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  • many-to-many query

    - by kofto4ka
    Hello, guys! I have a problem and I dont know what is better solution. Okay, I have 2 tables: posts(id, title), posts_tags(post_id, tag_id). I have next task: must select posts with tags ids for example 4, 10 and 11. Not exactly, post could have any other tags at the same time. So, how I could do it more optimized? Creating temporary table in each query? Or may be some kind of stored procedure? In the future, user could ask script to select posts with any count of tags (it could be 1 tag only or 10 at the same time) and I must be sure that method that I will choose would be the best method for my problem. Sorry for my english, thx for attention.

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  • Which should be created first ER Diagram OR Class Diagram?

    - by isthatacode
    The very first step i created a DFD. Then i moved on to create a Class Diagram. And while doing that i felt that i should create the ER diagram first. As there were many details which could not be captured in a Class diagram. So, my question should i create ERD first OR Class Diagrams ? your valuable inputs are appreciated guys!!! thanks for reading

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  • Which system modelling notation for showing interconnections and internal logical structures?

    - by user1043838
    I am trying to model a collection of systems, their various interconnections, as well as their internal logical structures, as a message is passed through them, initiated by an actor. I have been using BPMN 2.0 notation with Yaoqiang Editor. However I'm not sure if I'm doing this right, or even using the right notation. System example Is this correct, if not, can you recommend an alternate notation or method of displaying the systems? Thanks for all suggestions

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  • Python: Recursively access dict via attributes as well as index access?

    - by Luke Stanley
    I'd like to be able to do something like this: from dotDict import dotdictify life = {'bigBang': {'stars': {'planets': [] } } } dotdictify(life) #this would be the regular way: life['bigBang']['stars']['planets'] = {'earth': {'singleCellLife': {} }} #But how can we make this work? life.bigBang.stars.planets.earth = {'singleCellLife': {} } #Also creating new child objects if none exist, using the following syntax life.bigBang.stars.planets.earth.multiCellLife = {'reptiles':{},'mammals':{}} My motivations are to improve the succinctness of the code, and if possible use similar syntax to Javascript for accessing JSON objects for efficient cross platform development.(I also use Py2JS and similar.)

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  • How to move an element in a sorted list and keep the CouchDb write "atomic"

    - by karlthorwald
    I have elements of a list in couchdb documents. Let's say these are 3 elements in 3 documents: { "id" : "783587346", "type" : "aList", "content" : "joey", "sort" : 100.0 } { "id" : "358734ff6", "type" : "aList", "content" : "jill", "sort" : 110.0 } { "id" : "abf587346", "type" : "aList", "content" : "jack", "sort" : 120.0 } A view retrieves all "aList" documents and displays them sorted by "sort". Now I want to move the elements, when I want to move "jack" to the middle, I could do this atomic in one write and change it's sort key to 105.0. The view now returns the documents in the new sort order. After a lot of sorting I could end up with sort keys like 50.99999 and 50.99998 after some years and in extreme situations run out of digits? What can you recommend, is there a better way to do this? I'd rather keep the elements in seperate documents. Different users might edit different elements in parallel (which also can get tricky). Maybe there is a much better way?

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  • Is there any reason for an object pool to not be treated as a singleton?

    - by Chris Charabaruk
    I don't necessarily mean implemented using the singleton pattern, but rather, only having and using one instance of a pool. I don't like the idea of having just one pool (or one per pooled type). However, I can't really come up with any concrete situations where there's an advantage to multiple pools for mutable types, at least not any where a single pool can function just as well. What advantages are there to having multiple pools over a singleton pool?

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  • Meaning of Primary Key to Microsoft SQL Server 2008

    - by usr
    What meaning does the concept of a primary key have to the database engine of SQL Server? I don't mean the clustered/nonclustered index created on the "ID" column, i mean the constraint object "primary key". Does it matter if it exists or not? Alternatives: alter table add primary key clustered alter table create clustered index Does it make a difference?

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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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  • How to force grails GORM to respect DB scheme ?

