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  • Data access pattern, combining push and pull?

    - by andlju
    I need some advice on what kind of pattern(s) I should use for pushing/pulling data into my application. I'm writing a rule-engine that needs to hold quite a large amount of data in-memory in order to be efficient enough. I have some rather conflicting requirements; It is not acceptable for the engine to always have to wait for a full pre-load of all data before it is functional. Only fetching and caching data on-demand will lead to the engine taking too long before it is running quickly enough. An external event can trigger the need for specific parts of the data to be reloaded. Basically, I think I need a combination of pushing and pulling data into the application. A simplified version of my current "pattern" looks like this (in psuedo-C# written in notepad): // This interface is implemented by all classes that needs the data interface IDataSubscriber { void RegisterData(Entity data); } // This interface is implemented by the data access class interface IDataProvider { void EnsureLoaded(Key dataKey); void RegisterSubscriber(IDataSubscriber subscriber); } class MyClassThatNeedsData : IDataSubscriber { IDataProvider _provider; MyClassThatNeedsData(IDataProvider provider) { _provider = provider; _provider.RegisterSubscriber(this); } public void RegisterData(Entity data) { // Save data for later StoreDataInCache(data); } void UseData(Key key) { // Make sure that the data has been stored in cache _provider.EnsureLoaded(key); Entity data = GetDataFromCache(key); } } class MyDataProvider : IDataProvider { List<IDataSubscriber> _subscribers; // Make sure that the data for key has been loaded to all subscribers public void EnsureLoaded(Key key) { if (HasKeyBeenMarkedAsLoaded(key)) return; PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } // Force all subscribers to get a new version of the data for key public void ForceReload(Key key) { PublishDataToSubscribers(key); MarkKeyAsLoaded(key); } void PublishDataToSubscribers(Key key) { Entity data = FetchDataFromStore(key); foreach(var subscriber in _subscribers) { subscriber.RegisterData(data); } } } // This class will be spun off on startup and should make sure that all data is // preloaded as quickly as possible class MyPreloadingThread { IDataProvider _provider; MyPreloadingThread(IDataProvider provider) { _provider = provider; } void RunInBackground() { IEnumerable<Key> allKeys = GetAllKeys(); foreach(var key in allKeys) { _provider.EnsureLoaded(key); } } } I have a feeling though that this is not necessarily the best way of doing this.. Just the fact that explaining it seems to take two pages feels like an indication.. Any ideas? Any patterns out there I should have a look at?

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  • What situations does a Monostate pattern model?

    - by devoured elysium
    I know what both a Singleton or a Monostate are and how to implement them. Although I can see many uses for a Singleton, I can't imagine a situation where I would want to let the user create as many instances of my class although in reality only one really exists behind the scenes. Can anybody help me here? I know that for several reasons one should stay away from both patterns, but in theory, what kind of problems does the Monostate model? Thanks

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  • Copied App.config to (Assembly).exe.config but from folder debug application doesn't run

    - by uugan
    Gives error: "The specified named connection is either not found in the configuration, not intended to be used with the EntityClient provider, or not valid" App.config looks like and it's same as (Assembly.exe.config) config file for output: <?xml version="1.0" encoding="utf-8"?> <configuration> <connectionStrings> <add name="Entities1" connectionString="metadata=res://*/;provider=System.Data.SqlClient;provider connection string='data source=localhost;initial catalog=DatabaseName;integrated security=True;multipleactiveresultsets=True;App=EntityFramework'" providerName="System.Data.EntityClient" /> </connectionStrings> </configuration> How to run exe with it's configuration file? I tried to change '' to quot but nothing has changed.

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  • Factory Method Implementation

