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  • SQL Query in Ruby: Only select the changes

    - by JJ Liu
    Suppose I have a table (PriceHistory) like this, every time I change anything in the row, I will record the whole row again in the table. id | buy_price | sell_price | change_date 1 | 2 | 2 | 2012-06-22 2 | 3 | 2 | 2012-06-20 3 | 2 | 6 | 2012-06-15 4 | 5 | 5 | 2012-06-15 5 | 5 | 7 | 2012-06-15 6 | 4 | 8 | 2012-06-12 I only care about the change of BuyPrice, Is there a way to just select row 1, 2, 3, & 5? Here is the Ruby code I come up with, but it does not only select the changed rows PriceHistory.select("id, BuyPrice, change_date"). order("change_date DESC") Both Ruby and SQL answers are fine.

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  • One off errors with NSLog and NSString stringWithFormat

    - by David Liu
    Does anyone know why there would be one-off errors with NSLog and NSString? It works fine in 99% of my program, but for some reason this error appears in one of my model's description method: Example code: localFileId = 7; type = 2; localId = 5; NSLog(@"CachedFile localId=%d, 2=%d, localFileId=%d, type=%d, path=%@", localId, 2, localFileId, type, self.path); Example Result: CachedFile localId=5, 2=0, localFileId=2, type=7, path=(null) Notice the "0" that gets inserted in there, where it should be "2=2". This happens with NSString stringWithFormat as well.

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  • Is it bad practice to make a setter return "this"?

    - by Ken Liu
    Is it a good or bad idea to make setters in java return "this"? public Employee setName(String name){ this.name = name; return this; } This pattern can be useful because then you can chain setters like this: list.add(new Employee().setName("Jack Sparrow").setId(1).setFoo("bacon!")); instead of this: Employee e = new Employee(); e.setName("Jack Sparrow"); ...and so on... list.add(e); ...but it sort of goes against standard convention. I suppose it might be worthwhile just because it can make that setter do something else useful. I've seen this pattern used some places (e.g. JMock, JPA), but it seems uncommon, and only generally used for very well defined APIs where this pattern is used everywhere. Update: What I've described is obviously valid, but what I am really looking for is some thoughts on whether this is generally acceptable, and if there are any pitfalls or related best practices. I know about the Builder pattern but it is a little more involved then what I am describing - as Josh Bloch describes it there is an associated static Builder class for object creation.

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  • UITableViewCell is transparent when not supposed to be

    - by David Liu
    My UITableViewCell is being transparent when it's not supposed to be. My table view has a background color and it shows through the table cell, even though they're supposed to be opaque. I'm not sure why this is. Relevant code: UITableViewCell *cell = [table dequeueReusableCellWithIdentifier:emptyIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:emptyIdentifier] autorelease]; } cell.textLabel.text = @"Empty"; cell.textLabel.textAlignment = UITextAlignmentCenter; cell.textLabel.backgroundColor = [UIColor whiteColor]; return cell;

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  • return an ArrayList method

    - by Bopeng Liu
    This is a drive method for two other classes. which i posted here http://codereview.stackexchange.com/questions/33148/book-program-with-arraylist I need some help for the private static ArrayList getAuthors(String authors) method. I am kind a beginner. so please help me finish this drive method. or give me some directions. Instruction some of the elements of the allAuthors array contain asterisks “*” between two authors names. The getAuthors method uses this asterisk as a delimiter between names to store them separately in the returned ArrayList of Strings. import java.util.ArrayList; public class LibraryDrive { public static void main(String[] args) { String[] titles = { "The Hobbit", "Acer Dumpling", "A Christmas Carol", "Marley and Me", "Building Java Programs", "Java, How to Program" }; String[] allAuthors = { "Tolkien, J.R.", "Doofus, Robert", "Dickens, Charles", "Remember, SomeoneIdont", "Reges, Stuart*Stepp, Marty", "Deitel, Paul*Deitel, Harvery" }; ArrayList<String> authors = new ArrayList<String>(); ArrayList<Book> books = new ArrayList<Book>(); for (int i = 0; i < titles.length; i++) { authors = getAuthors(allAuthors[i]); Book b = new Book(titles[i], authors); books.add(b); authors.remove(0); } Library lib = new Library(books); System.out.println(lib); lib.sort(); System.out.println(lib); } private static ArrayList<String> getAuthors(String authors) { ArrayList books = new ArrayList<String>(); // need help here. return books; } }

