[−][src]Struct exonum_merkledb::migration::PersistentIter
Persistent iterator that stores its position in the database.
Persistent iterators iterate over an index and automatically persist iteration results in the DB. This allows to build fault-tolerant migration scripts that work correctly after being restarted while merging the intermediate changes to the database.
Like indexes, persistent iterators are identified by an address. Likewise, they are subject
to the borrowing rules (e.g., attempting to create two instances of the same iterator will
result in a runtime error). When migrating data, it makes sense to store iterators
in the associated Scratchpad
. In this way, iterators will be automatically removed
when the migration is over.
Examples
MigrationHelper
offers convenient iterator API via iter_loop
method, which covers
basic use cases. When iter_loop
is not enough, a persistent iterator can be instantiated
independently:
let db = TemporaryDB::new(); // Create data for migration. let fork = db.fork(); fork.get_proof_list("migration.list").extend((0..123).map(|i| i.to_string())); db.merge(fork.into_patch()).unwrap(); let helper = MigrationHelper::new(db, "migration"); // The old data is here. let list = helper.old_data().get_proof_list::<_, String>("list"); // In the context of migration, persistent iterators should use // the scratchpad data access. let iter = PersistentIter::new(&helper.scratchpad(), "list_iter", &list); // Now, we can use `iter` as any other iterator. Persistence is most useful // together with the `take` adapter; it allows to break migrated data // into manageable chunks. for (_, item) in iter.take(100) { // Migrate `item`. The first component of a tuple is the index of the item // in the list, which we ignore. } // If we recreate the iterator, it will resume iteration from the last // known position (the element with 0-based index 100, in our case). let mut iter = PersistentIter::new(&helper.scratchpad(), "list_iter", &list); let (i, item) = iter.next().unwrap(); assert_eq!(i, 100); assert_eq!(item, "100"); assert_eq!(iter.count(), 22); // number of remaining items
Methods
impl<'a, T, I> PersistentIter<'a, T, I> where
T: RawAccessMut,
I: IndexIterator,
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T: RawAccessMut,
I: IndexIterator,
pub fn new<A>(access: &A, name: &str, index: &'a I) -> Self where
A: Access<Base = T>,
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A: Access<Base = T>,
Creates a new persistent iterator.
pub fn skip_values(self) -> PersistentKeys<'a, T, I>
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Skips values in the iterator output without parsing them.
Trait Implementations
impl<'_, T, I> Debug for PersistentIter<'_, T, I> where
T: RawAccess,
I: IndexIterator,
I::Key: Debug,
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T: RawAccess,
I: IndexIterator,
I::Key: Debug,
impl<'_, T, I> Iterator for PersistentIter<'_, T, I> where
T: RawAccessMut,
I: IndexIterator,
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T: RawAccessMut,
I: IndexIterator,
type Item = (<I::Key as ToOwned>::Owned, I::Value)
The type of the elements being iterated over.
fn next(&mut self) -> Option<Self::Item>
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fn size_hint(&self) -> (usize, Option<usize>)
1.0.0[src]
fn count(self) -> usize
1.0.0[src]
fn last(self) -> Option<Self::Item>
1.0.0[src]
fn nth(&mut self, n: usize) -> Option<Self::Item>
1.0.0[src]
fn step_by(self, step: usize) -> StepBy<Self>
1.28.0[src]
fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter> where
U: IntoIterator<Item = Self::Item>,
1.0.0[src]
U: IntoIterator<Item = Self::Item>,
fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter> where
U: IntoIterator,
1.0.0[src]
U: IntoIterator,
fn map<B, F>(self, f: F) -> Map<Self, F> where
F: FnMut(Self::Item) -> B,
1.0.0[src]
F: FnMut(Self::Item) -> B,
fn for_each<F>(self, f: F) where
F: FnMut(Self::Item),
1.21.0[src]
F: FnMut(Self::Item),
fn filter<P>(self, predicate: P) -> Filter<Self, P> where
P: FnMut(&Self::Item) -> bool,
1.0.0[src]
P: FnMut(&Self::Item) -> bool,
fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F> where
F: FnMut(Self::Item) -> Option<B>,
1.0.0[src]
F: FnMut(Self::Item) -> Option<B>,
fn enumerate(self) -> Enumerate<Self>
1.0.0[src]
fn peekable(self) -> Peekable<Self>
1.0.0[src]
fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P> where
P: FnMut(&Self::Item) -> bool,
1.0.0[src]
P: FnMut(&Self::Item) -> bool,
fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where
P: FnMut(&Self::Item) -> bool,
1.0.0[src]
P: FnMut(&Self::Item) -> bool,
fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P> where
P: FnMut(Self::Item) -> Option<B>,
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P: FnMut(Self::Item) -> Option<B>,