    - by cedar715
    I was going through the 'Factory method' pages in SO and had come across this link. And this comment. The example looked as a variant and thought to implement in its original way: to defer instantiation to subclasses... Here is my attempt. Does the following code implements the Factory pattern of the example specified in the link? Please validate and suggest if this has to undergo any re-factoring. public class ScheduleTypeFactoryImpl implements ScheduleTypeFactory { @Override public IScheduleItem createLinearScheduleItem() { return new LinearScheduleItem(); } @Override public IScheduleItem createVODScheduleItem() { return new VODScheduleItem(); } } public class UseScheduleTypeFactory { public enum ScheduleTypeEnum { CableOnDemandScheduleTypeID, BroadbandScheduleTypeID, LinearCableScheduleTypeID, MobileLinearScheduleTypeID } public static IScheduleItem getScheduleItem(ScheduleTypeEnum scheduleType) { IScheduleItem scheduleItem = null; ScheduleTypeFactory scheduleTypeFactory = new ScheduleTypeFactoryImpl(); switch (scheduleType) { case CableOnDemandScheduleTypeID: scheduleItem = scheduleTypeFactory.createVODScheduleItem(); break; case BroadbandScheduleTypeID: scheduleItem = scheduleTypeFactory.createVODScheduleItem(); break; case LinearCableScheduleTypeID: scheduleItem = scheduleTypeFactory.createLinearScheduleItem(); break; case MobileLinearScheduleTypeID: scheduleItem = scheduleTypeFactory.createLinearScheduleItem(); break; default: break; } return scheduleItem; } }

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  • Need help to create database schema for wholesale online tee store

    - by techiepark
    Hi, I'm currently working on wholesale online t-shirt shop. I have done this for fixed quantity and price, and its working fine. Now i need to do this for variable quantity and price. Here is the reference link, like what i have to do. Basic tables i have created are - CREATE TABLE attribute ( attribute_id int(11) NOT NULL auto_increment, name varchar(100) NOT NULL, PRIMARY KEY (attribute_id) ); CREATE TABLE attribute_value ( attribute_value_id int(11) NOT NULL auto_increment, attribute_id int(11) NOT NULL, value varchar(100) NOT NULL, PRIMARY KEY (attribute_value_id), KEY idx_attribute_value_attribute_id (attribute_id) ); CREATE TABLE product ( product_id int(11) NOT NULL auto_increment, name varchar(100) NOT NULL, description varchar(1000) NOT NULL, price decimal(10,2) NOT NULL, image varchar(150) default NULL, thumbnail varchar(150) default NULL, PRIMARY KEY (product_id), FULLTEXT KEY idx_ft_product_name_description (name,description) ); CREATE TABLE product_attribute ( product_id int(11) NOT NULL, attribute_value_id int(11) NOT NULL, PRIMARY KEY (product_id,attribute_value_id) ); I'm not getting how to store the price based on variable quantity. Please help me to create product and its related tables. my requirement is same as above reference link.

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  • How do I get the Zend_Application's database into a model class?

    - by Billy ONeal
    I have a Zend_Framework application, which has a whole bunch of model classes. I need these model classes to be able to access the application's database (naturally). Currently I've put this in my index.php: Zend_Registry::set('db', $application->bootstrap()->getBootstrap() ->getPluginResource('db')->getDbAdapter()); And then $db = Zend_Registry::get('db'); in each of my model classes that require the database. But this seems like a horrible horrible hack. Am I missing something basic here?

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  • How to setup a Zend_Application with an application.ini and a user.ini

    - by Peter Smit
    I am using Zend_Application and it does not feel right that I am mixing in my application.ini both application and user configuration. What I mean with this is the following. For example, my application needs some library classes in the namespace MyApp_ . So in application.ini I put autoloaderNamespaces[] = "MyApp_". This is pure application configuration, no-one except a programmer would change these. On the other hand I put there a database configuration, something that a SysAdmin would change. My idea is that I would split options between an application.ini and an user.ini, where the options in user.ini take preference (so I can define standard values in application.ini). Is this a good idea? How can I best implement this? The idea's I have are Extending Zend_Application to take multiple config files Making an init function in my Bootstrap loading the user.ini Parsing the config files in my index.php and pass these to Zend_Application (sounds ugly) What shall I do? I would like to have the 'cleanest' solution, which is prepared for the future (newer ZF versions, and other developers working on the same app)

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  • What are appropriate ways to represent relationships between people in a database table?

    - by Emilio
    I've got a table of people - an ID primary key and a name. In my application, people can have 0 or more real-world relationships with other people, so Jack might "work for" Jane and Tom might "replace" Tony and Bob might "be an employee of" Rob and Bob might also "be married to" Mary. What's the best way to represent this in the database? A many to many intersect table? A series of self joins? A relationship table with one row per relationship pair and type, where I insert records for the relationship in both directions?

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  • add schema to path in postgresql

    - by veilig
    I'm the process of moving applications over from all in the public schema to each having their own schema. for each application, I have a small script that will create the schema and then create the tables,functions,etc... to that schema. Is there anyway to automatically add a newly created schema to the search_path? Currently, the only way I see is to find the users current path SHOW search_path; and then add the new schema to it SET search_path to xxx,yyy,zzz; I would like some way to just say, append schema zzz to the users_search path. is this possible?