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  • JavaFx 2.1, 2.2 TableView update issue

    - by Lewis Liu
    My application uses JPA read data into TableView then modify and display them. The table refreshed modified record under JavaFx 2.0.3. Under JavaFx 2.1, 2.2, the table wouldn't refresh the update anymore. I found other people have similar issue. My plan was to continue using 2.0.3 until someone fixes the issue under 2.1 and 2.2. Now I know it is not a bug and wouldn't be fixed. Well, I don't know how to deal with this. Following are codes are modified from sample demo to show the issue. If I add a new record or delete a old record from table, table refreshes fine. If I modify a record, the table wouldn't refreshes the change until a add, delete or sort action is taken. If I remove the modified record and add it again, table refreshes. But the modified record is put at button of table. Well, if I remove the modified record, add the same record then move the record to the original spot, the table wouldn't refresh anymore. Below is a completely code, please shine some light on this. import javafx.application.Application; import javafx.beans.property.SimpleStringProperty; import javafx.collections.FXCollections; import javafx.collections.ObservableList; import javafx.event.ActionEvent; import javafx.event.EventHandler; import javafx.geometry.HPos; import javafx.geometry.Insets; import javafx.geometry.Pos; import javafx.scene.Group; import javafx.scene.Scene; import javafx.scene.control.*; import javafx.scene.control.cell.PropertyValueFactory; import javafx.scene.layout.GridPane; import javafx.scene.layout.HBox; import javafx.scene.layout.VBox; import javafx.scene.text.Font; import javafx.stage.Modality; import javafx.stage.Stage; import javafx.stage.StageStyle; public class Main extends Application { private TextField firtNameField = new TextField(); private TextField lastNameField = new TextField(); private TextField emailField = new TextField(); private Stage editView; private Person fPerson; public static class Person { private final SimpleStringProperty firstName; private final SimpleStringProperty lastName; private final SimpleStringProperty email; private Person(String fName, String lName, String email) { this.firstName = new SimpleStringProperty(fName); this.lastName = new SimpleStringProperty(lName); this.email = new SimpleStringProperty(email); } public String getFirstName() { return firstName.get(); } public void setFirstName(String fName) { firstName.set(fName); } public String getLastName() { return lastName.get(); } public void setLastName(String fName) { lastName.set(fName); } public String getEmail() { return email.get(); } public void setEmail(String fName) { email.set(fName); } } private TableView<Person> table = new TableView<Person>(); private final ObservableList<Person> data = FXCollections.observableArrayList( new Person("Jacob", "Smith", "[email protected]"), new Person("Isabella", "Johnson", "[email protected]"), new Person("Ethan", "Williams", "[email protected]"), new Person("Emma", "Jones", "[email protected]"), new Person("Michael", "Brown", "[email protected]")); public static void main(String[] args) { launch(args); } @Override public void start(Stage stage) { Scene scene = new Scene(new Group()); stage.setTitle("Table View Sample"); stage.setWidth(535); stage.setHeight(535); editView = new Stage(); final Label label = new Label("Address Book"); label.setFont(new Font("Arial", 20)); TableColumn firstNameCol = new TableColumn("First Name"); firstNameCol.setCellValueFactory( new PropertyValueFactory<Person, String>("firstName")); firstNameCol.setMinWidth(150); TableColumn lastNameCol = new TableColumn("Last Name"); lastNameCol.setCellValueFactory( new PropertyValueFactory<Person, String>("lastName")); lastNameCol.setMinWidth(150); TableColumn emailCol = new TableColumn("Email"); emailCol.setMinWidth(200); emailCol.setCellValueFactory( new PropertyValueFactory<Person, String>("email")); table.setItems(data); table.getColumns().addAll(firstNameCol, lastNameCol, emailCol); //--- create a edit button and a editPane to edit person Button addButton = new Button("Add"); addButton.