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• Business entity: private instance VS single instance

  - by taoufik

  Suppose my WinForms application has a business entity Order, the entity is used in multiple views, each view handles a different domain or use-case in the application. As an example, one managing orders, the other one digging into one order and displaying additional data. If I'd use nHibernate (or any other ORM) and use one session/dataContext per view (or per db action), I'd end up getting two different instances for the same Order (let's say orderId = 1). Although functionally the same entity, they are technically two different instances. Yes, I could implement Equals/GetHashcode to make them "seem" the same. Why would you go for a single instance per entity vs private instances per view or per use-case? Having single instances has the advantage of sharing INotifyPropertyChanged events, and sharing additional (non-persistent) data. Having a private instance in each view would give you the flexibility of the undo functionality on a view level. In the example above, I'd allow the user to change order details, and give them the flexibility to not save the change. Here, synchronisation between the view/use-case happens on a data persistence level. What would your argument be?

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• What is ADO.NET?

  - by ChrisC

  I've written a few Access db's and used some light VBA, and had an OO class. Now I'm undertaking to write a C# db app. I've got VS and System.Data.SQLite installed and connected, and have entered my tables and columns, but that's where I'm stuck. I'm trying to find what info and tutorials I need to look for, but there are a lot of terms I don't understand and I don't know if or exactly how they apply to my project. I've read definitions for these terms (Wikipedia and elsewhere), but the definitions don't make sense to me because I don't know what they are or how they fit together or which ones are optional or not optional for my project. Some of the terms on the System.Data.SQLite website (I wanted to use System.Data.SQLite for my db). I figured my first step in my project would be to get the db and queries set up and tested. Please tell me if there are other pieces of this part of the puzzle I will need to know about, too. If I can figure out what's what, I can start looking for the tutorials I need. (btw, I know I don't want to use an ORM because my app is so simple, and because I want to keep from biting off too much too soon.) Thank you very much. SQLite.NET ADO.NET ADO.NET provider ADO.NET 2.0 Provider for SQLite SQLite Entity Framework SQLite Entity Framework provider

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• Complex derived attributes in Django models

  - by rabidpebble

  What I want to do is implement submission scoring for a site with users voting on the content, much like in e.g. reddit (see the 'hot' function in http://code.reddit.com/browser/sql/functions.sql). My submission model currently keeps track of up and down vote totals. Currently, when a user votes I create and save a related Vote object and then use F() expressions to update the Submission object's voting totals. The problem is that I want to update the score for the submission at the same time, but F() expressions are limited to only simple operations (it's missing support for log(), date_part(), sign() etc.) From my limited experience with Django I can see 4 options here: extend F() somehow (haven't looked at the code yet) to support the missing SQL functions; this is my preferred option and seems to fit within the Django framework the best define a scoring function (much like reddit's 'hot' function) in my database, and have Django use the value of that function for the value of the score field; as far as I can tell, #2 is not possible wrap my two step voting process in a suitably isolated transaction so that I can calculate the voting totals in Python and then update the Submission's voting totals without fear that another vote against the submission could be added/changed in the meantime; I'm hesitant to take this route because it seems overly complex - what is a "suitably isolated transaction" in this case anyway? use raw SQL; I would prefer to avoid this entirely -- what's the point of an ORM if I have to revert to SQL for such a common use case as this! (Note that this coming from somebody who loves sprocs, but is using Django for ease of development.) Before I embark on this mission to extend F() (which I'm not sure is even possible), am I about to reinvent the wheel? Is there a more standard way to do this? It seems like such a common use case and yet in an hour of searching I have yet to find a common solution...

