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• Hibernate Communications Link Failure in Restlet-Hibernate Based Java application powered by MySQL

  - by Vatsala

  Let me describe my question - I have a Java application - Hibernate as the DB interfacing layer over MySQL. I get the communications link failure error in my application. The occurence of this error is a very specific case. I get this error , When I leave mysql server unattended for more than approximately 6 hours (i.e. when there are no queries issued to MySQL for more than approximately 6 hours). I am pasting a top 'exception' level description below, and adding a pastebin link for a detailed stacktrace description. javax.persistence.PersistenceException: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: org.hibernate.exception.JDBCConnectionException: Cannot open connection - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure - The last packet successfully received from the server was 1,274,868,181,212 milliseconds ago. The last packet sent successfully to the server was 0 milliseconds ago. - Caused by: java.net.ConnectException: Connection refused: connect the link to the pastebin for further investigation - http://pastebin.com/4KujAmgD What I understand from these exception statements is that MySQL is refusing to take in any connections after a period of idle/nil activity. I have been reading up a bit about this via google search, and came to know that one of the possible ways to overcome this is to set values for c3p0 properties as c3p0 comes bundled with Hibernate. Specifically, I read from here http://www.mchange.com/projects/c3p0/index.html that setting two properties idleConnectionTestPeriod and preferredTestQuery will solve this for me. But these values dont seem to have had an effect. Is this the correct approach to fixing this? If not, what is the right way to get over this? The following are related Communications Link Failure questions at stackoverflow.com, but I've not found a satisfactory answer in their answers. http://stackoverflow.com/questions/2121829/java-db-communications-link-failure http://stackoverflow.com/questions/298988/how-to-handle-communication-link-failure Note 1 - i dont get this error when I am using my application continuosly. Note 2 - I use JPA with Hibernate and hence my hibernate.dialect,etc hibernate properties reside within the persistence.xml in the META-INF folder (does that prevent the c3p0 properties from working?)

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• How to pass operators as parameters

  - by Rodion Ingles

  I have to load an array of doubles from a file, multiply each element by a value in a table (different values for different elements), do some work on it, invert the multiplication (that is, divide) and then save the data back to file. Currently I implement the multiplication and division process in two separate methods. Now there is some extra work behind the scenes but apart from the specific statements where the multiplication/division occurs, the rest of the code is identical. As you can imagine, with this approach you have to be very careful making any changes. The surrounding code is not trivial, so its either a case of manually editing each method or copying changes from one method to the other and remembering to change the * and / operators. After too many close calls I am fed up of this and would like to make a common function which implements the common logic and two wrapper functions which pass which operator to use as a parameter. My initial approach was to use function pointers: MultiplyData(double data) { TransformData(data, &(operator *)); } DivideData(double data) { TransformData(data, &(operator /)); } TransformData(double data, double (*func)(double op1, double op2)) { /* Do stuff here... */ } However, I can't pass the operators as pointers (is this because it is an operator on a native type?), so I tried to use function objects. Initially I thought that multiplies and divides functors in <functional> would be ideal: MultiplyData(double data) { std::multiplies<double> multFunct; TransformData(data, &multFunct); } DivideData(double data) { std::divides<double> divFunct; TransformData(data, &divFunct); } TransformData(double data, std::binary_function<double, double, double> *funct) { /* Do stuff here... */ } As you can see I was trying to use a base class pointer to pass the functor polymorphically. The problem is that std::binary_function does not declare an operator() member for the child classes to implement. Is there something I am missing, or is the solution to implement my own functor heirarchy (which really seems more trouble than it is worth)?

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• devise register confirmation

  - by mattherick

  hello! i have a user and an admin role in my project. i created my authentification with devise, really nice and goot tool for handling the authentification. in my admin role i don´t have any confirmation or something like that. it is really simple and doesn´t make problems. but in my user model i have following things: model: devise :database_authenticatable, :confirmable, :recoverable, :rememberable, :trackable, :validatable, :timeoutable, :registerable # Setup accessible (or protected) attributes for your model attr_accessible :email, :username, :prename, :surname, :phone, :street, :number, :location, :password, :password_confirmation and few validations, but they aren´t relevant this time. my migration looks like following one: class DeviseCreateUsers < ActiveRecord::Migration def self.up create_table(:users) do |t| t.database_authenticatable :null = false t.confirmable t.recoverable t.rememberable t.trackable t.timeoutable t.validateable t.string :username t.string :prename t.string :surname t.string :phone t.string :street t.integer :number t.string :location t.timestamps end add_index :users, :email, :unique => true add_index :users, :confirmation_token, :unique => true add_index :users, :reset_password_token, :unique => true add_index :users, :username, :unique => true add_index :users, :prename, :unique => false add_index :users, :surname, :unique => false add_index :users, :phone, :unique => false add_index :users, :street, :unique => false add_index :users, :number, :unique => false add_index :users, :location, :unique => false end def self.down drop_table :users end end into my route.rb I added following statements: map.devise_for :admins map.devise_for :users, :path_names = { :sign_up = "register", :sign_in = "login" } map.root :controller = "main" and now my problem.. if I register a new user, I fill in all my data in the register form and submit it. After that I get redirected to the controller main with the flash-notice "You have signed up successfully." And I am logged in. But I don´t want to be logged in, because I don´t have confirmed my new user account yet. If I open the console I see the last things in the logs and there I see the confirmation-mail and the text and all stuff, but I am already logged in... I can´t explain why, ... does somebody of you have an idea? If I copy out the confirmation-token from the logs and confirm my account, I can log in, but if I don´t confirm, I also can log in..

