Questions tagged [orm]

Object-relational mapping (ORM) is a technique for mapping between object-oriented systems and relational databases.

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81 views

Select from many-to-many in one query

A common issue I run into when building CRUD applications is how to retrieve many-to-many relationships from the database and put them into an object model. Say, for example, I have the following data ...
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1answer
122 views

Express SQL Query As Abstract Object Model

Goal: write code to express SQL queries in C# that get converted to SQL at the data layer level and will be compatible with any common data layer / ORM such as Dapper or Entity Framework (EF). Edit: ...
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Is it ok to cache the user password in Hibernate two-level cache, if not, how to avoid it?

I am working on a blog system, and use Hibernate as my ORM framework. The blog system has Post and Comment entities. Both of them has a nested author field, associated with the User entity by a ...
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1answer
57 views

Mapping of time based models to database

Currently I'm developing a movie reservation system for diving into Spring Framework. I'm using Spring Data JPA for database modeling. I have several model classes but I am stuck with time-based logic ...
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55 views

DDD Value Objects and Entity Without ORM Mapping in PHP

First, as I know, Entity in DDD is almost same with Value Object except Entity has identity. Every article I have read say same thing that entity id has ORM mapping with any ORM tool. But I don’t want ...
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81 views

Should database model POJO contain *entities* or *ids* when having 1:M, M:N relationships?

Though this seems less like a software engineering problem, IMHO it is actually about programming paradigms, instead of specific "how to solve this bug" questions... Say we have article, author and ...
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1answer
44 views

Converting a table to an ORM schema

I'm trying to convert this table into an ORM schema: The solution given by the book is this one: It connects all the paramether to the Member one. This is my solution, which I think it's less ...
4
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2answers
193 views

How to write dynamic (non ORM) repositories that can return only the necessary data without creating many methods or data-objecs?

We're currently developing a Spring application that uses jdbcTemplates for the repository. We have a lot of functions that only require specific combinations of columns in our database. It would be ...
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2answers
188 views

Does references between entities of the same aggregate hurt the Aggregate Pattern from DDD?

Consider an application being implemented following Domain Driven Design. In the same aggregation, there are Car and Computer entities that should have a one to many relationship between them (Car ...
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1answer
51 views

Questions about Direct access to data source from Services

Background: I'm trying to separate my concerns in the application architecture the best possible way. In a nutshell: The requests are parsed and go to an Action Action decides which service(s) to ...
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79 views

Need some design advice on my ORM for Immutable objects & ref passing

I'm adding Immutable objects support to my Micro ORM called "Symbiotic" In the case of a create, I need to pass back a newly created version of the value passed in because the object is immutable and ...
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2answers
109 views

How to keep track of db tables used in various apps [closed]

I have N applications using ORM, SQL-statements and stored procedures to access M tables from an MSSQL Server 2017. There are some shared tables that are used by various apps. Let's say I am forced to ...
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2answers
152 views

Query with a lot of fields and joins

I have to map a legacy database with tables that have a lot of fields and relations. For example (simplified code), @Entity @Table(name = "VISIT") public class VisitEntity { @Id private ...
2
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1answer
50 views

At what size array in Swift would you consider switching to CoreData?

I've developed a reading tracking app in Swift and for simplicity's sake I used arrays for my model. It stores some data about the books a user reads and a small image of the cover. I save them to ...
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1answer
191 views

DDD persistence through non-orm tools in java

So our domain model drove our database and ORMs worked for DDD implementations. Now the tables have been altered a lot and as a consequence ORM impedence is too much in our domain model to use ...
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2answers
368 views

Domain models vs entity models vs Hibernate lazy loading

In a new Java project I plan to use an extra layer above Hibernate entities. So there would be a CustomerEntity and CustomerDomain. The reason for that is that the CustomerDomain can contain extra ...
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1answer
50 views

Combining web app and CLI to python package

I'm writing a program in Python that has two different entry points. There's a CLI that processes some data and needs to be installed to run hourly on a server, this populates a database. There's also ...
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0answers
37 views

What layer should resolve pre-existing Hibernate entities?

Imagine an application that consumes an external data stream and creates objects of this type: @Entity public class Event { @OneToOne(cascade = CascadeType.ALL) private EventInfo info; @...
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1answer
526 views

Updating sub-properties via Entity Framework

I was wondering how to updated nested objects/sub-properties when using Entity Framework. But to make things clear, let's start with an example. I have an object, which can own a number of other ...
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1answer
582 views

Any solid reason to have getters/setters in entities? ORM, Doctrine

I've been trying to decide if I should include getters/setters in business entities. A few reason I have been through to include getters/setters but those are accompanied by an anti-reason as well. ...
4
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1answer
91 views

Maintaining parallel libraries: Binary files access + Metadata Database ORM design

I'm dealing with a higher-level data abstraction that I would appreciate some input on. I'm working on an application that uses a large data lake. The data lake is consisted of thousands of large ...
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2answers
3k views

Should Entity Framework 6 not be used with repository pattern?

So I am asking this after reading the following: Why shouldn't I use the repository pattern with Entity Framework?. It seems there is a large split of people who say yay and those that say nay. ...
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1answer
770 views

Entity Framework and static entity instances

I'm always having the problem on how to properly design having static entity instances and it being attached to Entity Framework's Dbcontext. For example, we have the following: using Microsoft....
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1answer
64 views

Using frameworks that map database to RESTful APIs?

While researching RESTful API frameworks I've come across (generally speaking) two types of frameworks: The first type will (more or less) directly (or nearly directly) map an ORM/ODM scheme of your ...
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1answer
114 views

Patterns for loading related objects in memory (without an ORM)

I am using ADO.NET to read a bunch of data from the database into in-memory objects. This is my domain model: // Question.cs public class Question { public int ID { get; set; } public ...
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1answer
64 views

How to handle different pages of a web application having different levels of access to a database model

I am working on an ASP.NET Core application that grabs a model from a database via Entity Framework, and will pass a "subset" of that model to our Angular front end. For example: I have a list of ...
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1answer
96 views

Private class in ORM Repository?

