Line data Source code
1 : use std::collections::BTreeMap;
2 : use std::ops::Range;
3 :
4 : use tracing::info;
5 :
6 : use super::layer_coverage::LayerCoverageTuple;
7 : use crate::tenant::storage_layer::PersistentLayerDesc;
8 :
9 : /// Layers in this module are identified and indexed by this data.
10 : ///
11 : /// This is a helper struct to enable sorting layers by lsn.start.
12 : ///
13 : /// These three values are enough to uniquely identify a layer, since
14 : /// a layer is obligated to contain all contents within range, so two
15 : /// deltas (or images) with the same range have identical content.
16 : #[derive(Debug, PartialEq, Eq, Clone)]
17 : pub struct LayerKey {
18 : // TODO I use i128 and u64 because it was easy for prototyping,
19 : // testing, and benchmarking. If we can use the Lsn and Key
20 : // types without overhead that would be preferable.
21 : pub key: Range<i128>,
22 : pub lsn: Range<u64>,
23 : pub is_image: bool,
24 : }
25 :
26 : impl PartialOrd for LayerKey {
27 0 : fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
28 0 : Some(self.cmp(other))
29 0 : }
30 : }
31 :
32 : impl Ord for LayerKey {
33 297175 : fn cmp(&self, other: &Self) -> std::cmp::Ordering {
34 297175 : // NOTE we really care about comparing by lsn.start first
35 297175 : self.lsn
36 297175 : .start
37 297175 : .cmp(&other.lsn.start)
38 297175 : .then(self.lsn.end.cmp(&other.lsn.end))
39 297175 : .then(self.key.start.cmp(&other.key.start))
40 297175 : .then(self.key.end.cmp(&other.key.end))
41 297175 : .then(self.is_image.cmp(&other.is_image))
42 297175 : }
43 : }
44 :
45 : impl From<&PersistentLayerDesc> for LayerKey {
46 10860 : fn from(layer: &PersistentLayerDesc) -> Self {
47 10860 : let kr = layer.get_key_range();
48 10860 : let lr = layer.get_lsn_range();
49 10860 : LayerKey {
50 10860 : key: kr.start.to_i128()..kr.end.to_i128(),
51 10860 : lsn: lr.start.0..lr.end.0,
52 10860 : is_image: !layer.is_incremental(),
53 10860 : }
54 10860 : }
55 : }
56 :
57 : /// Efficiently queryable layer coverage for each LSN.
58 : ///
59 : /// Allows answering layer map queries very efficiently,
60 : /// but doesn't allow retroactive insertion, which is
61 : /// sometimes necessary. See BufferedHistoricLayerCoverage.
62 : pub struct HistoricLayerCoverage<Value> {
63 : /// The latest state
64 : head: LayerCoverageTuple<Value>,
65 :
66 : /// TODO: this could be an ordered vec using binary search.
67 : /// We push into this map everytime we add a layer, so might see some benefit
68 : /// All previous states
69 : historic: BTreeMap<u64, LayerCoverageTuple<Value>>,
70 : }
71 :
72 : impl<T: Clone> Default for HistoricLayerCoverage<T> {
73 0 : fn default() -> Self {
74 0 : Self::new()
75 0 : }
76 : }
77 :
78 : impl<Value: Clone> HistoricLayerCoverage<Value> {
79 948 : pub fn new() -> Self {
80 948 : Self {
81 948 : head: LayerCoverageTuple::default(),
82 948 : historic: BTreeMap::default(),
83 948 : }
84 948 : }
85 :
86 : /// Add a layer
87 : ///
88 : /// Panics if new layer has older lsn.start than an existing layer.
89 : /// See BufferedHistoricLayerCoverage for a more general insertion method.
