I'm more familiar with Postgres, but it basically instructs the table storage provider to clean up unused disk. Think of it roughly as defragmentation. You're

I'm more familiar with Postgres, but it basically instructs the table storage provider to clean up unused disk. Think of it roughly as defragmentation. You're trading work (in the form of writes and CPU) for reclaimed space. Unless SQLite has some semantics around it, replacing it with "xxxxxx;" will likely just cause it to run a bad command...might be more correct to replace it with something like "------;" (comment characters).