[−][src]Struct sled::Db
The sled
embedded database!
Methods
impl Db
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pub fn start_default<P: AsRef<Path>>(path: P) -> Result<Db, ()>
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Load existing or create a new Db
with a default configuration.
pub fn start(config: Config) -> Result<Db, ()>
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Load existing or create a new Db
.
pub fn generate_id(&self) -> Result<usize, ()>
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Generate a monotonic ID. Not guaranteed to be
contiguous. Written to disk every idgen_persist_interval
operations, followed by a blocking flush. During recovery, we
take the last recovered generated ID and add 2x
the idgen_persist_interval
to it. While persisting, if the
previous persisted counter wasn't synced to disk yet, we will do
a blocking flush to fsync the latest counter, ensuring
that we will never give out the same counter twice.
pub fn open_tree(&self, name: Vec<u8>) -> Result<Arc<Tree>, ()>
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Open or create a new disk-backed Tree with its own keyspace,
accessible from the Db
via the provided identifier.
pub fn drop_tree(&self, name: &[u8]) -> Result<bool, ()>
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Remove a disk-backed collection.
pub fn was_recovered(&self) -> bool
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Returns true
if the database was
recovered from a previous process.
Note that database state is only
guaranteed to be present up to the
last call to flush
! Otherwise state
is synced to disk periodically if the
sync_every_ms
configuration option
is set to Some(number_of_ms_between_syncs)
or if the IO buffer gets filled to
capacity before being rotated.
pub fn mark_pending_tx(&self, _pages: Vec<PageId>, _txid: u64) -> Result<(), ()>
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Record a set of pages as being involved in
a transaction that is about to be written to
one of the structures in the Db. Do this
before performing transactions in case
the system crashes before all changes
can be written. During recovery,
you can call possibly_dirty_pages
to get the set of pages that may have
transactional state written to them.
pub fn abort_tx(&self, _txid: u64) -> Result<(), ()>
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Mark a transaction as being aborted. This ensures that during recovery we know that this transaction is not the last one that should be recovered, because the process finished the transaction, but we may need to clean up its pending state still.
pub fn commit_tx(&self, _txid: u64) -> Result<(), ()>
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Mark a transaction as being completed. This ensures that during recovery we know that this transaction completed, and that we can safely remove its entry in the transaction table.
pub fn cleanup_tx(&self, _txid: u64) -> Result<(), ()>
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Remove entries associated with this transaction in the transaction table, because we have completed the transaction and finished applying or removing pending state, and do not need to know about it during crash recovery.
pub fn possibly_dirty_pages(&self) -> Result<Vec<(u64, Vec<PageId>)>, ()>
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Call this during recovery to retrieve the set of pages that were involved in a transaction that was in a pending or aborted (but not yet fully cleaned up) state during process termination.
Methods from Deref<Target = Tree>
ⓘImportant traits for Subscriberpub fn watch_prefix(&self, prefix: Vec<u8>) -> Subscriber
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Subscribe to Event
s that happen to keys that have
the specified prefix. Events for particular keys are
guaranteed to be witnessed in the same order by all
threads, but threads may witness different interleavings
of Event
s across different keys. If subscribers don't
keep up with new writes, they will cause new writes
to block. There is a buffer of 1024 items per
Subscriber
. This can be used to build reactive
and replicated systems.
Examples
use sled::{Event, ConfigBuilder}; let config = ConfigBuilder::new().temporary(true).build(); let tree = sled::Db::start(config).unwrap(); // watch all events by subscribing to the empty prefix let mut events = tree.watch_prefix(vec![]); let tree_2 = tree.clone(); let thread = std::thread::spawn(move || { tree.set(vec![0], vec![1]).unwrap(); }); // events is a blocking `Iterator` over `Event`s for event in events.take(1) { match event { Event::Set(key, value) => assert_eq!(key, vec![0]), Event::Merge(key, partial_value) => {} Event::Del(key) => {} } } thread.join().unwrap();
pub fn clear(&self) -> Result<(), ()>
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Clears the Tree
, removing all values.