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• Setting attributes of a class during construction from **kwargs

  - by Carson Myers

  Python noob here, Currently I'm working with SQLAlchemy, and I have this: from __init__ import Base from sqlalchemy.schema import Column, ForeignKey from sqlalchemy.types import Integer, String from sqlalchemy.orm import relationship class User(Base): __tablename__ = "users" id = Column(Integer, primary_key=True) username = Column(String, unique=True) email = Column(String) password = Column(String) salt = Column(String) openids = relationship("OpenID", backref="users") User.__table__.create(checkfirst=True) #snip definition of OpenID class def create(**kwargs): user = User() if "username" in kwargs.keys(): user.username = kwargs['username'] if "email" in kwargs.keys(): user.username = kwargs['email'] if "password" in kwargs.keys(): user.password = kwargs['password'] return user This is in /db/users.py, so it would be used like: from db import users new_user = users.create(username="Carson", password="1234") new_user.email = "[email protected]" users.add(new_user) #this function obviously not defined yet but the code in create() is a little stupid, and I'm wondering if there's a better way to do it that doesn't require an if ladder, and that will fail if any keys are added that aren't in the User object already. Like: for attribute in kwargs.keys(): if attribute in User: user.__attribute__[attribute] = kwargs[attribute] else: raise Exception("blah") that way I could put this in its own function (unless one hopefully already exists?) So I wouldn't have to do the if ladder again and again, and so I could change the table structure without modifying this code. Any suggestions?

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• Linq 2 SQL Store inherited classes - not mapped to tables in the database

  - by user348672

  Hi. I'm trying to introduce the Linq2SQL technique into the project and have encountered the following issue: I've created ORM classes based on the Northwind database. In some other application I create several classes derived from the Linq2SQL classes. I'm able to add such a class to EntitySet but the application fails to submit changes. Is there any way around this? Sample code(MyClass is derived from the Order): DataClasses1DataContext northwind = new DataClasses1DataContext(); Product chai = northwind.Products.Single(p => p.ProductName == "Chai"); Product tofu = northwind.Products.Single(p => p.ProductName == "Tofu"); Order myOrder = new Order(); myOrder.OrderDate = DateTime.Now; myOrder.RequiredDate = DateTime.Now.AddDays(1); myOrder.Freight = 34; Order_Detail myItem1 = new Order_Detail(); myItem1.Product = chai; myItem1.Quantity = 12345; Order_Detail myItem2 = new Order_Detail(); myItem2.Product = tofu; myItem2.Quantity = 3; myOrder.Order_Details.Add(myItem1); myOrder.Order_Details.Add(myItem2); Customer myCustomer = northwind.Customers.Single(c => c.CompanyName == "B's Beverages"); MyClass newOrder = new MyClass(); newOrder.OrderDate = DateTime.Now; newOrder.RequiredDate = DateTime.Now.AddDays(31); newOrder.Freight = 35; Order_Detail myItem3 = new Order_Detail(); myItem3.Product = tofu; myItem3.Quantity = 3; newOrder.Order_Details.Add(myItem3); myCustomer.Orders.Add(myOrder); myCustomer.Orders.Add(newOrder); As I said I'm able to add the newOrder object but unable to submit into the database.

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• how to set SqlMapClient outside of spring xmls

  - by Omnipresent

  I have the following in my xml configurations. I would like to convert these to my code because I am doing some unit/integration testing outside of the container. xmls: <bean id="MyMapClient" class="org.springframework.orm.ibatis.SqlMapClientFactoryBean"> <property name="configLocation" value="classpath:sql-map-config-oracle.xml"/> <property name="dataSource" ref="IbatisDataSourceOracle"/> </bean> <bean id="IbatisDataSource" class="org.springframework.jndi.JndiObjectFactoryBean"> <property name="jndiName" value="jdbc/my/mydb"/> </bean> code I used to fetch stuff from above xmls: this.setSqlMapClient((SqlMapClient)ApplicationInitializer.getApplicationContext().getBean("MyMapClient")); my code (for unit testing purposes): SqlMapClientFactoryBean bean = new SqlMapClientFactoryBean(); UrlResource urlrc = new UrlResource("file:/data/config.xml"); bean.setConfigLocation(urlrc); DriverManagerDataSource dataSource = new DriverManagerDataSource(); dataSource.setDriverClassName("oracle.jdbc.OracleDriver"); dataSource.setUrl("jdbc:oracle:thin:@123.210.85.56:1522:ORCL"); dataSource.setUsername("dbo_mine"); dataSource.setPassword("dbo_mypwd"); bean.setDataSource(dataSource); SqlMapClient sql = (SqlMapClient) bean; //code fails here when the xml's are used then SqlMapClient is the class that sets up then how come I cant convert SqlMapClientFactoryBean to SqlMapClient

