LCOV - code coverage report
Current view: top level - pageserver/src/tenant/layer_map - historic_layer_coverage.rs (source / functions) Coverage Total Hit
Test: a2f0f8a80fbf1089336086fa360ce27fa555cb1a.info Lines: 96.6 % 470 454
Test Date: 2024-11-20 17:59:39 Functions: 91.9 % 37 34

            Line data    Source code
       1              : use std::collections::BTreeMap;
       2              : use std::ops::Range;
       3              : 
       4              : use tracing::info;
       5              : 
       6              : use crate::tenant::storage_layer::PersistentLayerDesc;
       7              : 
       8              : use super::layer_coverage::LayerCoverageTuple;
       9              : 
      10              : /// Layers in this module are identified and indexed by this data.
      11              : ///
      12              : /// This is a helper struct to enable sorting layers by lsn.start.
      13              : ///
      14              : /// These three values are enough to uniquely identify a layer, since
      15              : /// a layer is obligated to contain all contents within range, so two
      16              : /// deltas (or images) with the same range have identical content.
      17              : #[derive(Debug, PartialEq, Eq, Clone)]
      18              : pub struct LayerKey {
      19              :     // TODO I use i128 and u64 because it was easy for prototyping,
      20              :     //      testing, and benchmarking. If we can use the Lsn and Key
      21              :     //      types without overhead that would be preferable.
      22              :     pub key: Range<i128>,
      23              :     pub lsn: Range<u64>,
      24              :     pub is_image: bool,
      25              : }
      26              : 
      27              : impl PartialOrd for LayerKey {
      28            0 :     fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
      29            0 :         Some(self.cmp(other))
      30            0 :     }
      31              : }
      32              : 
      33              : impl Ord for LayerKey {
      34       148554 :     fn cmp(&self, other: &Self) -> std::cmp::Ordering {
      35       148554 :         // NOTE we really care about comparing by lsn.start first
      36       148554 :         self.lsn
      37       148554 :             .start
      38       148554 :             .cmp(&other.lsn.start)
      39       148554 :             .then(self.lsn.end.cmp(&other.lsn.end))
      40       148554 :             .then(self.key.start.cmp(&other.key.start))
      41       148554 :             .then(self.key.end.cmp(&other.key.end))
      42       148554 :             .then(self.is_image.cmp(&other.is_image))
      43       148554 :     }
      44              : }
      45              : 
      46              : impl From<&PersistentLayerDesc> for LayerKey {
      47         5322 :     fn from(layer: &PersistentLayerDesc) -> Self {
      48         5322 :         let kr = layer.get_key_range();
      49         5322 :         let lr = layer.get_lsn_range();
      50         5322 :         LayerKey {
      51         5322 :             key: kr.start.to_i128()..kr.end.to_i128(),
      52         5322 :             lsn: lr.start.0..lr.end.0,
      53         5322 :             is_image: !layer.is_incremental(),
      54         5322 :         }
      55         5322 :     }
      56              : }
      57              : 
      58              : /// Efficiently queryable layer coverage for each LSN.
      59              : ///
      60              : /// Allows answering layer map queries very efficiently,
      61              : /// but doesn't allow retroactive insertion, which is
      62              : /// sometimes necessary. See BufferedHistoricLayerCoverage.
      63              : pub struct HistoricLayerCoverage<Value> {
      64              :     /// The latest state
      65              :     head: LayerCoverageTuple<Value>,
      66              : 
      67              :     /// All previous states
      68              :     historic: BTreeMap<u64, LayerCoverageTuple<Value>>,
      69              : }
      70              : 
      71              : impl<T: Clone> Default for HistoricLayerCoverage<T> {
      72            0 :     fn default() -> Self {
      73            0 :         Self::new()
      74            0 :     }
      75              : }
      76              : 
      77              : impl<Value: Clone> HistoricLayerCoverage<Value> {
      78          440 :     pub fn new() -> Self {
      79          440 :         Self {
      80          440 :             head: LayerCoverageTuple::default(),
      81          440 :             historic: BTreeMap::default(),
      82          440 :         }
      83          440 :     }
      84              : 
      85              :     /// Add a layer
      86              :     ///
      87              :     /// Panics if new layer has older lsn.start than an existing layer.
      88              :     /// See BufferedHistoricLayerCoverage for a more general insertion method.
