Thread: slow seqscan after vacuum analize

I have a simple query that scans each record, like this: select * from
utente where luogorilasciodoc='ciao'
The execution time BEFORE vacuum is: 1203ms The execution time AFTER
vacuum is: 6656ms !!!
What is going on? Thought that one vaccum the db to get better
performance!

PostgreSQL Ver. 7.3.4 on linux

Thank you
Edoardo