Upgrade PostgreSQL JSON column to JSONB?
In the context of Rails, here is an ActiveRecord migration alternative:
def change reversible do |dir| dir.up { change_column :models, :attribute, 'jsonb USING CAST(attribute AS jsonb)' } dir.down { change_column :models, :attribute, 'json USING CAST(attribute AS json)' } endendI tested this on a table with 120 000 records, each record having four json columns and it took me about a minute to migrate that table. Of course, it depends on how complex the json structure is.
Also, notice that if your existing records have a default value of {}, you have to add to the above statements default: {}, because otherwise you'll have jsonb columns, but the default value will remain as '{}'::json.