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• What guarantees are there on the run-time complexity (Big-O) of LINQ methods?

  - by tzaman

  I've recently started using LINQ quite a bit, and I haven't really seen any mention of run-time complexity for any of the LINQ methods. Obviously, there are many factors at play here, so let's restrict the discussion to the plain IEnumerable LINQ-to-Objects provider. Further, let's assume that any Func passed in as a selector / mutator / etc. is a cheap O(1) operation. It seems obvious that all the single-pass operations (Select, Where, Count, Take/Skip, Any/All, etc.) will be O(n), since they only need to walk the sequence once; although even this is subject to laziness. Things are murkier for the more complex operations; the set-like operators (Union, Distinct, Except, etc.) work using GetHashCode by default (afaik), so it seems reasonable to assume they're using a hash-table internally, making these operations O(n) as well, in general. What about the versions that use an IEqualityComparer? OrderBy would need a sort, so most likely we're looking at O(n log n). What if it's already sorted? How about if I say OrderBy().ThenBy() and provide the same key to both? I could see GroupBy (and Join) using either sorting, or hashing. Which is it? Contains would be O(n) on a List, but O(1) on a HashSet - does LINQ check the underlying container to see if it can speed things up? And the real question - so far, I've been taking it on faith that the operations are performant. However, can I bank on that? STL containers, for example, clearly specify the complexity of every operation. Are there any similar guarantees on LINQ performance in the .NET library specification?

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• Field to display Previous 30 Day Total

  - by whytheq

  I've got this table: CREATE TABLE #Data1 ( [Market] VARCHAR(100) NOT NULL, [Operator] VARCHAR(100) NOT NULL, [Date] DATETIME NOT NULL, [Measure] VARCHAR(100) NOT NULL, [Amount] NUMERIC(36,10) NOT NULL, --new calculated fields [DailyAvg_30days] NUMERIC(38,6) NULL DEFAULT 0 ) I've populated all the fields apart from DailyAvg_30days. This field needs to show the total for the preceding 30 days e.g. 1. if Date for a particular record is 2nd Dec then it will be the total for the period 3rd Nov - 2nd Dec inclusive. 2. if Date for a particular record is 1st Dec then it will be the total for the period 2nd Nov - 1st Dec inclusive. My attempt to try to find these totals before updating the table is as follows: SELECT a.[Market], a.[Operator], a.[Date], a.[Measure], a.[Amount], [DailyAvg_30days] = SUM(b.[Amount]) FROM #Data1 a INNER JOIN #Data1 b ON a.[Market] = b.[Market] AND a.[Operator] = b.[Operator] AND a.[Measure] = b.[Measure] AND a.[Date] >= b.[Date]-30 AND a.[Date] <= b.[Date] GROUP BY a.[Market], a.[Operator], a.[Date], a.[Measure], a.[Amount] ORDER BY 1,2,4,3 Is this a valid approach or do I need to approach this from a different angle?

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• mysql report sql help

  - by sfgroups

  I have mysql table with data like this. record will have server with total cpu and virtual server with cpu assinged type, cpu srv1, 10 vsrv11, 2 vsrv12, 3 srv2, 15 vsrv21, 6 vsrv22, 7 vsrv23, 1 from the above data, I want to create output like this. server, total cpu, assigned cpu, free cpu srv1, 10, 5, 5 srv2, 15, 14, 1 Can you help me on creating sql query for this report? I have changed my table and data like this. CREATE TABLE `cpuallocation` ( `servertype` varchar(10) DEFAULT NULL, `servername` varchar(20) DEFAULT NULL, `hostname` varchar(20) DEFAULT NULL, `cpu_count` float DEFAULT NULL, UNIQUE KEY `server_uniq_idx` (`servertype`,`servername`,`hostname`) insert into cpuallocation values('srv', 'server1', '',16); insert into cpuallocation values('vir', 'server1', 'host1',5); insert into cpuallocation values('vir', 'server1', 'host2',2.5); insert into cpuallocation values('vir', 'server1', 'host3',4.5); insert into cpuallocation values('srv', 'server2', '',8); insert into cpuallocation values('vir', 'server2', 'host1',5); insert into cpuallocation values('vir', 'server2', 'host2',2.5); insert into cpuallocation values('srv', 'server3', '',24); insert into cpuallocation values('vir', 'server3', 'host1',12); insert into cpuallocation values('vir', 'server3', 'host2',2); insert into cpuallocation values('srv', 'server4', '',12); Update: I created two view, now I getting the result I want. create view v1 as select servername, sum(cpu_count) as cpu_allocated from cpuallocation where servertype='vir' group by servername; create view v2 as select servername, cpu_count as total_cpu from cpuallocation where servertype='srv'; select a.servername, a.total_cpu, b.cpu_allocated from v2 as a left join v1 as b on a.servername=b.servername; +------------+-----------+---------------+ | servername | total_cpu | cpu_allocated | +------------+-----------+---------------+ | server1 | 16 | 12 | | server2 | 8 | 7.5 | | server3 | 24 | 14 | | server4 | 12 | NULL | +------------+-----------+---------------+ 4 rows in set (0.00 sec) Is it possible to create a query with-out creating views?

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• SQL - Query to display average as either "longer than" or "shorter than"

  - by user1840801

  Here are the tables I've created: CREATE TABLE Plane_new (Pnum char(3), Feature varchar2(20), Ptype varchar2(15), primary key (Pnum)); CREATE TABLE Employee_new (eid char(3), ename varchar(10), salary number(7,2), mid char(3), PRIMARY KEY (eid), FOREIGN KEY (mid) REFERENCES Employee_new); CREATE TABLE Pilot_new (eid char(3), Licence char(9), primary key (eid), foreign key (eid) references Employee_new on delete cascade); CREATE TABLE FlightI_new (Fnum char(4), Fdate date, Duration number(2), Pid char(3), Pnum char(3), primary key (Fnum), foreign key (Pid) references Pilot_new (eid), foreign key (Pnum) references Plane_new); And here is the query I must complete: For each flight, display its number, the name of the pilot who implemented the flight and the words ‘Longer than average’ if the flight duration was longer than average or the words ‘Shorter than average’ if the flight duration was shorter than or equal to the average. For the column holding the words ‘Longer than average’ or ‘Shorter than average’ make a header Length. Here is what I've come up with - with no luck! SELECT F.Fnum, E.ename, CASE Length WHEN F.Duration>(SELECT AVG(F.Duration) FROM FlightI_new F) THEN "Longer than average" WHEN F.Duration<=(SELECT AVG(F.Duration) FROM FlightI_new F) THEN 'Shorter than average' END FROM FlightI_new F LEFT OUTER JOIN Employee_new E ON F.Pid=E.eid GROUP BY F.Fnum, E.ename; Where am I going wrong?