      89         5068 :     pub fn insert(&mut self, layer_key: LayerKey, value: Value) {
      90              :         // It's only a persistent map, not a retroactive one
      91         5068 :         if let Some(last_entry) = self.historic.iter().next_back() {
      92         4678 :             let last_lsn = last_entry.0;
      93         4678 :             if layer_key.lsn.start < *last_lsn {
      94            0 :                 panic!("unexpected retroactive insert");
      95         4678 :             }
      96          390 :         }
      97              : 
      98              :         // Insert into data structure
      99         5068 :         let target = if layer_key.is_image {
     100         2026 :             &mut self.head.image_coverage
     101              :         } else {
     102         3042 :             &mut self.head.delta_coverage
     103              :         };
     104              : 
     105         5068 :         target.insert(layer_key.key, layer_key.lsn.clone(), value);
     106         5068 : 
     107         5068 :         // Remember history. Clone is O(1)
     108         5068 :         self.historic.insert(layer_key.lsn.start, self.head.clone());
     109         5068 :     }
     110              : 
     111              :     /// Query at a particular LSN, inclusive
     112       542953 :     pub fn get_version(&self, lsn: u64) -> Option<&LayerCoverageTuple<Value>> {
     113       542953 :         match self.historic.range(..=lsn).next_back() {
     114       317279 :             Some((_, v)) => Some(v),
     115       225674 :             None => None,
     116              :         }
     117       542953 :     }
     118              : 
     119              :     /// Remove all entries after a certain LSN (inclusive)
     120         1366 :     pub fn trim(&mut self, begin: &u64) {
     121         1366 :         self.historic.split_off(begin);
     122         1366 :         self.head = self
     123         1366 :             .historic
     124         1366 :             .iter()
     125         1366 :             .next_back()
     126         1366 :             .map(|(_, v)| v.clone())
     127         1366 :             .unwrap_or_default();
     128         1366 :     }
     129              : }
     130              : 
     131              : /// This is the most basic test that demonstrates intended usage.
     132              : /// All layers in this test have height 1.
     133              : #[test]
     134            2 : fn test_persistent_simple() {
     135            2 :     let mut map = HistoricLayerCoverage::<String>::new();
     136            2 :     map.insert(
     137            2 :         LayerKey {
     138            2 :             key: 0..5,
     139            2 :             lsn: 100..101,
     140            2 :             is_image: true,
     141            2 :         },
     142            2 :         "Layer 1".to_string(),
     143            2 :     );
     144            2 :     map.insert(
     145            2 :         LayerKey {
     146            2 :             key: 3..9,
     147            2 :             lsn: 110..111,
     148            2 :             is_image: true,
     149            2 :         },
     150            2 :         "Layer 2".to_string(),
     151            2 :     );
     152            2 :     map.insert(
     153            2 :         LayerKey {
     154            2 :             key: 5..6,
     155            2 :             lsn: 120..121,
     156            2 :             is_image: true,
     157            2 :         },
     158            2 :         "Layer 3".to_string(),
     159            2 :     );
     160            2 : 
     161            2 :     // After Layer 1 insertion
     162            2 :     let version = map.get_version(105).unwrap();
     163            2 :     assert_eq!(version.image_coverage.query(1), Some("Layer 1".to_string()));
     164            2 :     assert_eq!(version.image_coverage.query(4), Some("Layer 1".to_string()));
     165              : 
     166              :     // After Layer 2 insertion
     167            2 :     let version = map.get_version(115).unwrap();
     168            2 :     assert_eq!(version.image_coverage.query(4), Some("Layer 2".to_string()));
     169            2 :     assert_eq!(version.image_coverage.query(8), Some("Layer 2".to_string()));
     170            2 :     assert_eq!(version.image_coverage.query(11), None);
     171              : 
     172              :     // After Layer 3 insertion
     173            2 :     let version = map.get_version(125).unwrap();
     174            2 :     assert_eq!(version.image_coverage.query(4), Some("Layer 2".to_string()));
     175            2 :     assert_eq!(version.image_coverage.query(5), Some("Layer 3".to_string()));
     176            2 :     assert_eq!(version.image_coverage.query(7), Some("Layer 2".to_string()));
     177            2 : }
     178              : 
     179              : /// Cover simple off-by-one edge cases
     180              : #[test]
     181            2 : fn test_off_by_one() {
     182            2 :     let mut map = HistoricLayerCoverage::<String>::new();
     183            2 :     map.insert(
     184            2 :         LayerKey {
     185            2 :             key: 3..5,
     186            2 :             lsn: 100..110,
     187            2 :             is_image: true,
     188            2 :         },
     189            2 :         "Layer 1".to_string(),
     190            2 :     );
     191            2 : 
     192            2 :     // Check different LSNs
     193            2 :     let version = map.get_version(99);