90 10368 : pub fn insert(&mut self, layer_key: LayerKey, value: Value) {
91 : // It's only a persistent map, not a retroactive one
92 10368 : if let Some(last_entry) = self.historic.iter().next_back() {
93 9496 : let last_lsn = last_entry.0;
94 9496 : if layer_key.lsn.start < *last_lsn {
95 0 : panic!("unexpected retroactive insert");
96 9496 : }
97 872 : }
98 :
99 : // Insert into data structure
100 10368 : let target = if layer_key.is_image {
101 4168 : &mut self.head.image_coverage
102 : } else {
103 6200 : &mut self.head.delta_coverage
104 : };
105 :
106 10368 : target.insert(layer_key.key, layer_key.lsn.clone(), value);
107 10368 :
108 10368 : // Remember history. Clone is O(1)
109 10368 : self.historic.insert(layer_key.lsn.start, self.head.clone());
110 10368 : }
111 :
112 : /// Query at a particular LSN, inclusive
113 2450235 : pub fn get_version(&self, lsn: u64) -> Option<&LayerCoverageTuple<Value>> {
114 2450235 : match self.historic.range(..=lsn).next_back() {
115 1782596 : Some((_, v)) => Some(v),
116 667639 : None => None,
117 : }
118 2450235 : }
119 :
120 : /// Remove all entries after a certain LSN (inclusive)
121 2880 : pub fn trim(&mut self, begin: &u64) {
122 2880 : self.historic.split_off(begin);
123 2880 : self.head = self
124 2880 : .historic
125 2880 : .iter()
126 2880 : .next_back()
127 2880 : .map(|(_, v)| v.clone())
128 2880 : .unwrap_or_default();
129 2880 : }
130 : }
131 :
132 : /// This is the most basic test that demonstrates intended usage.
133 : /// All layers in this test have height 1.
134 : #[test]
135 4 : fn test_persistent_simple() {
136 4 : let mut map = HistoricLayerCoverage::<String>::new();
137 4 : map.insert(
138 4 : LayerKey {
139 4 : key: 0..5,
140 4 : lsn: 100..101,
141 4 : is_image: true,
142 4 : },
143 4 : "Layer 1".to_string(),
144 4 : );
145 4 : map.insert(
146 4 : LayerKey {
147 4 : key: 3..9,
148 4 : lsn: 110..111,
149 4 : is_image: true,
150 4 : },
151 4 : "Layer 2".to_string(),
152 4 : );
153 4 : map.insert(
154 4 : LayerKey {
155 4 : key: 5..6,
156 4 : lsn: 120..121,
157 4 : is_image: true,
158 4 : },
159 4 : "Layer 3".to_string(),
160 4 : );
161 4 :
162 4 : // After Layer 1 insertion
163 4 : let version = map.get_version(105).unwrap();
164 4 : assert_eq!(version.image_coverage.query(1), Some("Layer 1".to_string()));
165 4 : assert_eq!(version.image_coverage.query(4), Some("Layer 1".to_string()));
166 :
167 : // After Layer 2 insertion
168 4 : let version = map.get_version(115).unwrap();
169 4 : assert_eq!(version.image_coverage.query(4), Some("Layer 2".to_string()));
170 4 : assert_eq!(version.image_coverage.query(8), Some("Layer 2".to_string()));
171 4 : assert_eq!(version.image_coverage.query(11), None);
172 :
173 : // After Layer 3 insertion
174 4 : let version = map.get_version(125).unwrap();
175 4 : assert_eq!(version.image_coverage.query(4), Some("Layer 2".to_string()));
176 4 : assert_eq!(version.image_coverage.query(5), Some("Layer 3".to_string()));
177 4 : assert_eq!(version.image_coverage.query(7), Some("Layer 2".to_string()));
178 4 : }
179 :
180 : /// Cover simple off-by-one edge cases
181 : #[test]
182 4 : fn test_off_by_one() {
183 4 : let mut map = HistoricLayerCoverage::<String>::new();
184 4 : map.insert(
185 4 : LayerKey {
186 4 : key: 3..5,
187 4 : lsn: 100..110,
188 4 : is_image: true,
189 4 : },
190 4 : "Layer 1".to_string(),
191 4 : );
192 4 :
193 4 : // Check different LSNs
194 4 : let version = map.get_version(99);
195 4 : assert!(version.is_none());
196 4 : let version = map.get_version(100).unwrap();
197 4 : assert_eq!(version.image_coverage.query(4), Some("Layer 1".to_string()));
198 4 : let version = map.get_version(110).unwrap();
199 4 : assert_eq!(version.image_coverage.query(4), Some("Layer 1".to_string()));
200 :
201 : // Check different keys
202 4 : let version = map.get_version(105).unwrap();
203 4 : assert_eq!(version.image_coverage.query(2), None);
204 4 : assert_eq!(version.image_coverage.query(3), Some("Layer 1".to_string()));
205 4 : assert_eq!(version.image_coverage.query(4), Some("Layer 1".to_string()));
206 4 : assert_eq!(version.image_coverage.query(5), None);
207 4 : }
208 :
209 : /// White-box regression test, checking for incorrect removal of node at key.end
210 : #[test]
211 4 : fn test_regression() {
212 4 : let mut map = HistoricLayerCoverage::<String>::new();
213 4 : map.insert(
214 4 : LayerKey {
215 4 : key: 0..5,
216 4 : lsn: 0..5,
217 4 : is_image: false,
218 4 : },
219 4 : "Layer 1".to_string(),
220 4 : );
221 4 : map.insert(
222 4 : LayerKey {
223 4 : key: 0..5,
224 4 : lsn: 1..2,
225 4 : is_image: false,
226 4 : },
227 4 : "Layer 2".to_string(),
228 4 : );
229 4 :
230 4 : // If an insertion operation improperly deletes the endpoint of a previous layer
231 4 : // (which is more likely to happen with layers that collide on key.end), we will
232 4 : // end up with an infinite layer, covering the entire keyspace. Here we assert
233 4 : // that there's no layer at key 100 because we didn't insert any layer there.