Note that this is not atomic.
pub fn flush(&self) -> Result<(), ()>
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Flushes all dirty IO buffers and calls fsync. If this succeeds, it is guaranteed that all previous writes will be recovered if the system crashes.
pub fn contains_key<K: AsRef<[u8]>>(&self, key: K) -> Result<bool, ()>
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Returns true
if the Tree
contains a value for
the specified key.
pub fn get<K: AsRef<[u8]>>(&self, key: K) -> Result<Option<PinnedValue>, ()>
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Retrieve a value from the Tree
if it exists.
pub fn get_lt<K: AsRef<[u8]>>(
&self,
key: K
) -> Result<Option<(Vec<u8>, PinnedValue)>, ()>
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&self,
key: K
) -> Result<Option<(Vec<u8>, PinnedValue)>, ()>
Retrieve the key and value before the provided key, if one exists.
Examples
use sled::{ConfigBuilder, Error}; let config = ConfigBuilder::new().temporary(true).build(); let tree = sled::Db::start(config).unwrap(); for i in 0..10 { tree.set(vec![i], vec![i]).expect("should write successfully"); } assert!(tree.get_lt(vec![]).unwrap().is_none()); assert!(tree.get_lt(vec![0]).unwrap().is_none()); assert!(tree.get_lt(vec![1]).unwrap().unwrap().1 == vec![0]); assert!(tree.get_lt(vec![9]).unwrap().unwrap().1 == vec![8]); assert!(tree.get_lt(vec![10]).unwrap().unwrap().1 == vec![9]); assert!(tree.get_lt(vec![255]).unwrap().unwrap().1 == vec![9]);
pub fn get_gt<K: AsRef<[u8]>>(
&self,
key: K
) -> Result<Option<(Vec<u8>, PinnedValue)>, ()>
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&self,
key: K
) -> Result<Option<(Vec<u8>, PinnedValue)>, ()>
Retrieve the next key and value from the Tree
after the
provided key.
Examples
use sled::{ConfigBuilder, Error}; let config = ConfigBuilder::new().temporary(true).build(); let tree = sled::Db::start(config).unwrap(); for i in 0..10 { tree.set(vec![i], vec![i]).expect("should write successfully"); } assert!(tree.get_gt(vec![]).unwrap().unwrap().1 == vec![0]); assert!(tree.get_gt(vec![0]).unwrap().unwrap().1 == vec![1]); assert!(tree.get_gt(vec![1]).unwrap().unwrap().1 == vec![2]); assert!(tree.get_gt(vec![8]).unwrap().unwrap().1 == vec![9]); assert!(tree.get_gt(vec![9]).unwrap().is_none());
pub fn cas<K: AsRef<[u8]>>(
&self,
key: K,
old: Option<&[u8]>,
new: Option<Vec<u8>>
) -> Result<(), Option<PinnedValue>>
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&self,
key: K,
old: Option<&[u8]>,
new: Option<Vec<u8>>
) -> Result<(), Option<PinnedValue>>
Compare and swap. Capable of unique creation, conditional modification, or deletion. If old is None, this will only set the value if it doesn't exist yet. If new is None, will delete the value if old is correct. If both old and new are Some, will modify the value if old is correct. If Tree is read-only, will do nothing.
Examples
use sled::{ConfigBuilder, Error}; let config = ConfigBuilder::new().temporary(true).build(); let t = sled::Db::start(config).unwrap(); // unique creation assert_eq!(t.cas(&[1], None, Some(vec![1])), Ok(())); // assert_eq!(t.cas(&[1], None, Some(vec![1])), Err(Error::CasFailed(Some(vec![1])))); // conditional modification assert_eq!(t.cas(&[1], Some(&*vec![1]), Some(vec![2])), Ok(())); // assert_eq!(t.cas(&[1], Some(vec![1]), Some(vec![2])), Err(Error::CasFailed(Some(vec![2])))); // conditional deletion assert_eq!(t.cas(&[1], Some(&[2]), None), Ok(())); assert_eq!(t.get(&[1]), Ok(None));
pub fn set<K: AsRef<[u8]>>(
&self,
key: K,
value: Vec<u8>
) -> Result<Option<PinnedValue>, ()>
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&self,
key: K,
value: Vec<u8>
) -> Result<Option<PinnedValue>, ()>
Set a key to a new value, returning the old value if it was set.
pub fn del<K: AsRef<[u8]>>(&self, key: K) -> Result<Option<PinnedValue>, ()>
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Delete a value, returning the last result if it existed.
