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  • Starting to construct a data access layer. Things to consider?

    - by Phil
    Our organisation uses inline sql. We have been tasked with providing a suitable data access layer and are weighing up the pro's and cons of which way to go... Datasets ADO.net Linq Entity framework Subsonic Other? Some tutorials and articles I have been using for reference: http://www.asp.net/(S(pdfrohu0ajmwt445fanvj2r3))/learn/data-access/tutorial-01-vb.aspx http://www.simple-talk.com/dotnet/.net-framework/designing-a-data-access-layer-in-linq-to-sql/ http://msdn.microsoft.com/en-us/magazine/cc188750.aspx http://msdn.microsoft.com/en-us/library/aa697427(VS.80).aspx http://www.subsonicproject.com/ I'm extremely torn, and finding it very difficult to make a decision on which way to go. Our site is a series of 2 internal portals and a public web site. We are using vs2008 sp1 and framework version 3.5. Please can you give me advise on what factors to consider and any pro's and cons you have faced with your data access layer. Thanks.

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  • Performance of looping over an Unboxed array in Haskell

    - by Joey Adams
    First of all, it's great. However, I came across a situation where my benchmarks turned up weird results. I am new to Haskell, and this is first time I've gotten my hands dirty with mutable arrays and Monads. The code below is based on this example. I wrote a generic monadic for function that takes numbers and a step function rather than a range (like forM_ does). I compared using my generic for function (Loop A) against embedding an equivalent recursive function (Loop B). Having Loop A is noticeably faster than having Loop B. Weirder, having both Loop A and B together is faster than having Loop B by itself (but slightly slower than Loop A by itself). Some possible explanations I can think of for the discrepancies. Note that these are just guesses: Something I haven't learned yet about how Haskell extracts results from monadic functions. Loop B faults the array in a less cache efficient manner than Loop A. Why? I made a dumb mistake; Loop A and Loop B are actually different. Note that in all 3 cases of having either or both Loop A and Loop B, the program produces the same output. Here is the code. I tested it with ghc -O2 for.hs using GHC version 6.10.4 . import Control.Monad import Control.Monad.ST import Data.Array.IArray import Data.Array.MArray import Data.Array.ST import Data.Array.Unboxed for :: (Num a, Ord a, Monad m) => a -> a -> (a -> a) -> (a -> m b) -> m () for start end step f = loop start where loop i | i <= end = do f i loop (step i) | otherwise = return () primesToNA :: Int -> UArray Int Bool primesToNA n = runSTUArray $ do a <- newArray (2,n) True :: ST s (STUArray s Int Bool) let sr = floor . (sqrt::Double->Double) . fromIntegral $ n+1 -- Loop A for 4 n (+ 2) $ \j -> writeArray a j False -- Loop B let f i | i <= n = do writeArray a i False f (i+2) | otherwise = return () in f 4 forM_ [3,5..sr] $ \i -> do si <- readArray a i when si $ forM_ [i*i,i*i+i+i..n] $ \j -> writeArray a j False return a primesTo :: Int -> [Int] primesTo n = [i | (i,p) <- assocs . primesToNA $ n, p] main = print $ primesTo 30000000

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  • WPF performance for large number of elements on the screen

