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• Data Flow Object Graph and An Execution Engine for it

  - by M Dotnet

  I would like to build a custom workflow engine from scratch. The input to this workflow is a data flow diagram which is composed of a series of activities connected together through lines where each each represent the data flow. Each activity can export multiple outputs. Activities are complex math functions but the logic is hidden from the user. My workflow engine job is to execute the given data flow diagram. Each activity within the data flow diagram is a custom activity and each activity can output different outputs. How do you suggest to model the data flow diagram object? I need to be able to construct the data flow diagram problematically (no need for drag and drop) but I need to display the final result graphically (for display and debugging purposes). Are there any libraries out there that I could use? Should I keep the workflow presentable as an xml? I know that there are many projects out there trying to essentially doing similar thing by building such workflow engines but I need something light weight and open source. I do not need any state machine execution engine and mine is primarily sequential workflow with fork and join capabilities. My activities are wrappable as basic C# classes and I do NOT want to use anything as heavy as .NET workflow foundation.

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• Need advice on comparing the performance of 2 equivalent linq to sql queries

  - by uvita

  I am working on tool to optimize linq to sql queries. Basically it intercepts the linq execution pipeline and makes some optimizations like for example removing a redundant join from a query. Of course, there is an overhead in the execution time before the query gets executed in the dbms, but then, the query should be processed faster. I don't want to use a sql profiler because I know that the generated query will be perform better in the dbms than the original one, I am looking for a correct way of measuring the global time between the creation of the query in linq and the end of its execution. Currently, I am using the Stopwatch class and my code looks something like this: var sw = new Stopwatch(); sw.Start(); const int amount = 100; for (var i = 0; i < amount; i++) { ExecuteNonOptimizedQuery(); } sw.Stop(); Console.Writeline("Executing the query {2} times took: {0}ms. On average, each query took: {1}ms", sw.ElapsedMilliseconds, sw.ElapsedMilliseconds / amount, amount); Basically the ExecutenNonOptimizedQuery() method creates a new DataContext, creates a query and then iterates over the results. I did this for both versions of the query, the normal one and the optimized one. I took the idea from this post from Frans Bouma. Is there any other approach/considerations I should take? Thanks in advance!

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• DATE_FORMAT in DQL symfon2

  - by schurtertom

  I would like to use some MySQL functions such as DATE_FORMAT in my QueryBuilder. I saw this post did not understand totally how I should achieve it: SELECT DISTINCT YEAR Doctrine class SubmissionManuscriptRepository extends EntityRepository { public function findLayoutDoneSubmissions( $fromDate, $endDate, $journals ) { if( true === is_null($fromDate) ) return null; $commQB = $this->createQueryBuilder( 'c' ) ->join('c.submission_logs', 'k') ->select("DATE_FORMAT(k.log_date,'%Y-%m-%d')") ->addSelect('c.journal_id') ->addSelect('COUNT(c.journal_id) AS numArticles'); $commQB->where("k.hash_key = c.hash_key"); $commQB->andWhere("k.log_date >= '$fromDate'"); $commQB->andWhere("k.log_date <= '$endDate'"); if( $journals != null && is_array($journals) && count($journals)>0 ) $commQB->andWhere("c.journal_id in (" . implode(",", $journals) . ")"); $commQB->andWhere("k.new_status = '20'"); $commQB->orderBy("k.log_date", "ASC"); $commQB->groupBy("c.hash_key"); $commQB->addGroupBy("c.journal_id"); $commQB->addGroupBy("DATE_FORMAT(k.log_date,'%Y-%m-%d')"); return $commQB->getQuery()->getResult(); } } Entity SubmissionManuscript /** * MDPI\SusyBundle\Entity\SubmissionManuscript * * @ORM\Entity(repositoryClass="MDPI\SusyBundle\Repository\SubmissionManuscriptRepository") * @ORM\Table(name="submission_manuscript") * @ORM\HasLifecycleCallbacks() */ class SubmissionManuscript { ... /** * @ORM\OneToMany(targetEntity="SubmissionManuscriptLog", mappedBy="submission_manuscript") */ protected $submission_logs; ... } Entity SubmissionManuscriptLog /** * MDPI\SusyBundle\Entity\SubmissionManuscriptLog * * @ORM\Entity(repositoryClass="MDPI\SusyBundle\Repository\SubmissionManuscriptLogRepository") * @ORM\Table(name="submission_manuscript_log") * @ORM\HasLifecycleCallbacks() */ class SubmissionManuscriptLog { ... /** * @ORM\ManyToOne(targetEntity="SubmissionManuscript", inversedBy="submission_logs") * @ORM\JoinColumn(name="hash_key", referencedColumnName="hash_key") */ protected $submission_manuscript; ... } any help I would appreciate a lot. EDIT 1 I have now successfully be able to add the Custom Function DATE_FORMAT. But now if I try with my Group By I get the following Error: [Semantical Error] line 0, col 614 near '(k.logdate,'%Y-%m-%d')': Error: Cannot group by undefined identification variable. Anyone knows about this?

