What's the best way to determine whether a polymorphic join table is appropriate

I'm trying to figure out whether I should make a polymorphic join table for a many to many relationship or whether I should make multiple join tables. For things like comments, I always use a polymorphic join table. For relationships between users, like following on Twitter, I don't use polymorphic join tables. This is just out of habit.

Polymorphic models like rails in Django? [closed]

rails models by declare :polymorphic => true i could using that as Polymorphic model.. But how can i create polymorphic model in Django I know it's not just simple like doing in rails but i need some introduction for doing this in Django...

Examples and advices on combining a Polymorphic Association and a Single Table Inheritance

I am using Ruby on Rails 3 and I would like to know a real world example (or more) and some advice on when I should\can\must use the combination of a Polymorphic Association and a Single Table Inheritance as implemented here at the Polymorphic Association paragraph...

Routing Polymorphic Requests Rails

In rails 3, I have several polymorphic models such as Image and Comment , so my question is, When someone makes a request to Create/Update/Destroy a polymorphic object, should the request go to a single controller for the polymorphic object CommentController , or should the request be routed to the controller of the polymorphic accessor...

problem about tables join order

hi，everybody I have a when I tuning a query. the Sql is something like this : Code: select XXXXX FROM T1 LEFT JOIN T2 ON T1.C1 =T2.C1 INNER JOIN T3 ON T1.C2 = T3.C2 INNER JOIN T4 ON T3.C1= T4.C1 WHERE T4.C2 = 'xxxxxx'; The optimizer chose a bad join order for this query: T4 cross join T1 and then left join T2 and then inner jo...

Does the compiler optimize non-polymorphic calls to virtual methods?

Does the compiler optimize/inline non-polymorphic calls to virtual methods? I mean when the call is in a non-polymorphic context so everything is known at compile time?...

Should we use the abstracted rails polymorphic migration syntax?

There are two ways to write a polymorphic migration in Rails. Generally, I've done this: class CreateFeatures < ActiveRecord::Migration def change create_table :features do |t| t.integer :featureable_id t.string :featurable_type t.timestamps end end However, we can also do this: class CreateFeatures <...

How to handle bi-directional references with polymorphic types and JSON?

Summary: Is there any way for Jackson to handle bidirectional references with polymorphic types where @JsonTypeInfo is also used? A note at the bottom of this page states no but it was written in 2010 and applied to Jackson v1.6.0 so I'm hoping maybe something has changed or someone can suggest an alternative approach Background: I'm ge...

Rails - has many polymorphic tagging not working correctly

I have two tables for tagging so that I can attach tags to any models, it works likes so… There's a tagged item join table which has a tag_id column and then two other columns for polymorphism: taggable_type and taggable_id… class TaggedItem < ActiveRecord::Base attr_accessible :taggable_id, :taggable_type, :tag_id belongs_to :taggable,...

playframework polymorphic associations workflow

I need help with making one model belong to any other model, polymorphic way? As an example I'd like to use Comment model, which can belong to user, post and some other entity?...

More than 2 tables JOIN in LINQ, scope issue

I am trying to join 3 table in LINQ. var fromCities = from c in cityRepository.Cities join r in routeRepository.Routes on c.Id equals r.FromCityId join cr in rentDetailRepository.CarRentDetails on cr.CityId equals c.Id select c; I am getting that cr and c do not exist in the second join statement? Could somebody help?...

Polymorphic has_many: through in rails

I have a tags model that I'd like to be polymorphic, but I don't want five records for a tag of "video" for example, I want to create the tag once and be able to use it on a variety of models. I've ready some of the questions here about doing that, but I'm not quite getting how to make it work. So I've got: class Tag < ActiveRecord::Ba...

Rails 3: Devise user with Polymorphic association for different user profiles

I have a Rails app. I installed Devise. I want to have a polymorphic association between the User model and the different profiles, for example: Student and Mentor. This is what I'm trying to do: have a student registration page with the regular devise fields such as: email password password_confirmation . But I also want to have fields s...

Devise user with Polymorphic association for different user profiles

I have a Rails app. I installed Devise. I want to have a polymorphic association between the User model and the different profiles, for example: Student and Mentor. This is what I'm trying to do: have a student registration page with the regular devise fields such as: email password password_confirmation . But I also want to have fields s...