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• SQL Table design question

  - by Projapati

  Please ignore this question if it sounds stupid to you. I have SQL table (SQL Server) for photo albums and it has 20+ columns & it will hold millions of albums. I need to designate some albums as Promoted and some as Featured every week. I also need a very efficient way to get these albums (page by page) when I show it to users. How should I design this? option 1: I can create another table just to store the ids of the promoted and featured albums like this and then join the main albums table to get the set of columns I need. table designated_albums: album_id promoted_featured 1 1 5 0 7 1 15 0 The query for promoted will return 1, 7 The query for featured will return 5, 15 Option 2: I can add 1 column store 1 if promoted and 0 if featured. Otherwise it is null I can then query to check for 1 in that column for promoted albums & 0 for featured. Option 3: I can add 2 bit columns: one for promoted (0/1) and one for featured(0/1) Which way would perform better? EDIT: The design should be efficient in SQL 2008 as well. Right now I have SQL 2005.

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• Adding image to html markup

  - by user1491991

  Hello guys i'm having a problem appending a image to my html markup which is generated when a button is clicked... wondering if i could some dirction __--------------------------SCRIPT----------------------------------------------------------- (function($){ $.confirm = function(params){ if($('#confirmOverlay').length){ // A confirm is already shown on the page: return false; } var buttonHTML = ''; $.each(params.buttons,function(name,obj){ // Generating the markup for the buttons: buttonHTML += '<a href="#" class="button '+obj['class']+'">'+name+'<span></span></a>'; if(!obj.action){ obj.action = function(){}; } }); var closetext= 'close'; var markup = [ '<div id="confirmOverlay">', '<div id ="model">','<div id="confirmBox">', '<div id="header">','<div id ="title">',params.title,'</div>', '<div id="close">','<ol id = "olclose">','<li id = "liclose">','<a id="close" href = "#">',closetext,'</a></li>', '<li id = "liclose">','<a id="close" href = "#">','<img src="../modal-close.gif"/>','</a></li>','</ol></div></div>', '<div id ="textbox">','<p>',params.message,'<br>','<br>' ,buttonHTML,'</p>', '</div>', '</div></div></div></div>' ].join(''); $(markup).hide().appendTo('body').fadeIn(); var buttons = $('#confirmBox .button'), i = 0; $.each(params.buttons,function(name,obj){ buttons.eq(i++).click(function(){ // Calling the action attribute when a // click occurs, and hiding the confirm. obj.action(); $.confirm.hide(); return false; }); }); } $.confirm.hide = function(){ $('#confirmOverlay').fadeOut(function(){ $(this).remove(); }); } })(jQuery); i've used firebug to check and its unable to fetch the image here

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• Ordering a set of lines so that they follow one from the other

  - by george

  Line# Lat. Lon. 1a 1573313.042320 6180142.720910 .. .. 1z 1569171.442602 6184932.867930 3a 1569171.764930 6184934.045650 .. .. 3z 1570412.815667 6190358.086690 5a 1570605.667770 6190253.392920 .. .. 5z 1570373.562963 6190464.146120 4a 1573503.842910 6189595.286870 .. .. 4z 1570690.065390 6190218.190575 Each pair of lines above (a..z) represents the first and last coordinate pair of a number of points which together define a line. The lines are not listed in sequence because I don't know what the correct sequence is just by looking at the coordinates (unless I look at the lines in a map). Hence my question: how can I find programmatically (in Python) what the correct sequence is, so I can join the lines into one long line, keeping in mind the following problem: - a 'z' point (the last point in a line) may well be the first point if the line is described as proceeding in the opposite direction to other lines. e.g. one line may go from left to right, another from right to left (or top to bottom and viceversa). Thank you in advance...

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• Complex Forms Generating Error

  - by user1648020

  I am working on an application that allows students to create a catalog of courses they are taking for a semester. I have created models for user; course; subject and category. Users can have many courses. Each course can have many subjects and categories. The tables for courses, subjects and categories include the following: Catalog: user_id; subject_id, category_id and course_id Courses: user_id; coursedetail_id Coursedetail: name; description Subject: name; description Category: name; description The idea is that an Admin can create a list of courses; subjects and categories and that the user can select the courses they want to add to their catalog. I have seperated courses and coursedetails because I envision that the coursedetails will grow overtime and the courses table will allow me to join the user_id and cousres details to rreport on if necessary. I attempted to follow Ryan's railscast on Complex Forms thinking that that I should use a complex form and has many relationship to get things working -- but I get an error in the catalog controller - cannot locate catalog_id which I know is in the table. I am now not sure if complex forms is the way to go or I should be looking at another direction to get the appropriate form in place. Any assistance would be appreciated.

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• Replace beginning words

  - by Newbie

  I have the below tables. tblInput Id WordPosition Words -- ----------- ----- 1 1 Hi 1 2 How 1 3 are 1 4 you 2 1 Ok 2 2 This 2 3 is 2 4 me tblReplacement Id ReplacementWords --- ---------------- 1 Hi 2 are 3 Ok 4 This The tblInput holds the list of words while the tblReplacement hold the words that we need to search in the tblInput and if a match is found then we need to replace those. But the problem is that, we need to replace those words if any match is found at the beginning. i.e. in the tblInput, in case of ID 1, the words that will be replaced is only 'Hi' and not 'are' since before 'are', 'How' is there and it is not in the tblReplacement list. in case of Id 2, the words that will be replaced are 'Ok' & 'This'. Since these both words are present in the tblReplacement table and after the first word i.e. 'Ok' is replaced, the second word which is 'This' here comes first in the list of ID category 2 . Since it is available in the tblReplacement, and is the first word now, so this will also be replaced. So the desired output will be Id NewWordsAfterReplacement --- ------------------------ 1 How 1 are 1 you 2 is 2 me My approach so far: ;With Cte1 As( Select t1.Id ,t1.Words ,t2.ReplacementWords From tblInput t1 Cross Join tblReplacement t2) ,Cte2 As( Select Id, NewWordsAfterReplacement = REPLACE(Words,ReplacementWords,'') From Cte1) Select * from Cte2 where NewWordsAfterReplacement <> '' But I am not getting the desired output. It is replacing all the matching words. Urgent help needed*.( SET BASED )* I am using SQL Server 2005. Thanks