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• How to get XML element/attribute name in SQL Server 2005

  - by OG Dude

  Hi, I have a simple procedure in SQL Server 2005 which takes some XML as input. The element attributes correspond to field names in tables. I'd like to be able to determine <elementName>, <attribNameX> dynamically as to avoid having to hardcode them into the procedure. How can I do this? The XML looks like this: <ROOT> <elementName attribName1 = "xxx" attribName2 = "yyy"/> <elementName attribName1 = "aaa" attribName2 = "bbb"/> ... </ROOT> The stored procedure like this: CREATE PROC dbo.myProc ( @XMLInput varchar(1000) ) AS BEGIN SET NOCOUNT ON DECLARE @XMLDocHandle int EXEC sp_xml_preparedocument @XMLDocHandle OUTPUT, @XMLInput SELECT someTable.someCol FROM dbo.someTable JOIN OPENXML (@XMLDocHandle, '/ROOT/elementName',1) WITH (attrib1Name int, attrib2Name int) AS XMLData ON someTable.attribName1 = XMLData.attribName1 AND someTable.attribName2 = XMLData.attribName2 EXEC sp_xml_removedocument @XMLDocHandle END GO The question has been asked here before but maybe there is a cleaner solution. Additionally, I'd like to pass the tablename as a parameter as well - I read some stuff arguing that this is bad style - so what would be a good solution for having a dynamic tablename? Thanks a lot in advance, /David

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• Find out which row caused the error

  - by Felipe Fiali

  I have a big fat query that's written dynamically to integrate some data. Basically what it does is query some tables, join some other ones, treat some data, and then insert it into a final table. The problem is that there's too much data, and we can't really trust the sources, because there could be some errored or inconsistent data. For example, I've spent almost an hour looking for an error while developing using a customer's database because somewhere in the middle of my big fat query there was an error converting some varchar to datetime. It turned out to be that they had some sales dating '2009-02-29', an out-of-range date. And yes, I know. Why was that stored as varchar? Well, the source database has 3 columns for dates, 'Month', 'Day' and 'Year'. I have no idea why it's like that, but still, it is. But how the hell would I treat that, if the source is not trustable? I can't HANDLE exceptions, I really need that it comes up to another level with the original message, but I wanted to provide some more info, so that the user could at least try to solve it before calling us. So I thought about displaying to the user the row number, or some ID that would at least give him some idea of what record he'd have to correct. That's also a hard job because there will be times when the integration will run up to 80000 records. And in an 80000 records integration, a single dummy error message: 'The conversion of a varchar data type to a datetime data type resulted in an out-of-range datetime value' means nothing at all. So any idea would be appreciated. Oh I'm using SQL Server 2005 with Service Pack 3.

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• wpf dispatcher/threading issue

  - by phm

  Hello I have a problem in my code and I am not able to fix it at all. private static void SetupImages(object o) { int i = (int)o; BitmapImage bi = GetBitmapObject(i); img = new System.Windows.Controls.Image();//declared as static outside img.Source = bi;//crash here img.Stretch = Stretch.Uniform; img.Margin = new Thickness(5, 5, 5, 5); } which is called like this: for (int i = 0; i < parameters.ListBitmaps.Count; i++) { ParameterizedThreadStart ts = new ParameterizedThreadStart(SetupImages); Thread t = new Thread(ts); t.SetApartmentState(ApartmentState.STA); t.Start(i); t.Join(); //SetupImages(i); parameters.ListImageControls.Add(img); } It always crashes on this line: img.Source = bi; The error is: "An unhandled exception of type 'System.InvalidOperationException' occurred in WindowsBase.dll Additional information: The calling thread cannot access this object because a different thread owns it." Thanks