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { fPerson = null; firtNameField.setText(""); lastNameField.setText(""); emailField.setText(""); editView.show(); } }); Button editButton = new Button("Edit"); editButton.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { if (table.getSelectionModel().getSelectedItem() != null) { fPerson = table.getSelectionModel().getSelectedItem(); firtNameField.setText(fPerson.getFirstName()); lastNameField.setText(fPerson.getLastName()); emailField.setText(fPerson.getEmail()); editView.show(); } } }); Button deleteButton = new Button("Delete"); deleteButton.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { if (table.getSelectionModel().getSelectedItem() != null) { data.remove(table.getSelectionModel().getSelectedItem()); } } }); HBox addEditDeleteButtonBox = new HBox(); addEditDeleteButtonBox.getChildren().addAll(addButton, editButton, deleteButton); addEditDeleteButtonBox.setAlignment(Pos.CENTER_RIGHT); addEditDeleteButtonBox.setSpacing(3); GridPane editPane = new GridPane(); editPane.getStyleClass().add("editView"); editPane.setPadding(new Insets(3)); editPane.setHgap(5); editPane.setVgap(5); Label personLbl = new Label("Person:"); editPane.add(personLbl, 0, 1); GridPane.setHalignment(personLbl, HPos.LEFT); firtNameField.setPrefWidth(250); lastNameField.setPrefWidth(250); emailField.setPrefWidth(250); Label firstNameLabel = new Label("First Name:"); Label lastNameLabel = new Label("Last Name:"); Label emailLabel = new Label("Email:"); editPane.add(firstNameLabel, 0, 3); editPane.add(firtNameField, 1, 3); editPane.add(lastNameLabel, 0, 4); editPane.add(lastNameField, 1, 4); editPane.add(emailLabel, 0, 5); editPane.add(emailField, 1, 5); GridPane.setHalignment(firstNameLabel, HPos.RIGHT); GridPane.setHalignment(lastNameLabel, HPos.RIGHT); GridPane.setHalignment(emailLabel, HPos.RIGHT); Button saveButton = new Button("Save"); saveButton.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { if (fPerson == null) { fPerson = new Person( firtNameField.getText(), lastNameField.getText(), emailField.getText()); data.add(fPerson); } else { int k = -1; if (data.size() > 0) { for (int i = 0; i < data.size(); i++) { if (data.get(i) == fPerson) { k = i; } } } fPerson.setFirstName(firtNameField.getText()); fPerson.setLastName(lastNameField.getText()); fPerson.setEmail(emailField.getText()); data.set(k, fPerson); table.setItems(data); // The following will work, but edited person has to be added to the button // // data.remove(fPerson); // data.add(fPerson); // add and remove refresh the table, but now move edited person to original spot, // it failed again with the following code // while (data.indexOf(fPerson) != k) { // int i = data.indexOf(fPerson); // Collections.swap(data, i, i - 1); // } } editView.close(); } }); Button cancelButton = new Button("Cancel"); cancelButton.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { editView.close(); } }); HBox saveCancelButtonBox = new HBox(); saveCancelButtonBox.getChildren().addAll(saveButton, cancelButton); saveCancelButtonBox.setAlignment(Pos.CENTER_RIGHT); saveCancelButtonBox.setSpacing(3); VBox editBox = new VBox(); editBox.getChildren().addAll(editPane, saveCancelButtonBox); Scene editScene = new Scene(editBox); editView.setTitle("Person"); editView.initStyle(StageStyle.UTILITY); editView.initModality(Modality.APPLICATION_MODAL); editView.setScene(editScene); editView.close(); final VBox vbox = new VBox(); vbox.setSpacing(5); vbox.getChildren().addAll(label, table, addEditDeleteButtonBox); vbox.setPadding(new Insets(10, 0, 0, 10)); ((Group) scene.getRoot()).getChildren().addAll(vbox); stage.setScene(scene); stage.show(); } }

