Struct Cursor

pub struct Cursor<K: TransactionKind, T: Table> { /* private fields */ }

Available on crate feature mdbx only.

Cursor wrapper to access KV items.

Trait Implementations

impl<K: TransactionKind, T: Table> DbCursorRO<T> for Cursor<K, T>

fn first(&mut self) -> PairResult<T>

Positions the cursor at the first entry in the table, returning it.

fn seek_exact(&mut self, key: <T as Table>::Key) -> PairResult<T>

Seeks to the KV pair exactly at key.

fn seek(&mut self, key: <T as Table>::Key) -> PairResult<T>

Seeks to the KV pair whose key is greater than or equal to key.

fn next(&mut self) -> PairResult<T>

Position the cursor at the next KV pair, returning it.

fn prev(&mut self) -> PairResult<T>

Position the cursor at the previous KV pair, returning it.

fn last(&mut self) -> PairResult<T>

Positions the cursor at the last entry in the table, returning it.

fn current(&mut self) -> PairResult<T>

Get the KV pair at the cursor’s current position.

fn walk( &mut self, start_key: Option<T::Key>, ) -> Result<Walker<'_, T, Self>, DatabaseError>

Get an iterator that walks through the table.

fn walk_range( &mut self, range: impl RangeBounds<T::Key>, ) -> Result<RangeWalker<'_, T, Self>, DatabaseError>

Get an iterator that walks over a range of keys in the table.

fn walk_back( &mut self, start_key: Option<T::Key>, ) -> Result<ReverseWalker<'_, T, Self>, DatabaseError>

Get an iterator that walks through the table in reverse order.

impl<T: Table> DbCursorRW<T> for Cursor<RW, T>

fn upsert(&mut self, key: T::Key, value: T::Value) -> Result<(), DatabaseError>

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

For a DUPSORT table, upsert will not actually update-or-insert. If the key already exists, it will append the value to the subkey, even if the subkeys are the same. So if you want to properly upsert, you’ll need to seek_exact & delete_current if the key+subkey was found, before calling upsert.

fn append(&mut self, key: T::Key, value: T::Value) -> Result<(), DatabaseError>

Appends the data to the end of the table. Consequently, the append operation will fail if the inserted key is less than the last table key

fn insert(&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 delete_current(&mut self) -> Result<(), DatabaseError>

Delete current value that cursor points to

impl<K: TransactionKind, T: DupSort> DbDupCursorRO<T> for Cursor<K, T>

fn next_dup(&mut self) -> PairResult<T>

Returns the next (key, value) pair of a DUPSORT table.

fn next_no_dup(&mut self) -> PairResult<T>

Returns the next (key, value) pair skipping the duplicates.

fn next_dup_val(&mut self) -> ValueOnlyResult<T>

Returns the next value of a duplicate key.

fn walk_dup( &mut self, key: Option<T::Key>, subkey: Option<T::SubKey>, ) -> Result<DupWalker<'_, T, Self>, DatabaseError>

Depending on its arguments, returns an iterator starting at:

• Some(key), Some(subkey): a key item whose data is >= than subkey
• Some(key), None: first item of a specified key
• None, Some(subkey): like first case, but in the first key
• None, None: first item in the table of a DUPSORT table.

fn seek_by_key_subkey( &mut self, key: <T as Table>::Key, subkey: <T as DupSort>::SubKey, ) -> ValueOnlyResult<T>

Positions the cursor at the entry greater than or equal to the provided key/subkey pair.

impl<T: DupSort> DbDupCursorRW<T> for Cursor<RW, T>

fn delete_current_duplicates(&mut self) -> Result<(), DatabaseError>

Delete all duplicate entries for current key.

fn append_dup( &mut self, key: T::Key, value: T::Value, ) -> Result<(), DatabaseError>

Append duplicate value.

impl<K: Debug + TransactionKind, T: Debug + Table> Debug for Cursor<K, T>

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

Formats the value using the given formatter.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 48 bytes