Besides the use mentioned above, this patch allows one to dump Globals from their AWS RDS Postgres Database and have a complete backup as a part of their Disaster Recovery (DR) solution. This earlier required an inelegant hack (detailed here in another post of mine) that wasn't very convenient for a regular user.
For those interested, RDS Postgres (by design) doesn't allow you to read pg_authid, which was earlier necessary for pg_dumpall to work. With this patch checked-in, pg_dumpall now uses a workaround (pg_roles) to read the same data (except passwords) and generate the same SQL Script.
With that mentioned, let's get our hands dirty and see a working solution:
# Take RDS Postgres Dump
# We store the pgdb database in pgdb.sql and globals in pgdb_globals.sql
pg_dumpall --globals-only --no-role-password \
-U rdssuperuser -h rdsinstance \
2>stderr.txt > pgdb_globals.sql
pg_dump -U rdssuperuser -h rdsinstance pgdb 2>stderr.txt > pgdb.sql
psql -U postgres -c "CREATE DATABASE pgdb;"
# rdsadmin database (even if empty) is required for the next script
psql -U postgres -c "CREATE DATABASE rdsadmin;"
psql -U postgres pgdb < pgdb_globals.sql
psql -U postgres pgdb < pgdb.sql
Big thanks to Simon for ironing out a few issues, Stephen, David & Robert for their (critical) reviews.