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• Modeling a Generic Relationship (expressed in C#) in a Database

  - by StevenH

  This is most likely one for all you sexy DBAs out there: How would I effieciently model a relational database whereby I have a field in an "Event" table which defines a "SportType"? This "SportsType" field can hold a link to different sports tables E.g. "FootballEvent", "RubgyEvent", "CricketEvent" and "F1 Event". Each of these Sports tables have different fields specific to that sport. My goal is to be able to genericly add sports types in the future as required, yet hold sport specific event data (fields) as part of my Event Entity. Is it possible to use an ORM such as NHibernate / Entity framework / DataObjects.NET which would reflect such a relationship? I have thrown together a quick C# example to express my intent at a higher level: public class Event<T> where T : new() { public T Fields { get; set; } public Event() { EventType = new T(); } } public class FootballEvent { public Team CompetitorA { get; set; } public Team CompetitorB { get; set; } } public class TennisEvent { public Player CompetitorA { get; set; } public Player CompetitorB { get; set; } } public class F1RacingEvent { public List<Player> Drivers { get; set; } public List<Team> Teams { get; set; } } public class Team { public IEnumerable<Player> Squad { get; set; } } public class Player { public string Name { get; set; } public DateTime DOB { get; set;} }

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• Creating self-referential tables with polymorphism in SQLALchemy

  - by Jace

  I'm trying to create a db structure in which I have many types of content entities, of which one, a Comment, can be attached to any other. Consider the following: from datetime import datetime from sqlalchemy import create_engine from sqlalchemy import Column, ForeignKey from sqlalchemy import Unicode, Integer, DateTime from sqlalchemy.orm import relation, backref from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Entity(Base): __tablename__ = 'entities' id = Column(Integer, primary_key=True) created_at = Column(DateTime, default=datetime.utcnow, nullable=False) edited_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False) type = Column(Unicode(20), nullable=False) __mapper_args__ = {'polymorphic_on': type} # <...insert some models based on Entity...> class Comment(Entity): __tablename__ = 'comments' __mapper_args__ = {'polymorphic_identity': u'comment'} id = Column(None, ForeignKey('entities.id'), primary_key=True) _idref = relation(Entity, foreign_keys=id, primaryjoin=id == Entity.id) attached_to_id = Column(Integer, ForeignKey('entities.id'), nullable=False) #attached_to = relation(Entity, remote_side=[Entity.id]) attached_to = relation(Entity, foreign_keys=attached_to_id, primaryjoin=attached_to_id == Entity.id, backref=backref('comments', cascade="all, delete-orphan")) text = Column(Unicode(255), nullable=False) engine = create_engine('sqlite://', echo=True) Base.metadata.bind = engine Base.metadata.create_all(engine) This seems about right, except SQLAlchemy doesn't like having two foreign keys pointing to the same parent. It says ArgumentError: Can't determine join between 'entities' and 'comments'; tables have more than one foreign key constraint relationship between them. Please specify the 'onclause' of this join explicitly. How do I specify onclause?

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• Login with Kohana auth module - what am I doing wrong?

  - by keithjgrant

  I'm trying to login with the following controller action, but my login attempt keeps failing (I get the 'invalid username and/or password' message). What am I doing wrong? I also tried the other method given in the examples in the auth documentation, Auth::instance()->login($user->username, $form->password);, but I get the same result. Kohana version is 2.3.4. public function login() { $auth = Auth::instance(); if ($auth->logged_in()) { url::redirect('/account/summary'); } $view = new View('login'); $view->username = ''; $view->password = ''; $post = $this->input->post(); $form = new Validation($post); $form->pre_filter('trim', 'username') ->pre_filter('trim', 'password') ->add_rules('username', 'required'); $failed = false; if (!empty($post) && $form->validate()) { $login = array( 'username' => $form->username, 'password' => $form->password, ); if (ORM::factory('user')->login($login)) { url::redirect('/accounts/summary'); } else { $view->username = $form->username; $view->message = in_array('required', $form->errors()) ? 'Username and password are required.' : 'Invalid username and/or password.'; } } $view->render(true); }

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• What java web application framework to use?