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• Shutting down a windows service that has threads

  - by Dave

  I have a windows service written in .NET 3.5 (c#) with a System.Threading.Timer that spawns several Threads in each callback. These are just normal threads (no Thread Pool) and I've set the IsBackground = true on each thread since I'm only going to be running managed code. When a user stops the service, what happens to all the threads? Do they die gracefully? I don't have any code that manages the threads via calling join or abort. Is it correct to assume the IsBackground = true is enough to assume the threads will be disposed and stopped when a user stops the service? What exactly happens when someone stops a windows service via the Service Manager GUI? Does it kill the process after it fires the OnStop event? This would actually be acceptable for me because I've built a separate mechanism that allows a user know for sure there are no threads before they stop the service. This is done via 2 WCF methods exposed from a ServiceHost that runs inside the Windows Service. There's one method to stop spawning new threads and another method to query how many running threads there are left. I'm just curious what happens if they skip those steps and just stop the service... It seems the IsBackground helps achieve this:

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• Ruby GraphViz Binary Tree Record

  - by Jason M

  I'm using the ruby-graphviz gem and I'm trying to draw binary trees. I'd like to use the record shape so that each node can have a left, middle, and right field and, thus, if there are two edges leaving a node, the left and right edges can be distinguished. I tried specifying the field by concatenating the field name like this: @node1.name + ":left" But that did not work. What is the correct way of specifying the field? require 'rubygems' require 'graphviz' @graph = GraphViz.new( :G, :type => :digraph ) @node1 = @graph.add_node("1", "shape" => "record", "label" => "<left>|<f1> 1|<right>" ) @node2 = @graph.add_node("2", "shape" => "record", "label" => "<left>|<f1> 2|<right>" ) @graph.add_edge(@node1.name + ":left", @node2) # generate a random filename filename = "/tmp/#{(0...8).map{65.+(rand(25)).chr}.join}.png" @graph.output( :png => filename ) exec "open #{filename}"

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• Help Me With This Access Query

  - by yae

  I have 2 tables: "products" and "pieces" PRODUCTS idProd product price PIECES id idProdMain idProdChild quant idProdMain and idProdChild are related with the table: "products". Other considerations is that 1 product can have some pieces and 1 product can be a piece. Price product equal a sum of quantity * price of all their pieces. "Products" table contains all products (p EXAMPLE: TABLE PRODUCTS (idProd - product - price) 1 - Computer - 300€ 2 - Hard Disk - 100€ 3 - Memory - 50€ 4 - Main Board - 100€ 5 - Software - 50€ 6 - CDroms 100 un. - 30€ TABLE PIECES (id - idProdMain - idProdChild - Quant.) 1 - 1 - 2 - 1 2 - 1 - 3 - 2 3 - 1 - 4 - 1 WHAT I NEED? I need update the price of the main product when the price of the product child (piece) is changed. Following the previous example, if I change the price of this product "memory" (is a piece too) to 60€, then product "Computer" will must change his price to 320€ How I can do it using queries? Already I have tried this to obatin the price of the main product, but not runs. This query not returns any value: SELECT Sum(products.price*pieces.quant) AS Expr1 FROM products LEFT JOIN pieces ON (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdMain) WHERE (((pieces.idProdMain)=5)); MORE INFO The table "products" contains all the products to sell that it is in the shop. The table "pieces" is to take a control of the compound products. To know those who are the products children. For example of compound product: computers. This product is composed by other products (motherboard, hard disk, memory, cpu, etc.)

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• Hibernate Bi- Directional many to many mapping advice!

  - by Rob

  hi all, i woundered if anyone might be able to help me out. I am trying to work out what to google for (or any other ideas!!) basically i have a bidirectional many to many mapping between a user entity and a club entity (via a join table called userClubs) I now want to include a column in userClubs that represents the role so that when i call user.getClubs() I can also work out what level access they have. Is there a clever way to do this using hibernate or do i need to rethink the database structure? Thank you for any help (or just for reading this far!!) the user.hbm.xml looks a bit like <set name="clubs" table="userClubs" cascade="save-update"> <key column="user_ID"/> <many-to-many column="activity_ID" class="com.ActivityGB.client.domain.Activity"/> </set> the activity.hbm.xml part <set name="members" inverse="true" table="userClubs" cascade="save-update"> <key column="activity_ID"/> <many-to-many column="user_ID" class="com.ActivityGB.client.domain.User"/> </set> The current userClubs table contains the fields id | user_ID | activity_ID I would like to include in there id | user_ID | activity_ID | role and be able to access the role on both sides...