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  • Problem with Zend_Date and ISO_8601 format

    - by Noah Goodrich
    Frankly, I'm flummoxed. Can anyone tell me why I would get a failure message with this code? $date = Zend_Date::now(); $date = $date->getIso(); if(Zend_Date::isDate($date, Zend_Date::ISO_8601)) { print('success'); } else { print('failure'); } exit; It also fails if I just pass in a Zend_Date object. UPDATE: a var_dump of the initial $date object looks like this: object(Zend_Date)#107 (8) { ["_locale:private"]= string(5) "en_US" ["_fractional:private"]= int(0) ["_precision:private"]= int(3) ["_unixTimestamp:private"]= int(1257508100) ["_timezone:private"]= string(14) "America/Denver" ["_offset:private"]= int(25200) ["_syncronised:private"]= int(0) ["_dst:protected"]= bool(true) } And a var_dump of the $date string after calling $date-getIso() looks like this: string(25) "2009-11-06T04:48:20-07:00" I am using ZF 1.9.5 on PHP 5.2.8. I am using XAMPP for Windows too if that makes a difference.

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  • Best practice for DAO pattern ?

    - by Tony
    I've seen a lot of codes use a service-dao pattern , I don't know the origin of this pattern . It force the front layer call service , then delegates some of the service task to dao. I want to ask : Does DAO layer do purely data access related task ? What about exception encapsulation ? Is there other pattern can be used to replace this ?

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  • How to override Equals on a object created by an Entity Data Model?

    - by jamone
    I have an Entity Data Model that I have created, and its pulling in records from a SQLite DB. One of the Tables is People, I want to override the person.Equals() method but I'm unsure where to go to make such a change since the Person object is auto-generated and I don't even see where that autogen code resides. I know how to override Equals on a hand made object, its just where to do that on an autogen one.

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  • exception 'Zend_Controller_Action_Exception' with message 'Action "index" does not exist and was not

    - by princyp
    Anyone know what this error means? after googling I found a bunch of sites that appear to have the same error? thanks exception 'Zend_Controller_Action_Exception' with message 'Action "index" does not exist and was not trapped in __call()' in /usr/local/zend/apache2/htdocs/pintsy/lib/Zend/Controller/Action.php:485 Stack trace: #0 /usr/local/zend/apache2/htdocs/pintsy/lib/Zend/Controller/Action.php(515): Zend_Controller_Action->__call('indexAction', Array) #1 /usr/local/zend/apache2/htdocs/pintsy/lib/Zend/Controller/Dispatcher/Standard.php(289): Zend_Controller_Action->dispatch('indexAction') #2 /usr/local/zend/apache2/htdocs/pintsy/lib/Zend/Controller/Front.php(946): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http)) #3 /usr/local/zend/apache2/htdocs/pintsy/html/index.php(114): Zend_Controller_Front->dispatch() #4 {main}

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  • ASP.NET application using old connection string.

    - by Doug S.
    I am trying to publish a website using ASP.NET MVC3 EF and CODEFIRST with a SQL Server 2008 backend. On my local machine I was using a sql express db for development, but now that I am pushing live, I want to use my hosted production database. The problem is that when I try to run the application, it is still using my local db connection string. I have completely removed the old connection string from my web.config file and am using the <clear /> tag before creating the new connection string. I have also cleaned the solution and rebuilt, but somehow it is still connecting to the old db. What am I missing? This is the new connection string: <connectionStrings> <clear /> <add name="CellularAutomataDBContext" connectionString=" Server=XXX; Database=CellularAutomata; User ID=XXX; Password=XXX; Trusted_Connection=False" providerName="System.Data.SqlClient" /> </connectionStrings>

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  • how to run this qt script? (newbie question)