    - by fabien-barbier
    I have two domains : class CodeSet { String id String owner String comments String geneRLF String systemAPF static hasMany = [cartridges:Cartridge] static constraints = { id(unique:true,blank:false) } static mapping = { table 'code_set' version false columns { id column:'code_set_id', generator: 'assigned' owner column:'owner' comments column:'comments' geneRLF column:'gene_rlf' systemAPF column:'system_apf' } } and : class Cartridge { String id String code_set_id Date runDate static belongsTo = CodeSet static constraints = { id(unique:true,blank:false) } static mapping = { table 'cartridge' version false columns { id column:'cartridge_id', generator: 'assigned' code_set_id column:'code_set_id' runDate column:'run_date' } } Actually, with those models, I get tables : - code_set, - cartridge, - and table : code_set_cartridge (two fields : code_set_cartridges_id, cartridge_id) I would like to not have code_set_cartridge table, but keep relationship : code_set -- 1:n -- cartridge In other words, how can I keep association between code_set and cartridge without intermediate table ? (using code_set_id as primary key in code_set and code_set_id as foreign key in cartridge). Mapping with GORM can be done without intermediate table?

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  • Value objects in DDD - Why immutable?

    - by Hobbes
    I don't get why value objects in DDD should be immutable, nor do I see how this is easily done. (I'm focusing on C# and Entity Framework, if that matters.) For example, let's consider the classic Address value object. If you needed to change "123 Main St" to "123 Main Street", why should I need to construct a whole new object instead of saying myCustomer.Address.AddressLine1 = "123 Main Street"? (Even if Entity Framework supported structs, this would still be a problem, wouldn't it?) I understand (I think) the idea that value objects don't have an identity and are part of a domain object, but can someone explain why immutability is a Good Thing? EDIT: My final question here really should be "Can someone explain why immutability is a Good Thing as applied to Value Objects?" Sorry for the confusion! EDIT: To clairfy, I am not asking about CLR value types (vs reference types). I'm asking about the higher level DDD concept of Value Objects. For example, here is a hack-ish way to implement immutable value types for Entity Framework: http://rogeralsing.com/2009/05/21/entity-framework-4-immutable-value-objects. Basically, he just makes all setters private. Why go through the trouble of doing this?

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  • What is the basic pattern for using (N)Hibernate?

    - by Vilx-
    I'm creating a simple Windows Forms application with NHibernate and I'm a bit confused about how I'm supposed to use it. To quote the manual: ISession (NHibernate.ISession) A single-threaded, short-lived object representing a conversation between the application and the persistent store. Wraps an ADO.NET connection. Factory for ITransaction. Holds a mandatory (first-level) cache of persistent objects, used when navigating the object graph or looking up objects by identifier. Now, suppose I have the following scenario: I have a simple classifier which is a MSSQL table with two columns - ID (auto_increment) and Name (nvarchar). To edit this classifier I create a form which contains a single gridview and two buttons - OK and Cancel. The user can nearly directly edit the table in the gridview, and when he hits OK the changes he made are persisted to the DB (or if he hits cancel, nothing happens). Now, I have several questions about how to organize this: What should the lifetime of my ISession be? Should I create a single ISession for my whole application; an ISession for each of my forms (the application is single-threaded MDI); or an ISession for every DB operation/transaction? Does NHibernate offer some kind of built-in dirty tracking or must I do this myself? The manual mentions something like it here and there but does not go into details. How is this done? Is there not a huge overhead? Is it somehow tied with the cache(s) that NHibernate has? What are these caches for? Are they not specific to a single ISession? That is, if I use a seperate ISession for every transaction, won't it break the dirty tracking? How does the built-in dirty tracking detect deleted objects?

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  • Where should Nhibernate IPostInsertEventListener go in the 3 tier architecture

    - by Quintin Par
    I have a IPostInsertEventListener implementation like public class NHibernateEventListener : IPostInsertEventListener, IPostUpdateEventListener which catches some entity inserts and does an additional insert to another table for ETL. Essentially it requires references to the Nhibernate, Domain entity and Repository<> Now where do I go about adding this class? If I add it to ApplicationServices I’ll end up referencing Nhibernate at that layer. If I add this to the Data layer, I’ll have to reference Domain (circular). How do I go implementing this class with S#arp principles? Any thoughts?