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• Save PyML.classifiers.multi.OneAgainstRest(SVM()) object?

  - by Michael Aaron Safyan

  I'm using PYML to construct a multiclass linear support vector machine (SVM). After training the SVM, I would like to be able to save the classifier, so that on subsequent runs I can use the classifier right away without retraining. Unfortunately, the .save() function is not implemented for that classifier, and attempting to pickle it (both with standard pickle and cPickle) yield the following error message: pickle.PicklingError: Can't pickle : it's not found as __builtin__.PySwigObject Does anyone know of a way around this or of an alternative library without this problem? Thanks. Edit/Update I am now training and attempting to save the classifier with the following code: mc = multi.OneAgainstRest(SVM()); mc.train(dataset_pyml,saveSpace=False); for i, classifier in enumerate(mc.classifiers): filename=os.path.join(prefix,labels[i]+".svm"); classifier.save(filename); Notice that I am now saving with the PyML save mechanism rather than with pickling, and that I have passed "saveSpace=False" to the training function. However, I am still gettting an error: ValueError: in order to save a dataset you need to train as: s.train(data, saveSpace = False) However, I am passing saveSpace=False... so, how do I save the classifier(s)? P.S. The project I am using this in is pyimgattr, in case you would like a complete testable example... the program is run with "./pyimgattr.py train"... that will get you this error. Also, a note on version information: [michaelsafyan@codemage /Volumes/Storage/classes/cse559/pyimgattr]$ python Python 2.6.1 (r261:67515, Feb 11 2010, 00:51:29) [GCC 4.2.1 (Apple Inc. build 5646)] on darwin Type "help", "copyright", "credits" or "license" for more information. import PyML print PyML.__version__ 0.7.0

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• How do I access the CodeDomProvider from a class inheriting from Microsoft.VisualStudio.TextTemplating.VSHost.BaseCodeGeneratorWithSite?

  - by Charlie

  Does anyone know how to get a CodeDomProvider in the new Microsoft.VisualStudio.TextTemplating.VSHost.BaseCodeGeneratorWithSite from the Visual Studio 2010 SDK? I used to get access to it just by in mere inheritance of the class Microsoft.CustomTool.BaseCodeGeneratorWithSite, but now with this new class it is not there. I see a GlobalServiceProvider and a SiteServiceProvider but I can't find any example on how to use them. Microsoft.VisualStudio.TextTemplating.VSHost.BaseCodeGeneratorWithSite: http://msdn.microsoft.com/en-us/library/bb932625.aspx I was to do this: public class Generator : Microsoft.VisualStudio.TextTemplating.VSHost.BaseCodeGeneratorWithSite { public override string GetDefaultExtension() { // GetDefaultExtension IS ALSO NOT ACCESSIBLE... return this.InputFilePath.Substring(this.InputFilePath.LastIndexOf(".")) + ".designer" + base.GetDefaultExtension(); } // This method is being called every time the attached xml is saved. protected override byte[] GenerateCode(string inputFileName, string inputFileContent) { try { // Try to generate the wrapper file. return GenerateSourceCode(inputFileName); } catch (Exception ex) { // In case of a faliure - print the exception // as a comment in the source code. return GenerateExceptionCode(ex); } } public byte[] GenerateSourceCode(string inputFileName) { Dictionary<string, CodeCompileUnit> oCodeUnits; // THIS IS WHERE CodeProvider IS NOT ACCESSIBLE CodeDomProvider oCodeDomProvider = this.CodeProvider; string[] aCode = new MyCustomAPI.GenerateCode(inputFileName, ref oCodeDomProvider); return Encoding.ASCII.GetBytes(String.Join(@" ", aCode)); } private byte[] GenerateExceptionCode(Exception ex) { CodeCompileUnit oCode = new CodeCompileUnit(); CodeNamespace oNamespace = new CodeNamespace("System"); oNamespace.Comments.Add(new CodeCommentStatement(MyCustomAPI.Print(ex))); oCode.Namespaces.Add(oNamespace); string sCode = null; using (StringWriter oSW = new StringWriter()) { using (IndentedTextWriter oITW = new IndentedTextWriter(oSW)) { this.CodeProvider.GenerateCodeFromCompileUnit(oCode, oITW, null); sCode = oSW.ToString(); } } return Encoding.ASCII.GetBytes(sCode ); } } Thanks for your help!