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• Playing a sequence of sounds without gaps (iPhone)

  - by Fiire

  I thought maybe the fastest way was to go with Sound Services. It is quite efficient, but I need to play sounds in a sequence, not overlapped. Therefore I used a callback method to check when the sound has finished. This cycle produces around 0.3 seconds in lag. I know this sounds very strict, but it is basically the main axis of the program. EDIT: I now tried using AVAudioPlayer, but I can't play sounds in a sequence without using audioPlayerDidFinishPlaying since that would put me in the same situation as with the callback method of SoundServices. EDIT2: I think that if I could somehow get to join the parts of the sounds I want to play into a large file, I could get the whole audio file to sound continuously. EDIT3: I thought this would work, but the audio overlaps: waitTime = player.deviceCurrentTime; for (int k = 0; k < [colores count]; k++) { player.currentTime = 0; [player playAtTime:waitTime]; waitTime += player.duration; } Thanks

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• Get Local IP-Address using Boost.Asio

  - by MOnsDaR

  Hey, I'm currently searching for a portable way of getting the local IP-addresses. Because I'm using Boost anyway I thought it would be a good idea to use Boost.Asio for this task. There are serveral examples on the net which should do the trick. Examples: Official Boost.Asio Documentation Some Asian Page I tried both codes with just slight modifications. The Code on Boost.Doc was changed to not resolve "www.boost.org" but "localhost" or my hostname instead. For getting the hostname I used boost::asio::ip::host_name() or typed it directly as a string. Additionally I wrote my own code which was a merge of the above examples and my (little) knowledge I gathered from the Boost Documentation and other examples. All the sources worked, but they did just return the following IP: 127.0.1.1 (Thats not a typo, its .1.1 at the end) I run and compiled the code on Ubuntu 9.10 with GCC 4.4.1 A colleague tried the same code on his machine and got 127.0.0.2 (Not a typo too...) He compiled and run on Suse 11.0 with GCC 4.4.1 (I'm not 100% sure) I don't know if it is possible to change the localhost (127.0.0.1), but I know that neither me or my colleague did it. ifconfig says loopback uses 127.0.0.1. ifconfig also finds the public IP I am searching for (141.200.182.30 in my case, subnet is 255.255.0.0) So is this a Linux-issue and the code is not as portable as I thought? Do I have to change something else or is Boost.Asio not working as a solution for my problem at all? I know there are much questions about similar topics on Stackoverflow and other pages, but I cannot find information which is useful in my case. If you got useful links, it would be nice if you could point me to it. Thanks in advance, MOnsDaR PS: Here is the modified code I used from Boost.Doc: #include <boost/asio.hpp> using boost::asio::ip::tcp; boost::asio::io_service io_service; tcp::resolver resolver(io_service); tcp::resolver::query query(boost::asio::ip::host_name(), ""); tcp::resolver::iterator iter = resolver.resolve(query); tcp::resolver::iterator end; // End marker. while (iter != end) { tcp::endpoint ep = *iter++; std::cout << ep << std::endl; }

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• WpfToolkit DataGrid does not work in Windows Phone 7

  - by Igor Zevaka

  I am trying to use WpfToolkit DataGrid in Windows Phone 7 project (Silverligt 4) and it's not working. Here is the XAML: <UserControl x:Class="SilverlightControls.Grid" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" xmlns:wtk="clr-namespace:Microsoft.Windows.Controls;assembly=WPFToolkit" d:DesignHeight="480" d:DesignWidth="480"> <Grid x:Name="LayoutRoot" Background="#FF1F1F1F" Width="960"> <Grid x:Name="TitleGrid"> <TextBlock Text="{Binding Title}" Style="{StaticResource PhoneTextPageTitle2Style}"/> </Grid> <wtk:DataGrid> </wtk:DataGrid> </Grid> </UserControl> The project compiles fine but crashes at runtime trying to load this control. The best clue I got so far is from Visual Studio Designer. Once I add wtk:DataGrid to the control the visual designer does not load and below is the exception it displays. Could it be that WpfToolkit relies on PresentationFramework.dll and it's not available in SL4? System.Reflection.Adds.UnresolvedAssemblyException Type universe cannot resolve assembly: PresentationFramework, Version=3.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35. at System.Reflection.Adds.AssemblyProxy.GetResolvedAssembly() at System.Reflection.Adds.AssemblyProxy.get_FullName() at Microsoft.Windows.Design.Metadata.ReflectionMetadataContext.PrepareAttributes(Reflectable`1 reflectableAssembly) at Microsoft.Windows.Design.Metadata.ReflectionMetadataContext.PrepareAttributes(Reflectable`1 reflectableType) at MS.Internal.Metadata.ClrType.GetAttributes[T](ReflectionMetadataContext context, IReflectable`1 member, ITypeMetadata attributeType, Boolean merge, AttributeMergeCache& cache) at MS.Internal.Metadata.ClrMember`1.GetLocalAttributes(ITypeMetadata attributeType) at MS.Internal.Design.Metadata.Xaml.XamlType.GetSpecialProperty(Int32 idx, PropertyIdentifier pid) at MS.Internal.Design.Metadata.Xaml.XamlType.get_ContentProperty() at Microsoft.Windows.Design.Metadata.Xaml.XamlExtensionImplementations.GetContentProperty(ITypeMetadata sourceType) at Microsoft.Windows.Design.Metadata.Xaml.XamlExtensions.GetContentProperty(ITypeMetadata source) at MS.Internal.Design.Metadata.ReflectionTypeNode.get_ContentProperty() at MS.Internal.Design.Markup.XmlElement.CalcChildWhitespaceImportant(XamlElement element) at MS.Internal.Design.Markup.XmlElement.ConvertChildrenToXaml(XamlElement result, PrefixScope scope, IParseContext context, IMarkupSourceProvider provider, Boolean childrenAsString) at MS.Internal.Design.Markup.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider) at MS.Internal.Design.Markup.XmlElement.ConvertChildrenToXaml(XamlElement result, PrefixScope scope, IParseContext context, IMarkupSourceProvider provider, Boolean childrenAsString) at MS.Internal.Design.Markup.XmlElement.ConvertToXaml(XamlElement parent, PrefixScope parentScope, IParseContext context, IMarkupSourceProvider provider) at MS.Internal.Design.DocumentModel.DocumentTrees.Markup.XamlSourceDocument.ParseElementFromSkeleton(XamlParseContext context, SkeletonNode node, XamlElement parent, Boolean fullElement) at MS.Internal.Design.DocumentModel.DocumentTrees.Markup.XamlSourceDocument.UpdateSkeleton(IDamageListener listener) at Microsoft.Windows.Design.DocumentModel.Trees.MarkupDocumentTreeManager.Update() at Microsoft.Windows.Design.DocumentModel.MarkupProducer.Update() at Microsoft.Windows.Design.DocumentModel.MarkupProducer.HandleMessage(DocumentTreeCoordinator sender, MessageKey key, MessageArguments args) at Microsoft.Windows.Design.DocumentModel.MarkupProducer.Microsoft.Windows.Design.DocumentModel.IDocumentTreeConsumer.HandleMessage(DocumentTreeCoordinator sender, MessageKey key, MessageArguments args) at Microsoft.Windows.Design.DocumentModel.DocumentTreeCoordinator.SendMessage[T](MessageKey`1 key, T args, Boolean isPrivateMessage) at Microsoft.Windows.Design.DocumentModel.DocumentTreeCoordinator.QueuedMessage`1.Microsoft.Windows.Design.DocumentModel.IQueuedMessage.Invoke() at Microsoft.Windows.Design.DocumentModel.DocumentTreeCoordinator.ProcessQueuedMessages(Object state) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)