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• Effective Data Validation

  - by John Conde

  What's an effective way to handle data validation, say, from a form submission? Originally I had a bunch of if statements that checked each value and collected invalid values in an array for later retrieval (and listing). // Store errors here $errors = array(); // Hypothetical check if a string is alphanumeric if (!preg_match('/^[a-z\d]+$/i', $fieldvalue)) { $errors[$fieldname] = 'Please only use letters and numbers for your street address'; } // etc... What I did next was create a class that handles various data validation scenarios and store the results in an internal array. After data validation was complete I would check to see if any errors occurred and handle accordingly: class Validation { private $errorList = array(); public function isAlphaNumeric($string, $field, $msg = '') { if (!preg_match('/^[a-z\d]+$/i', $string)) { $this->errorList[$field] = $msg; } } // more methods here public function creditCard($cardNumber, $field, $msg = '') { // Validate credit card number } // more methods here public function hasErrors() { return count($this->errorList); } } /* Client code */ $validate = new Validation(); $validate->isAlphaNumeric($fieldvalue1, $fieldname1, 'Please only use letters and numbers for your street address'); $validate->creditCard($fieldvalue2, $fieldname2, 'Please enter a valid credit card number'); if ($validate->hasErrors()) { // Handle as appropriate } Naturally it didn't take long before this class became bloated with the virtually unlimited types of data to be validated. What I'm doing now is using decorators to separate the different types of data into their own classes and call them only when needed leaving generic validations (i.e. isAlphaNumeric()) in the base class: class Validation { private $errorList = array(); public function isAlphaNumeric($string, $field, $msg = '') { if (!preg_match('/^[a-z\d]+$/i', $string)) { $this->errorList[$field] = $msg; } } // more generic methods here public function setError($field, $msg = '') { $this->errorList[$field] = $msg; } public function hasErrors() { return count($this->errorList); } } class ValidationCreditCard { protected $validate; public function __construct(Validation $validate) { $this->validate = $validate; } public function creditCard($cardNumber, $field, $msg = '') { // Do validation // ... // if there is an error $this->validate->setError($field, $msg); } // more methods here } /* Client code */ $validate = new Validation(); $validate->isAlphaNumeric($fieldvalue, $fieldname, 'Please only use letters and numbers for your street address'); $validateCC = new ValidationCreditCard($validate); $validateCC->creditCard($fieldvalue2, $fieldname2, 'Please enter a valid credit card number'); if ($validate->hasErrors()) { // Handle as appropriate } Am I on the right track? Or did I just complicate data validation more then I needed to?

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• check if directory exists c#

  - by Ant

  I am trying to see if a directory exists based on an input field from the user. When the user types in the path, I want to check if the path actually exists. I have some c# code already. It returns 1 for any local path, but always returns 0 when I am checking a network path. static string checkValidPath(string path) { //Insert your code that runs under the security context of the authenticating user here. using (ImpersonateUser user = new ImpersonateUser(user, "", password)) { //DirectoryInfo d = new DirectoryInfo(quotelessPath); bool doesExist = Directory.Exists(path); //if (d.Exists) if(doesExist) { user.Dispose(); return "1"; } else { user.Dispose(); return "0"; } } } public class ImpersonateUser : IDisposable { [DllImport("advapi32.dll", SetLastError = true)] private static extern bool LogonUser(string lpszUsername, string lpszDomain, string lpszPassword, int dwLogonType, int dwLogonProvider, out IntPtr phToken); [DllImport("kernel32", SetLastError = true)] private static extern bool CloseHandle(IntPtr hObject); private IntPtr userHandle = IntPtr.Zero; private WindowsImpersonationContext impersonationContext; public ImpersonateUser(string user, string domain, string password) { if (!string.IsNullOrEmpty(user)) { // Call LogonUser to get a token for the user bool loggedOn = LogonUser(user, domain, password, 9 /*(int)LogonType.LOGON32_LOGON_NEW_CREDENTIALS*/, 3 /*(int)LogonProvider.LOGON32_PROVIDER_WINNT50*/, out userHandle); if (!loggedOn) throw new Win32Exception(Marshal.GetLastWin32Error()); // Begin impersonating the user impersonationContext = WindowsIdentity.Impersonate(userHandle); } } public void Dispose() { if (userHandle != IntPtr.Zero) CloseHandle(userHandle); if (impersonationContext != null) impersonationContext.Undo(); } } Any help is appreciated. Thanks! EDIT 3: updated code to use BrokenGlass's impersonation functions. However, I need to initialize "password" to something... EDIT 2: I updated the code to try and use impersonation as suggested below. It still fails everytime. I assume I am using impersonation improperly... EDIT: As requested by ChrisF, here is the function that calls the checkValidPath function. Frontend aspx file... $.get('processor.ashx', { a: '7', path: x }, function(o) { alert(o); if (o=="0") { $("#outputPathDivValid").dialog({ title: 'Output Path is not valid! Please enter a path that exists!', width: 500, modal: true, resizable: false, buttons: { 'Close': function() { $(this).dialog('close'); } } }); } }); Backend ashx file... public void ProcessRequest (HttpContext context) { context.Response.Cache.SetExpires(DateTime.Now); string sSid = context.Request["sid"]; switch (context.Request["a"]) {//a bunch of case statements here... case "7": context.Response.Write(checkValidPath(context.Request["path"].ToString())); break;

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• How to return the value from MySql Stored Proc ??

  - by karthik

  I am using the below storedproc to generate the Insert statements of a specified table It is build-ed without any errors. Now i want to return the result set in "V_string" as output of the SP DELIMITER $$ DROP PROCEDURE IF EXISTS `demo`.`InsertGenerator` $$ CREATE DEFINER=`root`@`localhost` PROCEDURE `InsertGenerator`() SWL_return: BEGIN -- SQLWAYS_EVAL# to retrieve column specific information -- SQLWAYS_EVAL# table DECLARE v_string NATIONAL VARCHAR(3000); -- SQLWAYS_EVAL# first half -- SQLWAYS_EVAL# tement DECLARE v_stringData NATIONAL VARCHAR(3000); -- SQLWAYS_EVAL# data -- SQLWAYS_EVAL# statement DECLARE v_dataType NATIONAL VARCHAR(1000); -- SQLWAYS_EVAL# -- SQLWAYS_EVAL# columns DECLARE v_colName NATIONAL VARCHAR(50); DECLARE NO_DATA INT DEFAULT 0; DECLARE cursCol CURSOR FOR SELECT column_name,data_type FROM `columns` -- WHERE table_name = v_tableName; WHERE table_name = 'tbl_users'; DECLARE CONTINUE HANDLER FOR SQLEXCEPTION BEGIN SET NO_DATA = -2; END; DECLARE CONTINUE HANDLER FOR NOT FOUND SET NO_DATA = -1; OPEN cursCol; SET v_string = CONCAT('INSERT ',v_tableName,'('); SET v_stringData = ''; SET NO_DATA = 0; FETCH cursCol INTO v_colName,v_dataType; IF NO_DATA <> 0 then -- NOT SUPPORTED print CONCAT('Table ',@tableName, ' not found, processing skipped.') close cursCol; LEAVE SWL_return; end if; WHILE NO_DATA = 0 DO IF v_dataType in('varchar','char','nchar','nvarchar') then SET v_stringData = CONCAT(v_stringData,'SQLWAYS_EVAL# ll(',v_colName,'SQLWAYS_EVAL# ''+'); ELSE if v_dataType in('text','ntext') then -- SQLWAYS_EVAL# -- SQLWAYS_EVAL# else SET v_stringData = CONCAT(v_stringData,'SQLWAYS_EVAL# ll(cast(',v_colName,'SQLWAYS_EVAL# 00)),'''')+'''''',''+'); ELSE IF v_dataType = 'money' then -- SQLWAYS_EVAL# doesn't get converted -- SQLWAYS_EVAL# implicitly SET v_stringData = CONCAT(v_stringData,'SQLWAYS_EVAL# y,''''''+ isnull(cast(',v_colName,'SQLWAYS_EVAL# 0)),''0.0000'')+''''''),''+'); ELSE IF v_dataType = 'datetime' then SET v_stringData = CONCAT(v_stringData,'SQLWAYS_EVAL# time,''''''+ isnull(cast(',v_colName, 'SQLWAYS_EVAL# 0)),''0'')+''''''),''+'); ELSE IF v_dataType = 'image' then SET v_stringData = CONCAT(v_stringData,'SQLWAYS_EVAL# ll(cast(convert(varbinary,',v_colName, 'SQLWAYS_EVAL# 6)),''0'')+'''''',''+'); ELSE SET v_stringData = CONCAT(v_stringData,'SQLWAYS_EVAL# ll(cast(',v_colName,'SQLWAYS_EVAL# 0)),''0'')+'''''',''+'); end if; end if; end if; end if; end if; SET v_string = CONCAT(v_string,v_colName,','); SET NO_DATA = 0; FETCH cursCol INTO v_colName,v_dataType; END WHILE; END $$ DELIMITER ;

