我尝试使用宝石安装pg,但它似乎不工作。

Gem install pg给出这个错误

Temporarily enhancing PATH to include DevKit...
Building native extensions.  This could take a while...
ERROR:  Error installing pg:
        ERROR: Failed to build gem native extension.

C:/Ruby/bin/ruby.exe 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
        --without-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=C:/Ruby/bin/ruby
        --with-pg
        --without-pg
        --with-pg-dir
        --without-pg-dir
        --with-pg-include
        --without-pg-include=${pg-dir}/include
        --with-pg-lib
        --without-pg-lib=${pg-dir}/lib
        --with-pg-config
        --without-pg-config
        --with-pg_config
        --without-pg_config


Gem files will remain installed in C:/Ruby/lib/ruby/gems/1.8/gems/pg-0.10.1 for
inspection.
Results logged to C:/Ruby/lib/ruby/gems/1.8/gems/pg-0.10.1/ext/gem_make.out

当前回答

不管你运行的是什么操作系统,都要查看“Makefile”的日志文件,看看发生了什么,而不是盲目地安装东西。

在我的例子中,MAC OS,日志文件在这里:

/Users/za/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/extensions/x86_64-darwin-15/2.3.0-static/pg-1.0.0/mkmf.log

日志提示无法创建make文件,原因如下:

Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers

在mkmf.log中,您将看到它无法找到完成构建所需的库。

checking for pg_config... no
Can't find the 'libpq-fe.h header
blah blah

运行“brew install postgresql”后,我可以看到所有需要的库都在那里:

za:myapp za$ cat /Users/za/.rbenv/versions/2.3.0/lib/ruby/gems/2.3.0/extensions/x86_64-darwin-15/2.3.0-static/pg-1.0.0/mkmf.log | grep yes
find_executable: checking for pg_config... -------------------- yes
find_header: checking for libpq-fe.h... -------------------- yes
find_header: checking for libpq/libpq-fs.h... -------------------- yes
find_header: checking for pg_config_manual.h... -------------------- yes
have_library: checking for PQconnectdb() in -lpq... -------------------- yes
have_func: checking for PQsetSingleRowMode()... -------------------- yes
have_func: checking for PQconninfo()... -------------------- yes
have_func: checking for PQsslAttribute()... -------------------- yes
have_func: checking for PQencryptPasswordConn()... -------------------- yes
have_const: checking for PG_DIAG_TABLE_NAME in libpq-fe.h... -------------------- yes
have_header: checking for unistd.h... -------------------- yes
have_header: checking for inttypes.h... -------------------- yes
checking for C99 variable length arrays... -------------------- yes

其他回答

$ PATH=$PATH:/Library/PostgreSQL/9.1/bin sudo gem install pg

将9.1版本替换为系统上安装的版本。

如果你使用的是jruby而不是ruby,在安装pg gem时也会遇到类似的问题。相反,你需要安装适配器:

gem 'activerecord-jdbcpostgresql-adapter'

我有个问题,这个方法对我很管用:

安装postgresql-devel包,这将解决pg_config缺失的问题。

sudo apt-get install libpq-dev

你只要到这里看看你的pg版本是否支持Win32平台,然后使用这个命令来安装:

Gem install pg -v 0.14.1——platform=x86-mingw32

在Mac上安装postgres然后捆绑安装