being said, if you have code that solves the above problems, I would love to see it. Thanks in advance.

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• Take advantage of multiple cores executing SQL statements

  - by willvv

  I have a small application that reads XML files and inserts the information on a SQL DB. There are ~ 300 000 files to import, each one with ~ 1000 records. I started the application on 20% of the files and it has been running for 18 hours now, I hope I can improve this time for the rest of the files. I'm not using a multi-thread approach, but since the computer I'm running the process on has 4 cores I was thinking on doing it to get some improvement on the performance (although I guess the main problem is the I/O and not only the processing). I was thinking on using the BeginExecutingNonQuery() method on the SqlCommand object I create for each insertion, but I don't know if I should limit the max amount of simultaneous threads (nor I know how to do it). What's your advice to get the best CPU utilization? Thanks

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• When is BIG, big enough for a database?

  - by David ???

  I'm developing a Java application that has performance at its core. I have a list of some 40,000 "final" objects, i.e., I have an initialization input data of 40,000 vectors. This data is unchanged throughout the program's run. I am always preforming lookups against a single ID property to retrieve the proper vectors. Currently I am using a HashMap over a sub-sample of a 1,000 vectors, but I'm not sure it will scale to production. When is BIG, actually big enough for a use of DB? One more thing, an SQLite DB is a viable option as no concurrency is involved, so I guess the "threshold" for db use, is perhaps lower.

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