Struct matterdb::migration::PersistentIter [−][src]
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_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_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
Implementations
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>ⓘNotable traits for PersistentKeys<'_, T, I>
impl<T, I> Iterator for PersistentKeys<'_, T, I> where
T: RawAccessMut,
I: IndexIterator, type Item = <I::Key as ToOwned>::Owned;
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Notable traits for PersistentKeys<'_, T, I>
impl<T, I> Iterator for PersistentKeys<'_, T, I> where
T: RawAccessMut,
I: IndexIterator, type Item = <I::Key as ToOwned>::Owned;
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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pub fn size_hint(&self) -> (usize, Option<usize>)
1.0.0[src]
pub fn count(self) -> usize
1.0.0[src]
pub fn last(self) -> Option<Self::Item>
1.0.0[src]
pub fn advance_by(&mut self, n: usize) -> Result<(), usize>
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pub fn nth(&mut self, n: usize) -> Option<Self::Item>
1.0.0[src]
pub fn step_by(self, step: usize) -> StepBy<Self>
1.28.0[src]
pub 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>,
pub fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter> where
U: IntoIterator,
1.0.0[src]
U: IntoIterator,
pub fn intersperse(self, separator: Self::Item) -> Intersperse<Self> where
Self::Item: Clone,
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Self::Item: Clone,
pub fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G> where
G: FnMut() -> Self::Item,
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G: FnMut() -> Self::Item,
pub 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,
pub fn for_each<F>(self, f: F) where
F: FnMut(Self::Item),
1.21.0[src]
F: FnMut(Self::Item),
pub fn filter<P>(self, predicate: P) -> Filter<Self, P> where
P: FnMut(&Self::Item) -> bool,
1.0.0[src]
P: FnMut(&Self::Item) -> bool,
pub 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>,
pub fn enumerate(self) -> Enumerate<Self>
1.0.0[src]
pub fn peekable(self) -> Peekable<Self>
1.0.0[src]
pub 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,
pub 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,
pub 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>,
pub fn skip(self, n: usize) -> Skip<Self>
1.0.0[src]
pub fn take(self, n: usize) -> Take<Self>
1.0.0[src]
pub 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>,
pub 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,
pub fn flatten(self) -> Flatten<Self> where
Self::Item: IntoIterator,
1.29.0[src]
Self::Item: IntoIterator,
pub fn fuse(self) -> Fuse<Self>
1.0.0[src]
pub fn inspect<F>(self, f: F) -> Inspect<Self, F> where
F: FnMut(&Self::Item),
1.0.0[src]
F: FnMut(&Self::Item),
pub 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"]pub fn collect<B>(self) -> B where
B: FromIterator<Self::Item>,
1.0.0[src]
B: FromIterator<Self::Item>,
pub fn partition<B, F>(self, f: F) -> (B, B) where
F: FnMut(&Self::Item) -> bool,
B: Default + Extend<Self::Item>,
1.0.0[src]
F: FnMut(&Self::Item) -> bool,
B: Default + Extend<Self::Item>,
pub fn partition_in_place<'a, T, P>(self, predicate: P) -> usize where
Self: DoubleEndedIterator<Item = &'a mut T>,
T: 'a,
P: FnMut(&T) -> bool,
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Self: DoubleEndedIterator<Item = &'a mut T>,
T: 'a,
P: FnMut(&T) -> bool,
pub fn is_partitioned<P>(self, predicate: P) -> bool where
P: FnMut(Self::Item) -> bool,
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P: FnMut(Self::Item) -> bool,
pub 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>,
pub 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 = ()>,
pub 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,
pub fn reduce<F>(self, f: F) -> Option<Self::Item> where
F: FnMut(Self::Item, Self::Item) -> Self::Item,
1.51.0[src]
F: FnMut(Self::Item, Self::Item) -> Self::Item,
pub fn all<F>(&mut self, f: F) -> bool where
F: FnMut(Self::Item) -> bool,
1.0.0[src]
F: FnMut(Self::Item) -> bool,
pub fn any<F>(&mut self, f: F) -> bool where
F: FnMut(Self::Item) -> bool,
1.0.0[src]
F: FnMut(Self::Item) -> bool,
pub 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,
pub 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>,
pub fn try_find<F, R>(
&mut self,
f: F
) -> Result<Option<Self::Item>, <R as Try>::Error> where
F: FnMut(&Self::Item) -> R,
R: Try<Ok = bool>,
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&mut self,
f: F
) -> Result<Option<Self::Item>, <R as Try>::Error> where
F: FnMut(&Self::Item) -> R,
R: Try<Ok = bool>,
pub fn position<P>(&mut self, predicate: P) -> Option<usize> where
P: FnMut(Self::Item) -> bool,
1.0.0[src]
P: FnMut(Self::Item) -> bool,
pub fn rposition<P>(&mut self, predicate: P) -> Option<usize> where
Self: ExactSizeIterator + DoubleEndedIterator,
P: FnMut(Self::Item) -> bool,
1.0.0[src]
Self: ExactSizeIterator + DoubleEndedIterator,