234 4 : let version = map.get_version(100).unwrap();
235 4 : assert_eq!(version.delta_coverage.query(100), None);
236 4 : }
237 :
238 : /// Cover edge cases where layers begin or end on the same key
239 : #[test]
240 4 : fn test_key_collision() {
241 4 : let mut map = HistoricLayerCoverage::<String>::new();
242 4 :
243 4 : map.insert(
244 4 : LayerKey {
245 4 : key: 3..5,
246 4 : lsn: 100..110,
247 4 : is_image: true,
248 4 : },
249 4 : "Layer 10".to_string(),
250 4 : );
251 4 : map.insert(
252 4 : LayerKey {
253 4 : key: 5..8,
254 4 : lsn: 100..110,
255 4 : is_image: true,
256 4 : },
257 4 : "Layer 11".to_string(),
258 4 : );
259 4 : map.insert(
260 4 : LayerKey {
261 4 : key: 3..4,
262 4 : lsn: 200..210,
263 4 : is_image: true,
264 4 : },
265 4 : "Layer 20".to_string(),
266 4 : );
267 4 :
268 4 : // Check after layer 11
269 4 : let version = map.get_version(105).unwrap();
270 4 : assert_eq!(version.image_coverage.query(2), None);
271 4 : assert_eq!(
272 4 : version.image_coverage.query(3),
273 4 : Some("Layer 10".to_string())
274 4 : );
275 4 : assert_eq!(
276 4 : version.image_coverage.query(5),
277 4 : Some("Layer 11".to_string())
278 4 : );
279 4 : assert_eq!(
280 4 : version.image_coverage.query(7),
281 4 : Some("Layer 11".to_string())
282 4 : );
283 4 : assert_eq!(version.image_coverage.query(8), None);
284 :
285 : // Check after layer 20
286 4 : let version = map.get_version(205).unwrap();
287 4 : assert_eq!(version.image_coverage.query(2), None);
288 4 : assert_eq!(
289 4 : version.image_coverage.query(3),
290 4 : Some("Layer 20".to_string())
291 4 : );
292 4 : assert_eq!(
293 4 : version.image_coverage.query(5),
294 4 : Some("Layer 11".to_string())
295 4 : );
296 4 : assert_eq!(
297 4 : version.image_coverage.query(7),
298 4 : Some("Layer 11".to_string())
299 4 : );
300 4 : assert_eq!(version.image_coverage.query(8), None);
301 4 : }
302 :
303 : /// Test when rectangles have nontrivial height and possibly overlap
304 : #[test]
305 4 : fn test_persistent_overlapping() {
306 4 : let mut map = HistoricLayerCoverage::<String>::new();
307 4 :
308 4 : // Add 3 key-disjoint layers with varying LSN ranges
309 4 : map.insert(
310 4 : LayerKey {
311 4 : key: 1..2,
312 4 : lsn: 100..200,
313 4 : is_image: true,
314 4 : },
315 4 : "Layer 1".to_string(),
316 4 : );
317 4 : map.insert(
318 4 : LayerKey {
319 4 : key: 4..5,
320 4 : lsn: 110..200,
321 4 : is_image: true,
322 4 : },
323 4 : "Layer 2".to_string(),
324 4 : );
325 4 : map.insert(
326 4 : LayerKey {
327 4 : key: 7..8,
328 4 : lsn: 120..300,
329 4 : is_image: true,
330 4 : },
331 4 : "Layer 3".to_string(),
332 4 : );
333 4 :
334 4 : // Add wide and short layer
335 4 : map.insert(
336 4 : LayerKey {
337 4 : key: 0..9,
338 4 : lsn: 130..199,
339 4 : is_image: true,
340 4 : },
341 4 : "Layer 4".to_string(),
342 4 : );
343 4 :
344 4 : // Add wide layer taller than some
345 4 : map.insert(
346 4 : LayerKey {
347 4 : key: 0..9,
348 4 : lsn: 140..201,
349 4 : is_image: true,
350 4 : },
351 4 : "Layer 5".to_string(),
352 4 : );
353 4 :
354 4 : // Add wide layer taller than all
355 4 : map.insert(
356 4 : LayerKey {
357 4 : key: 0..9,
358 4 : lsn: 150..301,
359 4 : is_image: true,
360 4 : },
361 4 : "Layer 6".to_string(),
362 4 : );
363 4 :
364 4 : // After layer 4 insertion
365 4 : let version = map.get_version(135).unwrap();
