Heroku部署Ruby Active Record插入PostgreSQL时字符串长度限制问题

在Ruby中向Heroku上的PostgreSQL Active Record数据库插入数据时存在字符串长度限制吗？

本地环境中可以向名为Devices的表创建并插入记录，但在Heroku部署环境中，当identifier和push_token的长度过长时无法创建记录。

设备表迁移代码：

class CreateDevices < ActiveRecord::Migration[6.1]
    def change
      create_table :devices do |t|
        t.string :identifier, null: false
        t.string :push_token, null: false
      end
    end
end

测试端点代码：

get "\/test\/devices\/:device_id\/:push_tokens" do
     Device.create(identifier: params[:device_id], push_token: params[:push_tokens])
     puts "device_count is"
     puts Device.count
end

本地测试时，使用278b5d5668b7e2df3b686e0c0d19a0b9作为identifier、1319f7e0f6dd345304c5e8e84e5ec3f52213b8f485e4783861b476373f000dde作为push_token，Active Record能正常更新，设备计数增加。但在Heroku部署环境中使用这些值时，计数未更新，记录也未创建。

Heroku测试日志：

2022-09-23T13:47:45.399683+00:00 heroku[router]: at=info method=GET path="\/test\/devices\/123456789123456789\/123456789123456789" host=japsoc-passes-server-2.herokuapp.com request_id=21779202-b9b6-4e02-9195-6ead6cc63ba6 fwd="147.12.186.203" dyno=web.1 connect=0ms service=9ms status=200 bytes=191 protocol=https
2022-09-23T13:47:45.394194+00:00 app[web.1]: device_count is
2022-09-23T13:47:45.395126+00:00 app[web.1]: 8
2022-09-23T13:47:59.284900+00:00 heroku[router]: at=info method=GET path="\/test\/devices\/123456789123456789123456789\/123456789123456789123456789" host=japsoc-passes-server-2.herokuapp.com request_id=04ef6dab-71c3-4237-b52f-bf2ea16576f0 fwd="147.12.186.203" dyno=web.1 connect=0ms service=7ms status=200 bytes=191 protocol=https
2022-09-23T13:47:59.279643+00:00 app[web.1]: device_count is
2022-09-23T13:47:59.280339+00:00 app[web.1]: 9
2022-09-23T13:48:17.720446+00:00 heroku[router]: at=info method=GET path="\/test\/devices\/123456789123456789123456789123456789\/123456789123456789123456789123456789" host=japsoc-passes-server-2.herokuapp.com request_id=1c221b82-f142-44a0-b0ec-774a8515365a fwd="147.12.186.203" dyno=web.1 connect=0ms service=9ms status=200 bytes=191 protocol=https
2022-09-23T13:48:17.715182+00:00 app[web.1]: device_count is
2022-09-23T13:48:17.715917+00:00 app[web.1]: 10
2022-09-23T13:48:35.566064+00:00 heroku[router]: at=info method=GET path="\/test\/devices\/123456789123456789123456789123456789123456789\/123456789123456789123456789123456789123456789" host=japsoc-passes-server-2.herokuapp.com request_id=2539f65b-7f82-42dc-9c4e-c078b93412d1 fwd="147.12.186.203" dyno=web.1 connect=0ms service=6ms status=200 bytes=191 protocol=https
2022-09-23T13:48:35.560941+00:00 app[web.1]: device_count is
2022-09-23T13:48:35.561519+00:00 app[web.1]: 11
2022-09-23T13:49:00.943300+00:00 heroku[router]: at=info method=GET path="\/test\/devices\/123456789123456789123456789123456789123456789123456789\/123456789123456789123456789123456789123456789123456789" host=japsoc-passes-server-2.herokuapp.com request_id=01acc954-8cf9-4327-8e84-b1958298b14d fwd="147.12.186.203" dyno=web.1 connect=0ms service=8ms status=200 bytes=191 protocol=https
2022-09-23T13:49:00.937948+00:00 app[web.1]: device_count is
2022-09-23T13:49:00.938685+00:00 app[web.1]: 12
2022-09-23T13:49:52.814962+00:00 heroku[router]: at=info method=GET path="\/test\/devices\/123456789123456789123456789123456789123456789123456789\/123456789123456789123456789123456789123456789123456789123456789123456789" host=japsoc-passes-server-2.herokuapp.com request_id=c834c2df-b822-4796-b8ae-ab29cce6bdc2 fwd="147.12.186.203" dyno=web.1 connect=0ms service=5ms status=200 bytes=191 protocol=https
2022-09-23T13:49:52.809811+00:00 app[web.1]: device_count is
2022-09-23T13:49:52.810427+00:00 app[web.1]: 12

从日志可见，当identifier或push_token字符串过长时，记录未创建但返回200状态码。

原因分析 #

1. Active Record string类型默认长度限制：Rails中t.string默认映射PostgreSQL的varchar(255)类型，插入字符串超过255字符时，PostgreSQL会抛出截断错误，但Device.create会捕获错误并返回false，不会主动抛出异常，导致无错误提示但记录未创建。
2. 本地与Heroku环境差异：本地通常使用SQLite，其TEXT类型无严格长度限制，即使定义string也能插入超长内容；而Heroku的PostgreSQL严格遵循varchar(255)的长度规则。

解决步骤 #

1. 修改数据库字段类型：创建新迁移，将identifier和push_token改为无长度限制的text类型：

class ChangeDevicesColumnsToText < ActiveRecord::Migration[6.1]
  def change
    change_column :devices, :identifier, :text, null: false
    change_column :devices, :push_token, :text, null: false
  end
end

2. 部署迁移到Heroku：

git add db/migrate/[你的迁移文件名]
git commit -m "Change devices identifier and push_token to text type"
git push heroku main
heroku run rails db:migrate

3. 优化测试端点的错误反馈：修改端点代码，检查创建结果并返回明确状态码和错误信息，便于调试：

get "\/test\/devices\/:device_id\/:push_tokens" do
  device = Device.new(identifier: params[:device_id], push_token: params[:push_tokens])
  if device.save
    puts "device_count is #{Device.count}"
    status 201
  else
    puts "Failed to create device: #{device.errors.full_messages}"
    status 400
    body device.errors.full_messages.join(', ')
  end
end

修改后，超长字符串可正常插入Heroku的PostgreSQL数据库，同时端点会返回明确的错误信息辅助调试。

内容的提问来源于stack exchange，提问作者Korokus