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  • Does deleting a branch in git remove it from the history?

    - by Ken Liu
    Coming from svn, just starting to become familiar with git. When a branch is deleted in git, is it removed from the history? In svn, you can easily recover a branch by reverting the delete operation (reverse merge). Like all deletes in svn, the branch is never really deleted, it's just removed from the current tree. If the branch is actually deleted from the history in git, what happens to the changes that were merged from that branch? Are they retained?

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  • C++ explicit template specialization of templated constructor of templated class

    - by Victor Liu
    I have a class like template <class T> struct A{ template <class U> A(U u); }; I would like to write an explicit specialization of this for a declaration like A<int>::A(float); In the following test code, if I comment out the specialization, it compiles with g++. Otherwise, it says I have the wrong number of template parameters: #include <iostream> template <class T> struct A{ template <class U> A(T t, U *u){ *u += U(t); } }; template <> template <> A<int>::A<int,float>(int t, float *u){ *u += U(2*t); } int main(){ float f = 0; int i = 1; A<int>(i, &f); std::cout << f << std::endl; return 0; }

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  • Determining polygon intersection and containment

    - by Victor Liu
    I have a set of simple (no holes, no self-intersections) polygons, and I need to check that they don't intersect each other (one can be entirely contained in another; that is okay). I can check this by simply checking the per-vertex inside-ness of one polygon versus other polygons. I also need to determine the containment tree, which is the set of relationships that say which polygon contains any given polygon. Since no polygon can intersect any other, then any contained polygon has a unique container; the "next-bigger" one. In other words, if A contains B contains C, then A is the parent of B, and B is the parent of C, and we don't consider A the parent of C. The question: How do I efficiently determine the containment relationships and check the non-intersection criterion? I ask this as one question because maybe a combined algorithm is more efficient than solving each problem separately. The algorithm should take as input a list of polygons, given by a list of their vertices. It should produce a boolean B indicating if none of the polygons intersect any other polygon, and also if B = true, a list of pairs (P, C) where polygon P is the parent of child C. This is not homework. This is for a hobby project I am working on.

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  • How to output floating point numbers with a custom output format in C++?

    - by Victor Liu
    The problem is that I want to output Mathematica compatible floating point numbers. The only difference with the standard IOStream or printf output format is that the exponential e is replaced by *^: Standard C/C++ output format: 1.23e-4 Mathematica format: 1.23*^-4 Is there a way to manipulate streams to achieve this effect? My original idea was just to use istringstream and dump it to a string and then replace all the e's. I would also be okay if someone posted code to parse through the bits of the floating point number and output it directly (i.e. a printf("%e") replacement).

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  • Verifying compiler optimizations in gcc/g++ by analyzing assembly listings

    - by Victor Liu
    I just asked a question related to how the compiler optimizes certain C++ code, and I was looking around SO for any questions about how to verify that the compiler has performed certain optimizations. I was trying to look at the assembly listing generated with g++ (g++ -c -g -O2 -Wa,-ahl=file.s file.c) to possibly see what is going on under the hood, but the output is too cryptic to me. What techniques do people use to tackle this problem, and are there any good references on how to interpret the assembly listings of optimized code or articles specific to the GCC toolchain that talk about this problem?

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  • Determining the order of a list of numbers (possibly without sorting)

    - by Victor Liu
    I have an array of unique integers (e.g. val[i]), in arbitrary order, and I would like to populate another array (ord[i]) with the the sorted indexes of the integers. In other words, val[ord[i]] is in sorted order for increasing i. Right now, I just fill in ord with 0, ..., N, then sort it based on the value array, but I am wondering if we can be more efficient about it since ord is not populated to begin with. This is more of a question out of curiousity; I don't really care about the extra overhead from having to prepopulate a list and then sort it (it's small, I use insertion sort). This may be a silly question with an obvious answer, but I couldn't find anything online.

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  • How to pass around event as parameter in c#

    - by Jerry Liu
    Am writing unit test for a multi-threading application, where I need to wait until a specific event triggered so that I know the asyn operation is done. E.g. When I call repository.add(something), I wait for event AfterChange before doing any assertion. So I write a util function to do that. public static void SyncAction(EventHandler event_, Action action_) { var signal = new object(); EventHandler callback = null; callback = new EventHandler((s, e) => { lock (signal) { Monitor.Pulse(signal); } event_ -= callback; }); event_ += callback; lock (signal) { action_(); Assert.IsTrue(Monitor.Wait(signal, 10000)); } } However, the compiler prevents from passing event out of the class. Is there a way to achieve that?

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  • About Web service ,how to use Ajax to call a specific member function of a class?