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• De-normalization alternative to specific MYSQL problem?

  - by Booker

  I am facing quite a specific optimization problem. I currently have 4 normalized tables of data. Every second, possibly thousands of users will pull down up-to-date info from these tables using AJAX. The thing is that I can predict relatively easily which subset of data they need... The most recent 100 or so entries in those 4 normalized tables. I have been researching de-normalization... but feel that perhaps there is an easier solution. I was thinking that I could somehow every second run one sql query to condense the needed info, store it in a temp cached table and then have all of the user queries just draw from this. This will allow the complex join of 4 tables to only be run once, and then from there the users just need to do a simple lookup from the cached table. I really don't know if this is feasible. Comments on this or any other suggestions would be much appreciated. Thanks!

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• How to get node without children in xQuery?

  - by mbrevoort

  So I have two nodes of elements that I'm essentially trying to join. I want the top level node to stay the same but the child nodes to be replaced by those cross referenced. Given: <stuff> <item foo="foo" boo="1"/> <item foo="bar" boo="2" /> <item foo="baz" boo="3"/> <item foo="blah boo="4""/> </stuff> <list a="1" b="2"> <foo>bar</foo> <foo>baz</foo> </list> I want to loop through "list" and cross reference elements in "stuff" for this result: <list a="1" b="2"> <item foo="bar" boo="2" /> <item foo="baz" boo="3"/> </list> I want to do this without having to know about what attributes might be on "list". In other words I don't want to have to explicitly call them out like attribute a { $list/@a }, attribute b { $list/@b }

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• Avoiding secondary selects or joins with Hibernate Criteria or HQL query

  - by Ben Benson

  I am having trouble optimizing Hibernate queries to avoid performing joins or secondary selects. When a Hibernate query is performed (criteria or hql), such as the following: return getSession().createQuery(("from GiftCard as card where card.recipientNotificationRequested=1").list(); ... and the where clause examines properties that do not require any joins with other tables... but Hibernate still performs a full join with other tables (or secondary selects depending on how I set the fetchMode). The object in question (GiftCard) has a couple ManyToOne associations that I would prefer to be lazily loaded in this case (but not necessarily all cases). I want a solution that I can control what is lazily loaded when I perform the query. Here's what the GiftCard Entity looks like: @Entity @Table(name = "giftCards") public class GiftCard implements Serializable { private static final long serialVersionUID = 1L; private String id_; private User buyer_; private boolean isRecipientNotificationRequested_; @Id public String getId() { return this.id_; } public void setId(String id) { this.id_ = id; } @ManyToOne @JoinColumn(name = "buyerUserId") @NotFound(action = NotFoundAction.IGNORE) public User getBuyer() { return this.buyer_; } public void setBuyer(User buyer) { this.buyer_ = buyer; } @Column(name="isRecipientNotificationRequested", nullable=false, columnDefinition="tinyint") public boolean isRecipientNotificationRequested() { return this.isRecipientNotificationRequested_; } public void setRecipientNotificationRequested(boolean isRecipientNotificationRequested) { this.isRecipientNotificationRequested_ = isRecipientNotificationRequested; } }

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• Will Apple bundle the Mono Touch runtime with every iPhone?