Model an undirected graph in Rails?

Importing the language of graph databases , understand nodes represented by circles edges represented by arrows ), and properties metadata of nodes / edges The graphic (courtesy of wikipedia) describes a directed graph What's the best way to model an undirected graph in Rails? That is to say, a graph where all edges are reciprocal ( as i...

polymorphic relationships and interfaces/abstract classes/protocols

I have a polymorphic model Comments that I associate with almost every other model. I have comments index page where I use the title of the model, which I call commentable What is the best way to ensure that the commentable model has a method or attribute called :title In Objective-C I would define a protocol and in other languages I wo...

FULL OUTER JOIN in oracle

I just noticed FULL OUTER JOIN is not working in Oracle Other queries work fine but when I fire the query with Full outer join, it takes time and gets disconnected throwing the error. ORA-03113: end-of-file on communication channel RIGHT OUTER JOIN and LEFT OUTER JOIN works fine. What can be alternative for the query below where I am u...

Determine min and max in gnuplot

I am new to gnuplot and i am trying to determine the mina nd max from a datafile and afterwards plot the data So far I have managed to determine the min and max like this: # Define two helper functions ismin(x) = (xmax)?max=x:0 # Initialise the 'global' vars max=-1e38 min=1e38 plot "Data.txt" u 0:(ismin($3)*ismax($3)) The problem is that...

All Forms/Types of Polymorphism in Java [closed]

I wanted to find out a list of all forms/types of Polymorphism supported in Java but not able to find one with satisfaction because various posts/articles talks about some forms while ignores others. By the word supported I mean Java internally uses or Java allows the programmers to implement. The following list is a compilation using goo...

How can I define a polymorphic relation between models in Django?

I am working on a Django application which contains an Offer model. An Offer instance contains the pricing conditions and points to a product definition. The product model is actually a hierarchy (I have a Television model, a Camcorder model, etc.). So I would like the Offer model to contain a polymorphic (or "generic") association to poi...

How to determine if form is docked?

How to determine in C++ Builder XE, if window is currently docked? All windows in my application are derived from base class TForm. How to catch change from docked to undocked state and vice versa?...

iOS determine if VoiceOver is still talking

Is there a way to determine whether VoiceOver is currently announcing and when it stops. I've tried UIAccessibilityVoiceOverStatusChanged but my understanding is that this is only if you switch VoiceOver on or off. Any help would be greatly appreciated. thanks.

Profiling the cost of polymorphism?

I have a codebase that is "needlessly" polymorphic in that almost every function is polymorphic in some way (why not, when you can?), but the end program uses functions with only a handful of concrete types. I've started spending some time throwing in SPECIALIZE INLINABLE pragmas to try to bring down the performance cost of all this poly...

how to determine which dataset is being used for a specific variable?

i would like to know how can i determine whether [FirstName] on the report is being pulled from dataset1 or dataset2???...

How to determine in .NET if a file is UCS-2 vs. UTF-16

I have flat files that I can load just fine in .NET in UTF-16, even though they are technically UCS2-LE (w/o BOM), and I understand this is because UCS-2 is an older standard that UTF-16 supercedes. However, what I'm interested in is being able to determine if a file actually is UCS-2. I know that this means I'd be guessing. I have tried...

boost serialization polymorphic issues

Boost serialization of polymorphic classes seems not working ( 1.40+ boost), e.g. with the following code, I believe I followed the rule: of exporting the class and I tried on both gcc4.4 (ubuntu) and windows VS2010(with boost 1.48): in following program, I expect both 10 and 100 are printed, but it only print 10, that means it only seria...

Rails upload form with carrierwave and polymorphic associations

I'm trying to wrap my head around using polymorphic associations to make file management less repetitive in a simple rails app. I'm using carrierwave to handle the file uploading. Here's what I have so far: app/uploaders/file_uploader.rb class FileUploader < CarrierWave::Uploader::Base def store_dir "uploads/#{model.class.to_s.underscor...

Log4J - determine if logger cannot write to file system

I am trying to use Log4J in my application, but my problem is that the machine where I want to run this app has not given me write permissions to the local drive. But Log4J is not throwing any errors, it simply skips the logging. So what I want to do is write some code in which if Log4J cannot write to the local file system it will return...

