pg_config, ruby pg, postgresql 9.0 problem after upgrade, centos 5

After upgrade postgresql 8.1 to 9.0 ive noticed issues with libraries dependency. Postgresql works fine (connection, queries).

yum list postgresql*
Installed Packages
postgresql.i386 9.0.0-1PGDG.el5 installed
postgresql-debuginfo.i386 9.0.0-1PGDG.el5 installed
postgresql-devel.i386 9.0.0-1PGDG.el5 installed
postgresql-libs.i386 9.0.0-1PGDG.el5 installed
postgresql-odbcng.i386 0.90.101-2.el5 installed
postgresql-plruby.i386 0.5.1-5.el5 installed
postgresql-server.i386 9.0.0-1PGDG.el5 install

but when im trying to install 'pg' for ruby, ive received

gem install pg
Building native extensions.  This could take a while...
ERROR:  Error installing pg:
        ERROR: Failed to build gem native extension.

/usr/local/bin/ruby extconf.rb
checking for pg_config... no
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.

When trying with another ruby-postgres driver, ive got

yum install ruby-postgres
ruby-postgres-0.7.1-5.el5.i386 from epel has depsolving problems
  --> Missing Dependency: libpq.so.4 is needed by package ruby-postgres-0.7.1-5.el5.i386 (epel)

and

locate libpq.so.4
/usr/lib/libpq.so.4
/usr/lib/libpq.so.4.1

also exported path

LD_LIBRARY_PATH=/usr/pgsql-9.0/lib
export LD_LIBRARY_PATH

after running ruby script with "require pg" (works on 8.1), ive got:

/usr/local/lib/r开发者_StackOverflow中文版uby/site_ruby/1.8/i686-linux/pg_ext.so: libpq.so.4: cannot open shared object file: No such file or directory - /usr/local/lib/ruby/site_ruby/1.8/i686-linux/pg_ext.so (LoadError)
        from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:29:in `require'
        from /usr/local/lib/ruby/site_ruby/1.8/pg.rb:12
        from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:29:in `gem_original_require'
        from /usr/local/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:29:in `require'

Any suggestions what to do more?

---

There are various config options you can add to the gem install, like -with-opt-dir, --with-pg-dir and --with-pg-config. Look at this mailing list thread:

http://www.ruby-forum.com/topic/409608

---

$ gem --version
1.3.7

$ ruby --version
ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-linux]

$ cat /etc/redhat-release 
CentOS release 5.4 (Final)

$ uname -m
x86_64

sudo yum list installed | grep postgre    (see what you have installed)
sudo yum list available | grep postgre    (I was missing postgresql-devel)
sudo yum install postgresql-devel         (I installed it)
sudo gem install pg                       (no error this time!)

$ gem list --local | grep pg
pg (0.11.0)

---

This seems like a pg config file location error,

gem install pg -- --with-pgsql-lib=/usr/pgsql-9.0/lib --with-pg-config=/usr/pgsql-9.1/bin/pg_config

solves it!!

gem install pg -- --with-pgsql-lib=/usr/pgsql-9.0/lib --with-pg-config=/usr/pgsql-9.1/bin/pg_config

/usr/local/lib/ruby/1.9.1/yaml.rb:56:in `<top (required)>':
It seems your ruby installation is missing psych (for YAML output).
To eliminate this warning, please install libyaml and reinstall your ruby.
Building native extensions.  This could take a while...
Successfully installed pg-0.14.0
1 gem installed
Installing ri documentation for pg-0.14.0...
Installing RDoc documentation for pg-0.14.0...

---

On Mac OSX 10.6.8, using the MacPorts install of Postgres 9, the following command worked for me:

gem install pg -- --with-pgsql-lib=/opt/local/lib/postgresql90/lib --with-pg-config=/opt/local/lib/postgresql90/bin/pg_config

---

libpq.so.4 is from an older version of PostgreSQL; 9.0 ships with /usr/pgsql-9.0/lib/libpq.so.5

If you have a program that was built against libpq.so.4, that file is provided by the compat-postgresql-libs packages, which you may not have installed. A lot of people remove it using "--force" because it can be hard to get the newer RPMs installed otherwise; that's a bad idea, but the alternative is complicated. If you've installed that package, you should find a /usr/lib/libpq.so.4 available that makes your existing program, compiled originally for the older PostgreSQL, happy.