What is VACUUM in database?

What does VACUUM a database mean?

In Postgres, vacuumdb identifies space that's occupied by deleted rows and catalogues it for future use. 'vacuum full' does a more comprehensive examination and moves records into the newly created space.

What does VACUUM do in SQL?

The VACUUM command works by copying the contents of the database into a temporary database file and then overwriting the original with the contents of the temporary file. When overwriting the original, a rollback journal or write-ahead log WAL file is used just as it would be for any other database transaction.

What is VACUUM analyze?

"Vacuum Analyze" actually performs 2 entirely different tasks. Vacuum is used to free up space occupied by dead tuples/rows. Analyze is used to analyze the contents of the table, which in turn helps planner to create better query plans.

Does VACUUM full lock database?

Here's a short concise answer. Vacuum full takes out an exclusive lock and rebuilds the table so that it has no empty blocks (we'll pretend fill factor is 100% for now).