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• DataReader - hardcode ordinals?

  - by David Neale

  When returning data from a DataReader I would typically use the ordinal reference on the DataReader to grab the relevant column: if (dr.HasRows) Console.WriteLine(dr[0].ToString()); (OR dr.GetString(0); OR (string)dr[0];)... I have always done this because I was advised at an early stage that using dr["ColumnName"] or a more elegant way of indexing causes a performance hit. However, whilst everything is becoming increasingly strongly-typed I feel more uncomfortable with this. I'm also aware that the above does not check for DBNull. How should data be returned from a DataReader?

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• Best practices for combining Lucene.NET and a relational database?

  - by FlySwat

  I'm working on a project where I will have a LOT of data, and it will be searchable by several forms that are very efficiently expressed as SQL Queries, but it also needs to be searched via natural language processing. My plan is to build an index using Lucene for this form of search. My question is that if I do this, and perform a search, Lucene will then return the ID's of matching documents in the index, I then have to lookup these entities from the relational database. This could be done in two ways (That I can think of so far): N amount of queries (Horrible) Pass all the ID's to a stored procedure at once (Perhaps as a comma delimited parameter). This has the downside of being limited to the max parameter size, and the slow performance of a UDF to split the string into a temporary table. I'm almost tempted to mirror everything into lucenes index, so that I can periodicly generate the index from the backing store, but only need to access it for the frontend. Advice?

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• ASP.NET Validator Controls Slowing Down Page

  - by Calvin Nguyen

  Hi all, I have an UpdatePanel that has user controls dynamically added to it. There can be a few dozen user controls at times. The page / UpdatePanel slows down big time on each postback as more user controls are added. After some digging, I was surprised to find the cause is the various CompareValidator, CustomValidator, RegularExpressionValidator and RequiredFieldValidator controls that exist on each user control. Dose anyone have suggestions? It strikes me as very peculiar that inclusion of these ASP.NET controls could have such a horrible effect on performance. Thanks, Calvin

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• Image Application in WPF and Perfomance.

  - by Harsha

  Hello All, I am planning to build Image processing application using WPF. Brightness /Contrast and Histogram are main operation of this application. I have downloaded the application " Foundations: Bitmaps and Pixel Bits" from http://msdn.microsoft.com/en-us/magazine/cc534995.aspx . But when I tried to open the images which are more than 1200x1600, It is very slow. How to increase the performance. Is any one worked on Image processing in WPF. Please suggest me how to solve this perfomance issue in WPF for image(more than 1600x1200) operation. Thanks you, Harsha

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• Query optimization

  - by Lijo

  Hi Team, I am trying to learn SQL query optimization using SQL Server 2005. However, I did not find any practical example where I can improve performance by tweaking query alone. Can you please list some example queries - prior and after optimization? It has to be query tuning – not adding index, not making covering index, not making any alteration to table. No change is supposed to be done on table and index. [ I understand that indexes are important. This is only for learning purpose] It would be great if you can exaplain using temp table instead of refering any sample databases like adventureworks. Expecting your support... Thanks Lijo

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• Custom broadcast events in AS3?

  - by Ender

  In Actionscript 3, most events use the capture/target/bubble model, which is pretty popular nowadays: When an event occurs, it moves through the three phases of the event flow: the capture phase, which flows from the top of the display list hierarchy to the node just before the target node; the target phase, which comprises the target node; and the bubbling phase, which flows from the node subsequent to the target node back up the display list hierarchy. However, some events, such as the Sprite class's enterFrame event, do not capture OR bubble - you must subscribe directly to the target to detect the event. The documentation refers to these as "broadcast events." I assume this is for performance reasons, since these events will be triggered constantly for each sprite on stage and you don't want to have to deal with all that superfluous event propagation. I want to dispatch my own broadcast events. I know you can prevent an event from bubbling (Event.bubbles = false), but can you get rid of capture as well?

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• How can I turn on DynamicCompression feature of IIS programmatically?

  - by LockeVN

  I'm making an installer program for my web application. My web application uses CSS and JS heavily, so I want to enable both Static and Dynamic HttpCompression for IIS7/7.5. It needs 2 steps: I can modified the web.config, put <httpcompression> tag, it's ok. DynamicContentCompression must be turned on in Windows Feature to make httpCompression work. Static HttpCompression is enable by default in IIS7 and IIS7.5, but Dynamic HttpCompression is not enable by default (although it's available). I can do manually by turn on: Start/ControlPanel/ProgramsAndFeatures/TurnWindowsFeatures on or Off/IIS/WWW Service/Performance features/Dynamic Content Compression, but How can I programmatically turn it on that Windows Feature? I can use PowerShell, C# in my installer. Any idea how I might be able to do this? Thanks.

