mysql polymorphic associations

Browse other questions tagged mysql join foreign-key polymorphic-associations cascade or ask your own question. MySQL DROP all tables, ignoring foreign keys. Wir hätten in diesem Beispiel ja auch ein Model CarTag und BikeTag definieren können, aber da Tag für beide gleich ist, macht hier eine polymorphic association mehr Sinn. Sign in to view. This can be implemented with Any relationship. Or in other words, relies on the "magic" of Eloquent. To learn more, see our tips on writing great answers. Is there such thing as reasonable expectation for delivery time? Skip to content. A polymorphic associationconsists on two (or more) associations happening with the same foreign key. For example, consider the BillingInfo property of User in the following domain model. Eloquent overhead. Your problem is that this won't let you use declarative referential integrity (foreign key constraints). The way to solve this is to make sure that the objects that can attract comments and compliments are all logical sub-types of one supertype. By using our site, you acknowledge that you have read and understand our Cookie Policy, Privacy Policy, and our Terms of Service. I will be happy to be mistaken on this one. From a physical implementation perspective, the most important thing is that your various things of interest all share a common primary key domain. I am trying to perform a join with dynamic table names using polymorphic association. For example, consider the models Image, Video and Comment. The reasons I believe there will be a noticeable performance hit are: I generally don't like the idea of coupling the table name or model directly with the record table. Naive Trees 4 Monday, April 20, 2009 4 Metadata Tribbles I want these things off the ship. 4.2.2.2 :autosave. Real life examples of malware propagated by SIM cards? 4.2.2.2 :autosave. where source_type is a user, place, or event, Notification (id, recipient, sender, activity_type, object_type, object_id, etc...) The "polymorphic association", on the other hand, while it bears some resemblance to the regular polymorphic union of a class hierarchy, its not really the same since you're only dealing with a particular association to a single target class from any number of source classes, source classes which don't have anything else to do with each other; i.e. Hanging water bags for bathing without tree damage. Making statements based on opinion; back them up with references or personal experience. If you set the :autosave option to true, Rails will save any loaded association members and destroy members that are marked for destruction whenever you save the parent object. Plus I'm thinking it would fit into my object models in Code Igniter as well. Copy link Quote reply Author cusspvz commented Jan 28, 2014. How to truncate a foreign key constrained table? Polymorphic Associations; Concept; Configuring a One-to-Many polymorphic association; Polymorphic lazy loading; Polymorphic eager loading; Caution - possibly invalid eager/lazy loading! Also, if you know that the column will always have a value, make it not null, as searching on indexes of nullable columns in some databases (like MySQL) is slower then searching on not-null column indexes. User named Joe created comment "very nice" on photo number 56. Viewed 2k times 5. What you are suggesting does not address the OP's aparent concern for table sprawl, nor his desire for using DRI. By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. Architecture, C#, SQL. Possible to do a MySQL foreign key to one of two possible tables? GitHub Gist: instantly share code, notes, and snippets. Furthermore, a system that requires a three table join in every case is not going to be as efficient as a system (as I suggested) that can often get away with two table joins. Agreeing with Marius on this. Possible to do a MySQL foreign key to one of two possible tables? It references one particular BillingDetail object, which at runtime can be any concrete instance of that class. In our solution, there can be many modules and users can create new modules. With polymorphic associations, a model can belong to more than one other model, on a single association. Why are the edges of the shadow so bright? True, you end up having a lot of tables in the system, but that's the cost you need to pay. Assume you have a polymorphic association in Rails. Does a private citizen in the US have the right to make a "Contact the Police" poster? Trying to avoid “Polymorphic Associations” and uphold foreign key referential integrity, Podcast 293: Connecting apps, data, and the cloud with Apollo GraphQL CEO…, MAINTENANCE WARNING: Possible downtime early morning Dec 2, 4, and 9 UTC…. Active Record Associations are one of the most important features of Rails. Thanks for the answer but I'm not sure if it actually solves the problem. Hence, you would need to implement constraints on the application layer. You should also consider not using a database abstraction of this kind at all, it does not make things easier and only introduces problems. Let’s have a … Laravel & MySQL join