  - by frohiky

  One of the main products of my company is an Oracle Forms (and Reports) based application, that "needs" to be re-written in another technology. Why? Users want a more rich interface experience, and we want, preferably, to reduce costs with an open source application server. For this (HUGE) project, we intend to use a java web application framework, keep these points in mind: We have: hundreds of tables on our database (the ORM must be as flexible as possible); some logic which is (and will still be) based on PL/SQL procedures/functions/packages; a lot of CRUDs (the application itself is of an considerable size); a demand to work with/generate documents and workflows; an intranet based user environment; We want: to offer a RIA interface experience; use (if possible) an open source app server; a rapid (as possible) development framework; a somewhat mature framework with a "wise" roadmap (and a considerable community support); a MVC approach combined with JS or GWT widgets (e.g. Vaadin or SmartGWT); Well, in the past weeks I've read a lot of posts, Q&As on stackoverflow, and much more: Wicket, JSF, Tapestry, Grails, GWT, Struts2, Play, Spring, Seam, Echo, .... the list goes on! I've even researched about Alfresco..! The obvious question: Which one to use? At this time, any insight, recommendation, shared experience, advice will be more then welcome!

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• How can I solve this NHibernate Querying in an n-tier architecture?

  - by Tyler Wright

  I've hit a wall with trying to decouple NHibernate from my services layer. My architecture looks like this: web - services - repositories - nhibernate - db I want to be able to spawn nhibernate queries from my services layer and possibly my web layer without those layers knowing what orm they are dealing with. Currently, I have a find method on all of my repositories that takes in IList<object[]> criteria. This allows me to pass in a list of criteria such as new object() {"Username", usernameVariable}; from anywhere in my architecture. NHibernate takes this in and creates a new Criteria object and adds in the passed in criteria. This works fine for basic searches from my service layer, but I would like to have the ability to pass in a query object that my repository translates into an NHibernate Criteria. Really, I would love to implement something like what is described in this question: Is there value in abstracting nhibernate criterion. I'm just not finding any good resources on how to implement something like this. Is the method described in that question a good approach? If so, could anyone provide some pointers on how to implement such a solution?

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• What is the most efficient/elegant way to parse a flat table into a tree?

  - by Tomalak

  Assume you have a flat table that stores an ordered tree hierarchy: Id Name ParentId Order 1 'Node 1' 0 10 2 'Node 1.1' 1 10 3 'Node 2' 0 20 4 'Node 1.1.1' 2 10 5 'Node 2.1' 3 10 6 'Node 1.2' 1 20 What minimalistic approach would you use to output that to HTML (or text, for that matter) as a correctly ordered, correctly intended tree? Assume further you only have basic data structures (arrays and hashmaps), no fancy objects with parent/children references, no ORM, no framework, just your two hands. The table is represented as a result set, which can be accessed randomly. Pseudo code or plain English is okay, this is purely a conceptional question. Bonus question: Is there a fundamentally better way to store a tree structure like this in a RDBMS? EDITS AND ADDITIONS To answer one commenter's (Mark Bessey's) question: A root node is not necessary, because it is never going to be displayed anyway. ParentId = 0 is the convention to express "these are top level". The Order column defines how nodes with the same parent are going to be sorted. The "result set" I spoke of can be pictured as an array of hashmaps (to stay in that terminology). For my example was meant to be already there. Some answers go the extra mile and construct it first, but thats okay. The tree can be arbitrarily deep. Each node can have N children. I did not exactly have a "millions of entries" tree in mind, though. Don't mistake my choice of node naming ('Node 1.1.1') for something to rely on. The nodes could equally well be called 'Frank' or 'Bob', no naming structure is implied, this was merely to make it readable. I have posted my own solution so you guys can pull it to pieces.