366 4 : assert_eq!(version.image_coverage.query(0), Some("Layer 4".to_string()));
367 4 : assert_eq!(version.image_coverage.query(1), Some("Layer 1".to_string()));
368 4 : assert_eq!(version.image_coverage.query(2), Some("Layer 4".to_string()));
369 4 : assert_eq!(version.image_coverage.query(4), Some("Layer 2".to_string()));
370 4 : assert_eq!(version.image_coverage.query(5), Some("Layer 4".to_string()));
371 4 : assert_eq!(version.image_coverage.query(7), Some("Layer 3".to_string()));
372 4 : assert_eq!(version.image_coverage.query(8), Some("Layer 4".to_string()));
373 :
374 : // After layer 5 insertion
375 4 : let version = map.get_version(145).unwrap();
376 4 : assert_eq!(version.image_coverage.query(0), Some("Layer 5".to_string()));
377 4 : assert_eq!(version.image_coverage.query(1), Some("Layer 5".to_string()));
378 4 : assert_eq!(version.image_coverage.query(2), Some("Layer 5".to_string()));
379 4 : assert_eq!(version.image_coverage.query(4), Some("Layer 5".to_string()));
380 4 : assert_eq!(version.image_coverage.query(5), Some("Layer 5".to_string()));
381 4 : assert_eq!(version.image_coverage.query(7), Some("Layer 3".to_string()));
382 4 : assert_eq!(version.image_coverage.query(8), Some("Layer 5".to_string()));
383 :
384 : // After layer 6 insertion
385 4 : let version = map.get_version(155).unwrap();
386 4 : assert_eq!(version.image_coverage.query(0), Some("Layer 6".to_string()));
387 4 : assert_eq!(version.image_coverage.query(1), Some("Layer 6".to_string()));
388 4 : assert_eq!(version.image_coverage.query(2), Some("Layer 6".to_string()));
389 4 : assert_eq!(version.image_coverage.query(4), Some("Layer 6".to_string()));
390 4 : assert_eq!(version.image_coverage.query(5), Some("Layer 6".to_string()));
391 4 : assert_eq!(version.image_coverage.query(7), Some("Layer 6".to_string()));
392 4 : assert_eq!(version.image_coverage.query(8), Some("Layer 6".to_string()));
393 4 : }
394 :
395 : /// Wrapper for HistoricLayerCoverage that allows us to hack around the lack
396 : /// of support for retroactive insertion by rebuilding the map since the
397 : /// change.
398 : ///
399 : /// Why is this needed? We most often insert new layers with newer LSNs,
400 : /// but during compaction we create layers with non-latest LSN, and during
401 : /// GC we delete historic layers.
402 : ///
403 : /// Even though rebuilding is an expensive (N log N) solution to the problem,
404 : /// it's not critical since we do something equally expensive just to decide
405 : /// whether or not to create new image layers.
406 : /// TODO It's not expensive but it's not great to hold a layer map write lock
407 : /// for that long.
408 : ///
409 : /// If this becomes an actual bottleneck, one solution would be to build a
410 : /// segment tree that holds PersistentLayerMaps. Though this would mean that
411 : /// we take an additional log(N) performance hit for queries, which will probably
412 : /// still be more critical.
413 : ///
414 : /// See this for more on persistent and retroactive techniques:
415 : /// <https://www.youtube.com/watch?v=WqCWghETNDc&t=581s>
416 : pub struct BufferedHistoricLayerCoverage<Value> {
417 : /// A persistent layer map that we rebuild when we need to retroactively update
418 : historic_coverage: HistoricLayerCoverage<Value>,
419 :
420 : /// We buffer insertion into the PersistentLayerMap to decrease the number of rebuilds.