  - by Zoran Simic

  It strikes me as a good idea for Apple to negotiate with Novell and bundle the Mono Touch runtime (only the runtime of course) into every iPhone and iPod Touch. Perhaps even make it a "one time install" that automatically gets downloaded from the App Store the first time one downloads an app build with Mono Touch, making every subsequent Mono Touch app much lighter to download (without the runtime). Doing so would be similar in a way to adding Bootcamp to OS X: it would make it easier for C# developers to join the party, but that wouldn't mean these developers will all stick to C#... What convinced me to buy a Mac is Bootcamp - I figured I could always install Windows if I didn't like OS X (and I liked the hardware, so no problem there). 6 months later, I'm using OS X full time... Would there be any technical issues in doing so? I see only advantages for all parties, not one disadvantage to anyone (except maybe for the few unfortunate Apple employees who would have to test the crap out of the Mono Touch runtime before bundling it): Novell wins because Mono Touch becomes much more viable (Mono Touch apps become much lighter all of the sudden) Developers win because now there's one more tool in the tool belt Many C# Developers would be very interested by this Apple wins because that would bring even more attention to the platform, more revenue in developer fees, more potential great apps, etc Users win because less space is used by different Apps having copies of the same runtime accumulating on their devices Would there be a major technical obstacle in bundling Mono Touch to iPhone OS? Edit: Changed the title from "Should" to "Will Apple bundle the runtime?", I think the consensus on predicting that means a lot to those considering going with Mono Touch.

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• Stored Procedure: Variable passed from PHP alters second half of query string

  - by Stephanie

  Hello everyone, Basically, we have an ASP website right now that I'm converting to PHP. We're still using the MSSQL server for the DB -- it's not moving. In the ASP, now, there's an include file with a giant sql query that's being executed. This include sits on a lot of pages and this is a simple version of what happens. Pages A, B and C all use this include file to return a listing. In ASP, Page A passes through variable A to the include file - page B passes through variable B -- page C passes through variable C, and so on. The include file builds the SQL query like this: sql = "SELECT * from table_one LEFT OUTER JOIN table_two ON table_one.id = table_two.id" then adds (remember, ASP), based on the variable passed through from the parent page, Select Case sType Case "A" sql = sql & "WHERE LOWER(column_a) <> 'no' AND LTRIM(ISNULL(column_b),'') <> '' ORDER BY column_a Case "B" sql = sql & "WHERE LOWER(column_c) <> 'no' ORDER BY lastname, firstname Case "C" sql = sql & "WHERE LOWER(column_f) <> 'no' OR LOWER(column_g) <> 'no' ORDER BY column_g As you notice, every string that's added on as the second part of the sql query is different than the previous; not just one variable can be substituted out, which is what has me stumped. How do I translate this case / switch into the stored procedure, based on the varchar input that I pass to the stored procedure via PHP? This stored procedure will actually handle a query listing for about 20 pages, so it's a hefty one and this is my first major complicated one. I'm getting there, though! I'm also just more used to MySQL, too. Not that they're that different. :P Thank you very much for your help in advance. Stephanie

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• Call to a member function num_rows() on a non-object

  - by Patrick

  I need to get the number of rows of a query (so I can paginate results). As I'm learning codeigniter (and OO php) I wanted to try and chain a -num_rows() to the query, but it doesn't work: //this works: $data['count'] = count($this->events->findEvents($data['date'], $data['keyword'])); //the following doesn't work and generates // Fatal Error: Call to a member function num_rows() on a non-object $data['count2'] = $this->events->findEvents($data['date'], $data['keyword'])->num_rows(); the model returns an array of objects, and I think this is the reason why I can't use a method on it. function findEvents($date, $keyword, $limit = NULL, $offset = NULL) { $data = array(); $this->db->select('events.*, venues.*, events.venue AS venue_id'); $this->db->join('venues', 'events.venue = venues.id'); if ($date) { $this->db->where('date', $date); } if ($keyword) { $this->db->like('events.description', $keyword); $this->db->or_like('venues.description', $keyword); $this->db->or_like('band', $keyword); $this->db->or_like('venues.venue', $keyword); $this->db->or_like('genre', $keyword); } $this->db->order_by('date', 'DESC'); $this->db->order_by('events.priority', 'DESC'); $this->db->limit($limit, $offset); //for pagination purposes $Q = $this->db->get('events'); if ($Q->num_rows() > 0) { foreach ($Q->result() as $row) { $data[] = $row; } } $Q->free_result(); return $data; } Is there anything that i can do to be able to use it? EG, instead of $data[] = $row; I should use another (OO) syntax?