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• ASP.NET application - Error when trying to connect to a SQL Server 2008 instance

  - by Pablo Dami

  Hi everyone! Despite that I’m a regular reader of this great forum, this is my first post on it. I believe that this community can help me with the following problem that I have. I’m trying to publish an ASP.NET website over an IIS 6.0 (Windows 2003 Server), and I have some troubles trying to connect to the database. Curiously, I have installed another ASP.NET website into the same IIS 6.0 with the same properties and security parameters and can connect without problems with the same database. The application that works fine is almost the same that the one that can’t connect with SQL Server (actually is the same but with several modifications). I’ll enumarate some information related to the problem: S.O: Windows 2003 Server SQL Server Engine: SQL Server 2008 SQL Server accept remote connections? Yes. ASP.NET version: 2.0.50727 The connections via TCP/IP are enabled to the SQL Server instance? Yes. The corresponding user that I have in the connection string, actually exists into the database with the “owner” role? Yes. ORM Tool used: nHibernate I get the following error when I try to run the aplication into the browser: Error while establishing a connection to the server. When connecting to SQL Server 2005, this failure may occur because the default settings SQL Server does not allow remote connections. (provider: Shared Memory Provider, error: 40 - Could not open a connection to SQL Server) In order to isolate the problem, I made some test. For example, using the web app that works fine I can connect without any problema with the database that uses the web app that can’t. With this evidence I concluded that the problem is within the web app and not into the SQL Server instance. I also google it my problem but sadly I can't find nothing usefull to solve it. If someone can help me I’ll appreciate that. Thank you so much for your time!

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• Importing hibernate configuration file into Spring applicationContext

  - by Himanshu Yadav

  I am trying to integrate Hibernate 3 with Spring 3.1.0. The problem is that application is not able to find mapping file which declared in hibernate.cfg.xml file. Initially hibernate configuration has datasource configuration, hibernate properties and mapping hbm.xml files. Master hibernate.cfg.xml file exist in src folder. this is how Master file looks: <hibernate-configuration> <session-factory> <!-- Mappings --> <mapping resource="com/test/class1.hbm.xml"/> <mapping resource="/class2.hbm.xml"/> <mapping resource="com/test/class3.hbm.xml"/> <mapping resource="com/test/class4.hbm.xml"/> <mapping resource="com/test/class5.hbm.xml"/> Spring config is: <bean id="sessionFactoryEditSolution" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean"> <property name="dataSource" ref="data1"/> <property name="mappingResources"> <list> <value>/master.hibernate.cfg.xml</value> </list> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect">org.hibernate.dialect.SQLServerDialect</prop> <prop key="hibernate.cache.use_second_level_cache">true</prop> </props> </property> </bean>

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• Getting the name of a child class in the parent class (static context)

  - by Benoit Myard

  Hi everybody, I'm building an ORM library with reuse and simplicity in mind; everything goes fine except that I got stuck by a stupid inheritance limitation. Please consider the code below: class BaseModel { /* * Return an instance of a Model from the database. */ static public function get (/* varargs */) { // 1. Notice we want an instance of User $class = get_class(parent); // value: bool(false) $class = get_class(self); // value: bool(false) $class = get_class(); // value: string(9) "BaseModel" $class = __CLASS__; // value: string(9) "BaseModel" // 2. Query the database with id $row = get_row_from_db_as_array(func_get_args()); // 3. Return the filled instance $obj = new $class(); $obj->data = $row; return $obj; } } class User extends BaseModel { protected $table = 'users'; protected $fields = array('id', 'name'); protected $primary_keys = array('id'); } class Section extends BaseModel { // [...] } $my_user = User::get(3); $my_user->name = 'Jean'; $other_user = User::get(24); $other_user->name = 'Paul'; $my_user->save(); $other_user->save(); $my_section = Section::get('apropos'); $my_section->delete(); Obviously, this is not the behavior I was expecting (although the actual behavior also makes sense).. So my question is if you guys know of a mean to get, in the parent class, the name of child class.