421 : buffer: BTreeMap<LayerKey, Option<Value>>,
422 :
423 : /// All current layers. This is not used for search. Only to make rebuilds easier.
424 : // TODO: This map is never cleared. Rebuilds could use the post-trim last entry of
425 : // [`Self::historic_coverage`] instead of doubling memory usage.
426 : // [`Self::len`]: can require rebuild and serve from latest historic
427 : // [`Self::iter`]: already requires rebuild => can serve from latest historic
428 : layers: BTreeMap<LayerKey, Value>,
429 : }
430 :
431 : impl<T: std::fmt::Debug> std::fmt::Debug for BufferedHistoricLayerCoverage<T> {
432 0 : fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
433 0 : f.debug_struct("RetroactiveLayerMap")
434 0 : .field("buffer", &self.buffer)
435 0 : .field("layers", &self.layers)
436 0 : .finish()
437 0 : }
438 : }
439 :
440 : impl<T: Clone> Default for BufferedHistoricLayerCoverage<T> {
441 920 : fn default() -> Self {
442 920 : Self::new()
443 920 : }
444 : }
445 :
446 : impl<Value: Clone> BufferedHistoricLayerCoverage<Value> {
447 928 : pub fn new() -> Self {
448 928 : Self {
449 928 : historic_coverage: HistoricLayerCoverage::<Value>::new(),
450 928 : buffer: BTreeMap::new(),
451 928 : layers: BTreeMap::new(),
452 928 : }
453 928 : }
454 :
455 9852 : pub fn insert(&mut self, layer_key: LayerKey, value: Value) {
456 9852 : self.buffer.insert(layer_key, Some(value));
457 9852 : }
458 :
459 1036 : pub fn remove(&mut self, layer_key: LayerKey) {
460 1036 : self.buffer.insert(layer_key, None);
461 1036 : }
462 :
463 3600 : pub fn rebuild(&mut self) {
464 : // Find the first LSN that needs to be rebuilt
465 3600 : let rebuild_since: u64 = match self.buffer.iter().next() {
466 2880 : Some((LayerKey { lsn, .. }, _)) => lsn.start,
467 720 : None => return, // No need to rebuild if buffer is empty
468 : };
469 :
470 : // Apply buffered updates to self.layers
471 2880 : let num_updates = self.buffer.len();
472 10888 : self.buffer.retain(|layer_key, layer| {
473 10888 : match layer {
474 9852 : Some(l) => {
475 9852 : self.layers.insert(layer_key.clone(), l.clone());
476 9852 : }
477 1036 : None => {
478 1036 : self.layers.remove(layer_key);
479 1036 : }
480 : };
481 10888 : false
482 10888 : });
483 2880 :
484 2880 : // Rebuild
485 2880 : let mut num_inserted = 0;
486 2880 : self.historic_coverage.trim(&rebuild_since);
487 10308 : for (layer_key, layer) in self.layers.range(
488 2880 : LayerKey {
489 2880 : lsn: rebuild_since..0,
490 2880 : key: 0..0,
491 2880 : is_image: false,
492 2880 : }..,
493 10308 : ) {
494 10308 : self.historic_coverage
495 10308 : .insert(layer_key.clone(), layer.clone());
496 10308 : num_inserted += 1;
497 10308 : }
498 :
499 : // TODO maybe only warn if ratio is at least 10
500 2880 : info!(
501 0 : "Rebuilt layer map. Did {} insertions to process a batch of {} updates.",
502 : num_inserted, num_updates,
503 : )
504 3600 : }
505 :
506 : /// Iterate all the layers
507 7336 : pub fn iter(&self) -> impl '_ + Iterator<Item = Value> {
508 7336 : // NOTE we can actually perform this without rebuilding,
509 7336 : // but it's not necessary for now.
510 7336 : if !self.buffer.is_empty() {
511 0 : panic!("rebuild pls")
512 7336 : }
513 7336 :
514 7336 : self.layers.values().cloned()
515 7336 : }
516 :
517 : /// Return a reference to a queryable map, assuming all updates
518 : /// have already been processed using self.rebuild()
519 2450167 : pub fn get(&self) -> anyhow::Result<&HistoricLayerCoverage<Value>> {
520 2450167 : // NOTE we error here instead of implicitly rebuilding because
521 2450167 : // rebuilding is somewhat expensive.
