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pageserver_api: remove overlaps from KeySpace

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This commit adds a function to `KeySpace` which updates a key key space
by removing all overlaps with a second key space. This can involve
splitting or removing of existing ranges.

The implementation is not particularly efficient: O(M * N * log(N))
where N is the number of ranges in the current key space and M is the
number of ranges in the key space we are checking against. In practice,
this shouldn't matter much since, in the short term, the only caller
of this function will be the vectored read path and the number of key
spaces invovled will be small. This follows from the upper bound placed
on the number of keys accepted by the vectored read path.

A couple other small utility functions are added. They'll be used by the
vectored search path as well.
This commit is contained in:
Vlad Lazar
2024-01-31 10:15:40 +00:00
parent ae77e5355c
commit 4c6627f3d9
1 changed files with 154 additions and 6 deletions
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160
libs/pageserver_api/src/keyspace.rs
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@@ -63,16 +63,64 @@ impl KeySpace {
KeyPartitioning { parts }
}
/// Update the keyspace such that it doesn't contain any range
/// that is overlapping with `other`. This can involve splitting or
/// removing of existing ranges.
pub fn remove_overlapping_with(&mut self, other: &KeySpace) {
for range in &other.ranges {
while let Some(overlap_at) = self.overlaps_at(range) {
let overlapped = self.ranges[overlap_at].clone();
if overlapped.start < range.start && overlapped.end <= range.end {
// Higher part of the range is completely overlapped.
self.ranges[overlap_at].end = range.start;
}
if overlapped.start >= range.start && overlapped.end > range.end {
// Lower part of the range is completely overlapped.
self.ranges[overlap_at].start = range.end;
}
if overlapped.start < range.start && overlapped.end > range.end {
// Middle part of the range is overlapped.
self.ranges[overlap_at].end = range.start;
self.ranges
.insert(overlap_at + 1, range.end..overlapped.end);
}
if overlapped.start >= range.start && overlapped.end <= range.end {
// Whole range is overlapped
self.ranges.remove(overlap_at);
}
}
}
}
#[allow(unused)]
pub fn start(&self) -> Option<Key> {
self.ranges.first().map(|range| range.start)
}
#[allow(unused)]
pub fn total_size(&self) -> usize {
self.ranges
.iter()
.map(|range| key_range_size(range) as usize)
.sum()
}
fn overlaps_at(&self, range: &Range<Key>) -> Option<usize> {
match self.ranges.binary_search_by_key(&range.end, |r| r.start) {
Ok(0) => None,
Err(0) => None,
Ok(index) if self.ranges[index - 1].end > range.start => Some(index - 1),
Err(index) if self.ranges[index - 1].end > range.start => Some(index - 1),
_ => None,
}
}
///
/// Check if key space contains overlapping range
///
pub fn overlaps(&self, range: &Range<Key>) -> bool {
match self.ranges.binary_search_by_key(&range.end, |r| r.start) {
Ok(0) => false,
Err(0) => false,
Ok(index) => self.ranges[index - 1].end > range.start,
Err(index) => self.ranges[index - 1].end > range.start,
}
self.overlaps_at(range).is_some()
}
}
@@ -441,4 +489,104 @@ mod tests {
// xxxxxxxxxxx
assert!(ks.overlaps(&kr(0..30))); // XXXXX This fails currently!
}
#[test]
fn test_remove_overlapping_with() {
// Test full overlaps
let mut key_space1 = KeySpace {
ranges: vec![
Key::from_i128(1)..Key::from_i128(4),
Key::from_i128(5)..Key::from_i128(8),
Key::from_i128(10)..Key::from_i128(12),
],
};
let key_space2 = KeySpace {
ranges: vec![
Key::from_i128(2)..Key::from_i128(3),
Key::from_i128(6)..Key::from_i128(7),
Key::from_i128(11)..Key::from_i128(13),
],
};
key_space1.remove_overlapping_with(&key_space2);
assert_eq!(
key_space1.ranges,
vec![
Key::from_i128(1)..Key::from_i128(2),
Key::from_i128(3)..Key::from_i128(4),
Key::from_i128(5)..Key::from_i128(6),
Key::from_i128(7)..Key::from_i128(8),
Key::from_i128(10)..Key::from_i128(11)
]
);
// Test partial ovelaps
let mut key_space1 = KeySpace {
ranges: vec![
Key::from_i128(1)..Key::from_i128(5),
Key::from_i128(7)..Key::from_i128(10),
Key::from_i128(12)..Key::from_i128(15),
],
};
let key_space2 = KeySpace {
ranges: vec![
Key::from_i128(3)..Key::from_i128(6),
Key::from_i128(8)..Key::from_i128(11),
Key::from_i128(14)..Key::from_i128(17),
],
};
key_space1.remove_overlapping_with(&key_space2);
assert_eq!(
key_space1.ranges,
vec![
Key::from_i128(1)..Key::from_i128(3),
Key::from_i128(7)..Key::from_i128(8),
Key::from_i128(12)..Key::from_i128(14),
]
);
// Test no overlaps
let mut key_space1 = KeySpace {
ranges: vec![
Key::from_i128(1)..Key::from_i128(5),
Key::from_i128(7)..Key::from_i128(10),
Key::from_i128(12)..Key::from_i128(15),
],
};
let key_space2 = KeySpace {
ranges: vec![
Key::from_i128(6)..Key::from_i128(7),
Key::from_i128(11)..Key::from_i128(12),
Key::from_i128(15)..Key::from_i128(17),
],
};
key_space1.remove_overlapping_with(&key_space2);
assert_eq!(
key_space1.ranges,
vec![
Key::from_i128(1)..Key::from_i128(5),
Key::from_i128(7)..Key::from_i128(10),
Key::from_i128(12)..Key::from_i128(15),
]
);
// Test one range overlaps multiple
let mut key_space1 = KeySpace {
ranges: vec![
Key::from_i128(1)..Key::from_i128(5),
Key::from_i128(7)..Key::from_i128(10),
Key::from_i128(12)..Key::from_i128(15),
],
};
let key_space2 = KeySpace {
ranges: vec![Key::from_i128(4)..Key::from_i128(14)],
};
key_space1.remove_overlapping_with(&key_space2);
assert_eq!(
key_space1.ranges,
vec![
Key::from_i128(1)..Key::from_i128(4),
Key::from_i128(14)..Key::from_i128(15),
]
);
}
}