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• Speeding up inner-joins and subqueries while restricting row size and table membership

  - by hiffy

  I'm developing an rss feed reader that uses a bayesian filter to filter out boring blog posts. The Stream table is meant to act as a FIFO buffer from which the webapp will consume 'entries'. I use it to store the temporary relationship between entries, users and bayesian filter classifications. After a user marks an entry as read, it will be added to the metadata table (so that a user isn't presented with material they have already read), and deleted from the stream table. Every three minutes, a background process will repopulate the Stream table with new entries (i.e. whenever the daemon adds new entries after the checks the rss feeds for updates). Problem: The query I came up with is hella slow. More importantly, the Stream table only needs to hold one hundred unread entries at a time; it'll reduce duplication, make processing faster and give me some flexibility with how I display the entries. The query (takes about 9 seconds on 3600 items with no indexes): insert into stream(entry_id, user_id) select entries.id, subscriptions_users.user_id from entries inner join subscriptions_users on subscriptions_users.subscription_id = entries.subscription_id where subscriptions_users.user_id = 1 and entries.id not in (select entry_id from metadata where metadata.user_id = 1) and entries.id not in (select entry_id from stream where user_id = 1); The query explained: insert into stream all of the entries from a user's subscription list (subscriptions_users) that the user has not read (i.e. do not exist in metadata) and which do not already exist in the stream. Attempted solution: adding limit 100 to the end speeds up the query considerably, but upon repeated executions will keep on adding a different set of 100 entries that do not already exist in the table (with each successful query taking longer and longer). This is close but not quite what I wanted to do. Does anyone have any advice (nosql?) or know a more efficient way of composing the query?

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• Does complex JOINs causes high coupling and maintenance problems ?

  - by ashkan.kh.nazary

  Our project has ~40 tables with complex relations.A colleague believes in using long join queries which enforces me to learn about tables outside of my module but I think I should not concern about tables not directly related to my module and use data access functions (written by those responsible for other modules) when I need data from them. Let me clarify: I am responsible for the ContactVendor module which enables the customers to contact the vendor and start a conversation about some specific product. Products module has it's own complex tables and relations with functions that encapsulate details (for example i18n, activation, product availability etc ...). Now I need to show the product title of some product related to some conversation between the vendor and customers. I may either write a long query that retrieves the product info along with conversation stuff in one shot (which enforces me to learn about Product tables) OR I may pass the relevant product_id to the get_product_info(int) function. First approach is obviously demanding and introduces many bad practices and things I normally consider fault in programming. The problem with the second approach seems to be the countless mini queries these access functions cause and performance loss is a concern when a loop tries to fetch product titles for 100 products using functions that each perform a separate query. So I'm stuck between "don't code to the implementation, code to interface" and performance. What is the right way of doing things ? UPDATE: I'm specially concerned about possible future modifications to those tables outside of my module. What if the Products module decided to change the way they are doing things? or for some reason modify the schema? It means some other modules would break or malfunction until the change is integrated to them. The usual ripple effect problem.

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• Hibernate HQL and Grails- How do I compare collections?

  - by BurtP

  Hi everyone (my first post!), I have an HQL question (in Groovy/Grails) I was hoping someone could help me with. I have a simple Asset object with a one-to-many Tags collection. class Asset { Set tags static hasMany = [tags:Tag] } class Tag { String name } What I'm trying to do in HQL: A user passes in some tags in params.tags (ex: groovy grails rocks) and wants to return Asset(s) that have those tags, and only those exact tags. Here's my HQL that returns Assets if one or more of the tags are present in an Assets tags: SELECT DISTINCT a FROM Asset a LEFT JOIN a.tags t WHERE t IN (:tags) assetList = Asset.executeQuery( hql, [tags:tokenizedTagListFromParams] The above code works perfect, but its really like an OR. If any of the tag(s) are found, it will return that Asset. I only want to return Assets that have those exact same tags (in number as well). Every time a new tag is created, I new Tag(name:xxx).save() so I can get the Tag instances and unique ID's for each tag that was asked for. I also tried converting the passed in tags to a list of Tag instances with Tag.findByName(t1) for each tag, and also a list of (unique) Tag Id's into the HQL above with no luck. I would appreciate any help/advice. Thank you for your time, Burt