    - by Mark
    Im currently trying to create a Scene in WPF where I have around 250 controls on my screen and the user can Pan and Zoom in and out of these controls using the mouse. I have run the WPF Performance Suite tools on the application when there are a large number of these controls on the screen (i.e. when the user has zoomed right out) the FPS drops down to around 15 which is not very good. Here is the basic outline of the XAML: <Window> <Window.Resources> <ControlTemplate x:Key="LandTemplate" TargetType="{x:Type local:LandControl}"> <Canvas> <Path Fill="White" Stretch="Fill" Stroke="Black" StrokeThickness="1" Width="55.5" Height="74.687" Data="M0.5,0.5 L55,0.5 L55,74.187 L0.5,74.187 z"/> <Canvas x:Name="DetailLevelCanvas" Width="24.5" Height="21" Canvas.Left="15.306" Canvas.Top="23.972"> <TextBlock Width="21" Height="14" Text="712" TextWrapping="Wrap" Foreground="Black"/> <TextBlock Width="17.5" Height="7" Canvas.Left="7" Canvas.Top="14" Text="614m2" TextWrapping="Wrap" FontSize="5.333" Foreground="Black"/> </Canvas> </Canvas> </ControlTemplate> </Window.Resources> ... <local:LandControl Width="55.5" Height="74.552" Canvas.Top="xxx" Template=" {StaticResource LandTemplate}" RenderTransformOrigin="0.5,0.5" Canvas.Left="xxx"> <local:LandControl Width="55.5" Height="74.552" Canvas.Top="xxx" Template=" {StaticResource LandTemplate}" RenderTransformOrigin="0.5,0.5" Canvas.Left="xxx"> <local:LandControl Width="55.5" Height="74.552" Canvas.Top="xxx" Template=" {StaticResource LandTemplate}" RenderTransformOrigin="0.5,0.5" Canvas.Left="xxx"> <local:LandControl Width="55.5" Height="74.552" Canvas.Top="xxx" Template=" {StaticResource LandTemplate}" RenderTransformOrigin="0.5,0.5" Canvas.Left="xxx"> ... and so on... </Window> Ive tried to minimise the details in the control template and I even did a massive find and replace of the controls to just put their raw elements inline instead of using a template, but with no noticeable performance improvements. I have seen other SO questions about this and people say to do custom drawing, but I dont really see how that make sense when you have to zoom and pan like I do. If anyone can help out here, that would be great! Mark

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  • Retrieving all objects in code upfront for performance reasons

    - by ming yeow
    How do you folks retrieve all objects in code upfront? I figure you can increase performance if you bundle all the model calls together? This makes for a bigger deal, especially if your DB cannot keep everything in memory def hitDBSeperately { get X users ...code get Y users... code get Z users... code } Versus: def hitDBInSingleCall { get X+Y+Z users code for X code for Y... }

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  • many-to-many performance concerns with fluent nhibernate.

    - by Ciel
    I have a situation where I have several many-to-many associations. In the upwards of 12 to 15. Reading around I've seen that it's generally believed that many-to-many associations are not 'typical', yet they are the only way I have been able to create the associations appropriate for my case, so I'm not sure how to optimize any further. Here is my basic scenario. class Page { IList<Tag> Tags { get; set; } IList<Modification> Modifications { get; set; } IList<Aspect> Aspects { get; set; } } This is one of my 'core' classes, and coincidentally one of my core tables. Virtually half of the objects in my code can have an IList<Page>, and some of them have IList<T> where T has its own IList<Page>. As you can see, from an object oriented standpoint, this is not really a problem. But from a database standpoint this begins to introduce a lot of junction tables. So far it has worked fine for me, but I am wondering if anyone has any ideas on how I could improve on this structure. I've spent a long time thinking and in order to achieve the appropriate level of association required, I cannot think of any way to improve it. The only thing I have come up with is to make intermediate classes for each object that has an IList<Page>, but that doesn't really do anything that the HasManyToMany does not already do except introduce another class. It does not extend the functionality and, from what I can tell, it does not improve performance. Any thoughts? I am also concerned about Primary Key limits in this scenario. Most everything needs to be able to have these properties, but the Pages cannot be unique to each object, because they are going to be frequently shared and joined between multiple objects. All relationships are one-sided. (That is, a Page has no knowledge of what owns it). Because of this, I also have no Inverse() mapped HasManyToMany collections. Also, I have read the similar question : Usage of ORMs like NHibernate when there are many associations - performance concerns But it really did not answer my concerns.

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  • SQL Server 2005 Performance Dashboard Missing Index

    - by n8wrl
    I am using the performance dashboard with our SQL Server 2005 databases and it lists what it considers to be missing indexes. But some of those indexes DO exist! They are not disabled, and they are defined exactly as the dashboard says they should be. Why are they reported as missing?