Is this a code smell? I have a repository which connects to a SQL server. This repository uses Dapper to map the results to an object. I have a method in this repository that checks a result, then ...
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3answers
618 views

How to handle a many to many relationship with an ORM mapped to a Domain Model when there are no technical constraints?

Domain Driven Design states that you should have a domain model, which reflects the ubiquitious language used by the domain experts. When using ORMs and many to many relationships I am use to doing ...
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2answers
206 views

Encapsulation and input validation duplication

Consider the following example (very simplified): public class Basket { private readonly List<BasketItem> _items = new List<BasketItem>(); public IReadOnlyCollection<BasketItem&...
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1answer
1k views

How should I design a 3-tier-architecture application with Entity Framework?

This is almost getting me crazy. EF bring us a very convenience experience in development. However, if we need to use the Entity model in the upper layer, we always put a reference from the upper ...
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1answer
57 views

Calculating time an object stays in a state

I use Python sqlalchemy to store my model in a MySql database. One of my objects has a 'state' field (for simplicity let's assume there are two states: AVAILABLE and UNAVAILABLE). There are ...
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2answers
128 views

When using an ORM when should I sacrifice performance for convenience?

I work with SQL Alchemy a lot and, as a "lazy programmer", I enjoy the convenience it offers. But the "diligent programmer" in me often worries about optimisation and the performance of the queries ...
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2answers
4k views

Separating Domain Object and Data Models

I looked through a lot of articles, blogs, and SO topics about separating domain object and data models. Almost every answer said: You should have separate classes for the domain and data persistence, ...
32
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5answers
23k views

Should I check if something exists in the db and fail fast or wait for db exception

Having two classes: public class Parent { public int Id { get; set; } public int ChildId { get; set; } } public class Child { ... } When assigning ChildId to Parent should I check first if ...
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0answers
710 views

Handling complex dynamic queries in Laravel 5

I am developing a project using Laravel. My workflow is: route directs to controller Controller calls eloquent models Eloquent models perform queries (tipically CRUD and find) Controller returns ...
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1answer
1k views

Entities and polymorphic relationships

Lets say that I have a shelf on which I can put items that are shelfable (not sure if that is actually a word but you can understand my point). So I have the following: class Shelf { /** @var ...
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4answers
102 views

How do I approach structuring when to read/write objects to db?

This is a problem I've faced in many languages over the years (js, go, c, f#, haskell, python, ...), but I haven't found a general approach to solving this yet. Learning about consistency models in ...
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1answer
2k views

ORM vs Web API differences

I'm struggling to understand the differences between an API such as a REST API and an ORM such as Entity Framework. I would also like to understand the benefits of each and in what situations either ...
1
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1answer
117 views

How can I model unknown and an unknown number of attributes on an object?

My example might be slightly contrived, because I've modified it so that the project isn't recognizable by my employer. I'm a newer developer at a very small company. We have an object - Posts - that ...
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2answers
80 views

Best practice for object relation mapping to execute delete/update

In doctrine (or any ORM in general), the easiest way to execute a delete/update operation is to select such entity, then remove entity or update single attribute in the code, ended by persist the ...
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1answer
627 views

Data Mapper Pattern and DDD - Does ist already reflect domain entities and repositories?

I'm getting used to DDD so don't assume I'm a DDD pro yet. I'm trying to implement a hexagonal architecture using the CakePHP framework in a completely custom made application that just utilizes the ...
2
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1answer
53 views

Should the ORM create the related objects (ForeignKey objects) when saving the entity?

This question is coming from a frustration when using the Entity Framework and ASP.NET MVC, but I assume it's a general frustration across more frameworks and languages. Lets say we have an object ...
4
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1answer
188 views

Split ORM module without creating cyclic imports or side-effects

Preface I have an ORM library for a relational real estate database. The used framework is peewee. The library contains ~60 models, each representing a distinct table. The models represent a (pre-...
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1answer
134 views

ORM for 600 tables

I am working on a huge application in php which contains almost 600 tables to work with, not to mention it requires complex joining for 10 or 15 tables together. i wanted to ask how much ORM is good ...
2
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1answer
224 views

Database modeling. Many to Many relationships. Link tables

Consider a database table for user info like: id, name, email now consider I have another table for video something like: id, name, description, length Say a many to many relationship exists ...
2
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1answer
55 views

Advice on AggregateRoot boundaries

I am confused on how to apply DDD principles for the design of domain entity clusters with Aggregate Root. According to my understanding, Aggregate Root enforces business validations and all entities ...
4
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1answer
426 views

Routing all SQL queries through a single micro-service

I currently have a website, made of about 20 micro-services and a (still too large) main monolithic web application. The monolith and multiple micro-services each run queries to the same database, ...
2
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2answers
765 views

Ways to store objects, inherited from one superclass in a database

For my personal project I need to store 2D shapes in a Postgres database. For example Circle, Pentagon, Rectangle and so on. At first I've done it like so: all shapes are inherited from an abstract ...
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1answer
149 views

Is generating Hibernate Entities from database tables considered a bad practices?

On my current project it is a common practice to generate Hibernate Entities from database tables using NetBeans functionality. I'm normally used to first write the Entity-class and define the mapping ...
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1answer
247 views

Is there a better design than reflection to deal with large numbers of ORM objects?

Here's a scenario I've encountered variations of on many occasions. Imagine an XML feed which displays data about three different types of event: concerts, plays and movies. Each has a different set ...

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