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• Timeout Expired error Using LINQ

  - by Refracted Paladin

  I am going to sum up my problem first and then offer massive details and what I have already tried. Summary: I have an internal winform app that uses Linq 2 Sql to connect to a local SQL Express database. Each user has there own DB and the DB stay in sync through Merge Replication with a Central DB. All DB's are SQL 2005(sp2or3). We have been using this app for over 5 months now but recently our users are getting a Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. Detailed: The strange part is they get that in two differnt locations(2 differnt LINQ Methods) and only the first time they fire in a given time period(~5mins). One LINQ method is pulling all records that match a FK ID and then Manipulating them to form a Heirarchy View for a TreeView. The second is pulling all records that match a FK ID and dumping them into a DataGridView. The only things I can find in common with the 2 are that the first IS an IEnumerable and the second converts itself from IQueryable - IEnumerable - DataTable... I looked at the query's in Profiler and they 'seemed' normal. They are not very complicated querys. They are only pulling back 10 - 90 records, from one table. Any thoughts, suggestions, hints whatever would be greatly appreciated. I am at my wit's end on this.... public IList<CaseNoteTreeItem> GetTreeViewDataAsList(int personID) { var myContext = MatrixDataContext.Create(); var caseNotesTree = from cn in myContext.tblCaseNotes where cn.PersonID == personID orderby cn.ContactDate descending, cn.InsertDate descending select new CaseNoteTreeItem { CaseNoteID = cn.CaseNoteID, NoteContactDate = Convert.ToDateTime(cn.ContactDate). ToShortDateString(), ParentNoteID = cn.ParentNote, InsertUser = cn.InsertUser, ContactDetailsPreview = cn.ContactDetails.Substring(0, 75) }; return caseNotesTree.ToList<CaseNoteTreeItem>(); } AND THIS ONE public static DataTable GetAllCNotes(int personID) { using (var context = MatrixDataContext.Create()) { var caseNotes = from cn in context.tblCaseNotes where cn.PersonID == personID orderby cn.ContactDate select new { cn.ContactDate, cn.ContactDetails, cn.TimeSpentUnits, cn.IsCaseLog, cn.IsPreEnrollment, cn.PresentAtContact, cn.InsertDate, cn.InsertUser, cn.CaseNoteID, cn.ParentNote }; return caseNotes.ToList().CopyLinqToDataTable(); } }

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• Chaining IQueryables together

  - by Matt Greer

  I have a RIA Services based app that is using Entity Framework on the server side (possibly not relevant). In my real app, I can do something like this. EntityQuery<Status> query = statusContext.GetStatusesQuery().Where(s => s.Description.Contains("Foo")); Where statusContext is the client side subclass of DomainContext that RIA Services was kind enough to generate for me. The end result is an EntityQuery<Status> object who's Query property is an object that implements IQueryable and represents my where clause. The WebDomainClient is able to take this EntityQuery and not just give me back all of my Statuses but also filtered with my where clause. I am trying to implement this in a mock DomainClient. This MockDomainClient accepts an IQueryably<Entity> which it returns when asked for. But what if the user makes the query and includes the ad hoc additional query? How can I merge the two together? My MockDomainClient is (this is modeled after this blog post) ... public class MockDomainClient : LocalDomainClient { private IQueryable<Entity> _entities; public MockDomainClient(IQueryable<Entity> entities) { _entities = entities; } public override IQueryable<Entity> DoQuery(EntityQuery query) { if (query.Query == null) { return _entities; } // otherwise want the union of _entities and query.Query, query.Query is IQueryable // the below does not work and was a total shot in the dark: //return _entities.Union(query.Query.Cast<Entity>()); } } public abstract class LocalDomainClient : System.ServiceModel.DomainServices.Client.DomainClient { private SynchronizationContext _syncContext; protected LocalDomainClient() { _syncContext = SynchronizationContext.Current; } ... public abstract IQueryable<Entity> DoQuery(EntityQuery query); protected override IAsyncResult BeginQueryCore(EntityQuery query, AsyncCallback callback, object userState) { IQueryable<Entity> localQuery = DoQuery(query); LocalAsyncResult asyncResult = new LocalAsyncResult(callback, userState, localQuery); _syncContext.Post(o => (o as LocalAsyncResult).Complete(), asyncResult); return asyncResult; } ... }

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• Which version of MSXML should I use?