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• Downloading large file with php

  - by Alessandro

  Hi, I have to write a php script to download potentially large files. The file I'm reporting here works fine most of the times. However, if the client's connection is slow the request ends (with status code 200) in the middle of the downloading, but not always at the very same point, and not at the very same time. I tried to overwrite some php.ini variables (see the first statements) but the problem remains. I don't know if it's relevant but my hosting server is SiteGround, and for simple static file requests, the download works fine also with slow connections. I've found Forced downloading large file with php but I didn't understand mario's answer. I'm new to web programming. So here's my code. <?php ini_set('memory_limit','16M'); ini_set('post_max_size', '30M'); set_time_limit(0); include ('../private/database_connection.php'); $downloadFolder = '../download/'; $fileName = $_POST['file']; $filePath = $downloadFolder . $fileName; if($fileName == NULL) { exit; } ob_start(); session_start(); if(!isset($_SESSION['Username'])) { // or redirect to login (remembering this download request) $_SESSION['previousPage'] = 'download.php?file=' . $fileName; header("Location: login.php"); exit; } if (file_exists($filePath)) { header('Content-Description: File Transfer'); header('Content-Type: application/octet-stream'); //header('Content-Disposition: attachment; filename='.$fileName); header("Content-Disposition: attachment; filename=\"$fileName\""); header('Content-Transfer-Encoding: binary'); header('Expires: 0'); header('Cache-Control: must-revalidate, post-check=0, pre-check=0'); //header('Pragma: public'); header('Content-Length: ' . filesize($filePath)); ob_clean(); flush(); // download // 1 // readfile($filePath); // 2 $file = @fopen($filePath,"rb"); if ($file) { while(!feof($file)) { print(fread($file, 1024*8)); flush(); if (connection_status()!=0) { @fclose($file); die(); } } @fclose($file); } exit; } else { header('HTTP/1.1 404 File not found'); exit; } ?>

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• Urgent help needed on How to update NSMutableDictionary. My code doesn't work.

  - by dawatson833

  I've populated an array using. arrSettings = [[NSMutableArray alloc] initWithContentsOfFile:[self settingsPath]]; The file is a plist with the root as an array and then a dictionary with three three keys defined as number. I've also tried setting the keys to string. I display the values in the plist file on a view using. diaper = [[arrSettings objectAtIndex:0] objectForKey:@"Diaper Expenses"]; oil = [[arrSettings objectAtIndex:0] objectForKey:@"Oil Used"]; tree = [[arrSettings objectAtIndex:0] objectForKey:@"Wood Used"]; This code works fine, the values in the dictionary are assigned to the variables and they are displayed. The user can make changes and then press a save button. I use this code to extract the dictionary part of the array so I can update it. The assignment to editDictionary works. I've double checked the key names including case and that is correct. editDictionary = [[NSMutableDictionary alloc] init]; editDictionary = [arrSettings objectAtIndex:0]; NSNumber *myNumber = [NSNumber numberWithFloat:diaperAmount]; [editDictionary setValue:myNumber forKey:@"Diaper Expenses"]; myNumber = [NSNumber numberWithFloat:oilAmount]; [editDictionary setValue:myNumber forKey:@"Oil Used"]; myNumber = [NSNumber numberWithFloat:treeAmount]; [editDictionary setValue:myNumber forKey:@"Wood Used"]; In this example I've used a nsnumber. But I've also tried the xxxAmount field as part of SetValue instead of creating a NSNumber. Neither implementation works. Several strange things happen. Sometimes the first two setvalue statements work, but the last setvalue fails with a EXC_BAD_ACCESS failure. Other times the first setValue fails with the same error. I have no idea why the first two sometimes work. I'm at a loss of what to do next. I've tried several implentations and none of them work. Also, in the debugger how can I display the editDictionary elements. I can see editDictionary, but I don't know how to display the individual elements.

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• .NET Extension Objects with XSLT -- how to iterate over a collection?

  - by Pandincus

  Help me, Stackoverflow! I have a simple .NET 3.5 console app that reads some data and sends emails. I'm representing the email format in an XSLT stylesheet so that we can easily change the wording of the email without needing to recompile the app. We're using Extension Objects to pass data to the XSLT when we apply the transformation: <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:msxsl="urn:schemas-microsoft-com:xslt" exclude-result-prefixes="msxsl" xmlns:EmailNotification="ext:EmailNotification"> -- this way, we can have statements like: <p> Dear <xsl:value-of select="EmailNotification:get_FullName()" />: </p> The above works fine. I pass the object via code like this (some irrelevant code omitted for brevity): // purely an example structure public struct EmailNotification { public string FullName { get; set; } } // Somewhere in some method ... var notification = new Notification("John Smith"); // ... XsltArgumentList xslArgs = new XsltArgumentList(); xslArgs.AddExtensionObject("ext:EmailNotification", notification); // ... // The part where it breaks! (This is where we do the transformation) xslt.Transform(fakeXMLDocument.CreateNavigator(), xslArgs, XmlWriter.Create(transformedXMLString)); So, all of the above code works. However, I wanted to get a little fancy (always my downfall) and pass a collection, so that I could do something like this: <p>The following accounts need to be verified:</p> <xsl:for-each select="EmailNotification:get_SomeCollection()"> <ul> <li> <xsl:value-of select="@SomeAttribute" /> </li> </ul> <xsl:for-each> When I pass the collection in the extension object and attempt to transform, I get the following error: "Extension function parameters or return values which have Clr type 'String[]' are not supported." or List, or IEnumerable, or whatever I try to pass in. So, my questions are: How can I pass in a collection to my XSLT? What do I put for the xsl:value-of select="" inside the xsl:for-each ? Is what I am trying to do impossible?