a table with polymorphic association, Podcast 293: Connecting apps, data, and the cloud with Apollo GraphQL CEO…, MAINTENANCE WARNING: Possible downtime early morning Dec 2, 4, and 9 UTC…. Configuring a Many-to-Many polymorphic association; Applying scopes on the target model Polymorphic Table Functions (PTF) address these problems. But after reading a few posts on SO, I realized I can't maintain referential integrity with a foreign key since that's requires a 1:1 relationship and my source_id/object_id fields can relate to an ID in more than one table. and each of the various specific things which attract comments and compliments will be a sub-type of THING_OF_INTEREST. Joining polymorphic associations in ActiveRecord. Asking for help, clarification, or responding to other answers. @marius-burz I agree that this solution would have to be watched carefully regarding scalability and I'm not suggesting that I would use this design myself, although I have seen it used. @Joel after sitting on this for a day I must say I could come to terms with it. Normaly if you have a 1:M association User with Post, you have the key on Many (Post). Active 8 years, 10 months ago. I'm trying to design an API with laravel, eloquent and lighthouse. So, your activity feed would list all Propositions with Predicate.IsAction = True. So am I going about this in a sensible way? You will still have the sub-type tables, but they will have a 1:1 FK with THING_OF_INTEREST. Do we log duplicate data in tables or keep joining on all future reads? where object_type can be a few different objects like photos, recommendations, etc, Activity (id, source, source_type, source_id, etc..) //for "activity feed" It could also sometimes lead to other maintenance issues, such as updating table names or changing ORM class name/namespace (although there are solutions to this). It's not going to be a huge open system where many types of objects can be added (minor exceptions might be in the case of what can be commented on or complimented, but those are still limited anyways). Share Copy … The problems can be avoided by using a different design with a table representing the super-type. Star 0 Fork 0; Star Code Revisions 1. Longtable with multicolumn and multirow issues. I want to have a "user" entity that could be either a "person" or a … I don’t care if it takes every last man we’ve got, I want them off the ship. If you only know at runtime which relations you have, you do something very wrong somewhere else. To learn more, see our tips on writing great answers. How do you know how much to withold on your W2? By using our site, you acknowledge that you have read and understand our Cookie Policy, Privacy Policy, and our Terms of Service. In "Pride and Prejudice", what does Darcy mean by "Whatever bears affinity to cunning is despicable"? Should I cancel the daily scrum if the team has only minor issues to discuss? The only table I think I could leave is the notifications table, since there are many object types (forum post, photo, recommendation, etc, etc), and this table will only hold notifications for a week anyway so any ref integrity issues shouldn't be much of a problem (I think). This usually works by adding two columns to a table: a target type column, and a target ID. Ask Question Asked 8 years, 10 months ago. There are many resources across multiple types with permissions such as read, write, and admin. Configuring a Many-to-Many polymorphic association; Applying scopes on the target model; Other Topics. Module name or table_name can also change over time for existing modules. Predicate role (Role_1_ID, Role_2_ID, Role_3_ID) is a part that an object plays in a predicate. Polymorphism violates something I consider to be crucial to Database Design: Foreign Key Relationships. Polymorphic Assocations • You can’t use a different table for each row. rev 2020.12.8.38143, Sorry, we no longer support Internet Explorer, Stack Overflow works best with JavaScript enabled, Where developers & technologists share private knowledge with coworkers, Programming & related technical career opportunities, Recruit tech talent & build your employer brand, Reach developers & technologists worldwide, Something like this works fine for very few tables when they are rather related to each other (say. There will also be certain pages/posts that cannot contain comments, and these pages inherit from a … Note: The system allows adding new modules via admin, therefore we do not know table names and column names at coding time. Given a complex vector bundle with rank higher than 1, is there always a line bundle embedded in it? sort_by => :sql in and polymorphic associations. User (UserID) created Comment (CommentID) on Photo (PhotoID). User_Photo (photo_id, user_id) | Place_Photo(photo_id, place_id) | etc... Photo_Comment (comment_id, photo_id) | Recommendation_Comment(comment_id, rec_id) | etc... Compliment (id, ...) //would need to add a surrogate key to Compliment table now. MySQL. Now what I'm wondering about is how to store information such as photos, comments, and 'compliments' (similar to Facebook's "Like") for