reth_db_api/cursor.rs
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use std::{
fmt,
ops::{Bound, RangeBounds},
};
use crate::{
common::{IterPairResult, PairResult, ValueOnlyResult},
table::{DupSort, Table, TableRow},
DatabaseError,
};
/// A read-only cursor over table `T`.
pub trait DbCursorRO<T: Table> {
/// Positions the cursor at the first entry in the table, returning it.
fn first(&mut self) -> PairResult<T>;
/// Seeks to the KV pair exactly at `key`.
fn seek_exact(&mut self, key: T::Key) -> PairResult<T>;
/// Seeks to the KV pair whose key is greater than or equal to `key`.
fn seek(&mut self, key: T::Key) -> PairResult<T>;
/// Position the cursor at the next KV pair, returning it.
#[allow(clippy::should_implement_trait)]
fn next(&mut self) -> PairResult<T>;
/// Position the cursor at the previous KV pair, returning it.
fn prev(&mut self) -> PairResult<T>;
/// Positions the cursor at the last entry in the table, returning it.
fn last(&mut self) -> PairResult<T>;
/// Get the KV pair at the cursor's current position.
fn current(&mut self) -> PairResult<T>;
/// Get an iterator that walks through the table.
///
/// If `start_key` is `None`, then the walker will start from the first entry of the table,
/// otherwise it starts at the entry greater than or equal to the provided key.
fn walk(&mut self, start_key: Option<T::Key>) -> Result<Walker<'_, T, Self>, DatabaseError>
where
Self: Sized;
/// Get an iterator that walks over a range of keys in the table.
fn walk_range(
&mut self,
range: impl RangeBounds<T::Key>,
) -> Result<RangeWalker<'_, T, Self>, DatabaseError>
where
Self: Sized;
/// Get an iterator that walks through the table in reverse order.
///
/// If `start_key` is `None`, then the walker will start from the last entry of the table,
/// otherwise it starts at the entry greater than or equal to the provided key.
fn walk_back(
&mut self,
start_key: Option<T::Key>,
) -> Result<ReverseWalker<'_, T, Self>, DatabaseError>
where
Self: Sized;
}
/// A read-only cursor over the dup table `T`.
pub trait DbDupCursorRO<T: DupSort> {
/// Positions the cursor at the next KV pair of the table, returning it.
fn next_dup(&mut self) -> PairResult<T>;
/// Positions the cursor at the next KV pair of the table, skipping duplicates.
fn next_no_dup(&mut self) -> PairResult<T>;
/// Positions the cursor at the next duplicate value of the current key.
fn next_dup_val(&mut self) -> ValueOnlyResult<T>;
/// Positions the cursor at the entry greater than or equal to the provided key/subkey pair.
///
/// # Note
///
/// The position of the cursor might not correspond to the key/subkey pair if the entry does not
/// exist.
fn seek_by_key_subkey(&mut self, key: T::Key, subkey: T::SubKey) -> ValueOnlyResult<T>;
/// Get an iterator that walks through the dup table.
///
/// The cursor will start at different points in the table depending on the values of `key` and
/// `subkey`:
///
/// | `key` | `subkey` | **Equivalent starting position** |
/// |--------|----------|-----------------------------------------|
/// | `None` | `None` | [`DbCursorRO::first()`] |
/// | `Some` | `None` | [`DbCursorRO::seek()`] |
/// | `None` | `Some` | [`DbDupCursorRO::seek_by_key_subkey()`] |
/// | `Some` | `Some` | [`DbDupCursorRO::seek_by_key_subkey()`] |
fn walk_dup(
&mut self,
key: Option<T::Key>,
subkey: Option<T::SubKey>,
) -> Result<DupWalker<'_, T, Self>, DatabaseError>
where
Self: Sized;
}
/// Read write cursor over table.
pub trait DbCursorRW<T: Table> {
/// Database operation that will update an existing row if a specified value already
/// exists in a table, and insert a new row if the specified value doesn't already exist
fn upsert(&mut self, key: T::Key, value: T::Value) -> Result<(), DatabaseError>;
/// Database operation that will insert a row at a given key. If the key is already
/// present, the operation will result in an error.
fn insert(&mut self, key: T::Key, value: T::Value) -> Result<(), DatabaseError>;
/// Append value to next cursor item.