  - by Cheeso

  Seems like this would be a common question, though I could not find it on SO. Which version of MSXML should I use in my applications, and more importantly, how should I decide? There is MSXML3, 4, 5 and 6. I recently posted some code in calling-wcf-service-by-vbscript that used MSXML v4. AnthonyWJones posted that I shouldn't use 4, but instead 3 or 6, but probably 3. Certainly not v5! Why? I'd like to know more about the criteria for selecting the version of MSXML to use in my apps. Bonus question: Does anyone have a summary of the differences between the various versions of MSXML over time? Summary so far: MSXML6 Should be first choice. was released in 2006, and includes perf and compliance fixes. Use this if you can. It's good. There are no merge modules; to bundle the MSXML6 runtime with your app, MS suggests packaging the MSXML6 msi file. MSXML6 is an upgrade from MSXML3/4 but does not replace them, because it discontinues some features. You can get the MSI here. MSXML3 Second choice. Most widely deployed version. Originally shipped in March 2000. Actively maintained, no new features. Currently supported, if you are on SP5 (shipped in 2005) or later. SP7 is current (also from 2005). MSXML5 was released only as part of MS-Office. Currently supported by Microsoft, but only as part of Office, not for building apps. Don't build apps that depend on MSXML5: Verboten. MSXML4 originally shipped? Currently in "maintenance mode". Microsoft is encouraging people to move off MSXML4 to MSXML6. Currently supported if you are on MSXML4SP2 or later, which shipped in 2003. download MSXML4SP2 here. Can be redisributed. Using the right version of MSXML in Internet Explorer is a good entry on the blog from Microsoft's xmlteam.

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• Guides for PostgreSQL query tuning?

  - by Joe

  I've found a number of resources that talk about tuning the database server, but I haven't found much on the tuning of the individual queries. For instance, in Oracle, I might try adding hints to ignore indexes or to use sort-merge vs. correlated joins, but I can't find much on tuning Postgres other than using explicit joins and recommendations when bulk loading tables. Do any such guides exist so I can focus on tuning the most run and/or underperforming queries, hopefully without adversely affecting the currently well-performing queries? I'd even be happy to find something that compared how certain types of queries performed relative to other databases, so I had a better clue of what sort of things to avoid. update: I should've mentioned, I took all of the Oracle DBA classes along with their data modeling and SQL tuning classes back in the 8i days ... so I know about 'EXPLAIN', but that's more to tell you what's going wrong with the query, not necessarily how to make it better. (eg, are 'while var=1 or var=2' and 'while var in (1,2)' considered the same when generating an execution plan? What if I'm doing it with 10 permutations? When are multi-column indexes used? Are there ways to get the planner to optimize for fastest start vs. fastest finish? What sort of 'gotchas' might I run into when moving from mySQL, Oracle or some other RDBMS?) I could write any complex query dozens if not hundreds of ways, and I'm hoping to not have to try them all and find which one works best through trial and error. I've already found that 'SELECT count(*)' won't use an index, but 'SELECT count(primary_key)' will ... maybe a 'PostgreSQL for experienced SQL users' sort of document that explained sorts of queries to avoid, and how best to re-write them, or how to get the planner to handle them better. update 2: I found a Comparison of different SQL Implementations which covers PostgreSQL, DB2, MS-SQL, mySQL, Oracle and Informix, and explains if, how, and gotchas on things you might try to do, and his references section linked to Oracle / SQL Server / DB2 / Mckoi /MySQL Database Equivalents (which is what its title suggests) and to the wikibook SQL Dialects Reference which covers whatever people contribute (includes some DB2, SQLite, mySQL, PostgreSQL, Firebird, Vituoso, Oracle, MS-SQL, Ingres, and Linter).

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• JPA @OneToMany and composite PK

  - by Fleuri F

  Good Morning, I am working on project using JPA. I need to use a @OneToMany mapping on a class that has three primary keys. You can find the errors and the classes after this. If anyone has an idea! Thanks in advance! FF javax.persistence.PersistenceException: No Persistence provider for EntityManager named JTA_pacePersistence: Provider named oracle.toplink.essentials.PersistenceProvider threw unexpected exception at create EntityManagerFactory: javax.persistence.PersistenceException javax.persistence.PersistenceException: Exception [TOPLINK-28018] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.EntityManagerSetupException Exception Description: predeploy for PersistenceUnit [JTA_pacePersistence] failed. Internal Exception: Exception [TOPLINK-7220] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.ValidationException Exception Description: The @JoinColumns on the annotated element [private java.util.Set isd.pacepersistence.common.Action.permissions] from the entity class [class isd.pacepersistence.common.Action] is incomplete. When the source entity class uses a composite primary key, a @JoinColumn must be specified for each join column using the @JoinColumns. Both the name and the referenceColumnName elements must be specified in each such @JoinColumn. at oracle.toplink.essentials.internal.ejb.cmp3.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:643) at oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider.createEntityManagerFactory(EntityManagerFactoryProvider.java:196) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:110) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:83) at isd.pacepersistence.common.DataMapper.(Unknown Source) at isd.pacepersistence.server.MainServlet.getDebugCase(Unknown Source) at isd.pacepersistence.server.MainServlet.doGet(Unknown Source) at javax.servlet.http.HttpServlet.service(HttpServlet.java:718) at javax.servlet.http.HttpServlet.service(HttpServlet.java:831) at org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:411) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:290) at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:271) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:202) There is the source code of my classes : Action : @Entity @Table(name="action") public class Action { @Id @GeneratedValue(strategy=GenerationType.IDENTITY) private int num; @ManyToOne(cascade= { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH }) @JoinColumn(name="domain_num") private Domain domain; private String name; private String description; @OneToMany @JoinTable(name="permission", joinColumns= { @JoinColumn(name="action_num", referencedColumnName="action_num", nullable=false, updatable=false) }, inverseJoinColumns= { @JoinColumn(name="num") }) private Set<Permission> permissions; public Action() { } Permission : @SuppressWarnings("serial") @Entity @Table(name="permission") public class Permission implements Serializable { @EmbeddedId private PermissionPK primaryKey; @ManyToOne @JoinColumn(name="action_num", insertable=false, updatable=false) private Action action; @ManyToOne @JoinColumn(name="entity_num", insertable=false, updatable=false) private isd.pacepersistence.common.Entity entity; @ManyToOne @JoinColumn(name="class_num", insertable=false, updatable=false) private Clazz clazz; private String kondition; public Permission() { } PermissionPK : @SuppressWarnings("serial") @Entity @Table(name="permission") public class Permission implements Serializable { @EmbeddedId private PermissionPK primaryKey; @ManyToOne @JoinColumn(name="action_num", insertable=false, updatable=false) private Action action; @ManyToOne @JoinColumn(name="entity_num", insertable=false, updatable=false) private isd.pacepersistence.common.Entity entity; @ManyToOne @JoinColumn(name="class_num", insertable=false, updatable=false) private Clazz clazz; private String kondition; public Permission() { }

