how to restore a postgresql database to the exact same state?

Question

I am trying to

1. create a snapshot of a PostgreSQL database (using pg_dump ),
2. do some random tests, and
3. restore to the exact same state as the snapshot, and do some other random tests.

These can happen over many/different days. Also I am in a multi-user environment where I am not DB admin. In particular, I cannot create new DB.

However, when I restore db using

 gunzip -c dump_file.gz | psql my_db 

changes in step 2 above remain.

For example, if I make a copy of a table:

 create table foo1 as (select * from foo);

and then restore, the copied table foo1 remains there.

Could some explain how can I restore to the exact same state as if step 2 never happened?

-- Update --

Following the comments @a_horse_with_no_name, I tried to to use

DROP OWNED BY my_db_user 

to drop all my objects before restore, but I got an error associated with an extension that I cannot control, and my tables remain intact.

ERROR:  cannot drop sequence bg_gid_seq because extension postgis_tiger_geocoder requires it
HINT:  You can drop extension postgis_tiger_geocoder instead.

Any suggestions?

Answer 1

You have to remove everything that's there by dropping and recreating the database or something like that. pg_dump basically just makes an SQL script that, when applied, will ensure all the tables, stored procs, etc. exist and have their data. It doesn't remove anything.

Answer 2

您可以使用PostgreSQL模式 。