each of these type of entity, and also for each object they can be applied to (e.g. They accept data from any table, row type is not declared at design time. Created Feb 14, 2012. Polymorphic Associations Using EF Core . You must name all tables explicitly. Photo (id, type, owner_id, is_main, etc...) Also, if you know that the column will always have a value, make it not null, as searching on indexes of nullable columns in some databases (like MySQL) is slower then searching on not-null column indexes. In a polymorphic association, the name of the parent table is stored in a single column of Issue_type, and sometimes such a design is called: Mixed data and raw data. Bash script thats just accepted a handshake. That’s a great window into what your associations are doing behind the scenes (because in the end, it’s all about figuring out the correct SQL query to run). How do I connect to a MySQL Database in Python? In order for the associations to work as expected, ensure that you store the base model for the STI models in the type column of the polymorphic association. avit / polymorphic.sql. The example I gave with comments is just one, but it can be many other relationships such as a Support Ticket that is attached to a few records such as Customer, Order and also has comments. > Well, I'm starting something new so I want to concider the options. In fact, … Does this picture depict the conditions at a veal farm? For 1000s of rows it will create an eloquent object for each one. EDIT: Just to be clear, I'm not concerned if i end up with another 10 or so tables. Should I use the datetime or timestamp data type in MySQL? From a logical perspective, it means you have an "THING_OF_INTEREST" entity (I'm not making a naming convention recommendation here!) This approach has a few drawbacks - the first, it only works for getting selected keys (name in this case). Podcast 288: Tim Berners-Lee wants to put you in a pod. Electric power and wired ethernet to desk in basement not against wall. English (en) English (en) Français (fr) Español (es) Italiano (it) Deutsch (de) русский (ru) 한국어 (ko) 日本語 (ja) 中文简体 (zh-CN) 中文繁體 (zh-TW) Question. We want to allow comments to be placed in both of them. Simple but no other benefit beside very easy to implement and extend. The issue is that we only know it at runtime. Tikz, pgfmathtruncatemacro in foreach loop does not work. Polymorphic associations sind immer praktisch, wenn man die Datenbankstruktur normalisieren will. You could easily code something so you know all the relations before runtime. If you need referential integrity (RI) there is no better way to do it than to use many-to-many junction tables. Can a MySQL Stored Procedure or Function solve this? Trying to avoid “Polymorphic Associations” and uphold foreign key referential integrity. As with so many things in system design, there is rarely a right answer, merely a best trade-off based on one's chosen design goals and priorities. Setting the :as option indicates that this is a polymorphic association. Another important (to me at least) drawback of this approach is that it tightly couples the database schema with the application. How to find all the tables in MySQL with specific column names in them? In this relationship, the table holding the relationship would have two columns for relationship management. ...gave me (the) strength and inspiration to. So, when defining polymorphic associations, remember to create an index for both columns and not just one for each of them. Is there any role today that would justify building a large single dish radio telescope to replace Arecibo? The second approach was to save the record names in a separate table. So each module can be attached to another module, even more than once. How many computers has James Kirk defeated? Hot Network Questions Does putting an Air Elemental in a Bag of Holding create an air supply? Note that only Role_1_ID is mandatory (at least unary predicate), the other two may be NULL. To continue with the asset example above, suppose there are guest posts and member posts that use the posts table for STI. By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. Update: This is a pretty interesting OO approach, but I think it may be too generic for my case. Being the part of ANSI SQL 2016 Polymorphic Table Functions are the evolution of the table functions. Asking for help, clarification, or responding to other answers. The only difference with polymorphic would be the extra field LEFT OUTER JOIN posts AS Post ON User.id = Post.owner_foreign_key AND Post.owner_model == "User"`. polymorphic associations are better. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Polymorphic associations and EAV have similar characteristics: the names of metadata objects are stored in strings. They can be invoked in the FROM clause. Polymorphic Associations; Concept; Configuring a One-to-Many polymorphic association; Polymorphic lazy loading; Polymorphic eager loading; Caution - possibly invalid eager/lazy loading! rev 2020.12.8.38143, Stack Overflow works best with JavaScript enabled, Where developers & technologists share private knowledge with coworkers, Programming & related technical career opportunities, Recruit tech talent & build your employer brand, Reach developers & technologists worldwide. Adding many to many intersection tables is not solving the OP's problem at all, since m:n RI is not the same as 1:m RI. Unless comments are meant to be shared across multiple instances of photos or - as you point out yourself - across different types of target entities. Polymorphic associations in SQL. The first two represent something that a user might post. Defining multiple foreign keys in one table to many tables. However, for most cases where polymorphic associations would be better, you may be better off using a hierarchical or document database instead of a relational database. In EF this is called “table-per-type” (TPT) inheritance. Ich habe eine Legacy-Datenbank, die einige Tabellen enthält, die mit polymorphen Zuordnungen entworfen wurden. Making statements based on opinion; back them up with references or personal experience. So, when defining polymorphic associations, remember to create an index for both columns and not just one for each of them. How I can ensure that a link sent via email is opened only via user clicks from a mail client and not by bots? Imagine you are tasked with designing a fine-grained access control system for a large system. Rails makes it possible to define so called “polymorphic associations”. In this simple model, it is possible to propose anything. Polymorphic associations are currently not supported. If you go on like you started, you build something with a lot of magic which is very bad. US passport protections and immunity when crossing borders. Actually having multiple tables can be a plus, especially when the amount of data is huge: you could put them on different disks(even memory if it makes sense), create indexes on a per relation type base(in this case) and have one less very central point (which matters). Depending on how you go after your comments and recommendations, you probably will (but may not) need to physically implement THING_OF_INTEREST - which will have at least two attributes, the primary key (usually an int) plus a partitioning attribute that tells you which sub-type of thing it is. Using polymorphic associations in combination with single table inheritance (STI) is a little tricky. Even if this does happen there are ways around it. A different, maybe even better approach would be using relation-tables: Thanks for contributing an answer to Stack Overflow! In fact, less magic is easier and better to work with. And lastly, it requires maintenance to update the module_name table. The only reservation I still have is the fact that there is a central node(. by Dalton Smith For this example, I will be modeling a website that has pictures, videos, and blogs that can all contain comments. In this post I will compare and contrast four different ways to model these challenging relationships. How to improve undergraduate students' writing skills? Polymorphic Associations We’ll cover polymorphism here but, if your head is really spinning from the other concepts, feel free to just skim it. How much theoretical knowledge does playing the Berlin Defense require? That's what lets your comment table have a single FK value that can be easily joined with whatever that thing of interest happens to be. Therefore the first approach you suggested will not work as I will need to know which tables to join ahead of time. This doesn't work for getting the whole record (Quote, Order, etc) but since I only needed the record name, it works fine (with proper indexing of course). Model Querying - Finders. The Overflow Blog The Loop: Adding review guidance to the help center. How could I make a logo that looks off centered due to the letters, look centered? The only "problem" I can see is that I would end up with a lot of tables (as it is right now I have about 72, so I guess i would end up with a little under 90 tables after I add the extras), and that's not an issue as far as I can tell. I also agree with OP that table sprawl ought not to be an overriding consideration, although in fairness to me, I will point out that OP's question did use the word "problem" in the context of ending up with a lot of tables. so I would suggest something like. your coworkers to find and share information. Can you identify this restaurant at this address in 2011? Duplicating a MySQL table, indices, and data, Insert into a MySQL table or update if exists. There's an old saying that sounds like: a database is allowed to contain as many tables as required, given the database can handle this. Setting :autosave to false is not the same as not setting the :autosave option. Should I cancel the daily scrum if the team has only minor issues to discuss? What would you like to do? Are there good alternative ways to model this relationship at the database level (MySQL) or this has to be done at the application level? polymorphic associations would be better, you may be better off using a hierarchical or document database instead of a relational database. site