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• Reproduce PIPE functionality in IronPython

  - by Muppet Geoff

  Hi, I am hoping some genious out there can help me out with this... I am using sox to merge and resample a group of WAV files, and pipe the output directly to the input of NeroAACEnc for encoding to AAC format. I originally ran the process in a script, which included: sox.exe d:\audio\1.wav d:\audio\2.wav d:\audio\3.wav -c 1 -r 22050 -t wav - | neroAacEnc.exe -q 0.5 -if - -of test.m4a This worked as expected. The '-' in the comand line translates as 'Pipe/redirect input/output (stdin/stdout)' - So Sox pipes to stdout, and NeroAACEnc reads from stdin, the | joins them together. I then migrated the whole solution to Python, and the equivalent command became: from subprocess import call, Popen, PIPE runwav = Popen(['sox.exe', 'd:\audio\1.wav', 'd:\audio\2.wav', 'd:\audio\3.wav', '-c', '1', '-r', '22050', '-t', 'wav', '-'], shell=False, stdout=PIPE) runm4b = call(['neroAacEnc.exe', '-q', '0.5', '-if', '-', '-of', 'test.m4a'], shell=False, stdin=runwav.stdout) This also worked like a charm, exactly as expected. Slightly more convoluted, but hey :) Well now I have to move it to IronPython, and the Subprocess module isn't available (the partial implementation that is, doesn't have Popen/PIPE support - plus it seems silly to add a custom library when there is probably a native alternative). I should mention here, that I opted for IronPython over C#, because I am comfortable with Python now - however, there is a chance of moving it again later to C# native, and I am using IronPython to ease myself into it :) I have no C# or .net experience. So far I have the following equivalent, that sets up the 2 processes: from System.Diagnostics import Process wav = Process() wav.StartInfo.UseShellExecute = False wav.StartInfo.RedirectStandardOutput = True wav.StartInfo.FileName = 'sox.exe' wav.StartInfo.Arguments = 'd:\audio\1.wav d:\audio\2.wav d:\audio\3.wav -c 1 -r 22050 -t wav -' wav.Start() m4b = Process() m4b.StartInfo.UseShellExecute = False m4b.StartInfo.RedirectStandardInput = True m4b.StartInfo.FileName = 'neroAacEnc.exe' m4b.StartInfo.Arguments = '-q 0.5 -if - -of test.m4a' m4b.Start() I know that these 2 processes start (I can see Nero and Sox in the task manager) but what I can't figure out (for the life of me) is how to string the two output/input streams together, as with the previous two solutions. I have searched and searched, so I thought I'd ask! If anyone knows either: How to join the two streams with the same net result as the Python and Commandline versions; or A better way to acheive what I am trying to do. I would be extremely grateful! Many thanks in advance, Geoff P.S. A code sample based off the above would be awesome :) or a specific code example of a similar process that I can easily translate... this has broked my brayne.

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• Populate Multiple PDFs

  - by gmcalab

  I am using itextsharp to populate my PDFs. I have no issues with this. Basically what I am doing is getting the PDF and populating the fields in memory then passing back the MemoryStream to be displayed on a webpage. All this is working with a single document PDF. What I am trying to figure out now, is merging multiple PDFs into one MemoryStream. The part I cant figure out is, the documents I am populating are identical. So for example, I have a List<Person> that contains 5 persons. I want to fill out a PDF for each person and merge them all into one, in memory. Bare in mind I am going to fill out the same type of document for each person. The problem I am getting is that when I try to add a second copy of the same PDF to be filled out for the second iteration, it just overwrites the first populated PDF, since it's the same document, therefore not adding a second copy for the second Person at all. So basically if I had the 5 people, I would end up with a single page with the data of the 5th person, instead of a PDF with 5 like pages that contain the data of each person respectively. Here's some code... MemoryStream ms = ms = new MemoryStream(); PdfReader docReader = null; PdfStamper Stamper = null; List<Person> persons = new List<Person>() { new Person("Larry", "David"), new Person("Dustin", "Byfuglien"), new Person("Patrick", "Kane"), new Person("Johnathan", "Toews"), new Person("Marian", "Hossa") }; try { // Iterate thru all persons and populate a PDF for each foreach(var person in persons){ PdfCopyFields Copier = new PdfCopyFields(ms); Copier.AddDocument(GetReader("Person.pdf")); Copier.Close(); docReader = new PdfReader(ms.ToArray()); Stamper = new PdfStamper(docReader, ms); AcroFields Fields = Stamper.AcroFields; Fields.SetField("FirstName", person.FirstName); } }catch(Exception e){ // handle error }finally{ if (Stamper != null) { Stamper.Close(); } if (docReader != null) { docReader.Close(); } }

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• JPA @ManyToOne and composite PK

