pub trait Storable: Debug {
type PageReferences: Iterator<Item = u64>;
// Required method
fn page_references(&self) -> Self::PageReferences;
// Provided methods
fn compare<T: LoadPage>(&self, _txn: &T, _b: &Self) -> Ordering { ... }
unsafe fn drop<T: AllocPage>(&self, txn: &mut T) -> Result<(), T::Error> { ... }
}Expand description
Types that can be stored on disk. This trait may be used in
conjunction with Sized in order to determine the on-disk size,
or with UnsizedStorable when special arrangements are needed.
The size limit for an entry depends on the datastructure. For B trees, nodes are guaranteed to be at least half-full (i.e. at least 2kiB), and we need at least two entries in each page in order to be able to rebalance in a deletion. A sufficient condition for this is that the size of any entry is less than 1/4th of the blocks. Now, internal nodes need 16 bytes of block header, and then 8 extra bytes for each entry. Entries must therefore not exceed 4080/4 - 8 = 1012 bytes.
Required Associated Types§
Sourcetype PageReferences: Iterator<Item = u64>
type PageReferences: Iterator<Item = u64>
An iterator over the offsets to pages contained in this
value. Only values from this crate can generate non-empty
iterators, but combined values (like tuples) must chain the
iterators returned by method page_offsets.
Required Methods§
Sourcefn page_references(&self) -> Self::PageReferences
fn page_references(&self) -> Self::PageReferences
If this value is an offset to another page at offset offset,
return Some(offset). Return None else.
Provided Methods§
Dyn Compatibility§
This trait is not dyn compatible.
In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.