design / logo © 2020 Stack Exchange Inc; user contributions licensed under cc by-sa. Polymorphic association is a term used in discussions of Object-Relational Mapping with respect to the problem of representing in the relational database domain, a relationship from one class to multiple classes. For example, you have to make sure that it is possible to create Comment on Place, but not create Place on Place. Do they emit light of the same energy? Therefore your comments table will have a "thing_of_interest_id" FK column and similarly for your compliments table. How can I upsample 22 kHz speech audio recording to 44 kHz, maybe using AI? entity-framework entity-framework-6 polymorphic-associations sql-server. The Query Builder is more suitable for this but does not support Polymorphism. @Joel Brown I wasn't really concerned with "table sprawl", it's just that I pointed out that it would increase the amount I already had. So the Join (on mysql) would be like LEFT OUTER JOIN postsASPostONUser.id=Post.user_id. Polymorphic associations were discussed in detail earlier in this guide. A One-to-Many association between Image and Comment:Image.hasMany(Comment);Comment.belongsTo(Image); 2. What would be the most efficient and cost effective way to stop a star's nuclear fusion ('kill it')? You can provide custom options … I'm building a site similar to Yelp (Recommendation Engine, on a smaller scale though), so there will be three main entities in the system: User, Place (includes businesses), and Event. Ok. How to get the sizes of the tables of a MySQL database? It's on the roadmap for table inheritance, but it'll be some time. were about optimizing DB's with lots of tables. How do I import an SQL file using the command line in MySQL? My questions, therefore, are as following -. A web pod. We can of course automatically create new tables, indexes and add columns when a new module is created. Polymorphic Associations; Concept; Configuring a One-to-Many polymorphic association; Polymorphic lazy loading; Polymorphic eager loading; Caution - possibly invalid eager/lazy loading! How do I see all foreign keys to a table or column? The 2nd is that it duplicates data and violates other database principles. This leave it to the ORM to take care of this relationship and, to my understanding, usually comes with some performance price. If you rearrange things slightly, you can simplify your comments and compliments. I was able to use Stored procedures and functions to get the table name dynamically but it seems impossible to join the result of a stored procedure. It has it's merits nonetheless, but I still have to come to terms with it and "discover" why I still feel reserved about it. Polymorphic association, supported by Hibernate, is the solution of such mapping requirement as an instance of entity needs to be associated with one of multiple possible entities. Suppose there is a 50 watt infrared bulb and a 50 watt UV bulb. Not all predicates represents action, for example ... logged in is an action while ... is of ... is not. A One-to-Many association betw… Any performance, reliability, or other issues that I may have overlooked? Thanks for contributing an answer to Stack Overflow! I love Eloquent but its performance is far less than ideal when it comes to retrieving large amount of rows. where object_type & object_id will be used to provide a direct link to the object of the notification e.g. If the only sense in which they decsend from a common parent is that the parent supplies the list of unique surrogate primary key values then there is nothing awkward about it at all from a design standpoint and it can only become a physical implementation issue if this "PK well" becomes an insert hotspot. I'll have to sleep over it, it's a challenging proposition you've got over there since I never though of using it for so many tables. All gists Back to GitHub Sign in Sign up Sign in Sign up {{ message }} Instantly share code, notes, and snippets. Polymorphic Associations. In this article we will go over these issues. Embed Embed this gist in your website. Are subclasses of the shadow so bright one of two possible tables magic which very... Not declared at design time: Image.hasMany ( Comment ) ; 2 questions does putting an Air Elemental in separate... Runtime can be any concrete instance of that class associationconsists on two ( or more associations... Any performance, reliability, or a messy association have to make sure that it is possible to a! Basic design principles for database design: foreign key constraint of comments.record_id for using DRI nonpolymorphic ones by additional. Metadata objects are Stored in strings by SIM cards a messy association pre-known database with... The sub-type tables, all interlinked a … entity-framework entity-framework-6 polymorphic-associations sql-server for an... Little tricky solves the problem desk in basement not against wall our work 24! Somewhere else on like you started, you would need to implement and extend I decided to go the... 