  - by Fleuri F

  Good Morning, I am working on project using JPA. I need to use a @ManyToOne mapping on a class that has three primary keys. You can find the errors and the classes after this. If anyone has an idea! Thanks in advance! FF javax.persistence.PersistenceException: No Persistence provider for EntityManager named JTA_pacePersistence: Provider named oracle.toplink.essentials.PersistenceProvider threw unexpected exception at create EntityManagerFactory: javax.persistence.PersistenceException javax.persistence.PersistenceException: Exception [TOPLINK-28018] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.EntityManagerSetupException Exception Description: predeploy for PersistenceUnit [JTA_pacePersistence] failed. Internal Exception: Exception [TOPLINK-7220] (Oracle TopLink Essentials - 2.0.1 (Build b09d-fcs (12/06/2007))): oracle.toplink.essentials.exceptions.ValidationException Exception Description: The @JoinColumns on the annotated element [private java.util.Set isd.pacepersistence.common.Action.permissions] from the entity class [class isd.pacepersistence.common.Action] is incomplete. When the source entity class uses a composite primary key, a @JoinColumn must be specified for each join column using the @JoinColumns. Both the name and the referenceColumnName elements must be specified in each such @JoinColumn. at oracle.toplink.essentials.internal.ejb.cmp3.EntityManagerSetupImpl.predeploy(EntityManagerSetupImpl.java:643) at oracle.toplink.essentials.ejb.cmp3.EntityManagerFactoryProvider.createEntityManagerFactory(EntityManagerFactoryProvider.java:196) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:110) at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:83) at isd.pacepersistence.common.DataMapper.(Unknown Source) at isd.pacepersistence.server.MainServlet.getDebugCase(Unknown Source) at isd.pacepersistence.server.MainServlet.doGet(Unknown Source) at javax.servlet.http.HttpServlet.service(HttpServlet.java:718) at javax.servlet.http.HttpServlet.service(HttpServlet.java:831) at org.apache.catalina.core.ApplicationFilterChain.servletService(ApplicationFilterChain.java:411) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:290) at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:271) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:202) There is the source code of my classes : Action : @Entity @Table(name="action") public class Action { @Id @GeneratedValue(strategy=GenerationType.IDENTITY) private int num; @ManyToOne(cascade= { CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH }) @JoinColumn(name="domain_num") private Domain domain; private String name; private String description; @OneToMany @JoinTable(name="permission", joinColumns= { @JoinColumn(name="action_num", referencedColumnName="action_num", nullable=false, updatable=false) }, inverseJoinColumns= { @JoinColumn(name="num") }) private Set<Permission> permissions; public Action() { } Permission : @SuppressWarnings("serial") @Entity @Table(name="permission") public class Permission implements Serializable { @EmbeddedId private PermissionPK primaryKey; @ManyToOne @JoinColumn(name="action_num", insertable=false, updatable=false) private Action action; @ManyToOne @JoinColumn(name="entity_num", insertable=false, updatable=false) private isd.pacepersistence.common.Entity entity; @ManyToOne @JoinColumn(name="class_num", insertable=false, updatable=false) private Clazz clazz; private String kondition; public Permission() { } PermissionPK : @SuppressWarnings("serial") @Entity @Table(name="permission") public class Permission implements Serializable { @EmbeddedId private PermissionPK primaryKey; @ManyToOne @JoinColumn(name="action_num", insertable=false, updatable=false) private Action action; @ManyToOne @JoinColumn(name="entity_num", insertable=false, updatable=false) private isd.pacepersistence.common.Entity entity; @ManyToOne @JoinColumn(name="class_num", insertable=false, updatable=false) private Clazz clazz; private String kondition; public Permission() { }

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• Using Effect For Fog of War

  - by Qua

  I'm trying to apply fog of war to areas on the screen not currently visible to the player. I do this by rendering the game content in one RenderTarget and the the fog of war into another, and then I merge them with an effect file that takes the color from the game RenderTarget and the alpha from the fog of war render target. The FOW RenderTarget is black where the FOW appears, and white where it doesn't. This does work, but it colors the fog of war (the unrevealed locations) white instead of the intended color of black. Before applying the effect I clear the backbuffer of the device to white. When I try to clear it to black, non of the fog of war appears at all, which I assume is a product of alpha blending with black. It works for all other colors, however - giving the resulting screen a tint of that color. How do I archieve a black fog while still being able to do alpha blending between the two render targets? The rendering code for applying the FOW: private RenderTarget2D mainTarget; private RenderTarget2D lightTarget; private void CombineRenderTargetsAndDraw() { batch.GraphicsDevice.SetRenderTarget(null); batch.GraphicsDevice.Clear(Color.White); fogOfWar.Parameters["LightsTexture"].SetValue(lightTarget); batch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend); fogOfWar.CurrentTechnique.Passes[0].Apply(); batch.Draw( mainTarget, new Rectangle(0, 0, batch.GraphicsDevice.PresentationParameters.BackBufferWidth, batch.GraphicsDevice.PresentationParameters.BackBufferHeight), Color.White ); batch.End(); } The effect file I'm using to apply the FOW: texture LightsTexture; sampler ColorSampler : register(s0); sampler LightsSampler = sampler_state{ Texture = <LightsTexture>; }; struct VertexShaderOutput { float4 Position : POSITION0; float2 TexCoord : TEXCOORD0; }; float4 PixelShaderFunction(VertexShaderOutput input) : COLOR0 { float2 tex = input.TexCoord; float4 color = tex2D(ColorSampler, tex); float4 alpha = tex2D(LightsSampler, tex); return float4(color.r, color.g, color.b, alpha.r); } technique Technique1 { pass Pass1 { PixelShader = compile ps_2_0 PixelShaderFunction(); } }

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• How to efficiently save changes made in UI/main thread with Core Data?

  - by Jaanus

  So, there have been several posts here about importing and saving data from an external data source into Core Data. Apple documents a reasonable pattern for this: "import and save on background thread, merge saved objects to main thread." All fine and good. I have a related but different problem: the user is modifying data in the UI and main thread, and thus modifies state of some objects in the managed object context (MOC). I would like to save these changes from time to time. What is a good way to do that? Now, you could say that I could do the same: create a background thread with its own MOC and pass the changed objectID-s there. The catch-22 for me with this is that an object's ID changes when it is saved, and I cannot guarantee the order of things happening. I may end up passing a different objectID into the background thread for the same object, based on whether the object has been previously saved or not, and I don't know if Core Data can resolve this and see that different objectID-s are pointing to the same object and not create duplicates for me. (I could test this, but I'm lazywebbing with this question first.) One thought I had: I could always do MOC saves on a background thread, and queue them up with operationqueue, so that there is always only one save in progress. I would not create a new MOC, I would just use the same MOC as in main thread. Now, this is not thread safe and when someone modifies the MOC in main thread while it is being saved in background thread, the results will probably be catastrophic. But, minus the thread safety, you can see what kind of solution I'd wish for. To be clear, the problem I need to fix is that if I just do the save in main thread, it blocks the UI for an unacceptably long period of time, I want to move the save to background thread. So, questions: what about the reasoning of an object ID changing during saving, and Core Data being able to resolve them to the same object? Would this be the right way of addressing this problem? any other good ways of doing this?

