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pageserver_api: remove overlaps from KeySpace (#6544)
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
GitHub
@@ -63,16 +63,84 @@ impl KeySpace {
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KeyPartitioning { parts }
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}
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/// Update the keyspace such that it doesn't contain any range
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/// that is overlapping with `other`. This can involve splitting or
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/// removing of existing ranges.
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pub fn remove_overlapping_with(&mut self, other: &KeySpace) {
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let (self_start, self_end) = match (self.start(), self.end()) {
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(Some(start), Some(end)) => (start, end),
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_ => {
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// self is empty
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return;
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}
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};
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// Key spaces are sorted by definition, so skip ahead to the first
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// potentially intersecting range. Similarly, ignore ranges that start
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// after the current keyspace ends.
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let other_ranges = other
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.ranges
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.iter()
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.skip_while(|range| self_start >= range.end)
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.take_while(|range| self_end > range.start);
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for range in other_ranges {
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while let Some(overlap_at) = self.overlaps_at(range) {
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let overlapped = self.ranges[overlap_at].clone();
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if overlapped.start < range.start && overlapped.end <= range.end {
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// Higher part of the range is completely overlapped.
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self.ranges[overlap_at].end = range.start;
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}
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if overlapped.start >= range.start && overlapped.end > range.end {
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// Lower part of the range is completely overlapped.
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self.ranges[overlap_at].start = range.end;
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}
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if overlapped.start < range.start && overlapped.end > range.end {
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// Middle part of the range is overlapped.
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self.ranges[overlap_at].end = range.start;
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self.ranges
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.insert(overlap_at + 1, range.end..overlapped.end);
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}
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if overlapped.start >= range.start && overlapped.end <= range.end {
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// Whole range is overlapped
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self.ranges.remove(overlap_at);
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}
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}
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}
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}
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pub fn start(&self) -> Option<Key> {
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self.ranges.first().map(|range| range.start)
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}
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pub fn end(&self) -> Option<Key> {
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self.ranges.last().map(|range| range.end)
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}
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#[allow(unused)]
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pub fn total_size(&self) -> usize {
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self.ranges
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.iter()
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.map(|range| key_range_size(range) as usize)
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.sum()
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}
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fn overlaps_at(&self, range: &Range<Key>) -> Option<usize> {
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match self.ranges.binary_search_by_key(&range.end, |r| r.start) {
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Ok(0) => None,
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Err(0) => None,
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Ok(index) if self.ranges[index - 1].end > range.start => Some(index - 1),
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Err(index) if self.ranges[index - 1].end > range.start => Some(index - 1),
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_ => None,
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}
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}
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///
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/// Check if key space contains overlapping range
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///
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pub fn overlaps(&self, range: &Range<Key>) -> bool {
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match self.ranges.binary_search_by_key(&range.end, |r| r.start) {
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Ok(0) => false,
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Err(0) => false,
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Ok(index) => self.ranges[index - 1].end > range.start,
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Err(index) => self.ranges[index - 1].end > range.start,
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}
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self.overlaps_at(range).is_some()
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}
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}
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@@ -441,4 +509,118 @@ mod tests {
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// xxxxxxxxxxx
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assert!(ks.overlaps(&kr(0..30))); // XXXXX This fails currently!
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}
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#[test]
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fn test_remove_full_overlapps() {
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let mut key_space1 = KeySpace {
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ranges: vec![
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Key::from_i128(1)..Key::from_i128(4),
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Key::from_i128(5)..Key::from_i128(8),
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Key::from_i128(10)..Key::from_i128(12),
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],
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};
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let key_space2 = KeySpace {
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ranges: vec![
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Key::from_i128(2)..Key::from_i128(3),
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Key::from_i128(6)..Key::from_i128(7),
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Key::from_i128(11)..Key::from_i128(13),
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],
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};
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key_space1.remove_overlapping_with(&key_space2);
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assert_eq!(
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key_space1.ranges,
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vec![
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Key::from_i128(1)..Key::from_i128(2),
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Key::from_i128(3)..Key::from_i128(4),
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Key::from_i128(5)..Key::from_i128(6),
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Key::from_i128(7)..Key::from_i128(8),
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Key::from_i128(10)..Key::from_i128(11)
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]
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);
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}
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#[test]
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fn test_remove_partial_overlaps() {
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// Test partial ovelaps
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let mut key_space1 = KeySpace {
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ranges: vec![
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Key::from_i128(1)..Key::from_i128(5),
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Key::from_i128(7)..Key::from_i128(10),
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Key::from_i128(12)..Key::from_i128(15),
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],
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};
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let key_space2 = KeySpace {
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ranges: vec![
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Key::from_i128(3)..Key::from_i128(6),
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Key::from_i128(8)..Key::from_i128(11),
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Key::from_i128(14)..Key::from_i128(17),
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],
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};
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key_space1.remove_overlapping_with(&key_space2);
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assert_eq!(
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key_space1.ranges,
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vec![
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Key::from_i128(1)..Key::from_i128(3),
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Key::from_i128(7)..Key::from_i128(8),
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Key::from_i128(12)..Key::from_i128(14),
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]
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);
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}
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#[test]
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fn test_remove_no_overlaps() {
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let mut key_space1 = KeySpace {
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ranges: vec![
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Key::from_i128(1)..Key::from_i128(5),
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Key::from_i128(7)..Key::from_i128(10),
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Key::from_i128(12)..Key::from_i128(15),
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],
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};
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let key_space2 = KeySpace {
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ranges: vec![
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Key::from_i128(6)..Key::from_i128(7),
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Key::from_i128(11)..Key::from_i128(12),
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Key::from_i128(15)..Key::from_i128(17),
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],
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};
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key_space1.remove_overlapping_with(&key_space2);
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assert_eq!(
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key_space1.ranges,
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vec![
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Key::from_i128(1)..Key::from_i128(5),
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Key::from_i128(7)..Key::from_i128(10),
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Key::from_i128(12)..Key::from_i128(15),
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]
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);
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}
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#[test]
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fn test_remove_one_range_overlaps_multiple() {
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let mut key_space1 = KeySpace {
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ranges: vec![
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Key::from_i128(1)..Key::from_i128(3),
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Key::from_i128(3)..Key::from_i128(6),
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Key::from_i128(6)..Key::from_i128(10),
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Key::from_i128(12)..Key::from_i128(15),
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Key::from_i128(17)..Key::from_i128(20),
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Key::from_i128(20)..Key::from_i128(30),
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Key::from_i128(30)..Key::from_i128(40),
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],
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};
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let key_space2 = KeySpace {
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ranges: vec![Key::from_i128(9)..Key::from_i128(19)],
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};
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key_space1.remove_overlapping_with(&key_space2);
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assert_eq!(
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key_space1.ranges,
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vec![
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Key::from_i128(1)..Key::from_i128(3),
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Key::from_i128(3)..Key::from_i128(6),
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Key::from_i128(6)..Key::from_i128(9),
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Key::from_i128(19)..Key::from_i128(20),
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Key::from_i128(20)..Key::from_i128(30),
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Key::from_i128(30)..Key::from_i128(40),
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]
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);
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}
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}
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