postgresql migrating JSON to JSONB [duplicate]
ALTER TABLE table_with_json ALTER COLUMN my_json SET DATA TYPE jsonb USING my_json::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 don't know how this compares to the accepted answer performance-wise, but I 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, I guess 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.