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• Best CPUs for speeding up compiling times of C++ w/ DistGCC

  - by Jay

  I'm putting together a distributed build farm with DistGCC to speed up our teams compile times and just looking for thoughts on which processors to use in the hosts. Are we going to get a noticeable decrease in time using 8 cores vs. 4-hyperthreaded cores? Big difference in time between i7 and Xeon? etc, etc. Just need advice from people who've put together kick-a build clusters. We've got a majority of the normal things to speed up builds in place (pre-compiled headers, ccache, local gigabit connections between them, tons of ram, etc) so please just give advice on the best processor to use. And money is a factor, but anythings doable if the performance increase is noticeable. Thanks. Jay

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• Alternative to Nested Loop For Comparison

  - by KGVT

  I'm currently writing a program that needs to compare each file in an ArrayList of variable size. Right now, the way I'm doing this is through a nested code loop: if(tempList.size()>1){ for(int i=0;i<=tempList.size()-1;i++) //Nested loops. I should feel dirty? for(int j=i+1;j<=tempList.size()-1;j++){ //*Gets sorted. System.out.println(checkBytes(tempList.get(i), tempList.get(j))); } } I've read a few differing opinions on the necessity of nested loops, and I was wondering if anyone had a more efficient alternative. At a glance, each comparison is going to need to be done, either way, so the performance should be fairly steady, but I'm moderately convinced there's a cleaner way to do this. Any pointers?

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• Cast to generic type in C#

  - by Andrej

  I have a Dictionary to map a certain type to a certain generic object for that type. For example: typeof(LoginMessage) maps to MessageProcessor<LoginMessage> Now the problem is to retrieve this generic object at runtime from the Dictionary. Or to be more specific: To cast the retrieved object to the specific generic type. I need it to work something like this: Type key = message.GetType(); MessageProcessor<key> processor = messageProcessors[key] as MessageProcessor<key>; Hope there is a easy solution to this. Edit: I do not want to use Ifs and switches. Due to performance issues I cannot use reflection of some sort either.

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• Entity Framework, full-text search and temporary tables

  - by markus

  I have a LINQ-2-Entity query builder, nesting different kinds of Where clauses depending on a fairly complex search form. Works great so far. Now I need to use a SQL Server fulltext search index in some of my queries. Is there any chance to add the search term directly to the LINQ query, and have the score available as a selectable property? If not, I could write a stored procedure to load a list of all row IDs matching the full-text search criteria, and then use a LINQ-2-Entity query to load the detail data and evaluate other optional filter criteria in a loop per row. That would be of course a very bad idea performance-wise. Another option would be to use a stored procedure to insert all row IDs matching the full-text search into a temporary table, and then let the LINQ query join the temporary table. Question is: how to join a temporary table in a LINQ query, as it cannot be part of the entity model?

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• How can a Delphi TForm / TPersistent object calculate its own deserialization time?

  - by mjustin

  For performance tests I need a way to measure the time needed for a form to load its definition from the DFM. All existing forms inherit a custom form class. To capture the current time, this base class needs overriden methods as "extension points": start of the deserialization process after the deserialization (can be implemented by overriding the Loaded procedure) the moment just before the execution of the OnFormCreate event So the log for TMyForm.Create(nil) could look like: - 00.000 instance created - 00.010 before deserialization - 01.823 after deserialization - 02.340 before OnFormCreate Which TObject (or TComponent) methods are best suited? Maybe there are other extension points in the form creation process, please feel free to make suggestions.

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• PHP/MySQL database connection priority?

  - by Josh

  Hello, I have a production database where usage statistics for a service we're working on. I use php to periodically roll up different resolutions (day, week, month, year) of interesting statistics in buckets dictated by the resolution. The php application I've written "completes" its data when its run, such that it will calculate all the rolled-up statistics for the resolutions and periods since it was last run. This is useful if we want to turn this off to debug database performance issues, because I can turn it back on and have it complete its data set. The problem I have, is the calculations are fairly intensive and drive the QPS of the production database server up. Is there a way to set a "priority" on a particular database connection so that it will only use "off-cycles" to do these calculations? Maybe a proper response would be to replicate the tables I'm working on into a different stats database, but, unfortunately I don't have the resources in place to attempt such a thing (yet). Thanks in advance for any help, Josh

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• PHP on Windows: Apache or IIS7?