Examples
let config = sled::ConfigBuilder::new().temporary(true).build(); let t = sled::Db::start(config).unwrap(); t.set(&[1], vec![1]); assert_eq!(t.del(&*vec![1]).unwrap().unwrap(), vec![1]); assert_eq!(t.del(&*vec![1]), Ok(None));
pub fn merge<K: AsRef<[u8]>>(&self, key: K, value: Vec<u8>) -> Result<(), ()>
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Merge state directly into a given key's value using the configured merge operator. This allows state to be written into a value directly, without any read-modify-write steps. Merge operators can be used to implement arbitrary data structures.
Panics
Calling merge
will panic if no merge operator has been
configured.
Examples
fn concatenate_merge( _key: &[u8], // the key being merged old_value: Option<&[u8]>, // the previous value, if one existed merged_bytes: &[u8] // the new bytes being merged in ) -> Option<Vec<u8>> { // set the new value, return None to delete let mut ret = old_value .map(|ov| ov.to_vec()) .unwrap_or_else(|| vec![]); ret.extend_from_slice(merged_bytes); Some(ret) } let config = sled::ConfigBuilder::new() .temporary(true) .merge_operator(concatenate_merge) .build(); let tree = sled::Db::start(config).unwrap(); let k = b"k1"; tree.set(k, vec![0]); tree.merge(k, vec![1]); tree.merge(k, vec![2]); // assert_eq!(tree.get(k).unwrap().unwrap(), vec![0, 1, 2]); // sets replace previously merged data, // bypassing the merge function. tree.set(k, vec![3]); // assert_eq!(tree.get(k), Ok(Some(vec![3]))); // merges on non-present values will add them tree.del(k); tree.merge(k, vec![4]); // assert_eq!(tree.get(k).unwrap().unwrap(), vec![4]);
ⓘImportant traits for Iter<'a>pub fn iter(&self) -> Iter
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Create a double-ended iterator over the tuples of keys and values in this tree.
Examples
let config = sled::ConfigBuilder::new().temporary(true).build(); let t = sled::Db::start(config).unwrap(); t.set(&[1], vec![10]); t.set(&[2], vec![20]); t.set(&[3], vec![30]); let mut iter = t.iter(); // assert_eq!(iter.next(), Some(Ok((vec![1], vec![10])))); // assert_eq!(iter.next(), Some(Ok((vec![2], vec![20])))); // assert_eq!(iter.next(), Some(Ok((vec![3], vec![30])))); // assert_eq!(iter.next(), None);
ⓘImportant traits for Iter<'a>pub fn scan<K>(&self, key: K) -> Iter where
K: AsRef<[u8]>,
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K: AsRef<[u8]>,
Create a double-ended iterator over tuples of keys and values, starting at the provided key.
