【发布时间】：2016-05-02 12:08:17
【问题描述】：
我总是使用默认为 sql 数据库语言的 rails new app_name 启动我的新 Rails 应用程序。我想知道三件事：
- 有没有办法在创建应用程序时将数据库语言默认为 pg？
-
创建应用程序后，如何将其从 sql 更改为 pg？我尝试更改 gem 文件中的数据库语言，但通常会收到此错误：
$ gem install pg -v '0.18.4' Building native extensions. This could take a while... ERROR: Error installing pg: ERROR: Failed to build gem native extension. current directory: /Users/eric.park/.rvm/gems/ruby-2.3.0/gems/pg-0.18.4/ext /Users/eric.park/.rvm/rubies/ruby-2.3.0/bin/ruby -r ./siteconf20160125-86030-51pvqj.rb extconf.rb checking for pg_config... no No pg_config... trying anyway. If building fails, please try again with --with-pg-config=/path/to/pg_config checking for libpq-fe.h... no Can't find the 'libpq-fe.h header *** extconf.rb failed *** Could not create Makefile due to some reason, probably lack of necessary libraries and/or headers. Check the mkmf.log file for more details. You may need configuration options. Provided configuration options: --with-opt-dir --with-opt-include --without-opt-include=${opt-dir}/include --with-opt-lib --without-opt-lib=${opt-dir}/lib --with-make-prog --without-make-prog --srcdir=. --curdir --ruby=/Users/eric.park/.rvm/rubies/ruby-2.3.0/bin/$(RUBY_BASE_NAME) --with-pg --without-pg --enable-windows-cross --disable-windows-cross --with-pg-config --without-pg-config --with-pg_config --without-pg_config --with-pg-dir --without-pg-dir --with-pg-include --without-pg-include=${pg-dir}/include --with-pg-lib --without-pg-lib=${pg-dir}/lib To see why this extension failed to compile, please check the mkmf.log which can be found here: /Users/eric.park/.rvm/gems/ruby-2.3.0/extensions/x86_64-darwin-14/2.3.0/pg-0.18.4/mkmf.log extconf failed, exit code 1 Gem files will remain installed in /Users/eric.park/.rvm/gems/ruby-2.3.0/gems/pg-0.18.4 for inspection. Results logged to /Users/eric.park/.rvm/gems/ruby-2.3.0/extensions/x86_64-darwin-14/2.3.0/pg-0.18.4/gem_make.out
最后，Heroku 不支持 sql 的地方在哪里？
【问题讨论】：
标签： ruby-on-rails sql-server heroku