///
/// This is efficient for pre-sorted data. If the data is not pre-sorted, use
/// [`DbCursorRW::insert`].
fn append(&mut self, key: T::Key, value: T::Value) -> Result<(), DatabaseError>;
/// Delete current value that cursor points to
fn delete_current(&mut self) -> Result<(), DatabaseError>;
}
/// Read Write Cursor over `DupSorted` table.
pub trait DbDupCursorRW<T: DupSort> {
/// Delete all duplicate entries for current key.
fn delete_current_duplicates(&mut self) -> Result<(), DatabaseError>;
/// Append duplicate value.
///
/// This is efficient for pre-sorted data. If the data is not pre-sorted, use `insert`.
fn append_dup(&mut self, key: T::Key, value: T::Value) -> Result<(), DatabaseError>;
}
/// Provides an iterator to `Cursor` when handling `Table`.
pub struct Walker<'cursor, T: Table, CURSOR: DbCursorRO<T>> {
/// Cursor to be used to walk through the table.
cursor: &'cursor mut CURSOR,
/// `(key, value)` where to start the walk.
start: IterPairResult<T>,
}
impl<T, CURSOR> fmt::Debug for Walker<'_, T, CURSOR>
where
T: Table,
CURSOR: DbCursorRO<T> + fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("Walker").field("cursor", &self.cursor).field("start", &self.start).finish()
}
}
impl<T: Table, CURSOR: DbCursorRO<T>> Iterator for Walker<'_, T, CURSOR> {
type Item = Result<TableRow<T>, DatabaseError>;
fn next(&mut self) -> Option<Self::Item> {
self.start.take().or_else(|| self.cursor.next().transpose())
}
}
impl<'cursor, T: Table, CURSOR: DbCursorRO<T>> Walker<'cursor, T, CURSOR> {
/// construct Walker
pub fn new(cursor: &'cursor mut CURSOR, start: IterPairResult<T>) -> Self {
Self { cursor, start }
}
/// convert current [`Walker`] to [`ReverseWalker`] which iterates reversely
pub fn rev(self) -> ReverseWalker<'cursor, T, CURSOR> {
let start = self.cursor.current().transpose();
ReverseWalker::new(self.cursor, start)
}
}
impl<T: Table, CURSOR: DbCursorRW<T> + DbCursorRO<T>> Walker<'_, T, CURSOR> {
/// Delete current item that walker points to.
pub fn delete_current(&mut self) -> Result<(), DatabaseError> {
self.start.take();
self.cursor.delete_current()
}
}
/// Provides a reverse iterator to `Cursor` when handling `Table`.
/// Also check [`Walker`]
pub struct ReverseWalker<'cursor, T: Table, CURSOR: DbCursorRO<T>> {
/// Cursor to be used to walk through the table.
cursor: &'cursor mut CURSOR,
/// `(key, value)` where to start the walk.
start: IterPairResult<T>,
}
impl<T, CURSOR> fmt::Debug for ReverseWalker<'_, T, CURSOR>
where
T: Table,
CURSOR: DbCursorRO<T> + fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("ReverseWalker")
.field("cursor", &self.cursor)
.field("start", &self.start)
.finish()
}
}
impl<'cursor, T: Table, CURSOR: DbCursorRO<T>> ReverseWalker<'cursor, T, CURSOR> {
/// construct `ReverseWalker`
pub fn new(cursor: &'cursor mut CURSOR, start: IterPairResult<T>) -> Self {
Self { cursor, start }
}
/// convert current [`ReverseWalker`] to [`Walker`] which iterate forwardly
pub fn forward(self) -> Walker<'cursor, T, CURSOR> {
let start = self.cursor.current().transpose();
Walker::new(self.cursor, start)
}
}
impl<T: Table, CURSOR: DbCursorRW<T> + DbCursorRO<T>> ReverseWalker<'_, T, CURSOR> {
/// Delete current item that walker points to.
pub fn delete_current(&mut self) -> Result<(), DatabaseError> {
self.start.take();
self.cursor.delete_current()
}
}
impl<T: Table, CURSOR: DbCursorRO<T>> Iterator for ReverseWalker<'_, T, CURSOR> {
type Item = Result<TableRow<T>, DatabaseError>;
fn next(&mut self) -> Option<Self::Item> {
let start = self.start.take();
if start.is_some() {
return start
}
self.cursor.prev().transpose()
}
}
/// Provides a range iterator to `Cursor` when handling `Table`.