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• How do we simplify this kind of code in Java? Something like macros in C?

  - by Terry Li

  public static boolean diagonals(char[][] b, int row, int col, int l) { int counter = 1; // because we start from the current position char charAtPosition = b[row][col]; int numRows = b.length; int numCols = b[0].length; int topleft = 0; int topright = 0; int bottomleft = 0; int bottomright = 0; for (int i=row-1,j=col-1;i>=0 && j>=0;i--,j--) { if (b[i][j]==charAtPosition) { topleft++; } else { break; } } for (int i=row-1,j=col+1;i>=0 && j<=numCols;i--,j++) { if (b[i][j]==charAtPosition) { topright++; } else { break; } } for (int i=row+1,j=col-1;i<=numRows && j>=0;i++,j--) { if (b[i][j]==charAtPosition) { bottomleft++; } else { break; } } for (int i=row+1,j=col+1;i<=numRows && j<=numCols;i++,j++) { if (b[i][j]==charAtPosition) { bottomright++; } else { break; } } return topleft + bottomright + 1 >= l || topright + bottomleft + 1 >= l; //in this case l is 5 } After I was done posting the code above here, I couldn't help but wanted to simplify the code by merging the four pretty much the same loops into one method. Here's the kind of method I want to have: public int countSteps(char horizontal, char vertical) { } Two parameters horizontal and vertical can be either + or - to indicate the four directions to walk in. What I want to see if possible at all is i++; is generalized to i horizontal horizontal; when horizontal taking the value of +. What I don't want to see is if or switch statements, for example: public int countSteps(char horizontal, char vertical) { if (horizontal == '+' && vertical == '-') { for (int i=row-1,j=col+1;i>=0 && j<=numCols;i--,j++) { if (b[i][j]==charAtPosition) { topright++; } else { break; } } } else if (horizontal == '+' && vertical == '+') { for (int i=row+1,j=col+1;i>=0 && j<=numCols;i++,j++) { if (b[i][j]==charAtPosition) { topright++; } else { break; } } } else if () { } else { } } Since it is as tedious as the original one. Note also that the comparing signs for the loop condition i>=0 && j<=numCols; for example, >= && <= have correspondence with the value combination of horizontal and vertical. Sorry for my bad wording, please let me know if anything is not clear.

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• ZF Autoloader to load ancestor and requested class

  - by Pekka

  I am integrating Zend Framework into an existing application. I want to switch the application over to Zend's autoloading mechanism to replace dozens of include() statements. I have a specific requirement for the autoloading mechanism, though. Allow me to elaborate. The existing application uses a core library (independent from ZF), for example: /Core/Library/authentication.php /Core/Library/translation.php /Core/Library/messages.php this core library is to remain untouched at all times and serves a number of applications. The library contains classes like class ancestor_authentication { ... } class ancestor_translation { ... } class ancestor_messages { ... } in the application, there is also a Library directory: /App/Library/authentication.php /App/Library/translation.php /App/Library/messages.php these includes extend the ancestor classes and are the ones that actually get instantiated in the application. class authentication extends ancestor_authentication { } class translation extends ancestor_translation { } class messages extends ancestor_messages { } usually, these class definitions are empty. They simply extend their ancestors and provide the class name to instantiate. $authentication = new authentication(); The purpose of this solution is to be able to easily customize aspects of the application without having to patch the core libraries. Now, the autoloader I need would have to be aware of this structure. When an object of the class authentication is requested, the autoloader would have to: 1. load /Core/Library/authentication.php 2. load /App/Library/authentication.php My current approach would be creating a custom function, and binding that to Zend_Loader_Autoloader for a specific namespace prefix. Is there already a way to do this in Zend that I am overlooking? The accepted answer in this question kind of implies there is, but that may be just a bad choice of wording. Are there extensions to the Zend Autoloader that do this? Can you - I am new to ZF - think of an elegant way, conforming with the spirit of the framework, of extending the Autoloader with this functionality? I'm not necessary looking for a ready-made implementation, some pointers (This should be an extension to the xyz method that you would call like this...) would already be enough.

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• Casting to derived type problem in C++

  - by GONeale

  Hey there everyone, I am quite new to C++, but have worked with C# for years, however it is not helping me here! :) My problem: I have an Actor class which Ball and Peg both derive from on an objective-c iphone game I am working on. As I am testing for collision, I wish to set an instance of Ball and Peg appropriately depending on the actual runtime type of actorA or actorB. My code that tests this as follows: // Actors that collided Actor *actorA = (Actor*) bodyA->GetUserData(); Actor *actorB = (Actor*) bodyB->GetUserData(); Ball* ball; Peg* peg; if (static_cast<Ball*> (actorA)) { // true ball = static_cast<Ball*> (actorA); } else if (static_cast<Ball*> (actorB)) { ball = static_cast<Ball*> (actorB); } if (static_cast<Peg*> (actorA)) { // also true?! peg = static_cast<Peg*> (actorA); } else if (static_cast<Peg*> (actorB)) { peg = static_cast<Peg*> (actorB); } if (peg != NULL) { [peg hitByBall]; } Once ball and peg are set, I then proceed to run the hitByBall method (objective c). Where my problem really lies is in the casting procedurel Ball casts fine from actorA; the first if (static_cast<>) statement steps in and sets the ball pointer appropriately. The second step is to assign the appropriate type to peg. I know peg should be a Peg type and I previously know it will be actorB, however at runtime, detecting the types, I was surprised to find actually the third if (static_cast<>) statement stepped in and set this, this if statement was to check if actorA was a Peg, which we already know actorA is a Ball! Why would it have stepped here and not in the fourth if statement? The only thing I can assume is how casting works differently from c# and that is it finds that actorA which is actually of type Ball derives from Actor and then it found when static_cast<Peg*> (actorA) is performed it found Peg derives from Actor too, so this is a valid test? This could all come down to how I have misunderstood the use of static_cast. How can I achieve what I need? :) I'm really uneasy about what feels to me like a long winded brute-casting attempt here with a ton of ridiculous if statements. I'm sure there is a more elegant way to achieve a simple cast to Peg and cast to Ball dependent on actual type held in actorA and actorB. Hope someone out there can help! :) Thanks a lot.