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• Advanced All In One .NET Framework

  - by alfredo dobrekk

  Hi, i m starting a new project that would basically take input from user and save them to database among about 30 screens, and i would like to find a framework that will allow the maximum number of these features out of the box : .net c#. windows form. unit testing continuous integration screens with lists, combo boxes, text boxes, add, delete, save, cancel that are easy to update when you add a property to your classes or a field to your database. auto completion on controls to help user find its way use of an orm like nhibernate easy multithreading and display of wait screens for user easy undo redo tabbed child windows search forms ability to grant access to some functionnalities according to user profiles mvp/mvvm or whatever design patterns either some code generation from database to c# classe or generation of database schema from c# classes some kind of database versioning / upgrade to easily update database when i release patches to application once in production automatic control resizing code metrics analysis some code generator i can use against my entities that would generate some rough form i can rearrange after code documentation generator ... Any ideas ? I know its lot but i really would like to use existing code to build upon so i can focus on business rules. Could splitting the requirements on 3 or 4 existing open source framework be possible ? Do u have any suggestion to add to the list before starting ? What open source tools would u use to achieve these ?

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• Trying to use a grails domain class from the shell

  - by ?????

  I'm new to Grails. I'm trying to experiement with my grails domains from the shell, and I can't get it to work. These domains work fine from the scaffold code when I run the app. Given this domain class class IncomingCall { String caller_id Date call_time int call_length static constraints = { } } I try to create an "IncomingCall" and save it from the shell. No matter what I do, I always get "Null"; the object isn't created. And if I try to create the object and then do a save, I get the "No hibernate session bound to thread" error (see below). groovy:000> new IncomingCall(caller_id:'555-1212', call_time: new Date(), call_length:10).save() ERROR org.hibernate.HibernateException: No Hibernate Session bound to thread, and configuration does not allow creation of non-transactional one here at org.springframework.orm.hibernate3.SpringSessionContext.currentSession (SpringSessionContext.java:63) at org.hibernate.impl.SessionFactoryImpl.getCurrentSession (SessionFactoryImpl.java:574) at groovysh_evaluate.run (groovysh_evaluate:3) ... groovy:000> How can I make this work from the shell?

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• LINQ to SQL - How to efficiently do either an AND or an OR search for multiple criteria

  - by Dan Diplo

  I have an ASP.NET MVC site (which uses Linq To Sql for the ORM) and a situation where a client wants a search facility against a bespoke database whereby they can choose to either do an 'AND' search (all criteria match) or an 'OR' search (any criteria match). The query is quite complex and long and I want to know if there is a simple way I can make it do both without having to have create and maintain two different versions of the query. For instance, the current 'AND' search looks something like this (but this is a much simplified version): private IQueryable<SampleListDto> GetSampleSearchQuery(SamplesCriteria criteria) { var results = from r in Table where (r.Id == criteria.SampleId) && (r.Status.SampleStatusId == criteria.SampleStatusId) && (r.Job.JobNumber.StartsWith(criteria.JobNumber)) && (r.Description.Contains(criteria.Description)) select r; } I could copy this and replace the && with || operators to get the 'OR' version, but feel there must be a better way of achieving this. Does anybody have any suggestions how this can be achieved in an efficient and flexible way that is easy to maintain? Thanks.

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• How can I get the user object from a service in Symfony2