/// Also check [`Walker`]
pub struct RangeWalker<'cursor, T: Table, CURSOR: DbCursorRO<T>> {
/// Cursor to be used to walk through the table.
cursor: &'cursor mut CURSOR,
/// `(key, value)` where to start the walk.
start: IterPairResult<T>,
/// `key` where to stop the walk.
end_key: Bound<T::Key>,
/// flag whether is ended
is_done: bool,
}
impl<T, CURSOR> fmt::Debug for RangeWalker<'_, T, CURSOR>
where
T: Table,
CURSOR: DbCursorRO<T> + fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("RangeWalker")
.field("cursor", &self.cursor)
.field("start", &self.start)
.field("end_key", &self.end_key)
.field("is_done", &self.is_done)
.finish()
}
}
impl<T: Table, CURSOR: DbCursorRO<T>> Iterator for RangeWalker<'_, T, CURSOR> {
type Item = Result<TableRow<T>, DatabaseError>;
fn next(&mut self) -> Option<Self::Item> {
if self.is_done {
return None
}
let next_item = self.start.take().or_else(|| self.cursor.next().transpose());
match next_item {
Some(Ok((key, value))) => match &self.end_key {
Bound::Included(end_key) if &key <= end_key => Some(Ok((key, value))),
Bound::Excluded(end_key) if &key < end_key => Some(Ok((key, value))),
Bound::Unbounded => Some(Ok((key, value))),
_ => {
self.is_done = true;
None
}
},
Some(res @ Err(_)) => Some(res),
None => {
self.is_done = matches!(self.end_key, Bound::Unbounded);
None
}
}
}
}
impl<'cursor, T: Table, CURSOR: DbCursorRO<T>> RangeWalker<'cursor, T, CURSOR> {
/// construct `RangeWalker`
pub fn new(
cursor: &'cursor mut CURSOR,
start: IterPairResult<T>,
end_key: Bound<T::Key>,
) -> Self {
// mark done if range is empty.
let is_done = match start {
Some(Ok((ref start_key, _))) => match &end_key {
Bound::Included(end_key) if start_key > end_key => true,
Bound::Excluded(end_key) if start_key >= end_key => true,
_ => false,
},
None => true,
_ => false,
};
Self { cursor, start, end_key, is_done }
}
}
impl<T: Table, CURSOR: DbCursorRW<T> + DbCursorRO<T>> RangeWalker<'_, T, CURSOR> {
/// Delete current item that walker points to.
pub fn delete_current(&mut self) -> Result<(), DatabaseError> {
self.start.take();
self.cursor.delete_current()
}
}
/// Provides an iterator to `Cursor` when handling a `DupSort` table.
///
/// Reason why we have two lifetimes is to distinguish between `'cursor` lifetime
/// and inherited `'tx` lifetime. If there is only one, rust would short circle
/// the Cursor lifetime and it wouldn't be possible to use Walker.
pub struct DupWalker<'cursor, T: DupSort, CURSOR: DbDupCursorRO<T>> {
/// Cursor to be used to walk through the table.
pub cursor: &'cursor mut CURSOR,
/// Value where to start the walk.
pub start: IterPairResult<T>,
}
impl<T, CURSOR> fmt::Debug for DupWalker<'_, T, CURSOR>
where
T: DupSort,
CURSOR: DbDupCursorRO<T> + fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("DupWalker")
.field("cursor", &self.cursor)
.field("start", &self.start)
.finish()
}
}
impl<T: DupSort, CURSOR: DbCursorRW<T> + DbDupCursorRO<T>> DupWalker<'_, T, CURSOR> {
/// Delete current item that walker points to.
pub fn delete_current(&mut self) -> Result<(), DatabaseError> {
self.start.take();
self.cursor.delete_current()
}
}
impl<T: DupSort, CURSOR: DbDupCursorRO<T>> Iterator for DupWalker<'_, T, CURSOR> {
type Item = Result<TableRow<T>, DatabaseError>;
fn next(&mut self) -> Option<Self::Item> {
let start = self.start.take();
if start.is_some() {
return start
}
self.cursor.next_dup().transpose()
}
}