RailsでHeroku の DB(Postgres) にローカルや外部サーバーなどからアクセスする方法

HerokuのPostgresの情報を見つける

$ heroku pg:info --app appname
=== HEROKU_POSTGRESQL_HOGE_URL (DATABASE_URL)
Plan:        Hobby-dev
Status:      Available
Connections: 1/20
PG Version:  9.3.6
Created:     2014-01-01 01:00 UTC
Data Size:   0.1 MB
Tables:      1
Rows:        1/10000 (In compliance)
Fork/Follow: Unsupported
Rollback:    Unsupported

$ heroku pg:credentials HEROKU_POSTGRESQL_HOGE --app appname
Connection info string:
   "dbname=db host=host port=port user=user password=password sslmode=require"
Connection URL:
    postgres://hogehoge~~~~

この情報を使っていきます。

pryで試してみます

Frame number: 0/6
[1] pry(main)> require 'pg'
true
[2] pry(main)> require 'active_record'
false
[3] pry(main)> ActiveRecord::Base.establish_connection(
[3] pry(main)*   adapter:  'postgresql',
[3] pry(main)*   host:     'host',
[3] pry(main)*   database: 'db',
[3] pry(main)*   port:     port,
[3] pry(main)*   username: 'user',
[3] pry(main)*   password: 'password',
[3] pry(main)*   sslmode:  'require'
[3] pry(main)* )
#<ActiveRecord::ConnectionAdapters::ConnectionPool:0x007f287aaba640
　・
　・
　・

[4] pry(main)> ActiveRecord::Base.connection.execute("SELECT version()").first
   (226.5ms)  SELECT version()
{
    "version" => "PostgreSQL 9.3.6 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3, 64-bit"
}

# 生SQLを使う版
[5] pry(main)> ActiveRecord::Base.connection.execute("SELECT * from hoges;").first
   (525.7ms)  SELECT * from product_comments;
{
                             "id" => "1",
                               .
                               .
                               .
}

# ActiveRecordを使う版
[6] pry(main)> Hoge.first
{
                             "id" => "1",
                               .
                               .
                               .
}

コードでは

  def get_data_from_heroku_pg
    require 'pg'
    require 'active_record' # 必要あれば

    # Change the following to reflect your database settings
    ActiveRecord::Base.establish_connection(
      adapter:  'postgresql',
      host:     'host',
      database: 'db',
      port:     port,
      username: 'user',
      password: 'password',
      sslmode:  'require'
    )

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References