  - by pogo

  My site is using a third party service for authentication as well as other bits of functionality so I have setup a service that does all the API calls for me and it's this service that I need to be able to access the user object. I've tried injecting the security.context service into my API service but I get a ServiceCircularReferenceException because my user authentication provider references the API service (it has to in order to authenticate the user). So I get a chain of security.context -> authentication provider -> user provider -> API service -> security.context I'm struggling to this of another way of getting the user object and I can't see any obvious way of splitting up this chain. My configs are all defined in config.yml, here are the relevant bits myapp.database: class: Pogo\MyAppBundle\Service\DatabaseService arguments: siteid: %siteid% entityManager: "@doctrine.orm.entity_manager" myapp.apiservice: class: Pogo\MyAppBundle\Service\TicketingService arguments: entityManager: "@myapp.database" myapp.user_provider: class: Pogo\MyAppBundle\Service\APIUserProvider arguments: entityManager: "@myapp.database" ticketingAdapter: "@myapp.apiservice" securityContext: "@security.context" myapp.authenticationprovider: class: Pogo\MyAppBundle\Service\APIAuthenticationProvider arguments: userChecker: "@security.user_checker" encoderFactory: "@security.encoder_factory" userProvider: "@myapp.user_provider" myapp.user_provider is the service that I've defined as my user provider service in security.yml which I presume is how it's being referenced by security.context

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• Dynamic Method Creation

  - by TJMonk15

  So, I have been trying to research this all morning, and have had no luck. I am trying to find a way to dynamically create a method/delegate/lambda that returns a new instance of a certain class (not known until runtime) that inherits from a certain base class. I can guarantee the following about the unknown/dynamic class It will always inherit from one known Class (Row) It will have atleast 2 constructors (one accepting a long, and one accepting an IDataRecord) I plan on doign the following: Finding all classes that have a certain attribute on them Creating a delegate/method/lambda/whatever that creates a new instance of the class Storing the delegate/whatever along with some properties in a struct/class Insert the struct into a hashtable When needed, pull the info out of the hashtable and calling the delegate/whatever to get a new instance of the class and returning it/adding it to a list/etc. I need help only with #2 above!!! I have no idea where to start. I really just need some reference material to get me started, or some keywords to throw into google. This is for a compact/simple to use ORM for our office here. I understand the above is not simple, but once working, should make maintaining the code incredibly simple. Please let me know if you need any more info! And thanks in advance! :)

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• php paging class

  - by Stick it to THE MAN

  Can anyone recommend a good PHP paging class? I have searched google, but have not seen anything that matches my requirements. Rather than "rolling my own" (and almost surely reinventing the wheel), I decided to check in here first. First some background: I am developing a website using Symfony 1.3.2 with Propel ORM on Ubuntu 9.10. I am currently using the Propel pager, which is OK, but I recently started using memcache to speed things up a little. At this point, the Propel pager is of little use, as it (AFAIK), only works with Propel objects. What I need is a class th:t meets the following requirents Has clean interface, with separation of concerns, so that the logic to retrieve records from the datasource (e.g. database) is encapsulated in a class (or at least a separate file). Can work with arrays of objects Provides pagination links, and only fetches the data required for the current page. Also, the pagination should 'split' the available page links if there are too many. For example, if there are potentially 1000 possible page links, the pages displayed should be something like FIRST 2,3 ....999 LAST Can return the number of all the records in the table being queried, so that the following links are available FIRST, LAST (this requirement is actually already covered in the previous requirement - but I just wanted to re-emphasise it). Can anyone recommend such a library, if they have used it succesfully in the past? Alternatively, someobe may have 'hacked' (e.g. derived from) the current Propel pager, to get it to do the things I listed about - please let me know.

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• Are document-oriented databases any more suitable than relational ones for persisting objects?

  - by Owen Fraser-Green

  In terms of database usage, the last decade was the age of the ORM with hundreds competing to persist our object graphs in plain old-fashioned RMDBS. Now we seem to be witnessing the coming of age of document-oriented databases. These databases are highly optimized for schema-free documents but are also very attractive for their ability to scale out and query a cluster in parallel. Document-oriented databases also hold a couple of advantages over RDBMS's for persisting data models in object-oriented designs. As the tables are schema-free, one can store objects belonging to different classes in an inheritance hierarchy side-by-side. Also, as the domain model changes, so long as the code can cope with getting back objects from an old version of the domain classes, one can avoid having to migrate the whole database at every change. On the other hand, the performance benefits of document-oriented databases mainly appear to come about when storing deeper documents. In object-oriented terms, classes which are composed of other classes, for example, a blog post and its comments. In most of the examples of this I can come up with though, such as the blog one, the gain in read access would appear to be offset by the penalty in having to write the whole blog post "document" every time a new comment is added. It looks to me as though document-oriented databases can bring significant benefits to object-oriented systems if one takes extreme care to organize the objects in deep graphs optimized for the way the data will be read and written but this means knowing the use cases up front. In the real world, we often don't know until we actually have a live implementation we can profile. So is the case of relational vs. document-oriented databases one of swings and roundabouts? I'm interested in people's opinions and advice, in particular if anyone has built any significant applications on a document-oriented database.

