Now, it is time to see VACUUM in action. I have included this section here because my practical work as a PostgreSQL consultant and supporter (http://postgresql-support.de/) indicates that most people only have a very vague understanding of what happens on the storage side.
To stress this point again, in most cases, VACUUM will not shrink your tables; space is usually not returned to the filesystem.
Here is my example, which shows how to create a small table with customized autovacuum settings. The table is filled with 100,000 rows:
CREATE TABLE t_test (id int) WITH (autovacuum_enabled = off); INSERT INTO t_test SELECT * FROM generate_series(1, 100000);
The idea is to create a simple table containing 100,000 rows. ...