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  • XQuery performance in SQL Server

    - by Carl Hörberg
    Why does this quite simple xquery takes 10min to execute in sql server (the 2mb xml document stored in one column) compared to 14 seconds when using oxygen/file based querying? SELECT model.query('declare default element namespace "http://www.sbml.org/sbml/level2"; for $all_species in //species, $all_reactions in //reaction where data($all_species/@compartment)="plasma_membrane" and $all_reactions/listOfReactants/speciesReference/@species=$all_species/@id return <result>{data($all_species/@id)}</result>') from sbml;

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  • References for better performance of newer JSF specifications

    - by Pentius
    Dear fellows, I'm looking for a reference to cite, which states that JSF 1.2 performs better than JSF 1.1. Or JSF 2.0 over JSF 1.2 respectively. I'm quite sure that I've read something like this before but can't find it anymore. Maybe you can help. Or is this mischief and there are no official statements regarding the performance?

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  • Postgresql performance on EC2/EBS

    - by matija
    What gives best performance for running PostgreSQL on EC2? EBS in RAID? PGData on /mnt? Do you have any preferences or experiences? Main "plus" for running pgsql on EBS is switching from one to another instances. Can this be the reason to be slower that /mnt partition? PS. im running postgresql 8.4 with datas/size about 50G, amazon ec2 xlarge(64) instance.

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  • Using Core Data Concurrently and Reliably

    - by John Topley
    I'm building my first iOS app, which in theory should be pretty straightforward but I'm having difficulty making it sufficiently bulletproof for me to feel confident submitting it to the App Store. Briefly, the main screen has a table view, upon selecting a row it segues to another table view that displays information relevant for the selected row in a master-detail fashion. The underlying data is retrieved as JSON data from a web service once a day and then cached in a Core Data store. The data previous to that day is deleted to stop the SQLite database file from growing indefinitely. All data persistence operations are performed using Core Data, with an NSFetchedResultsController underpinning the detail table view. The problem I am seeing is that if you switch quickly between the master and detail screens several times whilst fresh data is being retrieved, parsed and saved, the app freezes or crashes completely. There seems to be some sort of race condition, maybe due to Core Data importing data in the background whilst the main thread is trying to perform a fetch, but I'm speculating. I've had trouble capturing any meaningful crash information, usually it's a SIGSEGV deep in the Core Data stack. The table below shows the actual order of events that happen when the detail table view controller is loaded: Main Thread Background Thread viewDidLoad Get JSON data (using AFNetworking) Create child NSManagedObjectContext (MOC) Parse JSON data Insert managed objects in child MOC Save child MOC Post import completion notification Receive import completion notification Save parent MOC Perform fetch and reload table view Delete old managed objects in child MOC Save child MOC Post deletion completion notification Receive deletion completion notification Save parent MOC Once the AFNetworking completion block is triggered when the JSON data has arrived, a nested NSManagedObjectContext is created and passed to an "importer" object that parses the JSON data and saves the objects to the Core Data store. The importer executes using the new performBlock method introduced in iOS 5: NSManagedObjectContext *child = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; [child setParentContext:self.managedObjectContext]; [child performBlock:^{ // Create importer instance, passing it the child MOC... }]; The importer object observes its own MOC's NSManagedObjectContextDidSaveNotification and then posts its own notification which is observed by the detail table view controller. When this notification is posted the table view controller performs a save on its own (parent) MOC. I use the same basic pattern with a "deleter" object for deleting the old data after the new data for the day has been imported. This occurs asynchronously after the new data has been fetched by the fetched results controller and the detail table view has been reloaded. One thing I am not doing is observing any merge notifications or locking any of the managed object contexts or the persistent store coordinator. Is this something I should be doing? I'm a bit unsure how to architect this all correctly so would appreciate any advice.

