pg_upgrade performance with 150k tables

I received a private email report yesterday from someone using
pg_upgrade with PG 9.0 who found it took five hours for pg_upgrade to
upgrade a database with 150k tables.  Yes, that is a lot of tables, but
pg_upgrade should be able to do better than that.

I have modified pg_upgrade in git master to cache scandir() and reduce
array lookups and the time is down to 38 minutes.  (He prototyped a hash
implementation that was 30 minutes but it was too much code for my
taste.)

I don't think this is reasonable to backpatch.   If anyone else sees
cases for pg_upgrade improvement, please let me know.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + It's impossible for everything to be true. +