P: FnMut(Self::Item) -> bool,
pub fn max(self) -> Option<Self::Item> where
Self::Item: Ord,
1.0.0[src]
Self::Item: Ord,
pub fn min(self) -> Option<Self::Item> where
Self::Item: Ord,
1.0.0[src]
Self::Item: Ord,
pub fn max_by_key<B, F>(self, f: F) -> Option<Self::Item> where
F: FnMut(&Self::Item) -> B,
B: Ord,
1.6.0[src]
F: FnMut(&Self::Item) -> B,
B: Ord,
pub 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,
pub fn min_by_key<B, F>(self, f: F) -> Option<Self::Item> where
F: FnMut(&Self::Item) -> B,
B: Ord,
1.6.0[src]
F: FnMut(&Self::Item) -> B,
B: Ord,
pub 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,
pub fn rev(self) -> Rev<Self> where
Self: DoubleEndedIterator,
1.0.0[src]
Self: DoubleEndedIterator,
pub fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB) where
Self: Iterator<Item = (A, B)>,
FromA: Default + Extend<A>,
FromB: Default + Extend<B>,
1.0.0[src]
Self: Iterator<Item = (A, B)>,
FromA: Default + Extend<A>,
FromB: Default + Extend<B>,
pub 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,
pub 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,
pub fn cycle(self) -> Cycle<Self> where
Self: Clone,
1.0.0[src]
Self: Clone,
pub fn sum<S>(self) -> S where
S: Sum<Self::Item>,
1.11.0[src]
S: Sum<Self::Item>,
pub fn product<P>(self) -> P where
P: Product<Self::Item>,
1.11.0[src]
P: Product<Self::Item>,
pub 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,
pub fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering where
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,
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I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,
pub 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>,
pub fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering> where
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
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I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,
pub 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>,
pub fn eq_by<I, F>(self, other: I, eq: F) -> bool where
I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,
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I: IntoIterator,
F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,
pub 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>,
pub 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>,
pub 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>,
pub 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>,
pub 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>,
pub fn is_sorted(self) -> bool where
Self::Item: PartialOrd<Self::Item>,
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Self::Item: PartialOrd<Self::Item>,
pub 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>,
pub fn is_sorted_by_key<F, K>(self, f: F) -> bool where
K: PartialOrd<K>,
F: FnMut(Self::Item) -> K,
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K: PartialOrd<K>,
F: FnMut(Self::Item) -> 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: Unpin,
<<I as IndexIterator>::Key as ToOwned>::Owned: Unpin,
<I as IndexIterator>::Value: Unpin,
T: Unpin,
<T as RawAccess>::Changes: Unpin,
<I as IndexIterator>::Key: Unpin,
<<I as IndexIterator>::Key as ToOwned>::Owned: Unpin,
<I as IndexIterator>::Value: 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,
[src]
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
[src]
T: ?Sized,
pub 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,
[src]
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?
pub fn into_iter(self) -> I
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impl<I> IteratorRandom for I where
I: Iterator,
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I: Iterator,
pub fn choose<R>(self, rng: &mut R) -> Option<Self::Item> where
R: Rng + ?Sized,
[src]
R: Rng + ?Sized,
pub fn choose_stable<R>(self, rng: &mut R) -> Option<Self::Item> where
R: Rng + ?Sized,
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R: Rng + ?Sized,
pub fn choose_multiple_fill<R>(
self,
rng: &mut R,
buf: &mut [Self::Item]
) -> usize where
R: Rng + ?Sized,
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self,
rng: &mut R,
buf: &mut [Self::Item]
) -> usize where
R: Rng + ?Sized,
pub fn choose_multiple<R>(
self,
rng: &mut R,
amount: usize
) -> Vec<Self::Item, Global> where
R: Rng + ?Sized,
[src]
self,
rng: &mut R,
amount: usize
) -> Vec<Self::Item, Global> where
R: Rng + ?Sized,
impl<T> Pointable for T
pub const ALIGN: usize
type Init = T
The type for initializers.
pub unsafe fn init(init: <T as Pointable>::Init) -> usize
pub unsafe fn deref<'a>(ptr: usize) -> &'a T
pub unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T
pub unsafe fn drop(ptr: usize)
impl<T, U> TryFrom<U> for T where
U: Into<T>,
[src]
U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
pub 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>,
[src]
U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
pub 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>,