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  • Performance tune my sql query removing OR statements

    - by SmartestVEGA
    I need to performance tune following SQL query by removing "OR" statements Please help ... SELECT a.id, a.fileType, a.uploadTime, a.filename, a.userId, a.CID, ui.username, company.name companyName, a.screenName FROM TM_transactionLog a, TM_userInfo ui, TM_company company, TM_airlineCompany ac WHERE ( a.CID = 3049 ) OR ( a.CID = company.ID AND ac.SERVICECID = 3049 AND company.SPECIFICCID = ac.ID ) OR ( a.USERID = ui.ID AND ui.CID = 3049 );

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  • How to get child nodes after store load

    - by Azincourt
    Version: ExtJs 4.1 To change the child items I use this function: TreeStore (Ext.data.TreeStore) storeId : 'treeStore', ... constructor: function( oConfig ) { ... this.on( 'expand', function( oObj ) { oObj.eachChild(function(oNode) { switch(oNode.data.type) { case "report": oNode.set('icon', strIconReport); break; case "view": oNode.set('icon', strIconView); break; } }); }); Reload After removing or adding items in the tree, I reload the tree somewhere else with: var oStore = Ext.getStore('treeStore'); oStore.load({ node : oNode, params : { newpath : oNode.data.path, overwrite : true } }); Although it is the same store treeStore, after loading and expanding to the correct path, the icons are not changed since the .on( 'expand') function is not called. Why? Question How can I change the icons of this newly loaded store before it expands to the node path? What I tried Before calling .load() I tried to edit the children with oNode.eachChild(function(oChild) {} but no success.

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  • SQL Native Client 10 Performance miserable (due to server-side cursors)

    - by namezero
    we have an application that uses ODBC via CDatabase/CRecordset in MFC (VS2010). We have two backends implemented. MSSQL and MySQL. Now, when we use MSSQL (with the Native Client 10.0), retrieving records with SELECT is dramatically slow via slow links (VPN, for example). The MySQL ODBC driver does not exhibit this nasty behavior. For example: CRecordset r(&m_db); r.Open(CRecordset::snapshot, L"SELECT a.something, b.sthelse FROM TableA AS a LEFT JOIN TableB AS b ON a.ID=b.Ref"); r.MoveFirst(); while(!r.IsEOF()) { // Retrieve CString strData; crs.GetFieldValue(L"a.something", strData); crs.MoveNext(); } Now, with the MySQL driver, everything runs as it should. The query is returned, and everything is lightning fast. However, with the MSSQL Native Client, things slow down, because on every MoveNext(), the driver communicates with the server. I think it is due to server-side cursors, but I didn't find a way to disable them. I have tried using: ::SQLSetConnectAttr(m_db.m_hdbc, SQL_ATTR_ODBC_CURSORS, SQL_CUR_USE_ODBC, SQL_IS_INTEGER); But this didn't help either. There are still long-running exec's to sp_cursorfetch() et al in SQL Profiler. I have also tried a small reference project with SQLAPI and bulk fetch, but that hangs in FetchNext() for a long time, too (even if there is only one record in the resultset). This however only happens on queries with LEFT JOINS, table-valued functions, etc. Note that the query doesn't take that long - executing the same SQL via SQL Studio over the same connection returns in a reasonable time. Question1: Is is possible to somehow get the native client to "cache" all results locally use local cursors in a similar fashion as the MySQL driver seems to do it? Maybe this is the wrong approach altogether, but I'm not sure how else to do this. All we want is to retrieve all data at once from a SELECT, then never talk the server again until the next query. We don't care about recordset updates, deletes, etc or any of that nonsense. We only want to retrieve data. We take that recordset, get all the data, and delete it. Question2: Is there a more efficient way to just retrieve data in MFC with ODBC?

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  • OpenCV performance in different languages

    - by h0b0
    I'm doing some prototyping with OpenCV for a hobby project involving processing of real time camera data. I wonder if it is worth the effort to reimplement this in C or C++ when I have it all figured out or if no significant performance boost can be expected. The program basically chains OpenCV functions, so the main part of the work should be done in native code anyway.

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  • C vs. C++ for performance in memory allocation

    - by Andrei
    Hi, I am planning to participate in development of a code written in C language for Monte Carlo analysis of complex problems. This codes allocates huge data arrays in memory to speed up its performance, therefore the author of the code has chosen C instead of C++ claiming that one can make faster and more reliable (concerning memory leaks) code with C. Do you agree with that? What would be your choice, if you need to store 4-16 Gb of data arrays in memory during calculation?

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