Enum PageHandle 

pub enum PageHandle {
    Shared(Arc<Page>),
    Owned(Page),
}

Owning handle to a page returned by ReaderSnapshot::read_page.

#81: read_page used to return an owned Page (a 4 KiB body clone) on every call, including the common frozen-view hit. A point read descends catalog + primary and an index lookup descends two trees, so each op paid 3-5 such 4 KiB copies. PageHandle removes the copy on the hot path:

• PageHandle::Shared — frozen-view hit. Holds an Arc<Page> cloned from the snapshot’s view (a refcount bump, no body copy). Sound because committed pages are immutable: a new version is a fresh Arc under the same PageId, never an in-place mutation of a shared Arc (see frozen_view).
• PageHandle::Owned — disk / cache miss. Holds the freshly read, checksum-verified Page produced by the existing read_main_file_page / read_cache_or_main (read_through) path; integrity behaviour is unchanged.

Concrete enum, not dyn (Rule 9). Both arms are a single pointer (Arc<Page> and Page’s Box<[u8; PAGE_SIZE]>), so the variants are balanced and clippy::large_enum_variant does not fire.

Variants

Shared(Arc<Page>)

Frozen-view hit — shares the snapshot’s Arc<Page> with no 4 KiB body clone.

Owned(Page)

Disk / cache miss — owns the checksum-verified page bytes.

Implementations

impl PageHandle

pub fn as_bytes(&self) -> &[u8; 4096]

Borrow the page’s raw bytes for decoding, without copying.

The match over both arms is total — no Result, no unwrap/expect (Rule 7): every PageHandle always holds a readable page in exactly one of its two arms. Callers that only need to decode (e.g. BTree::get_via_snapshot, Catalog::lookup_via_snapshot) should keep the PageHandle alive for the duration of the borrow and call this.

pub fn into_page(self) -> Page

Consume the handle and produce an owned Page.

The Shared arm clones the body exactly once (only when an owned page is genuinely required, e.g. the public crate::ReadTxn::read_page whose pager lock guard cannot outlive the call); the Owned arm moves with no copy. This is the only place the hot-path frozen-view clone is paid, and only for callers that ask for ownership.

Trait Implementations

impl Clone for PageHandle

fn clone(&self) -> PageHandle

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for PageHandle

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.