Examples
let config = sled::ConfigBuilder::new() .temporary(true) .build(); let t = sled::Db::start(config).unwrap(); t.set(b"0", vec![0]).unwrap(); t.set(b"1", vec![10]).unwrap(); t.set(b"2", vec![20]).unwrap(); t.set(b"3", vec![30]).unwrap(); t.set(b"4", vec![40]).unwrap(); t.set(b"5", vec![50]).unwrap(); let mut r = t.scan(b"2"); assert_eq!(r.next().unwrap().unwrap().0, b"2"); assert_eq!(r.next().unwrap().unwrap().0, b"3"); assert_eq!(r.next().unwrap().unwrap().0, b"4"); assert_eq!(r.next().unwrap().unwrap().0, b"5"); assert_eq!(r.next(), None); let mut r = t.scan(b"2").rev(); assert_eq!(r.next().unwrap().unwrap().0, b"2"); assert_eq!(r.next().unwrap().unwrap().0, b"1"); assert_eq!(r.next().unwrap().unwrap().0, b"0"); assert_eq!(r.next(), None);
ⓘImportant traits for Iter<'a>pub fn range<K, R>(&self, range: R) -> Iter where
K: AsRef<[u8]>,
R: RangeBounds<K>,
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K: AsRef<[u8]>,
R: RangeBounds<K>,
Create a double-ended iterator over tuples of keys and values, where the keys fall within the specified range.
Examples
let config = sled::ConfigBuilder::new() .temporary(true) .build(); let t = sled::Db::start(config).unwrap(); t.set(b"0", vec![0]).unwrap(); t.set(b"1", vec![10]).unwrap(); t.set(b"2", vec![20]).unwrap(); t.set(b"3", vec![30]).unwrap(); t.set(b"4", vec![40]).unwrap(); t.set(b"5", vec![50]).unwrap(); let start: &[u8] = b"2"; let end: &[u8] = b"4"; let mut r = t.range(start..end); assert_eq!(r.next().unwrap().unwrap().0, b"2"); assert_eq!(r.next().unwrap().unwrap().0, b"3"); assert_eq!(r.next(), None); let start = b"2".to_vec(); let end = b"4".to_vec(); let mut r = t.range(start..end).rev(); assert_eq!(r.next().unwrap().unwrap().0, b"3"); assert_eq!(r.next().unwrap().unwrap().0, b"2"); assert_eq!(r.next(), None);
ⓘImportant traits for Keys<'a>pub fn keys<K>(&self, key: K) -> Keys where
K: AsRef<[u8]>,
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K: AsRef<[u8]>,
Create a double-ended iterator over keys, starting at the provided key.
Examples
let config = sled::ConfigBuilder::new().temporary(true).build(); let t = sled::Db::start(config).unwrap(); t.set(&[1], vec![10]); t.set(&[2], vec![20]); t.set(&[3], vec![30]); let mut iter = t.scan(&*vec![2]); // assert_eq!(iter.next(), Some(Ok(vec![2]))); // assert_eq!(iter.next(), Some(Ok(vec![3]))); // assert_eq!(iter.next(), None);
ⓘImportant traits for Values<'a>pub fn values<K: AsRef<[u8]>>(&self, key: K) -> Values
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Create a double-ended iterator over values, starting at the provided key.
Examples
let config = sled::ConfigBuilder::new().temporary(true).build(); let t = sled::Db::start(config).unwrap(); t.set(&[1], vec![10]); t.set(&[2], vec![20]); t.set(&[3], vec![30]); let mut iter = t.scan(&*vec![2]); // assert_eq!(iter.next(), Some(Ok(vec![20]))); // assert_eq!(iter.next(), Some(Ok(vec![30]))); // assert_eq!(iter.next(), None);
pub fn len(&self) -> usize
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Returns the number of elements in this tree.
Beware: performs a full O(n) scan under the hood.
pub fn is_empty(&self) -> bool
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Returns true
if the Tree
contains no elements.
Trait Implementations
impl Clone for Db
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fn clone(&self) -> Db
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fn clone_from(&mut self, source: &Self)
1.0.0[src]
Performs copy-assignment from source
. Read more
impl Send for Db
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impl Drop for Db
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impl Sync for Db
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impl Deref for Db
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Blanket Implementations
impl<T, U> Into for T where
U: From<T>,
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U: From<T>,
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
impl<T> From for T
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impl<T, U> TryFrom for T where
U: Into<T>,
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U: Into<T>,
type Error = !
try_from
)The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T> Borrow for T where
T: ?Sized,
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T: ?Sized,
impl<T, U> TryInto for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
try_from
)The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> BorrowMut for T where
T: ?Sized,
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T: ?Sized,