Removal of Role PostgreSQL Failed - cache lookup failed for database - ruby-on-rails

Question

This is my first time using PostgreSQL for production.
I made a database blog_production with username blog_production and generated password from gemfile capistrano-postgresql. Once it is generated, I tried to delete database blog_production with this command from terminal:
$ sudo -u postgres dropdb blog_production
After that I tried to delete user blog_production with this command:
$ sudo -u postgres droprole blog_production
And it returned dropuser: removal of role "blog_production" failed: ERROR: cache lookup failed for database 16417
1.) Why is this happening?
2.) I also tried to delete from psql using DELETE FROM pg_roles WHERE rolname='blog_production' but it returned the same error (cache lookup failed)
3.) How do I solve this problem?
Thank you.
Additional Information
PostgreSQL Version
PostgreSQL 9.1.15 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3, 64-bit
(1 row)
select * from pg_shdepend where dbid = 16417;
dbid | classid | objid | objsubid | refclassid | refobjid | deptype
-------+---------+-------+----------+------------+----------+---------
16417 | 1259 | 16419 | 0 | 1260 | 16418 | o
16417 | 1259 | 16426 | 0 | 1260 | 16418 | o
16417 | 1259 | 16428 | 0 | 1260 | 16418 | o
(3 rows)
select * from pg_database where oid = 16417;
datname | datdba | encoding | datcollate | datctype | datistemplate | datallowconn | datconnlimit | datlastsysoid | datfrozenxid | dattablespace | datacl
---------+--------+----------+------------+----------+---------------+--------------+--------------+---------------+--------------+---------------+--------
(0 rows)
select * from pg_authid where rolname = 'blog_production'
rolname | rolsuper | rolinherit | rolcreaterole | rolcreatedb | rolcatupdate | rolcanlogin | rolreplication | rolconnlimit | rolpassword | rolvaliduntil
-----------------+----------+------------+---------------+-------------+--------------+-------------+----------------+--------------+-------------------------------------+---------------
blog_production | f | t | f | f | f | t | f | -1 | md5d4d2f8789ab11ba2bd019bab8be627e6 |
(1 row)

Answer 1

Somehow the DROP database; didn't drop the shared dependencies correctly. PostgreSQL still thinks that your user owns three tables in the database you dropped.
Needless to say this should not happen; it's almost certainly a bug, though I don't know how we'd even begin tracking it down unless you know exactly what commands you ran etc to get to this point, right from creating the DB.
If the PostgreSQL install's data isn't very big and if you can share the contents, can I get you to stop the database server and make a tarball of the whole database directory, then send it to me? I'd like to see if I can tell what happened to get you to this point.
Send a dropbox link to craig#2ndquadrant.com . Just:
sudo service postgresql stop
sudo tar cpjf ~abrahamks/abrahamks-postgres.tar.gz \
/var/lib/postgresql/9.1/main \
/etc/postgresql/9.1/main \
/var/log/postgresql/postgresql-9.1-main-*.
/usr/lib/postgresql/9.1
sudo chown abrahamks ~abrahamks/abrahamks-postgres.tar.gz
and upload abrahamks-postgres.tar.gz from your home folder.
Replace abrahamks with your username on your system. You might need to adjust the paths above if I'm misremembering where the PostgreSQL data lives on Debian-derived systems.
Note that this contains all your databases not just the one that was an issue, and it also contains your PostgreSQL user accounts.
(If you're going to send me a copy, do so before continuing):
Anyway, since the database is dropped, it is safe to manually remove the dependencies that should've been removed by DROP DATABASE:
DELETE FROM pg_shdepend WHERE dbid = 16417
It should then be possible to DROP USER blog_production;