pub struct Snapshot { /* private fields */ }
Expand description
Read snapshot at a specific point in time.
All the changes from transactions committed at the specific point in time were the snapshot was create are readable from this snapshot, all subsequent transactions are ignored.
Copy of the data old data is kept on the disc, with indexing access from in memory structures, on drop of the Snapshot, if there are no older snapshot all the data old by this snapshot not existing anymore in the final state will be cleaned up.
Implementations
sourceimpl Snapshot
impl Snapshot
sourcepub fn read(
&self,
segment: impl ToSegmentId,
id: &PersyId
) -> Result<Option<Vec<u8>>, PE<ReadError>>
pub fn read(
&self,
segment: impl ToSegmentId,
id: &PersyId
) -> Result<Option<Vec<u8>>, PE<ReadError>>
Read the record content at the point of time the snapshot was taken ignoring all following committed transactions
Example
let mut tx = persy.begin()?;
let data = vec![1;20];
let id = tx.insert("seg", &data)?;
tx.prepare()?.commit()?;
let snapshot = persy.snapshot()?;
let read = snapshot.read("seg", &id)?.expect("record exists");
assert_eq!(data,read);
sourcepub fn scan(
&self,
segment: impl ToSegmentId
) -> Result<SnapshotSegmentIter, PE<SegmentError>>
pub fn scan(
&self,
segment: impl ToSegmentId
) -> Result<SnapshotSegmentIter, PE<SegmentError>>
Scan for records existing at the moment of snapshot creation, ignoring all the following committed transactions.
Example
let mut tx = persy.begin()?;
let data = vec![1;20];
let id = tx.insert("seg", &data)?;
tx.prepare()?.commit()?;
let snapshot = persy.snapshot()?;
let mut count = 0;
for (id,content) in snapshot.scan("seg")? {
println!("record size:{}",content.len());
count+=1;
}
assert_eq!(count,1);
sourcepub fn get<K, V>(
&self,
index_name: &str,
k: &K
) -> Result<ValueIter<V>, PE<IndexOpsError>>where
K: IndexType,
V: IndexType,
pub fn get<K, V>(
&self,
index_name: &str,
k: &K
) -> Result<ValueIter<V>, PE<IndexOpsError>>where
K: IndexType,
V: IndexType,
Get a value or a group of values from a key at the point the snapshot was taken ignoring all following committed transactions.
Example
tx.put::<u8,u8>("my_new_index",10,10)?;
tx.prepare()?.commit()?;
let snapshot = persy.snapshot()?;
let values = snapshot.get::<u8,u8>("my_new_index",&10)?;
for value in values {
//...
}
sourcepub fn one<K, V>(
&self,
index_name: &str,
k: &K
) -> Result<Option<V>, PE<IndexOpsError>>where
K: IndexType,
V: IndexType,
pub fn one<K, V>(
&self,
index_name: &str,
k: &K
) -> Result<Option<V>, PE<IndexOpsError>>where
K: IndexType,
V: IndexType,
Get a value or None from a key at the point the snapshot was taken ignoring all following committed transactions.
Example
tx.put::<u8,u8>("my_new_index",10,10)?;
tx.prepare()?.commit()?;
let snapshot = persy.snapshot()?;
if let Some(value) = snapshot.one::<u8,u8>("my_new_index",&10)?{
//...
}
sourcepub fn range<K, V, R>(
&self,
index_name: &str,
range: R
) -> Result<IndexIter<K, V>, PE<IndexOpsError>>where
K: IndexType,
V: IndexType,
R: RangeBounds<K>,
pub fn range<K, V, R>(
&self,
index_name: &str,
range: R
) -> Result<IndexIter<K, V>, PE<IndexOpsError>>where
K: IndexType,
V: IndexType,
R: RangeBounds<K>,
Browse a range of keys and values from an index at the pointing that the snapshot was created ignoring all the following committed transactions.
Example
let mut tx = persy.begin()?;
tx.put::<u8,u8>("my_new_index",10,10)?;
tx.prepare()?.commit()?;
let snapshot = persy.snapshot()?;
let iter:IndexIter<u8,u8> = snapshot.range("my_new_index",10..12)?;
for (k,values) in iter {
for value in values {
//...
}
}
sourcepub fn list_segments(
&self
) -> Result<Vec<(String, SegmentId)>, PE<GenericError>>
pub fn list_segments(
&self
) -> Result<Vec<(String, SegmentId)>, PE<GenericError>>
List all the existing segments, at the pointing that the snapshot was created ignoring all the following committed transactions.
Example
let mut tx = persy.begin()?;
tx.create_segment("seg")?;
tx.prepare()?.commit()?;
let snapshot = persy.snapshot()?;
let segments = snapshot.list_segments()?;
let names = segments.into_iter().map(|(name,_id)|name).collect::<Vec<String>>();
assert!(names.contains(&"seg".to_string()));
sourcepub fn list_indexes(&self) -> Result<Vec<(String, IndexInfo)>, PE<GenericError>>
pub fn list_indexes(&self) -> Result<Vec<(String, IndexInfo)>, PE<GenericError>>
List all the existing indexes, at the pointing that the snapshot was created ignoring all the following committed transactions.
Example
let mut tx = persy.begin()?;
tx.create_index::<u8, u8>("idx", ValueMode::Replace)?;
tx.prepare()?.commit()?;
let snapshot = persy.snapshot()?;
let indexes = snapshot.list_indexes()?;
let names = indexes.into_iter().map(|(name,_id)|name).collect::<Vec<String>>();
assert!(names.contains(&"idx".to_string()));
Trait Implementations
Auto Trait Implementations
impl !RefUnwindSafe for Snapshot
impl Send for Snapshot
impl Sync for Snapshot
impl Unpin for Snapshot
impl !UnwindSafe for Snapshot
Blanket Implementations
sourceimpl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more