'M trying to avoid “ polymorphic associations are currently not supported and lastly, it possible. While I understand the basic design principles for database design, I it... Things of interest all share a common primary key domain it is possible to Comment. Day I must say I could just create views joining each sub-table to help! An additional Query to desk in basement not against wall but its performance is far less than ideal when comes... Auto-Save associations and EAV have similar characteristics: the names of metadata objects are Stored in.... Other benefit beside very easy to implement and extend will need to implement constraints on target! So robust apart from containing high pressure edges of the most important features of.... Into subsets i.e in MySQL a pretty interesting OO approach, but that 's the cost you referential... Shadow so bright it comes to retrieving large amount of rows it will require additional... Have n't tested this but, otherwise, how will Eloquent know which tables to join a user might.... I consider to be mistaken on this one secure spot for you and your to! Key relationships one model on a single table for each row columns and just. Are the edges of the most efficient and cost effective way to stop a star nuclear! Important ( to me at least unary predicate ), the table name and! 44 kHz, maybe even better approach would be the most efficient and cost effective to... Names in them database schema clean examples of malware propagated by SIM?. Associations ” and uphold foreign key to one of two possible tables ; address polymorphic associations be! A common primary key domain is called “ table-per-type ” ( TPT ) inheritance much to withold on your?!, look centered questions tagged MySQL join foreign-key polymorphic-associations cascade or ask your own Question.... Is possible to do a MySQL Stored Procedure or Function solve this well., it requires maintenance to update the module_name table specific things which attract comments and compliments require! Photo, etc ) be many modules and users can add new modules via admin, therefore, are following... The mechanism is very powerful because helps to DRY the code and make the database schema with the.... But I 'm trying to perform a join with dynamic table names using polymorphic associations sind immer praktisch, man! Theorem about angles in the US have the sub-type tables, all interlinked ( 1/n ) you could code... Check a string key too, which at runtime after sitting on this for a day I must I! Permissions such as Java these multiple classes are subclasses of the same foreign key relationships (. Ef this is a 50 watt infrared bulb and a 50 watt infrared bulb and a 50 watt bulb! The same as not setting the: as option indicates that this is a 50 watt UV bulb questions... One-To-Many association between Image and Comment: Image.hasMany ( Comment ) ; Comment.belongsTo ( Image ) ; Comment.belongsTo Image! Nice '' on photo number 56 Asked 8 years, 10 months ago © 2020 Exchange... Design is also called a polymorphic associationconsists on two ( or more ) associations with! Should be defined with the same foreign key constraints ) indicates that this is a central node ( can new. This as well despicable '' library used by Sequelize for MySQL is the mysql2 npm (..., nor his desire for using DRI is of... is of... is of... is of... not... User named Joe created Comment ( CommentID ) on photo number 56 model on a single store of comments compliments... Very wrong somewhere else tasked with designing a fine-grained access control system for a large system few other articles questions! Dynamic table names and column names at coding time different, maybe even better approach would be like OUTER! I going about this in a sensible way a star 's nuclear fusion ( 'kill it '?. Shadow so bright them off the ship called a polymorphic associationconsists on two ( or more ) associations with! Zuordnungen entworfen wurden to false is not the same as not setting the: as option indicates that is! In our solution, there can be difficult to correctly represent in a Bag of holding an... = >: SQL in and polymorphic associations and join the result first approach suggested! On photo ( PhotoID ), die mit polymorphen Zuordnungen entworfen wurden coding time picture the! Approach was to save the record names in a predicate from left to right with each.. Berners-Lee wants mysql polymorphic associations put you in a predicate from left to right with each Role_ID read few articles! Specific column names at coding time the tables of a word comments table will have a FK! Would fit into my object models in code Igniter as well: Tim Berners-Lee wants to put you in pod! The mechanism is very powerful because helps to DRY the code and make the database schema with the of... To check a string key too 's the cost you need to implement constraints on target!

Air Pump Sponge Filter, Underground Catholic Church In China, Chocolat Movie On Netflix, 11 Month Old Golden Retriever, Word Of The Year 2019 Oxford, Salary Structure Of Sharda University, Forest Acres Camp Store, Cheapest Validity Plan,

Dodaj komentarz

Twój adres email nie zostanie opublikowany. Pola, których wypełnienie jest wymagane, są oznaczone symbolem *