  - by josecortesp

  Here's the thing: Due to a new project, I have to learn PHP from scratch. I'm now in windows and I DON'T want to change quickly, so, don't tell me to change. I need to setup a DreamWeaverCS4/PHP5 develop environment, and, I don't have a clue whether to use Apache or IIS7. I just need some advice relating to it. Remarks: I really don't care about performance(yet), neither portability, and so on. I just need to set it up quickly and easily. Thanks in advance

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• Can I draw Qt objects directly to Win32 DC (Device Context)?

  - by Kevin

  I can draw Qt objects to an QImage and then draw the image to HDC or CDC. This may hurt our application's performance. It would be great if I can draw Qt objects directly to Win32 HDC or MFC CDC. I expect that there is a class, say QWin32Image for clear, then I can use it in this way: QWin32Image image(hdc, 100, 100, Format_ARGB32_Premultiplied); QPainter painter(&image); painter.drawText(....); Is it possible for my thought? Or is there a better way to do that?

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• Programatically detect number of physical processors/cores or if hyper-threading is active on Window

  - by HTASSCPP

  I have a multithreaded c++ application that runs on Windows, Mac and a few Linux flavours. To make a long story short: Inorder for it to run at maximum efficiency I have to be able to instantiate a single thread per physical processor/core. Creating more threads than there are physical processors/cores degrades the performance of my program considerably. I can already correctly detect the number of logical processors/cores correctly on all three of these platforms. To be able to detect the number of physical processors/cores correctly I'll have to detect if hyper-treading is supported AND active. My question therefore is if there is a way to detect whether hyperthreading is supported AND ENABLED? If so, how exactly.

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• iPhone "slide to unlock" animation

  - by Russ

  Any ideas as to how Apple implemented the "slide to unlock" (also, "slide to power off" is another identical example) animation? I thought about some sort of animating mask - but masking is not available on the iPhone OS for performance reasons. Is there some private API effect (like SuckEffect) that they might have used? A spotlight type of effect? Some Core Animation thing? Edit: It's definitely not a series of stills. I've seen examples of being edit a plist value or something and customize the string on jailbroken iphones.

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• Core Data iPad/iPhone BLOBS vs File system for 20k PDFs

  - by jamone

  I'm designing an iPad/iPhone app using core data. The main focus of the app is sorting and viewing up to 20,000 PDFs They are ~200KB each. Typically its best to not store BLOBS in a DB, but for desktop systems I've typically seen it said that if the blobs are < 1 MB then its fine to use the DB. Any considerations I should take into count? If I store them in the file system can I store them all in one directory and not have performance issues (I won't need to ever get a directory list since I'd store each's path in the DB)? Should I divide them among a handful of directories? If so is there a good rule on # of files per dir?

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• best practices for setting development environment

  - by Sharique

  I use Linux as primary OS. I need some suggestions regarding how should I set up my desktop and development. I do work on mostly .Net and Drupal, but some time on other lamp products and C/C++, Qt. I'm also interested in mobile (android..) and embedded development. Currently I install everything on my main OS, even I use it a little. I use VMs a little. Should I use separate VM for each kind of development (like one for .Net/Mono, another C++, one for mobile and one for db only, one for xyz things etc) Keep primary development environment on main os and moveothers in VM. main os should be messed up keep things easy to organize (must) performance should be optimal

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• Efficiently Combine MatchCollections in .Net Regex

  - by Laramie

  In the simplified example, there are 2 Regular Expressions, one case sensitive, the other not. The idea would be to efficiently create an IEnumerable collection (see "combined" below) combining the results. string test = "abcABC"; string regex = "(?<grpa>a)|(?<grpb>b)|(?<grpc>c)]"; Regex regNoCase = new Regex(regex, RegexOptions.IgnoreCase); Regex regCase = new Regex(regex); MatchCollection matchNoCase = regNoCase.Matches(test); MatchCollection matchCase = regCase.Matches(test); //Combine matchNoCase and matchCase into an IEnumerable IEnumerable<Match> combined= null; foreach (Match match in combined) { //Use the Index and (successful) Groups properties //of the match in another operation } In practice, the MatchCollections might contain thousands of results and be run frequently using long dynamically created REGEXes, so I'd like to shy away from copying the results to arrays, etc. I am still learning LINQ and am fuzzy on how to go about combining these or what the performance hits to an already sluggish process will be.