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  • Decorator pattern in C++

    - by AlgoMan
    Can someone give me an example of Decorator pattern in C++ ? I have come across the Java version of it. But C++ i have found it difficult to understand the examples that are given.

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  • Understanding colors

    - by Ankur Gupta
    Hello everyone, Kindly point towards theory/material to read for understanding colors and what makes a good color combinations. Mind it that I am not interested in say "Color combinations for web application" etc. More of the lines of say "Colors and humans". Material free to read is what i am looking for. Thanks

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  • Why isn't JML implemented as Annotations in Java?

    - by devoured elysium
    Contrary to Code Contracts in C#, in JML Code Contracts are just text that's used in the form of comments in the header of a method. Wouldn't it be better to have them exposed as Annotations, then? That way even when compiling the information would persist on the .class's metadata, contrary to comments, that get erased. Am I missing something? Thanks

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  • SO what RDF database do i use for product attribute situation initially i thought about using EAV?

    - by keisimone
    Hi, i have a similar issue as espoused in http://stackoverflow.com/questions/695752/product-table-many-kinds-of-product-each-product-has-many-parameters i am convinced to use RDF now. only because of one of the comments made by Bill Karwin in the answer to the above issue but i already have a database in mysql and the code is in php. 1) So what RDF database should I use? 2) do i combine the approach? meaning i have a class table inheritance in the mysql database and just the weird product attributes in the RDF? I dont think i should move everything to a RDF database since it is only just products and the wide array of possible attributes and value that is giving me the problem. 3) what php resources, articles should i look at that will help me better in the creation of this? 4) more articles or resources that helps me to better understand RDF in the context of the above challenge of building something that will better hold all sorts of products' attributes and values will be greatly appreciated. i tend to work better when i have a conceptual understanding of what is going on. Do bear in mind i am a complete novice to this and my knowledge of programming and database is average at best.

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  • Ways to clean up java applications.

    - by Begui
    How do java people handle clean up of their apps when the program receives a kill signal? For instance, there is an application i connect to which wants any third party app ( my app) to send a "finish" command. What is the best say to send that "finish" command if one does a kill -9 on me.

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  • Text -> Diagram Tool

    - by Jon
    I'm looking for an diagram tool for producing diagrams from text. I only really need sequence and state type diagrams for now, but I'm curious as to what people would recommend? I need something which is standalone, not a web based tool that works on Linux, OSX and Windows.

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  • Bad method names and what it says about code structure.

    - by maxfridbe
    (Apologies in advance if this is a re-post but I didn't find similar posts) What bad method name patterns have you seen in code and what did it tell you about the code. For instance, I keep seeing: public void preform___X___IfNecessary(...); I believe that this is bad because the operation X has an inversion of conditions. Note that this is a public method because classes methods might legitimately require private helpers like this

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  • doubleton pattern in C++

    - by benjamin button
    I am aware of the singleton pattern in C++. but what is the logic to get two instances of the object? is there any such pattern where we could easily get 2 pattern. for the logic i could think of is that i can change the singleton pattern itself to have two objects created inside the class.this works. but if the requirement grows like if i need only 3 or only 4 what is the deswign pattern that i could think of to qualify such requirement?

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  • If you are forced to use an Anemic domain model, where do you put your business logic and calculated

    - by Jess
    Our current O/RM tool does not really allow for rich domain models, so we are forced to utilize anemic (DTO) entities everywhere. This has worked fine, but I continue to struggle with where to put basic object-based business logic and calculated fields. Current layers: Presentation Service Repository Data/Entity Our repository layer has most of the basic fetch/validate/save logic, although the service layer does a lot of the more complex validation & saving (since save operations also do logging, checking of permissions, etc). The problem is where to put code like this: Decimal CalculateTotal(LineItemEntity li) { return li.Quantity * li.Price; } or Decimal CalculateOrderTotal(OrderEntity order) { Decimal orderTotal = 0; foreach (LineItemEntity li in order.LineItems) { orderTotal += CalculateTotal(li); } return orderTotal; } Any thoughts?

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