[−][src]Struct hdbconnect::ResultSet
The result of a database query.
This is essentially a set of Row
s, which is a set of HdbValue
s.
In most cases, you will want to use the powerful method
try_into
to convert the data from this generic format
into your application specific format.
Methods
impl ResultSet
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pub fn try_into<'de, T>(self) -> HdbResult<T> where
T: Deserialize<'de>,
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T: Deserialize<'de>,
Translates a generic resultset into a given rust type that implements serde::Deserialize. The implementation of this function uses serde_db. See there for more details.
A resultset is essentially a two-dimensional structure, given as a list
of rows (a Vec<Row>
),
where each row is a list of fields (a
Vec<HdbValue>
); the name of each field is
given in the metadata of the resultset.
The method supports a variety of target data structures, with the only strong limitation that no data loss is supported.
-
It depends on the dimension of the resultset what target data structure you can choose for deserialization:
- You can always use a
Vec<line_struct>
, whereline_struct
matches the field list of the resultset.
- You can always use a
-
If the resultset contains only a single line (e.g. because you specified TOP 1 in your select), then you can optionally choose to deserialize into a plain
line_struct
. -
If the resultset contains only a single column, then you can optionally choose to deserialize into a
Vec<plain_field>
. -
If the resultset contains only a single value (one row with one column), then you can optionally choose to deserialize into a plain
line_struct
, or aVec<plain_field>
, or a plain variable. -
Also the translation of the individual field values provides a lot of flexibility. You can e.g. convert values from a nullable column into a plain field, provided that no NULL values are given in the resultset.
Vice versa, you always can use an
Option<plain_field>
, even if the column is
marked as NOT NULL.
- Similarly, integer types can differ, as long as the concrete values can be assigned without loss.
Note that you need to specify the type of your target variable
explicitly, so that try_into()
can derive the type it
needs to serialize into:
#[derive(Deserialize)] struct MyStruct { ... } let typed_result: Vec<MyStruct> = resultset.try_into()?;
pub fn metadata(&self) -> &ResultSetMetadata
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Access to metadata.
pub fn total_number_of_rows(&mut self) -> HdbResult<usize>
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Returns the total number of rows in the resultset, including those that still need to be fetched from the database, but excluding those that have already been removed from the resultset.
This method can be expensive, and it can fail, since it fetches all yet outstanding rows from the database.
pub fn next_row(&mut self) -> HdbResult<Option<Row>>
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Removes the next row and returns it, or None if the ResultSet is empty.
Consequently, the ResultSet has one row less after the call. May need to fetch further rows from the database, which can fail, and thus returns an HdbResult.
Using ResultSet::into_iter() is preferrable due to better performance.
pub fn fetch_all(&mut self) -> HdbResult<()>
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Fetches all not yet transported result lines from the server.
Bigger resultsets are typically not transported in one roundtrip from the database; the number of roundtrips depends on the total number of rows in the resultset and the configured fetch-size of the connection.
Trait Implementations
impl Iterator for ResultSet
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type Item = HdbResult<Row>
The type of the elements being iterated over.
fn next(&mut self) -> Option<HdbResult<Row>>
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fn size_hint(&self) -> (usize, Option<usize>)
1.0.0[src]
Returns the bounds on the remaining length of the iterator. Read more
fn count(self) -> usize
1.0.0[src]
Consumes the iterator, counting the number of iterations and returning it. Read more
fn last(self) -> Option<Self::Item>
1.0.0[src]
Consumes the iterator, returning the last element. Read more
fn nth(&mut self, n: usize) -> Option<Self::Item>
1.0.0[src]
Returns the n
th element of the iterator. Read more
fn step_by(self, step: usize) -> StepBy<Self>
1.28.0[src]
Creates an iterator starting at the same point, but stepping by the given amount at each iteration. Read more
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>,
Takes two iterators and creates a new iterator over both in sequence. Read more
fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter> where
U: IntoIterator,
1.0.0[src]
U: IntoIterator,
'Zips up' two iterators into a single iterator of pairs. Read more
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,
Takes a closure and creates an iterator which calls that closure on each element. Read more
fn for_each<F>(self, f: F) where
F: FnMut(Self::Item),
1.21.0[src]
F: FnMut(Self::Item),
Calls a closure on each element of an iterator. Read more
fn filter<P>(self, predicate: P) -> Filter<Self, P> where
P: FnMut(&Self::Item) -> bool,
1.0.0[src]
P: FnMut(&Self::Item) -> bool,
Creates an iterator which uses a closure to determine if an element should be yielded. Read more
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>,
Creates an iterator that both filters and maps. Read more
fn enumerate(self) -> Enumerate<Self>
1.0.0[src]
Creates an iterator which gives the current iteration count as well as the next value. Read more
fn peekable(self) -> Peekable<Self>
1.0.0[src]
Creates an iterator which can use peek
to look at the next element of the iterator without consuming it. Read more
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,
Creates an iterator that [skip
]s elements based on a predicate. Read more
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,
Creates an iterator that yields elements based on a predicate. Read more
fn skip(self, n: usize) -> Skip<Self>
1.0.0[src]
Creates an iterator that skips the first n
elements. Read more
fn take(self, n: usize) -> Take<Self>
1.0.0[src]
Creates an iterator that yields its first n
elements. Read more
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>,
An iterator adaptor similar to [fold
] that holds internal state and produces a new iterator. Read more
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,
Creates an iterator that works like map, but flattens nested structure. Read more
fn flatten(self) -> Flatten<Self> where
Self::Item: IntoIterator,
1.29.0[src]
Self::Item: IntoIterator,
Creates an iterator that flattens nested structure. Read more
fn fuse(self) -> Fuse<Self>
1.0.0[src]
Creates an iterator which ends after the first [None
]. Read more
fn inspect<F>(self, f: F) -> Inspect<Self, F> where
F: FnMut(&Self::Item),
1.0.0[src]
F: FnMut(&Self::Item),
Do something with each element of an iterator, passing the value on. Read more
fn by_ref(&mut self) -> &mut Self
1.0.0[src]
Borrows an iterator, rather than consuming it. Read more
#[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>,
