Struct fst::map::OpBuilder [−][src]
pub struct OpBuilder<'m>(_);
Expand description
A builder for collecting map streams on which to perform set operations on the keys of maps.
Set operations include intersection, union, difference and symmetric difference. The result of each set operation is itself a stream that emits pairs of keys and a sequence of each occurrence of that key in the participating streams. This information allows one to perform set operations on maps and customize how conflicting output values are handled.
All set operations work efficiently on an arbitrary number of streams with memory proportional to the number of streams.
The algorithmic complexity of all set operations is O(n1 + n2 + n3 + ...)
where n1, n2, n3, ...
correspond to the number of elements in each
stream.
The 'm
lifetime parameter refers to the lifetime of the underlying set.
Implementations
Add a stream to this set operation.
This is useful for a chaining style pattern, e.g.,
builder.add(stream1).add(stream2).union()
.
The stream must emit a lexicographically ordered sequence of key-value pairs.
Add a stream to this set operation.
The stream must emit a lexicographically ordered sequence of key-value pairs.
Performs a union operation on all streams that have been added.
Note that this returns a stream of (&[u8], &[IndexedValue])
. The
first element of the tuple is the byte string key. The second element
of the tuple is a list of all occurrences of that key in participating
streams. The IndexedValue
contains an index and the value associated
with that key in that stream. The index uniquely identifies each
stream, which is an integer that is auto-incremented when a stream
is added to this operation (starting at 0
).
Example
use fst::{IntoStreamer, Streamer, Map}; use fst::map::IndexedValue; let map1 = Map::from_iter(vec![ ("a", 1), ("b", 2), ("c", 3), ]).unwrap(); let map2 = Map::from_iter(vec![ ("a", 11), ("y", 12), ("z", 13), ]).unwrap(); let mut union = map1.op().add(&map2).union(); let mut kvs = vec![]; while let Some((k, vs)) = union.next() { kvs.push((k.to_vec(), vs.to_vec())); } assert_eq!(kvs, vec![ (b"a".to_vec(), vec![ IndexedValue { index: 0, value: 1 }, IndexedValue { index: 1, value: 11 }, ]), (b"b".to_vec(), vec![IndexedValue { index: 0, value: 2 }]), (b"c".to_vec(), vec![IndexedValue { index: 0, value: 3 }]), (b"y".to_vec(), vec![IndexedValue { index: 1, value: 12 }]), (b"z".to_vec(), vec![IndexedValue { index: 1, value: 13 }]), ]);
Performs an intersection operation on all streams that have been added.
Note that this returns a stream of (&[u8], &[IndexedValue])
. The
first element of the tuple is the byte string key. The second element
of the tuple is a list of all occurrences of that key in participating
streams. The IndexedValue
contains an index and the value associated
with that key in that stream. The index uniquely identifies each
stream, which is an integer that is auto-incremented when a stream
is added to this operation (starting at 0
).
Example
use fst::{IntoStreamer, Streamer, Map}; use fst::map::IndexedValue; let map1 = Map::from_iter(vec![ ("a", 1), ("b", 2), ("c", 3), ]).unwrap(); let map2 = Map::from_iter(vec![ ("a", 11), ("y", 12), ("z", 13), ]).unwrap(); let mut intersection = map1.op().add(&map2).intersection(); let mut kvs = vec![]; while let Some((k, vs)) = intersection.next() { kvs.push((k.to_vec(), vs.to_vec())); } assert_eq!(kvs, vec![ (b"a".to_vec(), vec![ IndexedValue { index: 0, value: 1 }, IndexedValue { index: 1, value: 11 }, ]), ]);
Performs a difference operation with respect to the first stream added. That is, this returns a stream of all elements in the first stream that don’t exist in any other stream that has been added.
Note that this returns a stream of (&[u8], &[IndexedValue])
. The
first element of the tuple is the byte string key. The second element
of the tuple is a list of all occurrences of that key in participating
streams. The IndexedValue
contains an index and the value associated
with that key in that stream. The index uniquely identifies each
stream, which is an integer that is auto-incremented when a stream
is added to this operation (starting at 0
).
While the interface is the same for all the operations combining multiple
maps, due to the nature of difference
there’s exactly one IndexValue
for each yielded value.
Example
use fst::{Streamer, Map}; use fst::map::IndexedValue; let map1 = Map::from_iter(vec![ ("a", 1), ("b", 2), ("c", 3), ]).unwrap(); let map2 = Map::from_iter(vec![ ("a", 11), ("y", 12), ("z", 13), ]).unwrap(); let mut difference = map1.op().add(&map2).difference(); let mut kvs = vec![]; while let Some((k, vs)) = difference.next() { kvs.push((k.to_vec(), vs.to_vec())); } assert_eq!(kvs, vec![ (b"b".to_vec(), vec![IndexedValue { index: 0, value: 2 }]), (b"c".to_vec(), vec![IndexedValue { index: 0, value: 3 }]), ]);
Performs a symmetric difference operation on all of the streams that have been added.
When there are only two streams, then the keys returned correspond to keys that are in either stream but not in both streams.
More generally, for any number of streams, keys that occur in an odd number of streams are returned.
Note that this returns a stream of (&[u8], &[IndexedValue])
. The
first element of the tuple is the byte string key. The second element
of the tuple is a list of all occurrences of that key in participating
streams. The IndexedValue
contains an index and the value associated
with that key in that stream. The index uniquely identifies each
stream, which is an integer that is auto-incremented when a stream
is added to this operation (starting at 0
).
Example
use fst::{IntoStreamer, Streamer, Map}; use fst::map::IndexedValue; let map1 = Map::from_iter(vec![ ("a", 1), ("b", 2), ("c", 3), ]).unwrap(); let map2 = Map::from_iter(vec![ ("a", 11), ("y", 12), ("z", 13), ]).unwrap(); let mut sym_difference = map1.op().add(&map2).symmetric_difference(); let mut kvs = vec![]; while let Some((k, vs)) = sym_difference.next() { kvs.push((k.to_vec(), vs.to_vec())); } assert_eq!(kvs, vec![ (b"b".to_vec(), vec![IndexedValue { index: 0, value: 2 }]), (b"c".to_vec(), vec![IndexedValue { index: 0, value: 3 }]), (b"y".to_vec(), vec![IndexedValue { index: 1, value: 12 }]), (b"z".to_vec(), vec![IndexedValue { index: 1, value: 13 }]), ]);
Trait Implementations
Extends a collection with the contents of an iterator. Read more
extend_one
)Extends a collection with exactly one element.
extend_one
)Reserves capacity in a collection for the given number of additional elements. Read more
Auto Trait Implementations
impl<'m> !RefUnwindSafe for OpBuilder<'m>
impl<'m> !UnwindSafe for OpBuilder<'m>