Struct mmtkvdb::TxnRo

pub struct TxnRo<'a> { /* private fields */ }

Read-only transaction

A read-only transaction can be started with Env::txn_ro.

The methods for read-only access to the database are accessible through the Txn trait (which is implemented by TxnRo and TxnRw).

Read-only transactions do not need to be committed or aborted; their handles can be simply dropped when not needed anymore.

Opposed to read-write transactions (TxnRw), read-only transactions (TxnRo) are Send. However, they are not Sync. Thus, if you want to use a read-only transaction from several threads concurrently, you have to synchronize the use, e.g. by wrapping the TxnRo in a Mutex.

Trait Implementations

impl<'a> Debug for TxnRo<'a>

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

Formats the value using the given formatter.

impl<'a> Txn for TxnRo<'a>

fn get<'kr, K, V, C, KRef>( &self, db: &Db<K, V, C>, key: KRef ) -> Result<Option<V::AlignedRef<'_>>>where K: ?Sized + Storable + 'kr, V: ?Sized + Storable, C: Constraint, KRef: StorableRef<'kr, K>,

Get reference to value in database

fn new_cursor<K, V, C>(&self, db: &Db<K, V, C>) -> Result<Cursor<K, V, C>>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Create a new cursor

fn cursor_get_current_value_count<K, V>( &self, cursor: &Cursor<K, V, KeysDuplicate> ) -> Result<usize>where K: ?Sized + Storable, V: ?Sized + Storable,

Get number of values for current cursor position

fn cursor_set_first<K, V, C>(&self, cursor: &Cursor<K, V, C>) -> Result<bool>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Set cursor to first entry in database

fn cursor_set_first_get_pair<K, V, C>( &self, cursor: &Cursor<K, V, C> ) -> Result<Option<(K::AlignedRef<'_>, V::AlignedRef<'_>)>>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Set cursor to first entry in database and get pair

fn cursor_set_last<K, V, C>(&self, cursor: &Cursor<K, V, C>) -> Result<bool>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Set cursor to last entry in database

fn cursor_set_last_get_pair<K, V, C>( &self, cursor: &Cursor<K, V, C> ) -> Result<Option<(K::AlignedRef<'_>, V::AlignedRef<'_>)>>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Set cursor to last entry in database and get pair

fn cursor_get_current_key<K, V, C>( &self, cursor: &Cursor<K, V, C> ) -> Result<Option<K::AlignedRef<'_>>>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Get key at current cursor position

fn cursor_get_current_value<K, V, C>( &self, cursor: &Cursor<K, V, C> ) -> Result<Option<V::AlignedRef<'_>>>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Get value at current cursor position

fn cursor_get_current_pair<K, V, C>( &self, cursor: &Cursor<K, V, C> ) -> Result<Option<(K::AlignedRef<'_>, V::AlignedRef<'_>)>>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Get key-value pair at current cursor position

fn cursor_set_key<'kr, K, V, C, KRef>( &self, cursor: &Cursor<K, V, C>, key: KRef ) -> Result<bool>where K: ?Sized + Storable + 'kr, V: ?Sized + Storable, C: Constraint, KRef: StorableRef<'kr, K>,

Set cursor to key

fn cursor_set_key_get_value<'kr, K, V, C, KRef>( &self, cursor: &Cursor<K, V, C>, key: KRef ) -> Result<Option<V::AlignedRef<'_>>>where K: ?Sized + Storable + 'kr, V: ?Sized + Storable, C: Constraint, KRef: StorableRef<'kr, K>,

Set cursor to key and get value

fn cursor_search_key<'kr, K, V, C, KRef>( &self, cursor: &Cursor<K, V, C>, key: KRef ) -> Result<bool>where K: ?Sized + Storable + 'kr, V: ?Sized + Storable, C: Constraint, KRef: StorableRef<'kr, K>,

Set cursor to key or next greater key if not existent

fn cursor_search_key_get_key<'kr, K, V, C, KRef>( &self, cursor: &Cursor<K, V, C>, key: KRef ) -> Result<Option<K::AlignedRef<'_>>>where K: ?Sized + Storable + 'kr, V: ?Sized + Storable, C: Constraint, KRef: StorableRef<'kr, K>,

👎Deprecated since 0.14.0: use <code>cursor_search_key</code> (with subsequent <code>cursor_get_current_key</code>) or <code>cursor_search_key_get_pair</code>

Set cursor to key or next greater key if not existent and get key

fn cursor_search_key_get_pair<'kr, K, V, C, KRef>( &self, cursor: &Cursor<K, V, C>, key: KRef ) -> Result<Option<(K::AlignedRef<'_>, V::AlignedRef<'_>)>>where K: ?Sized + Storable + 'kr, V: ?Sized + Storable, C: Constraint, KRef: StorableRef<'kr, K>,