fn skip(self, n: usize) -> Skip<Self>
1.0.0[src]
fn take(self, n: usize) -> Take<Self>
1.0.0[src]
fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F> where
F: FnMut(&mut St, Self::Item) -> Option<B>,
1.0.0[src]
F: FnMut(&mut St, Self::Item) -> Option<B>,
fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F> where
F: FnMut(Self::Item) -> U,
U: IntoIterator,
1.0.0[src]
F: FnMut(Self::Item) -> U,
U: IntoIterator,
fn flatten(self) -> Flatten<Self> where
Self::Item: IntoIterator,
1.29.0[src]
Self::Item: IntoIterator,
fn fuse(self) -> Fuse<Self>
1.0.0[src]
fn inspect<F>(self, f: F) -> Inspect<Self, F> where
F: FnMut(&Self::Item),
1.0.0[src]
F: FnMut(&Self::Item),
fn by_ref(&mut self) -> &mut Self
1.0.0[src]
#[must_use =
"if you really need to exhaust the iterator, consider `.for_each(drop)` instead"]fn collect<B>(self) -> B where
B: FromIterator<Self::Item>,
1.0.0[src]
B: FromIterator<Self::Item>,
fn partition<B, F>(self, f: F) -> (B, B) where
B: Default + Extend<Self::Item>,
F: FnMut(&Self::Item) -> bool,
1.0.0[src]
B: Default + Extend<Self::Item>,
F: FnMut(&Self::Item) -> bool,
fn partition_in_place<'a, T, P>(self, predicate: P) -> usize where
P: FnMut(&T) -> bool,
Self: DoubleEndedIterator<Item = &'a mut T>,
T: 'a,
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P: FnMut(&T) -> bool,
Self: DoubleEndedIterator<Item = &'a mut T>,
T: 'a,
fn is_partitioned<P>(self, predicate: P) -> bool where
P: FnMut(Self::Item) -> bool,
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P: FnMut(Self::Item) -> bool,
fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R where
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
1.27.0[src]
F: FnMut(B, Self::Item) -> R,
R: Try<Ok = B>,
fn try_for_each<F, R>(&mut self, f: F) -> R where
F: FnMut(Self::Item) -> R,
R: Try<Ok = ()>,
1.27.0[src]
F: FnMut(Self::Item) -> R,
R: Try<Ok = ()>,
fn fold<B, F>(self, init: B, f: F) -> B where
F: FnMut(B, Self::Item) -> B,
1.0.0[src]
F: FnMut(B, Self::Item) -> B,
fn fold_first<F>(self, f: F) -> Option<Self::Item> where
F: FnMut(Self::Item, Self::Item) -> Self::Item,
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F: FnMut(Self::Item, Self::Item) -> Self::Item,
fn all<F>(&mut self, f: F) -> bool where
F: FnMut(Self::Item) -> bool,
1.0.0[src]
F: FnMut(Self::Item) -> bool,
fn any<F>(&mut self, f: F) -> bool where
F: FnMut(Self::Item) -> bool,
1.0.0[src]
F: FnMut(Self::Item) -> bool,
fn find<P>(&mut self, predicate: P) -> Option<Self::Item> where
P: FnMut(&Self::Item) -> bool,
1.0.0[src]
P: FnMut(&Self::Item) -> bool,
fn find_map<B, F>(&mut self, f: F) -> Option<B> where
F: FnMut(Self::Item) -> Option<B>,
1.30.0[src]
F: FnMut(Self::Item) -> Option<B>,
fn try_find<F, E, R>(&mut self, f: F) -> Result<Option<Self::Item>, E> where
F: FnMut(&Self::Item) -> R,
R: Try<Ok = bool, Error = E>,
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F: FnMut(&Self::Item) -> R,
R: Try<Ok = bool, Error = E>,
fn position<P>(&mut self, predicate: P) -> Option<usize> where
P: FnMut(Self::Item) -> bool,
1.0.0[src]
P: FnMut(Self::Item) -> bool,
fn rposition<P>(&mut self, predicate: P) -> Option<usize> where
P: FnMut(Self::Item) -> bool,
Self: ExactSizeIterator + DoubleEndedIterator,
1.0.0[src]
P: FnMut(Self::Item) -> bool,
Self: ExactSizeIterator + DoubleEndedIterator,
fn max(self) -> Option<Self::Item> where
Self::Item: Ord,
1.0.0[src]
Self::Item: Ord,
fn min(self) -> Option<Self::Item> where
Self::Item: Ord,
1.0.0[src]
Self::Item: Ord,
fn max_by_key<B, F>(self, f: F) -> Option<Self::Item> where
B: Ord,
F: FnMut(&Self::Item) -> B,
1.6.0[src]
B: Ord,
F: FnMut(&Self::Item) -> B,
fn max_by<F>(self, compare: F) -> Option<Self::Item> where
F: FnMut(&Self::Item, &Self::Item) -> Ordering,
1.15.0[src]
F: FnMut(&Self::Item, &Self::Item) -> Ordering,
fn min_by_key<B, F>(self, f: F) -> Option<Self::Item> where
B: Ord,
F: FnMut(&Self::Item) -> B,
1.6.0[src]
B: Ord,
F: FnMut(&Self::Item) -> B,
fn min_by<F>(self, compare: F) -> Option<Self::Item> where
F: FnMut(&Self::Item, &Self::Item) -> Ordering,
1.15.0[src]
F: FnMut(&Self::Item, &Self::Item) -> Ordering,
fn rev(self) -> Rev<Self> where
Self: DoubleEndedIterator,
1.0.0[src]
Self: DoubleEndedIterator,
fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where
FromA: Default + Extend<A>,
FromB: Default + Extend<B>,
Self: Iterator<Item = (A, B)>,
1.0.0[src]
FromA: Default + Extend<A>,
FromB: Default + Extend<B>,
Self: Iterator<Item = (A, B)>,
fn copied<'a, T>(self) -> Copied<Self> where
Self: Iterator<Item = &'a T>,
T: 'a + Copy,
1.36.0[src]
Self: Iterator<Item = &'a T>,
T: 'a + Copy,
fn cloned<'a, T>(self) -> Cloned<Self> where
Self: Iterator<Item = &'a T>,
T: 'a + Clone,
1.0.0[src]
Self: Iterator<Item = &'a T>,
T: 'a + Clone,
fn cycle(self) -> Cycle<Self> where
Self: Clone,
