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

Question

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

yum list postgresql*
Installed         


        

Answer 1

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.