Transforms an iterator into a collection. Read more
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,
Consumes an iterator, creating two collections from it. Read more
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>,
An iterator method that applies a function as long as it returns successfully, producing a single, final value. Read more
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 = ()>,
An iterator method that applies a fallible function to each item in the iterator, stopping at the first error and returning that error. Read more
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,
An iterator method that applies a function, producing a single, final value. Read more
fn all<F>(&mut self, f: F) -> bool where
F: FnMut(Self::Item) -> bool,
1.0.0[src]
F: FnMut(Self::Item) -> bool,
Tests if every element of the iterator matches a predicate. Read more
fn any<F>(&mut self, f: F) -> bool where
F: FnMut(Self::Item) -> bool,
1.0.0[src]
F: FnMut(Self::Item) -> bool,
Tests if any element of the iterator matches a predicate. Read more
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,
Searches for an element of an iterator that satisfies a predicate. Read more
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>,
Applies function to the elements of iterator and returns the first non-none result. Read more
fn position<P>(&mut self, predicate: P) -> Option<usize> where
P: FnMut(Self::Item) -> bool,
1.0.0[src]
P: FnMut(Self::Item) -> bool,
Searches for an element in an iterator, returning its index. Read more
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,
Searches for an element in an iterator from the right, returning its index. Read more
fn max(self) -> Option<Self::Item> where
Self::Item: Ord,
1.0.0[src]
Self::Item: Ord,
Returns the maximum element of an iterator. Read more
fn min(self) -> Option<Self::Item> where
Self::Item: Ord,
1.0.0[src]
Self::Item: Ord,
Returns the minimum element of an iterator. Read more
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,
Returns the element that gives the maximum value from the specified function. Read more
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,
Returns the element that gives the maximum value with respect to the specified comparison function. Read more
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,
Returns the element that gives the minimum value from the specified function. Read more
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,
Returns the element that gives the minimum value with respect to the specified comparison function. Read more
fn rev(self) -> Rev<Self> where
Self: DoubleEndedIterator,
1.0.0[src]
Self: DoubleEndedIterator,
Reverses an iterator's direction. Read more
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)>,
Converts an iterator of pairs into a pair of containers. Read more
fn copied<'a, T>(self) -> Copied<Self> where
Self: Iterator<Item = &'a T>,
T: 'a + Copy,
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Self: Iterator<Item = &'a T>,
T: 'a + Copy,
iter_copied
)Creates an iterator which copies all of its elements. Read more
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,
Creates an iterator which [clone
]s all of its elements. Read more
fn cycle(self) -> Cycle<Self> where
Self: Clone,
1.0.0[src]
Self: Clone,
Repeats an iterator endlessly. Read more
fn sum<S>(self) -> S where
S: Sum<Self::Item>,
1.11.0[src]
S: Sum<Self::Item>,
Sums the elements of an iterator. Read more
fn product<P>(self) -> P where
P: Product<Self::Item>,
1.11.0[src]
P: Product<Self::Item>,
Iterates over the entire iterator, multiplying all the elements Read more
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,
Lexicographically compares the elements of this Iterator
with those of another. Read more
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>,
Lexicographically compares the elements of this Iterator
with those of another. Read more
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>,
Determines if the elements of this Iterator
are equal to those of another. Read more
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>,
Determines if the elements of this Iterator
are unequal to those of another. Read more
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>,
Determines if the elements of this Iterator
are lexicographically less than those of another. Read more
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>,
Determines if the elements of this Iterator
are lexicographically less or equal to those of another. Read more
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>,
Determines if the elements of this Iterator
are lexicographically greater than those of another. Read more
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>,
Determines if the elements of this Iterator
are lexicographically greater than or equal to those of another. Read more
fn is_sorted(self) -> bool where
Self::Item: PartialOrd<Self::Item>,
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Self::Item: PartialOrd<Self::Item>,
🔬 This is a nightly-only experimental API. (is_sorted
)
new API
Checks if the elements of this iterator are sorted. Read more
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>,
🔬 This is a nightly-only experimental API. (is_sorted
)
new API
Checks if the elements of this iterator are sorted using the given comparator function. Read more
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>,
🔬 This is a nightly-only experimental API. (is_sorted
)
new API
Checks if the elements of this iterator are sorted using the given key extraction function. Read more
impl Debug for ResultSet
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impl Display for ResultSet
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impl DeserializableResultset for ResultSet
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type ROW = Row
Concrete type for the DB row, which must implement DeserializabeRow.
type E = HdbError
Error type of the database driver.
fn has_multiple_rows(&mut self) -> Result<bool, DeserializationError>
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fn next(&mut self) -> DeserializationResult<Option<Row>>
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fn number_of_fields(&self) -> usize
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fn fieldname(&self, i: usize) -> Option<&String>
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fn into_typed<'de, T>(self) -> Result<T, Self::E> where
T: Deserialize<'de>,
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T: Deserialize<'de>,
A provided method that translates a resultset into a given rust type that implements serde::de::Deserialize. Read more
Auto Trait Implementations
Blanket Implementations
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<T, U> Into for T where
U: From<T>,
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U: From<T>,
impl<T> ToString for T where
T: Display + ?Sized,
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T: Display + ?Sized,
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,
fn borrow_mut(&mut self) -> &mut T
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impl<T> Same for T
type Output = T
Should always be Self