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• foreignkey problem

  - by realshadow

  Hey, Imagine you have this model: class Category(models.Model): node_id = models.IntegerField(primary_key = True) type_id = models.IntegerField(max_length = 20) parent_id = models.IntegerField(max_length = 20) sort_order = models.IntegerField(max_length = 20) name = models.CharField(max_length = 45) lft = models.IntegerField(max_length = 20) rgt = models.IntegerField(max_length = 20) depth = models.IntegerField(max_length = 20) added_on = models.DateTimeField(auto_now = True) updated_on = models.DateTimeField(auto_now = True) status = models.IntegerField(max_length = 20) node = models.ForeignKey(Category_info, verbose_name = 'Category_info', to_field = 'node_id' The important part is the foreignkey. When I try: Category.objects.filter(type_id = 15, parent_id = offset, status = 1) I get an error that get returned more than category, which is fine, because it is supposed to return more than one. But I want to filter the results trough another field, which would be type id (from the second Model) Here it is: class Category_info(models.Model): objtree_label_id = models.AutoField(primary_key = True) node_id = models.IntegerField(unique = True) language_id = models.IntegerField() label = models.CharField(max_length = 255) type_id = models.IntegerField() The type_id can be any number from 1 - 5. I am desparately trying to get only one result where the type_id would be number 1. Here is what I want in sql: SELECT c.*, ci.* FROM category c JOIN category_info ci ON (c.node_id = ci.node_id) WHERE c.type_id = 15 AND c.parent_id = 50 AND ci.type_id = 1 Any help is GREATLY appreciated. Regards

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• joining / merging two arrays

  - by Shishant

  I have two arrays like this, actually this is mysql data retrieved from two different servers: $array1 = array ( 0 => array ( 'id' => 1, 'name' => 'somename') , 1 => array ( 'id' => 2, 'name' => 'somename2') ); $array2 = array ( 0 => array ( 'thdl_id' => 1, 'otherdate' => 'spmethings') , 1 => array ( 'thdl_id' => 2, 'otherdate' => 'spmethings22') ); how can i join / merge array so it looks like this $new_array = array ( 0 => array ( 'id' => 1, 'name' => 'somename', 'otherdate' => 'spmethings') , 1 => array ( 'id' => 2, 'name' => 'somename2', 'otherdate' => 'spmethings22') );

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• How do you save and retrieve a Key/IV pair securely?

  - by Shawn Steward

  I'm using VB.Net's RijndaelManaged (RM) to encrypt files, using the RM.GenerateKey and RM.GenerateIV methods to generate the Key and IV and encrypting the file using the CryptoStream class. I'm planning on saving this Key and IV to a file and want to make sure I'm doing it the right way. I am combining the IV+Key, and encrypting that with my RSA Public key and writing it out to a file. Then, to decrypt I use the RSA Private key on this file to get the IV+Key, split them up and set RM.Key and RM.IV to these values and run the decryptor. Is this the best method to accomplish this, or is there a preferred method for saving the IV & Key? Also, what's the best way to construct and deconstruct the byte array? I used the .Concat method to join them together and that seems to work well but I can't seem to find something as easy to deconstruct it. I played with the .Take method that takes the first x # of bytes and it works for the first part but can't find anything that gets the rest of it.

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• Do complex JOINs cause high coupling and maintenance problems ?

  - by ashkan.kh.nazary

  Our project has ~40 tables with complex relations.A colleague believes in using long join queries which enforces me to learn about tables outside of my module but I think I should not concern about tables not directly related to my module and use data access functions (written by those responsible for other modules) when I need data from them. Let me clarify: I am responsible for the ContactVendor module which enables the customers to contact the vendor and start a conversation about some specific product. Products module has it's own complex tables and relations with functions that encapsulate details (for example i18n, activation, product availability etc ...). Now I need to show the product title of some product related to some conversation between the vendor and customers. I may either write a long query that retrieves the product info along with conversation stuff in one shot (which enforces me to learn about Product tables) OR I may pass the relevant product_id to the get_product_info(int) function. First approach is obviously demanding and introduces many bad practices and things I normally consider fault in programming. The problem with the second approach seems to be the countless mini queries these access functions cause and performance loss is a concern when a loop tries to fetch product titles for 100 products using functions that each perform a separate query. So I'm stuck between "don't code to the implementation, code to interface" and performance. What is the right way of doing things ? UPDATE: I'm specially concerned about possible future modifications to those tables outside of my module. What if the Products module decided to change the way they are doing things? or for some reason modify the schema? It means some other modules would break or malfunction until the change is integrated to them. The usual ripple effect problem.

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