Implementing a "Best Answer" Feature in a Q&A App using PostgreSQL and Drizzle ORM

To create a "best answer" feature in your Stack Overflow clone using PostgreSQL and Drizzle ORM, you have two main approaches to consider: adding a bestAnswerId field to the questions table or using a boolean flag on the answers table. Let's evaluate both options and choose the best one.

Recommended Approach: Adding bestAnswerId to the Questions Table

By adding a bestAnswerId field to your questions table, you can directly link each question to a single best answer. This approach is clean and efficient because it:

• Avoids redundancy: There is only one field in one table that defines the best answer, preventing multiple answers from being mistakenly marked as the best.
• Simplifies the data retrieval process: Fetching the best answer becomes straightforward as it involves a simple join based on the ID, without needing to filter through boolean flags.

Here’s how you can modify your database schema and update your ORM mapping:

1. Database Schema

   Update the questions table to include a bestAnswerId column, which is a foreign key referencing the id of the answers table:

   1ALTER TABLE questions
   2ADD COLUMN bestAnswerId INTEGER REFERENCES answers(id);
   

   1ALTER TABLE questions
   2ADD COLUMN bestAnswerId INTEGER REFERENCES answers(id);
   

2. Drizzle ORM Setup

   Update your Drizzle models to reflect this relationship. Assuming you have Question and Answer models, you would modify the Question model as follows:

   1import { Model, fk } from 'drizzle-orm';
   2
   3class Question extends Model {
   4    static tableName = 'questions';
   5    static fields = {
   6        id: { type: 'integer', primaryKey: true },
   7        bestAnswerId: fk({
   8            model: 'Answer',
   9            field: 'id',
   10            nullable: true
   11        }),
   12        // other fields...
   13    };
   14}
   

   1import { Model, fk } from 'drizzle-orm';
   2
   3class Question extends Model {
   4    static tableName = 'questions';
   5    static fields = {
   6        id: { type: 'integer', primaryKey: true },
   7        bestAnswerId: fk({
   8            model: 'Answer',
   9            field: 'id',
   10            nullable: true
   11        }),
   12        // other fields...
   13    };
   14}
   

   And ensure the Answer model is set up to recognize that it can be linked to a question as its best answer:

   1class Answer extends Model {
   2    static tableName = 'answers';
   3    static fields = {
   4       id: { type: 'integer', primaryKey: true }
   5    };
   6}
   

   1class Answer extends Model {
   2    static tableName = 'answers';
   3    static fields = {
   4       id: { type: 'integer', primaryKey: true }
   5    };
   6}
   

3. Marking an Answer as the Best

   When a question's author decides to mark an answer as the best, update the bestAnswerId field in the corresponding question record:

   1async function markAsBestAnswer(questionId, answerId) {
   2    const question = await Question.findOne({ where: { id: questionId } });
   3    question.bestAnswerId = answerId;
   4    await question.save();
   5}
   

   1async function markAsBestAnswer(questionId, answerId) {
   2    const question = await Question.findOne({ where: { id: questionId } });
   3    question.bestAnswerId = answerId;
   4    await question.save();
   5}
   

Conclusion

This solution provides a clean and efficient method to manage the "best answer" feature in your Q&A app. It simplifies both the schema design and the code needed to manipulate and retrieve the best answer data using Drizzle ORM.