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• Casting between variant and bstr_t causing inconsisten crash in Windows 2008

  - by user58470

  We have a C# application, calling a simple C++ wrapper class, that then calls an existing C++ DLL. The C++ code is all VC++ 6.0. We are getting inconsistent behaviour, but the crash, when it happens, always happens within the C++ wrapper DLL, and always in the same spot (have confirmed using painful logging statements). It never happens on any environment except on Windows 2008, so we suspect some bad-but-not-fatal memory trashing is going on that somehow Windows 2008 is being more mindful of. Here's the relevant code, if anyone has any ideas on why this might be crashing it would be much appreciated. We've been tearing our hair out for a few days and project timelines are slipping all for the want of being able to return a simple string back to C#... I've been told we've tried setting the VARIANT vresult using VariantInit, and clearing it when we are done with VariantClear, but that didn't help. // JobMgrDll.cpp : Defines the entry point for the DLL application. // #include "stdafx.h" #include "JobMgrDll.h" #include "jobmgr.h" CString gcontext; CString guser; CString ghost; CString glog; JOBMGRDLL_API int nJobMgrDll=0; extern "C" JOBMGRDLL_API char* perform_billcalc(char* cmd, char* context, char* user,char* host,BSTR* log,int* loglen) { char* result = new char[1000]; memset(result,0,999); result[999] = '\0'; bstr_t bt_command = cmd; UUID uuid = __uuidof(BRLib::Rules); VARIANT vresult; char *p_rv; gcontext = context; guser = user; ghost = host; write_log("execute_job"); p_rv = execute_job(uuid, "none", bt_command, &vresult); write_log("DONE execute_job"); CString message; write_log ("Intializing bstr_t with variant"); // WE ALWAYS GET HERE bstr_t res(vresult); //message.Format("%s result = %s",p_rv,res); //write_log(message); write_log("copying Result"); // WE DON'T ALWAYS GET HERE, BUT SOMETIMES WE DO strcpy(result,(char*)res); write_log(CString(result)); *loglen = glog.GetLength(); *log = glog.AllocSysString(); return result; } Again, any ideas much, much appreciated.

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• Is there a programming language with be semantics close to English ?

  - by ivo s

  Most languages allow to 'tweek' to certain extend parts of the syntax (C++,C#) and/or semantics that you will be using in your code (Katahdin, lua). But I have not heard of a language that can just completely define how your code will look like. So isn't there some language which already exists that has such capabilities to override all syntax & define semantics ? Example of what I want to do is basically from the C# code below: foreach(Fruit fruit in Fruits) { if(fruit is Apple) { fruit.Price = fruit.Price/2; } } I want do be able to to write the above code in my perfect language like this: Check if any fruits are Macintosh apples and discount the price by 50%. The advantages that come to my mind looking from a coder's perspective in this "imaginary" language are: It's very clear what is going on (self descriptive) - it's plain English after all even kid would understand my program Hides all complexities which I have to write in C#. But why should I care to learn that if statements, arithmetic operators etc since there are already implemented The disadvantages that I see for a coder who will maintain this program are: Maybe you would express this program differently from me so you may not get all the information that I've expressed in my sentence Programs can be quite verbose and hard to debug but if possible to even proximate this type of syntax above maybe more people would start programming right? That would be amazing I think. I can go to work and just write an essay to draw a square on a winform like this: Create a form called MyGreetingForm. Draw a square with in the middle of MyGreetingFormwith a side of 100 points. In the middle of the square write "Hello! Click here to continue" in Arial font. In the above code the parser must basically guess that I want to use the unnamed square from the previous sentence, it'd be hard to write such a smart parser I guess, yet it's so simple what I want to do. If the user clicks on square in the middle of MyGreetingForm show MyMainForm. In the above code 'basically' the compiler must: 1)generate an event handler 2) check if there is any square in the middle of the form and if there is - 3) hide the form and show another form It looks very hard to do but it doesn't look impossible IMO to me at least approximate this (I can personally generate a parser to perform the 3 steps above np & it's basically the same that it has to do any way when you add even in c# a.MyEvent=+handler; so I don't see a problem here) so I'm thinking maybe somebody already did something like this ? Or is there some practical burden of complexity to create such a 'essay style' programming language which I can't see ? I mean what's the worse that can happen if the parser is not that good? - your program will crash so you have to re-word it:)

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• ASP.Net / MySQL : Translating content into several languages

  - by philwilks

  I have an ASP.Net website which uses a MySQL database for the back end. The website is an English e-commerce system, and we are looking at the possibility of translating it into about five other languages (French, Spanish etc). We will be getting human translators to perform the translation - we've looked at automated services but these aren't good enough. The static text on the site (e.g. headings, buttons etc) can easily be served up in multiple languages via .Net's built in localization features (resx files etc). The thing that I'm not so sure about it how best to store and retrieve the multi-language content in the database. For example, there is a products table that includes these fields... productId (int) categoryId (int) title (varchar) summary (varchar) description (text) features (text) The title, summary, description and features text would need to be available in all the different languages. Here are the two options that I've come up with... Create additional field for each language For example we could have titleEn, titleFr, titleEs etc for all the languages, and repeat this for all text columns. We would then adapt our code to use the appropriate field depending on the language selected. This feels a bit hacky, and also would lead to some very large tables. Also, if we wanted to add additional languages in the future it would be time consuming to add even more columns. Use a lookup table We could create a new table with the following format... textId | languageId | content ------------------------------- 10 | EN | Car 10 | FR | Voiture 10 | ES | Coche 11 | EN | Bike 11 | FR | Vélo We'd then adapt our products table to reference the appropriate textId for the title, summary, description and features instead of having the text stored in the product table. This seems much more elegant, but I can't think of a simple way of getting this data out of the database and onto the page without using complex SQL statements. Of course adding new languages in the future would be very simple compared to the previous option. I'd be very grateful for any suggestions about the best way to achieve this! Is there any "best practice" guidance out there? Has anyone done this before?

