[PostgreSQL] If you want to delete the Rails app, delete the database first!

Introduction

If you repeatedly create and erase sample apps during learning, Suddenly, I was wondering, "Can I just delete the folder?"

When I looked it up, It seems that ** DB (database) ** must be deleted before ** folder ** can be deleted! Make a note of the two methods below.

-** DB deletion → App folder deletion ** -** How to delete the DB after deleting the application folder **

environment

• macOS Catalina
• Ruby 2.7.2
• Rails 6.0.3
• PostgreSQL 13.1

① Delete DB → Delete application folder

In the folder of the corresponding application

$ rails db:drop

Go to the parent directory

$ rm -rf app name

It seems good to be sure to delete it according to the procedure of ① above. Here's what to do if you've deleted the app folder first.

(2) How to delete the DB after deleting the application folder

$ psql -l     (List DB names

#Execution result (when you want to delete the sample application)

                             List of databases
             Name      | Owner | Encoding | Collate | Ctype | Access privileges 
-----------------------+-------+----------+---------+-------+-------------------
 sample_development    | user  | UTF8     | C       | C     | 
 sample_test           | user  | UTF8     | C       | C     | 
 postgres              | user  | UTF8     | C       | C     | 
 template0             | user  | UTF8     | C       | C     | =c/user           +
                       |       |          |         |       | user=CTc/user
 template1             | user  | UTF8     | C       | C     | =c/user           +
                       |       |          |         |       | user=CTc/user
(5 rows)

$ psql postgres      (Log in to PostgreSQL

---
(postgres=#) \du     (Check users and permissions
(postgres=#) \q      (Login from PostgreSQL
---

$ dropdb -U user name DB name you want to delete

* DB that should not be deleted (default)

postgres template0 template1

I have removed this supposed default postgres. .. (Great reflection) I uninstalled PostgreSQL because it was just a learning app. When I checked after reinstalling, the above three DBs were there from the beginning! !!

I will write down the procedure after deleting the above default with caution.

How to uninstall

$ ls /usr/local/Cellar/postgresql     (Check installed PostgreSQL version
$ brew info postgresql     (Check the latest version at the moment

$ brew uninstall --force postgresql     (Uninstall all versions

$ ls -l /usr/local/var/postgres     (Display configuration files, logs, data, etc.
$ rm -rf /usr/local/var/postgres     (Delete configuration files, logs, data, etc.

Subsequent installations are the same as when installing for the first time.

at the end

While learning, the number of sample apps was increasing, I was able to solve it this way. I would appreciate it if you could point out any mistakes.

Reference article

Ruby on Rails deletion related summary Forcibly delete database in PostgreSQL (https://qiita.com/sayama0402/items/b3d96c25ecb60733beb9) [MacOS] How to uninstall all versions of PostgreSQL ~ Homebrew Edition PostgreSQL documentation "dropdb"