1.0.0[src]
Self: Clone,
fn sum<S>(self) -> S where
S: Sum<Self::Item>,
1.11.0[src]
S: Sum<Self::Item>,
fn product<P>(self) -> P where
P: Product<Self::Item>,
1.11.0[src]
P: Product<Self::Item>,
fn cmp<I>(self, other: I) -> Ordering where
I: IntoIterator<Item = Self::Item>,
Self::Item: Ord,
1.5.0[src]
I: IntoIterator<Item = Self::Item>,
Self::Item: Ord,
fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering where
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,
I: IntoIterator,
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F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,
I: IntoIterator,
fn partial_cmp<I>(self, other: I) -> Option<Ordering> where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
1.5.0[src]
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering> where
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
I: IntoIterator,
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F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
I: IntoIterator,
fn eq<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialEq<<I as IntoIterator>::Item>,
1.5.0[src]
I: IntoIterator,
Self::Item: PartialEq<<I as IntoIterator>::Item>,
fn eq_by<I, F>(self, other: I, eq: F) -> bool where
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,
I: IntoIterator,
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F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,
I: IntoIterator,
fn ne<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialEq<<I as IntoIterator>::Item>,
1.5.0[src]
I: IntoIterator,
Self::Item: PartialEq<<I as IntoIterator>::Item>,
fn lt<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
1.5.0[src]
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
fn le<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
1.5.0[src]
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
fn gt<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
1.5.0[src]
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
fn ge<I>(self, other: I) -> bool where
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
1.5.0[src]
I: IntoIterator,
Self::Item: PartialOrd<<I as IntoIterator>::Item>,
fn is_sorted(self) -> bool where
Self::Item: PartialOrd<Self::Item>,
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Self::Item: PartialOrd<Self::Item>,
fn is_sorted_by<F>(self, compare: F) -> bool where
F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,
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F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>,
fn is_sorted_by_key<F, K>(self, f: F) -> bool where
F: FnMut(Self::Item) -> K,
K: PartialOrd<K>,
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F: FnMut(Self::Item) -> K,
K: PartialOrd<K>,
Auto Trait Implementations
impl<'a, T, I> !RefUnwindSafe for PersistentIter<'a, T, I>
impl<'a, T, I> !Send for PersistentIter<'a, T, I>
impl<'a, T, I> !Sync for PersistentIter<'a, T, I>
impl<'a, T, I> Unpin for PersistentIter<'a, T, I> where
T: Unpin,
<T as RawAccess>::Changes: Unpin,
<I as IndexIterator>::Key: BinaryKey + ToOwned + Unpin,
<<I as IndexIterator>::Key as ToOwned>::Owned: Unpin,
<I as IndexIterator>::Value: BinaryValue + Unpin,
T: Unpin,
<T as RawAccess>::Changes: Unpin,
<I as IndexIterator>::Key: BinaryKey + ToOwned + Unpin,
<<I as IndexIterator>::Key as ToOwned>::Owned: Unpin,
<I as IndexIterator>::Value: BinaryValue + Unpin,
impl<'a, T, I> !UnwindSafe for PersistentIter<'a, T, I>
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
fn borrow_mut(&mut self) -> &mut T
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impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<I> IntoIterator for I where
I: Iterator,
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I: Iterator,
type Item = <I as Iterator>::Item
The type of the elements being iterated over.
type IntoIter = I
Which kind of iterator are we turning this into?
fn into_iter(self) -> I
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impl<I> IteratorRandom for I where
I: Iterator,
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I: Iterator,
fn choose<R>(self, rng: &mut R) -> Option<Self::Item> where
R: Rng + ?Sized,
[src]
R: Rng + ?Sized,
fn choose_multiple_fill<R>(self, rng: &mut R, buf: &mut [Self::Item]) -> usize where
R: Rng + ?Sized,
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R: Rng + ?Sized,
fn choose_multiple<R>(self, rng: &mut R, amount: usize) -> Vec<Self::Item> where
R: Rng + ?Sized,
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R: Rng + ?Sized,
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
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, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
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<V, T> VZip<V> for T where
V: MultiLane<T>,
V: MultiLane<T>,