Trait PageStore

Source

pub trait PageStore: Send + Sync {
    // Required methods
    fn page_size(&self) -> usize;
    fn allocate_page(&self) -> Page;
    fn read_into(&self, id: PageId, page: &mut Page) -> PageResult<()>;
    fn write_page(&self, id: PageId, page: &mut Page) -> PageResult<()>;
    fn sync(&self) -> PageResult<()>;
}

Expand description

A backing store of fixed-size pages addressed by PageId.

This is the extension seam between the buffer pool and what holds the pages. PageFile is the implementation that matters — pages on disk through Direct I/O — but the pool is written against this trait so it can be driven by an in-memory store in tests, or by an alternative backend later, without change.

A store does not cache, pin, or track dirtiness; those are the pool’s job. A store only has to read a page by id, write a page to an id, allocate a blank page of the right size, and flush to durability.

§Examples

A PageFile is a PageStore, so it can back a pool:

use page_db::{BufferPool, PageFile, PageId, DEFAULT_PAGE_SIZE};

let file = PageFile::open(&path, DEFAULT_PAGE_SIZE)?;
let pool = BufferPool::new(file, 64);   // 64 frames over the file
let _ = pool.new_page(PageId::new(0))?;