The most effective way to test pg_upgrade, aside from testing on user
data, is by upgrading the PostgreSQL regression database.

This testing process first requires the creation of a valid regression
database dump.  Such files contain most database features and are
specific to each major version of Postgres.

Here are the steps needed to create a regression database dump file:

1)  Create and populate the regression database in the old cluster
    This database can be created by running 'gmake installcheck' from
    src/test/regression.

2)  Use pg_dump to dump out the regression database
    Use the new cluster's pg_dump on the old database to minimize
    whitespace differences in the diff.

3)  Adjust the regression database dump file

    a)  Change CREATE FUNCTION shared object paths to use '$libdir'
        The old and new cluster will have different shared object paths.

    b)  Remove 'regex_flavor' (not supported in Postgres 9.0)

    c)  Change CREATE OR REPLACE LANGUAGE to CREATE LANGUAGE
        The former syntax is only supported in Postgres 9.0.

    d)  Perform the load/dump twice
        This fixes problems with the ordering of COPY columns for
        inherited tables.

    e)  Fix any wrapping format differences
        Commands like CREATE TRIGGER and ALTER TABLE sometimes have
        differences.

    f)  Adjust extra_float_digits
	Postgres 9.0 pg_dump uses extra_float_digits=-2 for pre-9.0
	databases, and extra_float_digits=-3 for >= 9.0 databases.
	It is necessary to modify 9.0 pg_dump to always use -3, and
	modify the pre-9.0 old server to accept extra_float_digits=-3.

Once the dump is created, it can be repeatedly loaded into the old
database, upgraded, and dumped out of the new database, and then
compared to the original version. To test the dump file, perform these
steps:

1)  Create the old and new clusters in different directories.

2)  Copy the regression shared object files into the appropriate /lib
    directory for old and new clusters.

3)  Create the regression database in the old server.

4)  Load the dump file created above into the regression database; 
    check for errors while loading.

5)  Upgrade the old database to the new major version, as outlined in
    the pg_upgrade manual section.

6)  Use pg_dump to dump out the regression database in the new cluster.

7)  Diff the regression database dump file with the regression dump
    file loaded into the old server.




