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.