August 2010
Intermediate to advanced
526 pages
23h 39m
English
Content preview from Using SQLite
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Name
VACUUM — Recover free space and optimize database
Syntax
Common Usage
VACUUM;
Description
The VACUUM command recovers free space from the
database file and releases it to the filesystem. VACUUM can also defragment
database structures and repack individual database pages.
VACUUM can only be run
against the main database (the database used to create the
database connection). VACUUM
has no effect on in-memory databases.
When data objects (rows, whole tables, indexes, etc.) are deleted or dropped from a database, the file size remains unchanged. Any database pages that are recovered from deleted objects are simply marked as free and available for any future database storage needs. As a result, under normal operations the database file can only grow in size.
Additionally, as rows are inserted and deleted from the database, the tables and indexes can become fragmented. In a dynamic database that normally experiences a high number of inserts, updates, and deletes, it is common for free pages to be scattered all across the database file. If a table or index requires additional pages for more storage, these will first be allocated off the free list. This means the actual parts of the database file that hold a particular table or index may become scattered and mixed all across the database file, lowering seek performance.
Finally, as rows are inserted, updated, and deleted, unused data blocks ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.