Load existing or create a new Tree
.
Flushes any pending IO buffers to disk to ensure durability.
Retrieve a value from the Tree
if it exists.
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.
use sled::{ConfigBuilder, Error};
let config = ConfigBuilder::new().temporary(true).build();
let t = sled::Tree::start(config).unwrap();
assert_eq!(t.cas(vec![1], None, Some(vec![1])), Ok(()));
assert_eq!(t.cas(vec![1], None, Some(vec![1])), Err(Error::CasFailed(Some(vec![1]))));
assert_eq!(t.cas(vec![1], Some(vec![1]), Some(vec![2])), Ok(()));
assert_eq!(t.cas(vec![1], Some(vec![1]), Some(vec![2])), Err(Error::CasFailed(Some(vec![2]))));
assert_eq!(t.cas(vec![1], Some(vec![2]), None), Ok(()));
assert_eq!(t.get(&*vec![1]), Ok(None));
Set a key to a new value.
Merge a new value into the total state for a key.
fn concatenate_merge(
_key: &[u8],
old_value: Option<&[u8]>,
merged_bytes: &[u8]
) -> Option<Vec<u8>> {
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::Tree::start(config).unwrap();
let k = b"k1".to_vec();
tree.set(k.clone(), vec![0]);
tree.merge(k.clone(), vec![1]);
tree.merge(k.clone(), vec![2]);
assert_eq!(tree.get(&k), Ok(Some(vec![0, 1, 2])));
tree.set(k.clone(), vec![3]);
assert_eq!(tree.get(&k), Ok(Some(vec![3])));
tree.del(&k);
tree.merge(k.clone(), vec![4]);
assert_eq!(tree.get(&k), Ok(Some(vec![4])));
Delete a value, returning the last result if it existed.
let config = sled::ConfigBuilder::new().temporary(true).build();
let t = sled::Tree::start(config).unwrap();
t.set(vec![1], vec![1]);
assert_eq!(t.del(&*vec![1]), Ok(Some(vec![1])));
assert_eq!(t.del(&*vec![1]), Ok(None));
Iterate over tuples of keys and values, starting at the provided key.
let config = sled::ConfigBuilder::new().temporary(true).build();
let t = sled::Tree::start(config).unwrap();
t.set(vec![1], vec![10]);
t.set(vec![2], vec![20]);
t.set(vec![3], vec![30]);
let mut iter = t.scan(&*vec![2]);
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);
Iterate over the tuples of keys and values in this tree.
let config = sled::ConfigBuilder::new().temporary(true).build();
let t = sled::Tree::start(config).unwrap();
t.set(vec![1], vec![10]);
t.set(vec![2], vec![20]);
t.set(vec![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);