Set cursor to key or next greater key if not existent and get pair

fn cursor_set_next<K, V, C>(&self, cursor: &Cursor<K, V, C>) -> Result<bool>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Move cursor to next entry in database

fn cursor_set_next_get_pair<K, V, C>( &self, cursor: &Cursor<K, V, C> ) -> Result<Option<(K::AlignedRef<'_>, V::AlignedRef<'_>)>>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Move cursor to next entry in database and get pair

fn cursor_set_prev<K, V, C>(&self, cursor: &Cursor<K, V, C>) -> Result<bool>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Move cursor to previous entry in database

fn cursor_set_prev_get_pair<K, V, C>( &self, cursor: &Cursor<K, V, C> ) -> Result<Option<(K::AlignedRef<'_>, V::AlignedRef<'_>)>>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Move cursor to previous entry in database and get pair

fn cursor_set_next_key<K, V, C>(&self, cursor: &Cursor<K, V, C>) -> Result<bool>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Move cursor to first value of next key

fn cursor_set_next_key_get_pair<K, V, C>( &self, cursor: &Cursor<K, V, C> ) -> Result<Option<(K::AlignedRef<'_>, V::AlignedRef<'_>)>>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Move cursor to first value of next key and get pair

fn cursor_set_prev_key<K, V, C>(&self, cursor: &Cursor<K, V, C>) -> Result<bool>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Move cursor to last value of previous key

fn cursor_set_prev_key_get_pair<K, V, C>( &self, cursor: &Cursor<K, V, C> ) -> Result<Option<(K::AlignedRef<'_>, V::AlignedRef<'_>)>>where K: ?Sized + Storable, V: ?Sized + Storable, C: Constraint,

Move cursor to last value of previous key and get pair

fn cursor_set_first_value<K, V>( &self, cursor: &Cursor<K, V, KeysDuplicate> ) -> Result<bool>where K: ?Sized + Storable, V: ?Sized + Storable,

Move cursor to first value of current key

fn cursor_set_first_value_get_value<K, V>( &self, cursor: &Cursor<K, V, KeysDuplicate> ) -> Result<Option<V::AlignedRef<'_>>>where K: ?Sized + Storable, V: ?Sized + Storable,

Move cursor to first value of current key and get value

fn cursor_set_last_value<K, V>( &self, cursor: &Cursor<K, V, KeysDuplicate> ) -> Result<bool>where K: ?Sized + Storable, V: ?Sized + Storable,

Move cursor to last value of current key

fn cursor_set_last_value_get_value<K, V>( &self, cursor: &Cursor<K, V, KeysDuplicate> ) -> Result<Option<V::AlignedRef<'_>>>where K: ?Sized + Storable, V: ?Sized + Storable,

Move cursor to last value of current key and get value

fn cursor_set_pair<'kr, 'vr, K, V, KRef, VRef>( &self, cursor: &Cursor<K, V, KeysDuplicate>, key: KRef, value: VRef ) -> Result<bool>where K: ?Sized + Storable + 'kr, V: ?Sized + Storable + 'vr, KRef: StorableRef<'kr, K>, VRef: StorableRef<'vr, V>,

Set cursor to key-value pair

fn cursor_set_key_search_value<'kr, 'vr, K, V, KRef, VRef>( &self, cursor: &Cursor<K, V, KeysDuplicate>, key: KRef, value: VRef ) -> Result<bool>where K: ?Sized + Storable + 'kr, V: ?Sized + Storable + 'vr, KRef: StorableRef<'kr, K>, VRef: StorableRef<'vr, V>,

Set cursor to key and value or next greater value if not existent

fn cursor_set_key_search_value_get_value<'kr, 'vr, K, V, KRef, VRef>( &self, cursor: &Cursor<K, V, KeysDuplicate>, key: KRef, value: VRef ) -> Result<Option<V::AlignedRef<'_>>>where K: ?Sized + Storable + 'kr, V: ?Sized + Storable + 'vr, KRef: StorableRef<'kr, K>, VRef: StorableRef<'vr, V>,

Set cursor to key and value or next greater value if not existent and get value

fn cursor_set_next_value<K, V>( &self, cursor: &Cursor<K, V, KeysDuplicate> ) -> Result<bool>where K: ?Sized + Storable, V: ?Sized + Storable,

Move cursor to next value of current key

fn cursor_set_next_value_get_value<K, V>( &self, cursor: &Cursor<K, V, KeysDuplicate> ) -> Result<Option<V::AlignedRef<'_>>>where K: ?Sized + Storable, V: ?Sized + Storable,

Move cursor to next value of current key and get value

fn cursor_set_prev_value<K, V>( &self, cursor: &Cursor<K, V, KeysDuplicate> ) -> Result<bool>where K: ?Sized + Storable, V: ?Sized + Storable,

Move cursor to next value of current key

fn cursor_set_prev_value_get_value<K, V>( &self, cursor: &Cursor<K, V, KeysDuplicate> ) -> Result<Option<V::AlignedRef<'_>>>where K: ?Sized + Storable, V: ?Sized + Storable,

Move cursor to next value of current key and get value

fn get_owned<'a, 'kr, K, V, C, KRef>( &'a self, db: &Db<K, V, C>, key: KRef ) -> Result<Option<<V as ToOwned>::Owned>>where K: ?Sized + Storable + 'kr, V: ?Sized + Storable + ToOwned, C: Constraint, KRef: StorableRef<'kr, K>,

Get owned value from database

impl<'a> Send for TxnRo<'a>