HQL left join of un-related entities

I have 2 entities, . They are related but I do not want to add the relationship mapping to the beans. How can we use left outer join between using HQL or criteria There are some workarounds available for this, Use Native SQL as told Add a relationship and use select a from A a left join a.b We can do a inner join in the HQL as select *...

Doctrine DQL: erroneous sql generation (?)

I'm haveing big troubles while developing a quietly advanced DQL query for a tiny DMS: The schema: DmsObject is a superclass for which two subclasses exist (document and folder) UserRights and GroupRight (which are associative entities in the db, pointing respectively to user and group tables). User and Group represent (obvious) the dms "...

Comment on Deep link ratio: what makes a backlink profile look natural? by The Marketing View

Try analytic s and determine what ratio your competitors are using to determine best practice ratio usage, based on the 10 ten listed on Google pages. This will take out the guess work.

Why and when a LEFT JOIN with condition in WHERE clause is not equivalent to the same LEFT JOIN in ON?

I'm experiencing a very confusing situation that makes me question all my understanding of joins in SQL Server. SELECT t1.f2 FROM t1 LEFT JOIN t2 ON t1.f1 = t2.f1 AND cond2 AND t2.f3 > something Does not give the same results as : SELECT t1.f2 FROM t1 LEFT JOIN t2 ON t1.f1 = t2.f1 AND cond2 WHERE t2.f3 > something Can please someone help...

EntityFramework include vs join performance

I'd like to know, when using entity framework, which one yields better performance? I've read that if you have foreign relationships between your entites, it's preferred to use include over join. If I'm just retrieving 1 row with records from 2 different entites (with foreign key relationship), does it make a difference if I were to use i...

Polymorphic Enums

Polymorphic Enums? In C++, we often use polymorphism to allow old code to handle new code--for instance, as long as we subclass the interface expected by a function, we can pass in the new class and expect it to work correctly with the code that was written before the new class ever existed. Unfortunately, with enums, you can't re...

Mark C.'s Review of Zeolla Plumbing & Heating - Stoughton (5/5) on Yelp

Doug came over to do an estimate for a pipe liner for my cracked sewer pipe His camera work helped determine the cause of my break. He saved me thousands of dollars by helping to determine that the…...

Is there anything composition cannot accomplish that inheritance can?

Composition and inheritance. I am aware that they are both tools to be chosen when appropriate, and context is very important in choosing between composition and inheritance. However, the discussion about the appropriate context for each is usually a little fuzzy; this has me beginning to consider just how distinctly inheritance and polym...

How to determine in a Custom Resolver if I am publishing or unpublishing? Tridion 2009 SP1

I'm trying to capture when a component is unpublished. I try some approaches but I don't have the result that I want. My attempts are: In Event System. But this not works because there are a known bug in Windows about MSXML and COM+. I try to build my own IResolver but there I cannot determine if it's a publishing or unpublishing action.

GWT ListEditor with polymorphic types - impossible to update

My problem is almost the same as this one : ListEditor with polymorphic types Thomas had a good answer, but it is not enough for me. I want to display list of objects that could be differents, so each editor could be displayed differently. It almost work, except that I could not find the issue : it is impossible to get the current value a...

Вычисление функции через потоки - C# для начинающих

Добрый вечер, есть функция: Код: A = (B*MX)(MO(MT*MK)) И номера потоков, в которых задаются значения векторов и матриц Цитата: * B, A, MO = 1 * MX, MT = 3 * MK = 6 * N = 4000 - размер векторов и матриц Код: class Program static void Main(string[] args) Console.WriteLine("Start Program"); Data data = new Data(); Thread T1 = new Th...

Не получается составить LEFT JOIN - MS Access

Всем доброго времени суток, пожалуйста, помогите составить SQL запрос с LEFT JOIN в accesse. Вот что я написал: Код: SELECT listorder.*, customers.name, group_brend.name_group, car.model FROM listorder LEFT JOIN customers ON (listorder.id_client=customers.id_client ) LEFT JOIN group_brend ON (listorder.id_brend=group_brend.id_group ) LEFT J...