     194            2 :     assert!(version.is_none());
     195            2 :     let version = map.get_version(100).unwrap();
     196            2 :     assert_eq!(version.image_coverage.query(4), Some("Layer 1".to_string()));
     197            2 :     let version = map.get_version(110).unwrap();
     198            2 :     assert_eq!(version.image_coverage.query(4), Some("Layer 1".to_string()));
     199              : 
     200              :     // Check different keys
     201            2 :     let version = map.get_version(105).unwrap();
     202            2 :     assert_eq!(version.image_coverage.query(2), None);
     203            2 :     assert_eq!(version.image_coverage.query(3), Some("Layer 1".to_string()));
     204            2 :     assert_eq!(version.image_coverage.query(4), Some("Layer 1".to_string()));
     205            2 :     assert_eq!(version.image_coverage.query(5), None);
     206            2 : }
     207              : 
     208              : /// White-box regression test, checking for incorrect removal of node at key.end
     209              : #[test]
     210            2 : fn test_regression() {
     211            2 :     let mut map = HistoricLayerCoverage::<String>::new();
     212            2 :     map.insert(
     213            2 :         LayerKey {
     214            2 :             key: 0..5,
     215            2 :             lsn: 0..5,
     216            2 :             is_image: false,
     217            2 :         },
     218            2 :         "Layer 1".to_string(),
     219            2 :     );
     220            2 :     map.insert(
     221            2 :         LayerKey {
     222            2 :             key: 0..5,
     223            2 :             lsn: 1..2,
     224            2 :             is_image: false,
     225            2 :         },
     226            2 :         "Layer 2".to_string(),
     227            2 :     );
     228            2 : 
     229            2 :     // If an insertion operation improperly deletes the endpoint of a previous layer
     230            2 :     // (which is more likely to happen with layers that collide on key.end), we will
     231            2 :     // end up with an infinite layer, covering the entire keyspace. Here we assert
     232            2 :     // that there's no layer at key 100 because we didn't insert any layer there.
     233            2 :     let version = map.get_version(100).unwrap();
     234            2 :     assert_eq!(version.delta_coverage.query(100), None);
     235            2 : }
     236              : 
     237              : /// Cover edge cases where layers begin or end on the same key
     238              : #[test]
     239            2 : fn test_key_collision() {
     240            2 :     let mut map = HistoricLayerCoverage::<String>::new();
     241            2 : 
     242            2 :     map.insert(
     243            2 :         LayerKey {
     244            2 :             key: 3..5,
     245            2 :             lsn: 100..110,
     246            2 :             is_image: true,
     247            2 :         },
     248            2 :         "Layer 10".to_string(),
     249            2 :     );
     250            2 :     map.insert(
     251            2 :         LayerKey {
     252            2 :             key: 5..8,
     253            2 :             lsn: 100..110,
     254            2 :             is_image: true,
     255            2 :         },
     256            2 :         "Layer 11".to_string(),
     257            2 :     );
     258            2 :     map.insert(
     259            2 :         LayerKey {
     260            2 :             key: 3..4,
     261            2 :             lsn: 200..210,
     262            2 :             is_image: true,
     263            2 :         },
     264            2 :         "Layer 20".to_string(),
     265            2 :     );
     266            2 : 
     267            2 :     // Check after layer 11
     268            2 :     let version = map.get_version(105).unwrap();
     269            2 :     assert_eq!(version.image_coverage.query(2), None);
     270            2 :     assert_eq!(
     271            2 :         version.image_coverage.query(3),
     272            2 :         Some("Layer 10".to_string())
     273            2 :     );
     274            2 :     assert_eq!(
     275            2 :         version.image_coverage.query(5),
     276            2 :         Some("Layer 11".to_string())
     277            2 :     );
     278            2 :     assert_eq!(
     279            2 :         version.image_coverage.query(7),
     280            2 :         Some("Layer 11".to_string())
     281            2 :     );
     282            2 :     assert_eq!(version.image_coverage.query(8), None);
     283              : 
     284              :     // Check after layer 20
     285            2 :     let version = map.get_version(205).unwrap();
     286            2 :     assert_eq!(version.image_coverage.query(2), None);
     287            2 :     assert_eq!(
     288            2 :         version.image_coverage.query(3),
     289            2 :         Some("Layer 20".to_string())
     290            2 :     );
     291            2 :     assert_eq!(
     292            2 :         version.image_coverage.query(5),
     293            2 :         Some("Layer 11".to_string())
     294            2 :     );
     295            2 :     assert_eq!(
     296            2 :         version.image_coverage.query(7),
     297            2 :         Some("Layer 11".to_string())
     298            2 :     );
     299            2 :     assert_eq!(version.image_coverage.query(8), None);