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• How can I make this SQL query more efficient? PHP.

  - by Alan Grant

  Hi all, I have a system whereby a user can view categories that they've subscribed to individually, and also those that are available in the region they belong in by default. So, the tables are as follows: Categories UsersCategories RegionsCategories I'm querying the db for all the categories within their region, and also all the individual categories that they've subscribed to. My query is as follows: Select * FROM (categories c) LEFT JOIN users_categories uc on uc.category_id = c.id LEFT JOIN regions_categories rc on rc.category_id = c.id WHERE (rc.region_id = ? OR uc.user_id = ?) At least I believe that's the query, I'm creating it using Cake's ORM layer, so the exact one is: $conditions = array( array( "OR" => array ( 'RegionsCategories.region_id' => $region_id, 'UsersCategories.user_id' => $user_id ) )); $this->find('all', $conditions); This turns out to be incredibly slow (sometimes around 20 seconds or so. Each table has around 5,000 rows). Is my design at fault here? How can I retrieve both the users' individual categories and those within their region all in one query without it taking ages? Thanks!

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• Django: Paginator + raw SQL query

  - by Silver Light

  Hello! I'm using Django Paginator everywhere on my website and even wrote a special template tag, to make it more convenient. But now I got to a state, where I need to make a complex custom raw SQL query, that without a LIMIT will return about 100K records. How can I use Django Pagintor with custom query? Simplified example of my problem: My model: class PersonManager(models.Manager): def complicated_list(self): from django.db import connection #Real query is much more complex cursor.execute("""SELECT * FROM `myapp_person`"""); result_list = [] for row in cursor.fetchall(): result_list.append(row[0]); return result_list class Person(models.Model): name = models.CharField(max_length=255); surname = models.CharField(max_length=255); age = models.IntegerField(); objects = PersonManager(); The way I use pagintation with Django ORM: all_objects = Person.objects.all(); paginator = Paginator(all_objects, 10); try: page = int(request.GET.get('page', '1')) except ValueError: page = 1 try: persons = paginator.page(page) except (EmptyPage, InvalidPage): persons = paginator.page(paginator.num_pages) This way, Django get very smart, and adds LIMIT to a query when executing it. But when I use custom manager: all_objects = Person.objects.complicated_list(); all data is selected, and only then python list is sliced, which is VERY slow. How can I make my custom manager behave similar like built in one?

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• table design for storing large number of rows

  - by hyperboreean

  I am trying to store in a postgresql database some unique identifiers along with the site they have been seen on. I can't really decide which of the following 3 option to choose in order to be faster and easy maintainable. The table would have to provide the following information: the unique identifier which unfortunately it's text the sites on which that unique identifier has been seen The amount of data that would have to hold is rather large: there are around 22 millions unique identifiers that I know of. So I thought about the following designs of the table: id - integer identifier - text seen_on_site - an integer, foreign key to a sites table This approach would require around 22 mil multiplied by the number of sites. id - integer identifier - text seen_on_site_1 - boolean seen_on_site_2 - boolean ............ seen_on_site_n - boolean Hopefully the number of sites won't go past 10. This would require only the number of unique identifiers that I know of, that is around 20 millions, but it would make it hard to work with it from an ORM perspective. one table that would store only unique identifiers, like in: id - integer unique_identifier - text, one table that would store only sites, like in: id - integer site - text and one many to many relation, like: id - integer, unique_id - integer (fk to the table storing identifiers) site_id - integer (fk to sites table) another approach would be to have a table that stores unique identifiers for each site So, which one seems like a better approach to take on the long run?

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