    - by GB_J
    I have a qt script(barchart.qs) that creates a graph for me. I don't know how i can incorporate(ie show the graph) in my qt mainwindow. Can some one please help me look at the code and what its outputs are? I tried engine.evaluate, but i do not know what is the QScriptValue i'm getting in return. Thanks sooo much. This is the script: BarChart.prototype = new QWidget; BarChart.prototype.suffix = ""; function BarChart(parent) { QWidget.call(this, parent); } // find the maximum value and widest (pixel-wise) label and suffix BarChart.prototype.showEvent = function(event) { var fm = new QFontMetrics(this); this.margin = 20; this.titleHeight = fm.height(); this.barHeight = 1.5 * fm.height(); this.barSpacing = 0.6 * fm.height(); this.maxValue = this.suffixWidth = this.labelWidth = 0; var count = 0; for (d in this.data) { this.labelWidth = Math.max(this.labelWidth, fm.width(d)); this.maxValue = Math.max(this.maxValue, this.data[d]); this.suffixWidth = Math.max(this.suffixWidth, fm.width(String(this.data[d]) + " " + this.suffix)); count++; } this.startHue = 15; this.hueDelta = 360 / count; this.size = new QSize(640, this.titleHeight + 2 * this.margin + (this.barHeight + this.barSpacing) * count); } BarChart.prototype.paintEvent = function(event) { var p = new QPainter; p.begin(this); // background and title p.fillRect(this.rect, new QBrush(new QColor(255, 255, 255))); p.drawText(0, 0, this.width, this.margin + this.titleHeight, Qt.AlignCenter, this.windowTitle, 0); var ofs = this.labelWidth + this.margin; var ww = this.width - this.suffixWidth - ofs - 2 * this.margin; var hue = this.startHue; var y = 0; p.translate(this.margin, this.titleHeight + 1.5 * this.margin); for (d in this.data) { // label on the left side p.setPen(new QColor(Qt.black)); p.drawText(0, y, this.labelWidth, this.barHeight, Qt.AlignVCenter + Qt.AlignRight, d, 0); // the colored bar var gradient = new QLinearGradient(new QPoint(ofs, y), new QPoint(ofs, y + this.barHeight)); gradient.setColorAt(0, QColor.fromHsv(hue, 255, 240)); gradient.setColorAt(1, QColor.fromHsv(hue, 255, 92)); p.setBrush(new QBrush(gradient)); p.setPen(new QColor(96, 96, 96)); var bw = this.data[d] * ww / this.maxValue; p.drawRect(ofs, y, bw, this.barHeight); // extra text at the end of the bar var text = new String(this.data[d] + " " + this.suffix); p.setPen(new QColor(Qt.black)); p.drawText(ofs + bw + this.margin/2, y, this.suffixWidth, this.barHeight, Qt.AlignVCenter + Qt.AlignLeft, text, 0); // for the next bar y += (this.barHeight + this.barSpacing); hue += this.hueDelta; if (hue >= 360) hue -= 360; } p.end(); } BarChart.prototype.wheelEvent = function(event) { this.startHue += event.delta() / 8 / 5; if (this.startHue = 360) this.startHue -= 360; if (this.startHue < 0) this.startHue += 360; this.update(); event.ignore(); } BarChart.prototype.mousePressEvent = function(event) { var fname = QFileDialog.getSaveFileName(this, "Save", ".", "*.png", 0, 0); if (fname.length > 0) { var img = new QImage(this.size, QImage.Format_ARGB32_Premultiplied); this.render(img); img.save(new QFile(fname)); } } var chart = new BarChart; chart.windowTitle = "Monthly"; chart.suffix = "reports"; chart.data = { "September" : 45, "October" : 60, "November" : 56, "December" : 0 }; chart.show(); QCoreApplication.exec();

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  • Style guide for database metadata naming

    - by Nulldevice
    We want to establish some database metadata naming rules in our new project. For example: tables are named as nouns in a plural form (courses, books, lessons) if present, an adjective goes before a noun in a table name and is separated by an underscore (red_books, new_lessons) table index column is always named "id" foreign key names are derived from a table name with suffix _id (book_id, red_book_id) so on Does someone know any guide like this?

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  • Yii, yiic and console

    - by undsoft
    In the installation instructions for Yii it is nescessary to use console and command line utility - yiic. Well, on my shared hosting I don't have ssh access. This is why I have following questions: How often and for what reasons will I have to use console? Is there a way to avoid using yiic? May I run yiic on local server and then just transfer everything to the final web server? Thanks!

