在运行rake db：migrate VERSION = 0并重新进行迁移之后，我丢失了数据库中的所有内容

Question

Before I was trying to run rake db:migrate I ran into an error called column duplication so I ran rake db:migrate VERSION=0 instead and ran rake db:migrate again.

Basically I was clearing up my previous migration and by running a new migration from VERSION=0, I was finally able to finish my pending migration and had no issue with column duplication again.

But here's the thing, the command I ran actually cleared up all my previous data. Is there a way to retrieve what I had lost? And what is the safest way to run db:migrate if there's a column duplication error. I really don't want to go back to VERSION=0

Answer 1

Is there a way to retrieve what I had lost?

You deleted your database table and re-created it. All data that was stored in that table was also deleted and is lost. The only way to get your data back is to restore from a backup. Do you have a recent database backup?

And what is the safest way to run db:migrate if there's a column duplication error.

If you migration has an error, fix that migration and re-run it. In you example: If your migration fails with an error telling you that there is a duplicate column, just remove the code that tries to add a duplicate column and re-run the migration.

Answer 2

rails migration has a strict process to be followed. Suppose you have duplicate column. You should write another migration file to remove that duplicate column. When you have ran

rails db:migrate VERSION=0

It is creating your database all again so obvious that data will be lost.

So make sure any correction in Database used in Rails should follow strict process of creating new migration rather than editing the same.