     300            2 : }
     301              : 
     302              : /// Test when rectangles have nontrivial height and possibly overlap
     303              : #[test]
     304            2 : fn test_persistent_overlapping() {
     305            2 :     let mut map = HistoricLayerCoverage::<String>::new();
     306            2 : 
     307            2 :     // Add 3 key-disjoint layers with varying LSN ranges
     308            2 :     map.insert(
     309            2 :         LayerKey {
     310            2 :             key: 1..2,
     311            2 :             lsn: 100..200,
     312            2 :             is_image: true,
     313            2 :         },
     314            2 :         "Layer 1".to_string(),
     315            2 :     );
     316            2 :     map.insert(
     317            2 :         LayerKey {
     318            2 :             key: 4..5,
     319            2 :             lsn: 110..200,
     320            2 :             is_image: true,
     321            2 :         },
     322            2 :         "Layer 2".to_string(),
     323            2 :     );
     324            2 :     map.insert(
     325            2 :         LayerKey {
     326            2 :             key: 7..8,
     327            2 :             lsn: 120..300,
     328            2 :             is_image: true,
     329            2 :         },
     330            2 :         "Layer 3".to_string(),
     331            2 :     );
     332            2 : 
     333            2 :     // Add wide and short layer
     334            2 :     map.insert(
     335            2 :         LayerKey {
     336            2 :             key: 0..9,
     337            2 :             lsn: 130..199,
     338            2 :             is_image: true,
     339            2 :         },
     340            2 :         "Layer 4".to_string(),
     341            2 :     );
     342            2 : 
     343            2 :     // Add wide layer taller than some
     344            2 :     map.insert(
     345            2 :         LayerKey {
     346            2 :             key: 0..9,
     347            2 :             lsn: 140..201,
     348            2 :             is_image: true,
     349            2 :         },
     350            2 :         "Layer 5".to_string(),
     351            2 :     );
     352            2 : 
     353            2 :     // Add wide layer taller than all
     354            2 :     map.insert(
     355            2 :         LayerKey {
     356            2 :             key: 0..9,
     357            2 :             lsn: 150..301,
     358            2 :             is_image: true,
     359            2 :         },
     360            2 :         "Layer 6".to_string(),
     361            2 :     );
     362            2 : 
     363            2 :     // After layer 4 insertion
     364            2 :     let version = map.get_version(135).unwrap();
     365            2 :     assert_eq!(version.image_coverage.query(0), Some("Layer 4".to_string()));
     366            2 :     assert_eq!(version.image_coverage.query(1), Some("Layer 1".to_string()));
     367            2 :     assert_eq!(version.image_coverage.query(2), Some("Layer 4".to_string()));
     368            2 :     assert_eq!(version.image_coverage.query(4), Some("Layer 2".to_string()));
     369            2 :     assert_eq!(version.image_coverage.query(5), Some("Layer 4".to_string()));
     370            2 :     assert_eq!(version.image_coverage.query(7), Some("Layer 3".to_string()));
     371            2 :     assert_eq!(version.image_coverage.query(8), Some("Layer 4".to_string()));
     372              : 
     373              :     // After layer 5 insertion
     374            2 :     let version = map.get_version(145).unwrap();
     375            2 :     assert_eq!(version.image_coverage.query(0), Some("Layer 5".to_string()));
     376            2 :     assert_eq!(version.image_coverage.query(1), Some("Layer 5".to_string()));
     377            2 :     assert_eq!(version.image_coverage.query(2), Some("Layer 5".to_string()));
     378            2 :     assert_eq!(version.image_coverage.query(4), Some("Layer 5".to_string()));
     379            2 :     assert_eq!(version.image_coverage.query(5), Some("Layer 5".to_string()));
     380            2 :     assert_eq!(version.image_coverage.query(7), Some("Layer 3".to_string()));
     381            2 :     assert_eq!(version.image_coverage.query(8), Some("Layer 5".to_string()));
     382              : 
     383              :     // After layer 6 insertion
     384            2 :     let version = map.get_version(155).unwrap();
     385            2 :     assert_eq!(version.image_coverage.query(0), Some("Layer 6".to_string()));
     386            2 :     assert_eq!(version.image_coverage.query(1), Some("Layer 6".to_string()));
     387            2 :     assert_eq!(version.image_coverage.query(2), Some("Layer 6".to_string()));
     388            2 :     assert_eq!(version.image_coverage.query(4), Some("Layer 6".to_string()));
     389            2 :     assert_eq!(version.image_coverage.query(5), Some("Layer 6".to_string()));
     390            2 :     assert_eq!(version.image_coverage.query(7), Some("Layer 6".to_string()));
     391            2 :     assert_eq!(version.image_coverage.query(8), Some("Layer 6".to_string()));
     392            2 : }
     393              : 
     394              : /// Wrapper for HistoricLayerCoverage that allows us to hack around the lack
     395              : /// of support for retroactive insertion by rebuilding the map since the
     396              : /// change.