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• php connecting to mysql server(localhost) very slow

  - by Ahmad

  actually its little complicated: summary: the connection to DB is very slow. the page rendering takes around 10 seconds but the last statement on the page is an echo and i can see its output while the page is loading in firefox (IE is same). in google chrome the output becomes visible only when the loading finishes. loading time is approximately the same across browsers. on debugging i found out that its the DB connectivity that is creating problem. the DB was on another machine. to debug further. i deployed the DB on my local machine .. so now the DB connection is at 127.0.0.1 but the connectivity still takes long time. this means that the issue is with APACHE/PHP and not with mysql. but then i deployed my code on another machine which connects to DB remotely.and everything seems fine. basically the application uses couple of mod_rewrite.. but i removed all the .htaccess files and the slow connectivity issue remains.. i installed another APACHE on my machine and used default settings. the connection was still very slow. i added following statements to measure the execution time $stime = microtime(); $stime = explode(" ",$stime); $stime = $stime[1] + $stime[0]; // my code -- it involves connection to DB $mtime = microtime(); $mtime = explode(" ",$mtime); $mtime = $mtime[1] + $mtime[0]; $totaltime = ($mtime - $stime); echo $totaltime; the output is 0.0631899833679 but firebug Net panel shows total loading time of 10-11 seconds. same is the case with google chrome i tried to turn off windows firewall.. connectivity is still slow and i just can't quite find the reason.. i've tried multiple DB servers.. multiple apaches.. nothing seems to be working.. any idea of what might be the problem?

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• Remove specific definitions from a variable in PHP

  - by Amit

  Hi everyone, I have a PHP mail script that validates name, email address, and phone number before sending the mail. This then means that the Name, Email address, and Phone fields are Required Fields. I want to have it so that the Name and EITHER Email or Phone are required. Such that if a name and phone are inputted, it sends the mail, or if a name and an email are inputted, it also sends the email. The way the script works right now is it has several IF statements that check for (1) name, (2) email and (3) phone. Here's an example of an if statement of the code: if ( ($email == "") ) { $errors .= $emailError; // no email address entered $email_error = true; } if ( !(preg_match($match,$email)) ) { $errors .= $invalidEmailError; // checks validity of email $email_error = true; } And here's how it sends the mail: if ( !($errors) ) { mail ($to, $subject, $message, $headers); echo "<p id='correct'>"; echo "?????? ????? ??????!"; echo "</p>"; } else { if (($email_error == true)) { $errors != $phoneError; /*echo "<p id='errors'>"; echo $errors; echo "</p>";*/ } if (($phone_error == true)) { $errors != $emailError; $errors != $invalidEmailError; /*echo "<p id='errors'>"; echo $errors; echo "</p>";*/ } echo "<p id='errors'>"; echo $errors; echo "</p>"; } This doesn't work though. Basically this is what I want to do: If no email address was entered or if it was entered incorrectly, set a variable called $email_error to be true. Then check for that variable, and if it's true, then remove the $phoneError part of the $errors variable. Man I hope I'm making some sense here. Does anyone know why this doesn't work? It reports all errors if all fields are left empty :( Thanks! Amit

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• HttpWebRequest possibly slowing website

  - by Steven Smith

  Using Visual studio 2012, C#.net 4.5 , SQL Server 2008, Feefo, Nopcommerce Hey guys I have Recently implemented a new review service into a current site we have. When the change went live the first day all worked fine. Since then though the sending of sales to Feefo hasnt been working, There are no logs either of anything going wrong. In the OrderProcessingService.cs in Nop Commerce's Service, i call a HttpWebrequest when an order has been confirmed as completed. Here is the code. var email = HttpUtility.UrlEncode(order.Customer.Email.ToString()); var name = HttpUtility.UrlEncode(order.Customer.GetFullName().ToString()); var description = HttpUtility.UrlEncode(productVariant.ProductVariant.Product.MetaDescription != null ? productVariant.ProductVariant.Product.MetaDescription.ToString() : "product"); var orderRef = HttpUtility.UrlEncode(order.Id.ToString()); var productLink = HttpUtility.UrlEncode(string.Format("myurl/p/{0}/{1}", productVariant.ProductVariant.ProductId, productVariant.ProductVariant.Name.Replace(" ", "-"))); string itemRef = ""; try { itemRef = HttpUtility.UrlEncode(productVariant.ProductVariant.ProductId.ToString()); } catch { itemRef = "0"; } var url = string.Format("feefo Url", login, password,email,name,description,orderRef,productLink,itemRef); var request = (HttpWebRequest)WebRequest.Create(url); request.KeepAlive = false; request.Timeout = 5000; request.Proxy = null; using (var response = (HttpWebResponse)request.GetResponse()) { if (response.StatusDescription == "OK") { var stream = response.GetResponseStream(); if(stream != null) { using (var reader = new StreamReader(stream)) { var content = reader.ReadToEnd(); } } } } So as you can see its a simple webrequest that is processed on an order, and all product variants are sent to feefo. Now: this hasnt been happening all week since the 15th (day of the implementation) the site has been grinding to a halt recently. The stream and reader in the the var content is there for debugging. Im wondering does the code redflag anything to you that could relate to the process of website? Also note i have run some SQL statements to see if there is any deadlocks or large escalations, so far seems fine, Logs have also been fine just the usual logging of Bots. Any help would be much appreciated! EDIT: also note that this code is in a method that is called and wrapped in A try catch UPDATE: well forget about the "not sending", thats because i was just told my code was rolled back last week

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• What are the rules governing how a bind variable can be used in Postgres and where is this defined?

  - by Craig Miles

  I can have a table and function defined as: CREATE TABLE mytable ( mycol integer ); INSERT INTO mytable VALUES (1); CREATE OR REPLACE FUNCTION myfunction (l_myvar integer) RETURNS mytable AS $$ DECLARE l_myrow mytable; BEGIN SELECT * INTO l_myrow FROM mytable WHERE mycol = l_myvar; RETURN l_myrow; END; $$ LANGUAGE plpgsql; In this case l_myvar acts as a bind variable for the value passed when I call: SELECT * FROM myfunction(1); and returns the row where mycol = 1 If I redefine the function as: CREATE OR REPLACE FUNCTION myfunction (l_myvar integer) RETURNS mytable AS $$ DECLARE l_myrow mytable; BEGIN SELECT * INTO l_myrow FROM mytable WHERE mycol IN (l_myvar); RETURN l_myrow; END; $$ LANGUAGE plpgsql; SELECT * FROM myfunction(1); still returns the row where mycol = 1 However, if I now change the function definition to allow me to pass an integer array and try to this array in the IN clause, I get an error: CREATE OR REPLACE FUNCTION myfunction (l_myvar integer[]) RETURNS mytable AS $$ DECLARE l_myrow mytable; BEGIN SELECT * INTO l_myrow FROM mytable WHERE mycol IN (array_to_string(l_myvar, ',')); RETURN l_myrow; END; $$ LANGUAGE plpgsql; Analysis reveals that although: SELECT array_to_string(ARRAY[1, 2], ','); returns 1,2 as expected SELECT * FROM myfunction(ARRAY[1, 2]); returns the error operator does not exist: integer = text at the line: WHERE mycol IN (array_to_string(l_myvar, ',')); If I execute: SELECT * FROM mytable WHERE mycol IN (1,2); I get the expected result. Given that array_to_string(l_myvar, ',') evaluates to 1,2 as shown, why arent these statements equivalent. From the error message it is something to do with datatypes, but doesnt the IN(variable) construct appear to be behaving differently from the = variable construct? What are the rules here? I know that I could build a statement to EXECUTE, treating everything as a string, to achieve what I want to do, so I am not looking for that as a solution. I do want to understand though what is going on in this example. Is there a modification to this approach to make it work, the particular example being to pass in an array of values to build a dynamic IN clause without resorting to EXECUTE? Thanks in advance Craig