522 2450167 : // TODO maybe implicitly rebuild and log/sentry an error?
523 2450167 : if !self.buffer.is_empty() {
524 0 : anyhow::bail!("rebuild required")
525 2450167 : }
526 2450167 :
527 2450167 : Ok(&self.historic_coverage)
528 2450167 : }
529 :
530 952 : pub(crate) fn len(&self) -> usize {
531 952 : self.layers.len()
532 952 : }
533 : }
534 :
535 : #[test]
536 4 : fn test_retroactive_regression_1() {
537 4 : let mut map = BufferedHistoricLayerCoverage::new();
538 4 :
539 4 : map.insert(
540 4 : LayerKey {
541 4 : key: 0..21267647932558653966460912964485513215,
542 4 : lsn: 23761336..23761457,
543 4 : is_image: false,
544 4 : },
545 4 : "sdfsdfs".to_string(),
546 4 : );
547 4 :
548 4 : map.rebuild();
549 4 :
550 4 : let version = map.get().unwrap().get_version(23761457).unwrap();
551 4 : assert_eq!(
552 4 : version.delta_coverage.query(100),
553 4 : Some("sdfsdfs".to_string())
554 4 : );
555 4 : }
556 :
557 : #[test]
558 4 : fn test_retroactive_simple() {
559 4 : let mut map = BufferedHistoricLayerCoverage::new();
560 4 :
561 4 : // Append some images in increasing LSN order
562 4 : map.insert(
563 4 : LayerKey {
564 4 : key: 0..5,
565 4 : lsn: 100..101,
566 4 : is_image: true,
567 4 : },
568 4 : "Image 1".to_string(),
569 4 : );
570 4 : map.insert(
571 4 : LayerKey {
572 4 : key: 3..9,
573 4 : lsn: 110..111,
574 4 : is_image: true,
575 4 : },
576 4 : "Image 2".to_string(),
577 4 : );
578 4 : map.insert(
579 4 : LayerKey {
580 4 : key: 4..6,
581 4 : lsn: 120..121,
582 4 : is_image: true,
583 4 : },
584 4 : "Image 3".to_string(),
585 4 : );
586 4 : map.insert(
587 4 : LayerKey {
588 4 : key: 8..9,
589 4 : lsn: 120..121,
590 4 : is_image: true,
591 4 : },
592 4 : "Image 4".to_string(),
593 4 : );
594 4 :
595 4 : // Add a delta layer out of order
596 4 : map.insert(
597 4 : LayerKey {
598 4 : key: 2..5,
599 4 : lsn: 105..106,
600 4 : is_image: false,
601 4 : },
602 4 : "Delta 1".to_string(),
603 4 : );
604 4 :
605 4 : // Rebuild so we can start querying
606 4 : map.rebuild();
607 4 :
608 4 : {
609 4 : let map = map.get().expect("rebuilt");
610 4 :
611 4 : let version = map.get_version(90);
612 4 : assert!(version.is_none());
613 4 : let version = map.get_version(102).unwrap();
614 4 : assert_eq!(version.image_coverage.query(4), Some("Image 1".to_string()));
615 :
616 4 : let version = map.get_version(107).unwrap();
617 4 : assert_eq!(version.image_coverage.query(4), Some("Image 1".to_string()));
618 4 : assert_eq!(version.delta_coverage.query(4), Some("Delta 1".to_string()));
619 :
620 4 : let version = map.get_version(115).unwrap();
621 4 : assert_eq!(version.image_coverage.query(4), Some("Image 2".to_string()));
622 :
623 4 : let version = map.get_version(125).unwrap();
624 4 : assert_eq!(version.image_coverage.query(4), Some("Image 3".to_string()));
625 : }
626 :
627 : // Remove Image 3
628 4 : map.remove(LayerKey {
629 4 : key: 4..6,
630 4 : lsn: 120..121,
631 4 : is_image: true,
632 4 : });
633 4 : map.rebuild();
634 4 :
635 4 : {
636 4 : // Check deletion worked
637 4 : let map = map.get().expect("rebuilt");
638 4 : let version = map.get_version(125).unwrap();
639 4 : assert_eq!(version.image_coverage.query(4), Some("Image 2".to_string()));
640 4 : assert_eq!(version.image_coverage.query(8), Some("Image 4".to_string()));
641 : }
642 4 : }
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