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  • Writing fortran robust and "modern" code

    - by Blklight
    In some scientific environments, you often cannot go without FORTRAN as most of the developers only know that idiom, and there is lot of legacy code and related experience. And frankly, there are not many other cross-platform options for high performance programming ( C++ would do the task, but the syntax, zero-starting arrays, and pointers are too much for most engineers ;-) ). I'm a C++ guy but I'm stuck with some F90 projects. So, let's assume a new project must use FORTRAN (F90), but I want to build the most modern software architecture out of it. while being compatible with most "recent" compilers (intel ifort, but also including sun/HP/IBM own compilers) So I'm thinking of imposing: global variable forbidden, no gotos, no jump labels, "implicit none", etc. "object-oriented programming" (modules with datatypes + related subroutines) modular/reusable functions, well documented, reusable libraries assertions/preconditions/invariants (implemented using preprocessor statements) unit tests for all (most) subroutines and "objects" an intense "debug mode" (#ifdef DEBUG) with more checks and all possible Intel compiler checks possible (array bounds, subroutine interfaces, etc.) uniform and enforced legible coding style, using code processing tools C stubs/wrappers for libpthread, libDL (and eventually GPU kernels, etc.) C/C++ implementation of utility functions (strings, file operations, sockets, memory alloc/dealloc reference counting for debug mode, etc.) ( This may all seem "evident" modern programming assumptions, but in a legacy fortran world, most of these are big changes in the typical programmer workflow ) The goal with all that is to have trustworthy, maintainable and modular code. Whereas, in typical fortran, modularity is often not a primary goal, and code is trustworthy only if the original developer was very clever, and the code was not changed since then ! (i'm a bit joking here, but not much) I searched around for references about object-oriented fortran, programming-by-contract (assertions/preconditions/etc.), and found only ugly and outdated documents, syntaxes and papers done by people with no large-scale project involvement, and dead projects. Any good URL, advice, reference paper/books on the subject?

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  • Adding Parameters to Zend_Navigation

    - by Grant Collins
    I have a problem with Zend_Navigation that I am hoping for a little guidance on. I'm in the process of adding a Zend_Navigation to a legacy app as described [here on SO].1 The thing that I am not sure of is how to add parameters to the navigation menu after the data is loaded from the xml file. What I want to do is get 2 identifying parameters from the url and add them to the Zend_Navigation so that they are included in things such as the breadcrumb bar, so that if a user selects the previous item in the breadcrumb they are returned with the correct params in the url. The parameters, I believe need to be set at the Action level rather than the controller. Any help would be appreciated. Many thanks.

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  • How does this code break the Law of Demeter?

    - by Dave Jarvis
    The following code breaks the Law of Demeter: public class Student extends Person { private Grades grades; public Student() { } /** Must never return null; throw an appropriately named exception, instead. */ private synchronized Grades getGrades() throws GradesException { if( this.grades == null ) { this.grades = createGrades(); } return this.grades; } /** Create a new instance of grades for this student. */ protected Grades createGrades() throws GradesException { // Reads the grades from the database, if needed. // return new Grades(); } /** Answers if this student was graded by a teacher with the given name. */ public boolean isTeacher( int year, String name ) throws GradesException, TeacherException { // The method only knows about Teacher instances. // return getTeacher( year ).nameEquals( name ); } private Grades getGradesForYear( int year ) throws GradesException { // The method only knows about Grades instances. // return getGrades().getForYear( year ); } private Teacher getTeacher( int year ) throws GradesException, TeacherException { // This method knows about Grades and Teacher instances. A mistake? // return getGradesForYear( year ).getTeacher(); } } public class Teacher extends Person { public Teacher() { } /** * This method will take into consideration first name, * last name, middle initial, case sensitivity, and * eventually it could answer true to wild cards and * regular expressions. */ public boolean nameEquals( String name ) { return getName().equalsIgnoreCase( name ); } /** Never returns null. */ private synchronized String getName() { if( this.name == null ) { this.name == ""; } return this.name; } } Questions How is the LoD broken? Where is the code breaking the LoD? How should the code be written to uphold the LoD?

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  • Is it a good idea to cache data from web services into a database?

    - by Thierry Lam
    Let's assume that Stackoverflow offers web services where you can retrieve all the questions asked by a specific user. A request to get all question from user A can result in the following json output: { { "question": "What is rest?", "date_created": "20/02/2010", "votes": 1, }, { "question": "Which database to use for ...", "date_created": "20/07/2009", "votes": 5, }, } If I want to manipulate and present the data in any ways that I want, will it be wise to dump it in a local database? At some point, I will also want to retrieve all answers for each question and store them in a local database. The workflow that I'm thinking is: User logs in. Web services retrieve all questions asked by the logged in user, dump them in a local database. User wants all answers for a specific question, another web service does the retrieval and dump them in a local database. After user logs out, delete from the local database all questions and answers from that user.

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