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• trigger animation with timer, as3

  - by VideoDnd

  How do I trigger the animation in sync with my timer?My timer and flip animation work, but they are out of sync with each other. I'm lost with the IF ELSE statements. Each time the value of my textfield changes, my number needs to flip. See example. Example //IF ELSE FUNCTION function theFlip(event:TimerEvent):void { count++; if (count < 9) { oldcount = count - 1; } else { count++; fcount=int(count) count++; oldcount = count - 1; } } //Cont... Complete Codehere's the file //Timer var timer:Timer = new Timer(100); //Integer values var count:int = 0; var fcount:int = 0; var oldcount:int = 0; //Formatting String function formatCount(i:int):String { var fraction:int = i % 100; var whole:int = i / 100; return ("00" + whole).substr(-2, 2) + "." + (fraction < 10 ? "0" + fraction : fraction); } //Start the timer timer.start(); timer.addEventListener(TimerEvent.TIMER, theFlip); //IF ELSE FUNCTION function theFlip(event:TimerEvent):void { count++; if (count < 9) { oldcount = count - 1; } else { count++; fcount=int(count) count++; oldcount = count - 1; } var toText:String = formatCount(fcount); sec4.digit.text = toText.substr(4, 1); flip4.flip.digit.text = toText.substr(4, 1); flip4.gotoAndPlay(2); sec3.digit.text = toText.substr(3, 1); flip3.flip.digit.text = toText.substr(3, 1); flip3.gotoAndPlay(2); sec1.digit.text = toText.substr(1, 1); flip1.flip.digit.text = toText.substr(1, 1); flip1.gotoAndPlay(2); }

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• Is valgrind crazy or is this is a genuine std map iterator memory leak?

  - by Alberto Toglia

  Well, I'm very new to Valgrind and memory leak profilers in general. And I must say it is a bit scary when you start using them cause you can't stop wondering how many leaks you might have left unsolved before! To the point, as I'm not an experienced in c++ programmer, I would like to check if this is certainly a memory leak or is it that Valgrind is doing a false positive? typedef std::vector<int> Vector; typedef std::vector<Vector> VectorVector; typedef std::map<std::string, Vector*> MapVector; typedef std::pair<std::string, Vector*> PairVector; typedef std::map<std::string, Vector*>::iterator IteratorVector; VectorVector vv; MapVector m1; MapVector m2; vv.push_back(Vector()); m1.insert(PairVector("one", &vv.back())); vv.push_back(Vector()); m2.insert(PairVector("two", &vv.back())); IteratorVector i = m1.find("one"); i->second->push_back(10); m2.insert(PairVector("one", i->second)); m2.clear(); m1.clear(); vv.clear(); Why is that? Shouldn't the clear command call the destructor of every object and every vector? Now after doing some tests I found different solutions to the leak: 1) Deleting the line i-second-push_back(10); 2) adding a delete i-second; after it's been used. 3) Deleting the second vv.push_back(Vector()); and m2.insert(PairVector("two", &vv.back())); statements. Using solution 2) makes Valgring print: 10 allocs, 11 frees Is that OK? As I'm not using new why should I delete? Thanks, for any help!

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• How can I pipe input to a Java app with Perl?

  - by user319479

  I need to write a Perl script that pipes input into a Java program. This is related to this, but that didn't help me. My issue is that the Java app doesn't get the print statements until I close the handle. What I found online was that $| needs to be set to something greater than 0, in which case newline characters will flush the buffer. This still doesn't work. This is the script: #! /usr/bin/perl -w use strict; use File::Basename; $|=1; open(TP, "| java -jar test.jar") or die "fail"; sleep(2); print TP "this is test 1\n"; print TP "this is test 2\n"; print "tests printed, waiting 5s\n"; sleep(5); print "wait over. closing handle...\n"; close TP; print "closed.\n"; print "sleeping for 5s...\n"; sleep(5); print "script finished!\n"; exit And here is a sample Java app: import java.util.Scanner; public class test{ public static void main( String[] args ){ Scanner sc = new Scanner( System.in ); int crashcount = 0; while( true ){ try{ String input = sc.nextLine(); System.out.println( ":: INPUT: " + input ); if( "bananas".equals(input) ){ break; } } catch( Exception e ){ System.out.println( ":: EXCEPTION: " + e.toString() ); crashcount++; if( crashcount == 5 ){ System.out.println( ":: Looks like stdin is broke" ); break; } } } System.out.println( ":: IT'S OVER!" ); return; } } The Java app should respond to receiving the test prints immediately, but it doesn't until the close statement in the Perl script. What am I doing wrong? Note: the fix can only be in the Perl script. The Java app can't be changed. Also, File::Basename is there because I'm using it in the real script.

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• PyGTK: Radiobuttons are still displayed after removal