    - by Liu chwen
    I'm trying to build a web service by PHP. In my case, I called the getINFO(), but the return value on client side always null. Have no idea to solve this problem.. Here's the SOAPserver code(WS.WEB_s.php): require("WEB_s.php"); ini_set("soap.wsdl_cache_enabled", 0); $server = new SoapServer('wsdl/WEB_s.wsdl'); $server->setClass("WEB_s"); $server->handle(); Where the main Class is(WEB_s.php): final class WEB_s { public function getINFO(){ $JsonOutput = '{"key":"value",...}'; return $JsonOutput; } public function setWAN($setCommand,$newConfigfilePath){ $bOutput; return $bOutput; } } And Client side: $(document).ready(function(){ $('#qqq').button().click(function(){ var soapMessage = LoginSoap($('#uid').val(),$('#pwd').val()); alert('soapMessage'); $.ajax({ //url: 'libraries/WS.WEB_s.php/WEB_s/getINFO',//success , return null //url: 'libraries/WS.WEB_s.php/', //success , return null url: 'libraries/WS.WEB_s.php/getINFO',//success , return null type: 'GET', timeout: (10* 1000), contentType: "text/xml", dataType: "xml", success: function( data,textStatus,jqXHR){ alert('Server success(' + data+')('+ textStatus + ')(' + jqXHR + ')'); }, error: function (request, status, error) { alert('Server Error(' + status+')->'+error); }, complete: function (jqXHR, textStatus) { alert('Server success(' + jqXHR+')('+ textStatus + ')'); } }); }); }); The following is the corresponding WSDL file : http://codepaste.net/95wq9b

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  • jre1.6.0_27 HashMap values() sourcecode

    - by Liu guanghua
    Today, I opened jre1.6.0_27 HashMap values() method sourcecode 389 public Set<K> keySet() 390 { 391 Set localSet = this.keySet; 392 return (this.keySet = new KeySet(null)); 393 } 394 395 public Collection<V> values() 396 { 397 Collection localCollection = this.values; 398 return (this.values = new Values(null)); 399 } I think these sourcecode are error, but I don't know why they look like this. Who can tell me why?

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  • I want to make a 2D color plot showing stress magnitude (S) at very loctaion (x, y) based on continuous color change using limited data sets

    - by Alex Liu
    friends, I have to trouble you as I couldn't find a solution after trying for a long time. I have 3 columns of data. x, y, and the stress value (S) at every point (x, y). I want to generate a 2D color plot displaying continuous color change with the magnitude of the stress (S). The stress values increase from -3*10^4 Pa to 4*10^4 Pa. I only have hundreds of data sets for an area, but I want to see the stress magnitude (read from the color) at every location (x, y). What Matlab command should I use? Thank you very much! I want to make a 2D color plot showing stress magnitude (S) at very loctaion (x, y) based on continuous color change using limited

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  • JavaScript filter PHP results

    - by Nick Maddren
    Hey guys for a while now I have been trying to come up with a method that can filter PHP results for listing items using JS. Look at these examples: http://www.autotrader.co.uk/search/used/cars/ http://www.vcars.co.uk/used-cars/ You will notice that the actual filter uses JavaScript however my question is how does it query the database to bring back the results? It obviously using PHP however how does the JS control what the PHP drags from the DB? Thanks

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  • Merging Waterfall and Agile – Getting the Worst of Both Worlds

    - by Nick Harrison
    Many people have seen and appreciate the elegance and practicality of agile methodologies.   Sadly there is still not widespread adoption.   There is still push back from many directions and from many different sources.   Some people don't understand how it is supposed to work. Some people don't believe that it could possibly work. Some people mistakenly believe that it is just code for a lazy project team trying to wiggle out of structure Some people mistakenly believe that it can work only with a very small highly trained team Some people are afraid of the control that they feel they will be losing. I have seen some people try to merge agile and water fall hoping to achieve the best of both worlds.   Unfortunately, the reality is that you end up with the worst of both worlds.   And they both can get pretty bad. Another Sad Reality Some people in an effort to get buy in for following an Agile Methodology have attempted to merge these two practices.   Sometimes this may stem from trying to assuage individual fears that they are not losing relevance.   Sometimes it may be to meet contractual obligations or to fulfill regulatory requirements.   Sometimes may not know better. These two approaches to software development cannot coexist on the same project. Let's review the main tenants of the Agile Manifesto: Individuals and interactions over processes and tools Working software over comprehensive documentation Customer collaboration over contract negotiation Responding to change over following a plan That is, while there is value in the items on the right, we value the items on the left more. Meanwhile the main tenants of the Waterfall Approach could be summarized as: Processes and procedures over individuals Comprehensive documentation proves that the software works Well defined contracts and negotiations protects the customer relationship If the plan is made right, there should be no change  Merging these two approaches will always end badly.