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• Create links programmatically inside an EmberJS view

  - by Michael Gallego

  I have a pretty complex view to render which involves some kind of recursion (the typical folder/file nested list). The fact that it contains heterogeneous objects (folders and files) make it even harder to write Handlebars templates. Therefore, the only solution I've found is to create a view, and manually fill the render buffer. I came with the following solution: App.LibraryContentList = Ember.View.extend({ tagName: 'ol', classNames: ['project-list', 'dd-list'], nameChanged: function() { this.rerender(); }.observes('[email protected]'), render: function(buffer) { // We only start with depth of zero var content = this.get('content').filterProperty('depth', 0); content.forEach(function(item) { this.renderItem(buffer, item); }, this); }, renderItem: function(buffer, item) { switch (item.constructor.toString()) { case 'Photo.Folder': this.renderFolder(buffer, item); break; case 'Photo.File': this.renderFile(buffer, item); break; } }, renderFolder: function(buffer, folder) { buffer.push('<li class="folder dd-item">'); buffer.push('<span class="dd-handle">' + folder.get('name') + '</span>'); // Merge sub folders and files, and sort them by sort order var content = this.mergeAndSort(); if (content.get('length') > 0) { buffer.push('<ol>'); content.forEach(function(item) { this.renderItem(buffer, item); }, this); buffer.push('</ol>'); } buffer.push('</li>'); }, renderFile: function(buffer, album) { buffer.push('<li class="album dd-item">'); buffer.push('<span class="dd-handle">' + file.get('name') + '</span>'); buffer.push('</li>'); } }); Now, what I'd like is to be able to add links so that each folder and each file is clickable and redirect to another route. But how am I supposed to do that, as I don't have access to the linkTo helper? I've tried to play with the LinkView view, but without any success. Should I register handlers manually for each item? I've also thought about breaking that with a CollectionView instead, and splitting the content by depth so that I could render it using templates, but it seems more complicated. Any thoughts?

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• Am I using EJBs properly?

  - by kgrad

  I am using a JEE6 stack including JPA 2.0, JSF 2.0, EJB 3.1 etc. The way my architecture is setup is the following: I have JPA annotated DAOs using hibernate as my JPA provider. I have JSF Managed beans which correspond to my facelet/xhtml pages. I have EJBs that handle all of my database requests. My XHTML pages have JSF EL which make calls to my Managed beans. My managed beans contain references to my DAO entities which are managed by EJBs. For example, I have a user entity which is mapped to a db table. I have a user EJB which handles all CRUD operations that return Users. I have a page that edits a user. The highlevel workflow would be: navigate to user edit page - EL calls a method located in the managed bean that loads a user. The method calls userEJB.loadUser(user) from the EJB to get the user from the database. The user is edited and submit - a function is called in the managed bean which calls a function in the EJB to save the user. etc. I am running into issues accessing my data within my JSF pages using EJBs. I am having a lot of problems with lazy initialization errors, which I believe is due to how I have set things up. For example, I have a Client entity that has a List of users which are lazily loaded. In order to get a client I call a method in my EJB which goes to the database, finds a client and returns it. Later on i wish to access this clients list of users, in order to do so i have to go back to the EJB by calling some sort of method in order to load those users (since they are lazily loaded). This means that I have to create a method such as public List<User> getUserListByClient(Client c) { c = em.merge(c); return c.getUserList(); } The only purpose of this method is to load the users (and I'm not even positive this approach is good or works). If i was doing session management myself, I would like just leave the session open for the entire request and access the property directly, this would be fine as the session would be open anyway, there seems to be this one extra layer of indirection in EJBs which is making things difficult for me. I do like EJBs as I like the fact that they are controlled by the container, pooled, offer transaction management for free etc. However, I get the feeling that I am using them incorrectly, or I have set up my JSF app incorrectly. Any feedback would be greatly appreciated. thanks,

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• How to optimize my PostgreSQL DB for prefix search?

  - by asmaier

  I have a table called "nodes" with roughly 1.7 million rows in my PostgreSQL db =#\d nodes Table "public.nodes" Column | Type | Modifiers --------+------------------------+----------- id | integer | not null title | character varying(256) | score | double precision | Indexes: "nodes_pkey" PRIMARY KEY, btree (id) I want to use information from that table for autocompletion of a search field, showing the user a list of the ten titles having the highest score fitting to his input. So I used this query (here searching for all titles starting with "s") =# explain analyze select title,score from nodes where title ilike 's%' order by score desc; QUERY PLAN ----------------------------------------------------------------------------------------------------------------------- Sort (cost=64177.92..64581.38 rows=161385 width=25) (actual time=4930.334..5047.321 rows=161264 loops=1) Sort Key: score Sort Method: external merge Disk: 5712kB -> Seq Scan on nodes (cost=0.00..46630.50 rows=161385 width=25) (actual time=0.611..4464.413 rows=161264 loops=1) Filter: ((title)::text ~~* 's%'::text) Total runtime: 5260.791 ms (6 rows) This was much to slow for using it with autocomplete. With some information from Using PostgreSQL in Web 2.0 Applications I was able to improve that with a special index =# create index title_idx on nodes using btree(lower(title) text_pattern_ops); =# explain analyze select title,score from nodes where lower(title) like lower('s%') order by score desc limit 10; QUERY PLAN ------------------------------------------------------------------------------------------------------------------------------------------ Limit (cost=18122.41..18122.43 rows=10 width=25) (actual time=1324.703..1324.708 rows=10 loops=1) -> Sort (cost=18122.41..18144.60 rows=8876 width=25) (actual time=1324.700..1324.702 rows=10 loops=1) Sort Key: score Sort Method: top-N heapsort Memory: 17kB -> Bitmap Heap Scan on nodes (cost=243.53..17930.60 rows=8876 width=25) (actual time=96.124..1227.203 rows=161264 loops=1) Filter: (lower((title)::text) ~~ 's%'::text) -> Bitmap Index Scan on title_idx (cost=0.00..241.31 rows=8876 width=0) (actual time=90.059..90.059 rows=161264 loops=1) Index Cond: ((lower((title)::text) ~>=~ 's'::text) AND (lower((title)::text) ~<~ 't'::text)) Total runtime: 1325.085 ms (9 rows) So this gave me a speedup of factor 4. But can this be further improved? What if I want to use '%s%' instead of 's%'? Do I have any chance of getting a decent performance with PostgreSQL in that case, too? Or should I better try a different solution (Lucene?, Sphinx?) for implementing my autocomplete feature?

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