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• Very Slow WebResponse triggering TimeOut

  - by David Fdez

  Hello: I have a function in C# that fetches the status of Internet by retrieving a 64b XML from the router page public bool isOn() { HttpWebRequest hwebRequest = (HttpWebRequest)WebRequest.Create("http://" + this.routerIp + "/top_conn.xml"); hwebRequest.Timeout = 500; HttpWebResponse hWebResponse = (HttpWebResponse)hwebRequest.GetResponse(); XmlTextReader oXmlReader = new XmlTextReader(hWebResponse.GetResponseStream()); string value; while (oXmlReader.Read()) { value = oXmlReader.Value; if (value.Trim() != ""){ return !value.Substring(value.IndexOf("=") + 1, 1).Equals("0"); } } return false; } using Mozilla Firefox 3.5 & FireBug addon i guessed it normally takes 30ms to retrieve the page however at the very huge 500ms limit it stills reach it often. How can I dramatically improve the performance? Thanks in advance

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• 'schema' design for a social network

  - by Alan B

  I'm working on a proof of concept app for a twitter style social network with about 500k users. I'm unsure of how best to design the 'schema' should I embed a user's subscriptions or have a separate 'subscriptions' collection and use db references? If I embed, I still have to perform a query to get all of a user's followers. e.g. Given the following user: { "username" : "alan", "photo": "123.jpg", "subscriptions" : [ {"username" : "john", "status" : "accepted"}, {"username" : "paul", "status" : "pending"} ] } to find all of alan's subscribers, I'd have to run something like this: db.users.find({'subscriptions.username' : 'alan'}); from a performance point of view, is that any worse or better than having a separate subscriptions collection? also, when displaying a list of subscriptions/subscribers, I am currently having problems with n+1 because the subscription document tells me the username of the target user but not other attributes I may need such as the profile photo. Are there any recommended practices for such situations? thanks Alan

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• Add comma-separated value of grouped rows to existing query

  - by Peter Lang

  I've got a view for reports, that looks something like this: SELECT a.id, a.value1, a.value2, b.value1, /* (+50 more such columns)*/ FROM a JOIN b ON (b.id = a.b_id) JOIN c ON (c.id = b.c_id) LEFT JOIN d ON (d.id = b.d_id) LEFT JOIN e ON (e.id = d.e_id) /* (+10 more inner/left joins) */ It joins quite a few tables and returns lots of columns, but indexes are in place and performance is fine. Now I want to add another column to the result, showing comma-separated values ordered by value from table y outer joined via intersection table x if a.value3 IS NULL, else take a.value3 To comma-separate the grouped values I use Tom Kyte's stragg, could use COLLECT later. Pseudo-code for the SELECT would look like that: SELECT xx.id, COALESCE( a.value3, stragg( xx.val ) ) value3 FROM ( SELECT x.id, y.val FROM x WHERE x.a_id = a.id JOIN y ON ( y.id = x.y_id ) ORDER BY y.val ASC ) xx GROUP BY xx.id What is the best way to do it? Any tips?

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• UISearchDisplayController changing row height

  - by tewha

  I've set my UITableView row height to in Interface Builder to 54.0. I have a UISearchDisplayController on that view. When the user taps the search bar in it, the table resizes properly. However, when they start typing (and actually doing the search) the row height decreases. It stays wrong until the search taps Cancel. I could find no documentation on this behavior on Apple's site. I've tried setting the row height in UISearchDisplayDelegate delegate calls. This might be the right approach, but I don't know the details and couldn't get it ti work. I've also tried implementing -- (CGFloat)tableView:(UITableView *)tableView -heightForRowAtIndexPath:(NSIndexPath *)indexPath;. This worked, but I have thousands of entries in this list and can't take the performance hit. What's the right way to fix this?

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• Linux bash: when to use egrep instead of grep?

  - by Michael Mao

  Hi all : I am preparing for a Linux terminal assessment now, I tried to Google and found most resources are referring to the basic "grep" rather than the more powerful "egrep" -- well, that is at least what the professor said in lecture. I am always working with small samples so performance tuning is a thing too far away. So basically I'd like to know are there any areas where I must switch to egrep to do it in a better way? Is it safe to work with basic "grep" as for now? will there be potential risks? Sorry about my limited knowledge on Linux shell commands, the man page looks like a maze to me and honestly I haven't put much time in understanding all the features both command provide.

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