CODEWITHSUNDEEP
ruby-on-railspostgresql
Luke Dai
Luke Dai

Reputation: 31

rails db:migrate fails due to duplicate table

I got some problems about my database.

I've generated a model Comment once, but this Comment migration not what I wanted, so I drop it, and succeeded to drop. Now I try to re-generate it, and keep running rails db:migrate, but something went wrong.

It shows :

"PG::DuplicateTable: ERROR: relation "comments" already exists",

I've checked my schema.rb, did not have this comment table.

My database using "psql", and Rails version is "Rails 6.0.2.2". I've been searched related problem, but seems like not what I faced.

Upvotes: 2

Views: 2386

Answers (2)

Jake Bryant
Jake Bryant

Reputation: 31

according your description, I have also encountered this, this is what I tried and solved:

psql

rails db

\d:

drop table tablename;

hope to solve your problem

Upvotes: 3

kareem_emad
kareem_emad

Reputation: 1183

If the data is not important you could just start fresh by dropping the current database and create a new one

rake db:drop
rake db:create
rake db:migrate

If you are sure that those migrations already have been run before, then you can go and modify the schema migrations table directly where rails stores all migrations that have been run already.

First log into your postgres and choose the correct database

sudo -u postgres psql
\c db_name

then to view the current migrations in the schema table

select * from schema_migrations;

that will show you the current migrations that rails considers as done.

Then check you migrations folder, get the version of all the migration files you want to skip running, the file name starts with the version for example 20200401212538_add_country_name.rb the first numeric 20200401212538 part is the version

then insert them into the migrations table

insert  into schema_migrations VALUES ('version_of_migration');

Or you could also delete migrations so you could re-run them if you want to.

After that running rake db:migrate should work just fine without trying to recreate the tables.

Another solutions you might consider is that in your migrations you check first if table exists or not before trying to create it.

Upvotes: 0

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