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  • How to install mod_ssl for Apache

    - by Nick Foote
    Ok So I installed Apache httpd a while ago and have recently come back to it to try setup SSL and get it serving several different tomcat servers. At the moment I have two completely separate tomcat instances serving up to slightly different versions (one for dev and one for demo say) my web app to two different ports; mydomain.com:8081 and mydomain.com:8082 I've successfully (back in Jan) used mod_jk to get httpd to serve those same tomcat instances to http://www.mydomain.com:8090/dev and http://www.mydomain.com:8090/demo (8090 cos I've got another app running on 8080 via Jetty at this stage) using the following code in httpd.conf; LoadModule jk_module modules/mod_jk.so JkWorkersFile conf/workers.properties JkLogFile logs/mod_jk.log JkLogLevel debug <VirtualHost *:8090> JkMount /devd* tomcatDev JkMount /demo* tomcatDemo </VirtualHost> What I'm not trying to do is enable SSL I've added the following to httpd.conf Listen 443 <VirtualHost _default_:443> JkMount /dev* tomcatDev JkMount /demo* tomcatDemo SSLEngine on SSLCertificateFile "/opt/httpd/conf/localhost.crt" SSLCertificateKeyFile "/opt/httpd/conf/keystore.key" </VirtualHost> But when I try to restart Apache with "apachectl restart" (yes after shutting down that other app I mentioned so it doesn't toy with https connections) I continuously get the error; "Invalid command 'SSLEngine', perhaps misspelled or defined by a module not included in the server configuration. httpd not running, trying to start" I've looked in the httpd/modules dir and indeed there is no mod_ssl, only mod_jk.so and httpd.exp. I've tried using yum to install mod_ssl, it says its already installed. Indeed I can locate mod_ssl.so in /usr/lib/httpd/modules but this is NOT the path to where I've installed httpd which is /opt/httpd and in fact /usr/lib/httpd contains nothing but the modules dir. Can anyone tell me how to install mod_ssl properly for my installed location of httpd so I can get past this error:

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  • More SQL Smells

    - by Nick Harrison
    Let's continue exploring some of the SQL Smells from Phil's list. He has been putting together. Datatype mis-matches in predicates that rely on implicit conversion.(Plamen Ratchev) This is a great example poking holes in the whole theory of "If it works it's not broken" Queries will this probably will generally work and give the correct response. In fact, without careful analysis, you probably may be completely oblivious that there is even a problem. This subtle little problem will needlessly complicate queries and slow them down regardless of the indexes applied. Consider this example: CREATE TABLE [dbo].[Page](     [PageId] [int] IDENTITY(1,1) NOT NULL,     [Title] [varchar](75) NOT NULL,     [Sequence] [int] NOT NULL,     [ThemeId] [int] NOT NULL,     [CustomCss] [text] NOT NULL,     [CustomScript] [text] NOT NULL,     [PageGroupId] [int] NOT NULL;  CREATE PROCEDURE PageSelectBySequence ( @sequenceMin smallint , @sequenceMax smallint ) AS BEGIN SELECT [PageId] , [Title] , [Sequence] , [ThemeId] , [CustomCss] , [CustomScript] , [PageGroupId] FROM [CMS].[dbo].[Page] WHERE Sequence BETWEEN @sequenceMin AND @SequenceMax END  Note that the Sequence column is defined as int while the sequence parameter is defined as a small int. The problem is that the database may have to do a lot of type conversions to evaluate the query. In some cases, this may even negate the indexes that you have in place. Using Correlated subqueries instead of a join   (Dave_Levy/ Plamen Ratchev) There are two main problems here. The first is a little subjective, since this is a non-standard way of expressing the query, it is harder to understand. The other problem is much more objective and potentially problematic. You are taking much of the control away from the optimizer. Written properly, such a query may well out perform a corresponding query written with traditional joins. More likely than not, performance will degrade. Whenever you assume that you know better than the optimizer, you will most likely be wrong. This is the fundmental problem with any hint. Consider a query like this:  SELECT Page.Title , Page.Sequence , Page.ThemeId , Page.CustomCss , Page.CustomScript , PageEffectParams.Name , PageEffectParams.Value , ( SELECT EffectName FROM dbo.Effect WHERE EffectId = dbo.PageEffects.EffectId ) AS EffectName FROM Page INNER JOIN PageEffect ON Page.PageId = PageEffects.PageId INNER JOIN PageEffectParam ON PageEffects.PageEffectId = PageEffectParams.PageEffectId  This can and should be written as:  SELECT Page.Title , Page.Sequence , Page.ThemeId , Page.CustomCss , Page.CustomScript , PageEffectParams.Name , PageEffectParams.Value , EffectName FROM Page INNER JOIN PageEffect ON Page.PageId = PageEffects.PageId INNER JOIN PageEffectParam ON PageEffects.PageEffectId = PageEffectParams.PageEffectId INNER JOIN dbo.Effect ON dbo.Effects.EffectId = dbo.PageEffects.EffectId  The correlated query may just as easily show up in the where clause. It's not a good idea in the select clause or the where clause. Few or No comments. This one is a bit more complicated and controversial. All comments are not created equal. Some comments are helpful and need to be included. Other comments are not necessary and may indicate a problem. I tend to follow the rule of thumb that comments that explain why are good. Comments that explain how are bad. Many people may be shocked to hear the idea of a bad comment, but hear me out. If a comment is needed to explain what is going on or how it works, the logic is too complex and needs to be simplified. Comments that explain why are good. Comments may explain why the sql is needed are good. Comments that explain where the sql is used are good. Comments that explain how tables are related should not be needed if the sql is well written. If they are needed, you need to consider reworking the sql or simplify your data model. Use of functions in a WHERE clause. (Anil Das) Calling a function in the where clause will often negate the indexing strategy. The function will be called for every record considered. This will often a force a full table scan on the tables affected. Calling a function will not guarantee that there is a full table scan, but there is a good chance that it will. If you find that you often need to write queries using a particular function, you may need to add a column to the table that has the function already applied.

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  • Friend of Red Gate

    - by Nick Harrison
    Friend of Red Gate I recently joined the friend of Red Gate program.   I am very honored to be included in this group.    This program is a big part of Red Gates community outreach.   If you are not familiar with Red Gate, I urge you to check them out.    They have some wonderful tools for the SQL Server community and the DotNet community.    They are also building up some tools for Exchange and Oracle. I was invited to join this program primarliy because of my work with Simple Talk and promoting one of their newest products, Reflector. Reflector is a wonderful tool.   I doubt that anyone who has ever used it would argue that point. Red Gate did a wonderful job taking over the support of Reflector.   I know many people had their doubts.    The initial release under Red Gate should set those fears to rest.   I was very impressed with how their developers interacted with their users during the preview phase! Red Gate is also a good partner for the community.    They activly support the community, sponsoring Code Camps, sponsoring User Groups, supporting the Forums, etc. And their tools are pretty amazing as well.

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  • How to get more detailed reason for Thunderbird crashing?

    - by Nick
    I have a computer (10.04) that was previously running Thunderbird 12.0.1 just fine (installed via apt-get via official PPA). I don't know what happened at the time the problem started since this is a multi-user computer and I was not here. However, every time we try to launch TB, we immediately get a dialog that says: We're Sorry Thunderbird had a problem and crashed. Things I've tried: Running thunderbird from a terminal produces no output. I tried apt-get remove thunderbird --purge and then reinstalled Deleting the user's .thunderbird folder and launching still results in a crash Attempting to run thunderbird -safe-mode still results in a crash This problem occurs for all users of Thunderbird on this computer. Is there any way to get more details on why the program is crashing? For example, the specific error that TB is encountering? I tried thunderbird -g but I'm not sure what to do with the debugger.

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