  - by canavanin

  Hi everyone! I am using PyGTK and the gtk.assistant. On one page I would like to display two radiobuttons in case the user selected a certain option on a previous page. The labels of the buttons - and whether the buttons are to be present at all - are to depend entirely on that earlier selection. Furthermore, if the user goes back and changes that selection, the page containing the radiobuttons is to be updated accordingly. I have got as far as having the radiobuttons displayed when necessary, and with the correct labels. The trouble is that if I go back and change the determining selection, or if I move one page further than the 'radiobutton page' and then move back, the buttons are not only not removed (in case that would have been required), their number has also doubled. To show you what I'm doing, here's part of my code (I've left out bits that do unrelated things, that's why the function name doesn't fit). The function is called when the "prepare" signal is emitted prior to construction of the 'radiobutten page'. def make_class_skills_treestore(self): print self.trained_by_default_hbox.get_children() # PRINT 1 for child in self.trained_by_default_hbox.get_children(): if type(child) == gtk.RadioButton: self.trained_by_default_hbox.remove(child) #child.destroy() # <-- removed the labels, but not the buttons print self.trained_by_default_hbox.get_children() # PRINT 2 class_skills = self.data.data['classes'][selected_class].class_skills.values() default_trained_count = (class_skills.count([True, True]) , class_skills.count([True, False])) num_default_trained_skills = default_trained_count[1] / 2 # you have to pick one of a pair --> don't # count each as trained by default for i in range(default_trained_count[0]): # those are trained by default --> no choice num_default_trained_skills +=1 selected_class = self.get_classes_key_from_class_selection() if default_trained_count[1]: for skill in self.data.data['classes'][selected_class].class_skills.keys(): if self.data.data['classes'][selected_class].class_skills[skill] == [ True, False ] and not self.default_radio: self.default_radio.append(gtk.RadioButton(group=None, label=skill)) elif self.data.data['classes'][selected_class].class_skills[skill] == [ True, False ] and self.default_radio: self.default_radio.append(gtk.RadioButton(group=self.default_radio[0], label=skill)) if self.default_radio: for radio in self.default_radio: self.trained_by_default_hbox.add(radio) self.trained_by_default_hbox.show_all() self.trained_by_default_hbox and self.trained_by_default_label, as well as self.default_radio stem from the above function's class. I have two print statements (PRINT 1 and PRINT 2) in there for debugging. Here's what they give me: PRINT 1: [<gtk.Label object at 0x8fc4c84 (GtkLabel at 0x90a2f20)>, <gtk.RadioButton object at 0x8fc4d4c (GtkRadioButton at 0x90e4018)>, <gtk.RadioButton object at 0x8fc4cac (GtkRadioButton at 0x90ceec0)>] PRINT 2: [<gtk.Label object at 0x8fc4c84 (GtkLabel at 0x90a2f20)>] So the buttons have indeed been removed, yet they still show up on the page. I know the code requires some refactoring, but first I'd like to get it to work at all... If someone could help me out that would be great! Thanks a lot in advance for your replies - any kind of help is highly appreciated.

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• MySQL search for user and their roles

  - by Jenkz

  I am re-writing the SQL which lets a user search for any other user on our site and also shows their roles. An an example, roles can be "Writer", "Editor", "Publisher". Each role links a User to a Publication. Users can take multiple roles within multiple publications. Example table setup: "users" : user_id, firstname, lastname "publications" : publication_id, name "link_writers" : user_id, publication_id "link_editors" : user_id, publication_id Current psuedo SQL: SELECT * FROM ( (SELECT user_id FROM users WHERE firstname LIKE '%Jenkz%') UNION (SELECT user_id FROM users WHERE lastname LIKE '%Jenkz%') ) AS dt JOIN (ROLES STATEMENT) AS roles ON roles.user_id = dt.user_id At the moment my roles statement is: SELECT dt2.user_id, dt2.publication_id, dt.role FROM ( (SELECT 'writer' AS role, link_writers.user_id, link_writers.publication_id FROM link_writers) UNION (SELECT 'editor' AS role, link_editors.user_id, link_editors.publication_id FROM link_editors) ) AS dt2 The reason for wrapping the roles statement in UNION clauses is that some roles are more complex and require a table join to find the publication_id and user_id. As an example "publishers" might be linked accross two tables "link_publishers": user_id, publisher_group_id "link_publisher_groups": publisher_group_id, publication_id So in that instance, the query forming part of my UNION would be: SELECT 'publisher' AS role, link_publishers.user_id, link_publisher_groups.publication_id FROM link_publishers JOIN link_publisher_groups ON lpg.group_id = lp.group_id I'm pretty confident that my table setup is good (I was warned off the one-table-for-all system when researching the layout). My problem is that there are now 100,000 rows in the users table and upto 70,000 rows in each of the link tables. Initial lookup in the users table is fast, but the joining really slows things down. How can I only join on the relevant roles? -------------------------- EDIT ---------------------------------- Explain above (open in a new window to see full resolution). The bottom bit in red, is the "WHERE firstname LIKE '%Jenkz%'" the third row searches WHERE CONCAT(firstname, ' ', lastname) LIKE '%Jenkz%'. Hence the large row count, but I think this is unavoidable, unless there is a way to put an index accross concatenated fields? The green bit at the top just shows the total rows scanned from the ROLES STATEMENT. You can then see each individual UNION clause (#6 - #12) which all show a large number of rows. Some of the indexes are normal, some are unique. It seems that MySQL isn't optimizing to use the dt.user_id as a comparison for the internal of the UNION statements. Is there any way to force this behaviour? Please note that my real setup is not publications and writers but "webmasters", "players", "teams" etc.

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• How can I improve my select query for storing large versioned data sets?

  - by Jason Francis

  At work, we build large multi-page web applications, consisting mostly of radio and check boxes. The primary purpose of each application is to gather data, but as users return to a page they have previously visited, we report back to them their previous responses. Worst-case scenario, we might have up to 900 distinct variables and around 1.5 million users. For several reasons, it makes sense to use an insert-only approach to storing the data (as opposed to update-in-place) so that we can capture historical data about repeated interactions with variables. The net result is that we might have several responses per user per variable. Our table to collect the responses looks something like this: CREATE TABLE [dbo].[results]( [id] [bigint] IDENTITY(1,1) NOT NULL, [userid] [int] NULL, [variable] [varchar](8) NULL, [value] [tinyint] NULL, [submitted] [smalldatetime] NULL) Where id serves as the primary key. Virtually every request results in a series of insert statements (one per variable submitted), and then we run a select to produce previous responses for the next page (something like this): SELECT t.id, t.variable, t.value FROM results t WITH (NOLOCK) WHERE t.userid = '2111846' AND (t.variable='internat' OR t.variable='veteran' OR t.variable='athlete') AND t.id IN (SELECT MAX(id) AS id FROM results WITH (NOLOCK) WHERE userid = '2111846' AND (t.variable='internat' OR t.variable='veteran' OR t.variable='athlete') GROUP BY variable) Which, in this case, would return the most recent responses for the variables "internat", "veteran", and "athlete" for user 2111846. We have followed the advice of the database tuning tools in indexing the tables, and against our data, this is the best-performing version of the select query that we have been able to come up with. Even so, there seems to be significant performance degradation as the table approaches 1 million records (and we might have about 150x that). We have a fairly-elegant solution in place for sharding the data across multiple tables which has been working quite well, but I am open for any advice about how I might construct a better version of the select query. We use this structure frequently for storing lots of independent data points, and we like the benefits it provides. So the question is, how can I improve the performance of the select query? I assume the nested select statement is a bad idea, but I have yet to find an alternative that performs as well. Thanks in advance. NB: Since we emphasize creating over reading in this case, and since we never update in place, there doesn't seem to be any penalty (and some advantage) for using the NOLOCK directive in this case.

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