Although it is not something so common to happen, sometimes we came across a table on the database where the id of the primary key column are not synchronized, for example, the last record saved is id=200, but when we try to create a new record, Postgres tries to create with a different id from the default order, which would be id=201, in this case.

In my case, what made the sequence to get lost was a Ruby task that I’ve created to import data from another applicaton. Moreover, in order to not lose reference of links, I set the ids according to the old table and after import, the new records were trying to use an id that was already being saved, giving me the following error:

Googling this issue, I came across with several solutions using only Postgres, but in this article I want to share with you a solution that works very well, using just Rails console, as it follows:

Personaly, I prefer this solution for three reasons:

  • Access to Postgres console is not required;
  • Although the access to Postgres console is usually easy to have, in some projects/companies, this may be time-consuming;
  • It fixes the problems in all tables of the project at once;
  • Code easy to read and to understand.

I hope this tip can save you some time :)