     397              : ///
     398              : /// Why is this needed? We most often insert new layers with newer LSNs,
     399              : /// but during compaction we create layers with non-latest LSN, and during
     400              : /// GC we delete historic layers.
     401              : ///
     402              : /// Even though rebuilding is an expensive (N log N) solution to the problem,
     403              : /// it's not critical since we do something equally expensive just to decide
     404              : /// whether or not to create new image layers.
     405              : /// TODO It's not expensive but it's not great to hold a layer map write lock
     406              : ///      for that long.
     407              : ///
     408              : /// If this becomes an actual bottleneck, one solution would be to build a
     409              : /// segment tree that holds PersistentLayerMaps. Though this would mean that
     410              : /// we take an additional log(N) performance hit for queries, which will probably
     411              : /// still be more critical.
     412              : ///
     413              : /// See this for more on persistent and retroactive techniques:
     414              : /// <https://www.youtube.com/watch?v=WqCWghETNDc&t=581s>
     415              : pub struct BufferedHistoricLayerCoverage<Value> {
     416              :     /// A persistent layer map that we rebuild when we need to retroactively update
     417              :     historic_coverage: HistoricLayerCoverage<Value>,
     418              : 
     419              :     /// We buffer insertion into the PersistentLayerMap to decrease the number of rebuilds.
     420              :     buffer: BTreeMap<LayerKey, Option<Value>>,
     421              : 
     422              :     /// All current layers. This is not used for search. Only to make rebuilds easier.
     423              :     layers: BTreeMap<LayerKey, Value>,
     424              : }
     425              : 
     426              : impl<T: std::fmt::Debug> std::fmt::Debug for BufferedHistoricLayerCoverage<T> {
     427            0 :     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
     428            0 :         f.debug_struct("RetroactiveLayerMap")
     429            0 :             .field("buffer", &self.buffer)
     430            0 :             .field("layers", &self.layers)
     431            0 :             .finish()
     432            0 :     }
     433              : }
     434              : 
     435              : impl<T: Clone> Default for BufferedHistoricLayerCoverage<T> {
     436          426 :     fn default() -> Self {
     437          426 :         Self::new()
     438          426 :     }
     439              : }
     440              : 
     441              : impl<Value: Clone> BufferedHistoricLayerCoverage<Value> {
     442          430 :     pub fn new() -> Self {
     443          430 :         Self {
     444          430 :             historic_coverage: HistoricLayerCoverage::<Value>::new(),
     445          430 :             buffer: BTreeMap::new(),
     446          430 :             layers: BTreeMap::new(),
     447          430 :         }
     448          430 :     }
     449              : 
     450         4848 :     pub fn insert(&mut self, layer_key: LayerKey, value: Value) {
     451         4848 :         self.buffer.insert(layer_key, Some(value));
     452         4848 :     }
     453              : 
     454          488 :     pub fn remove(&mut self, layer_key: LayerKey) {
     455          488 :         self.buffer.insert(layer_key, None);
     456          488 :     }
     457              : 
     458         1900 :     pub fn rebuild(&mut self) {
     459              :         // Find the first LSN that needs to be rebuilt
     460         1900 :         let rebuild_since: u64 = match self.buffer.iter().next() {
     461         1366 :             Some((LayerKey { lsn, .. }, _)) => lsn.start,
     462          534 :             None => return, // No need to rebuild if buffer is empty
     463              :         };
     464              : 
     465              :         // Apply buffered updates to self.layers
     466         1366 :         let num_updates = self.buffer.len();
     467         5336 :         self.buffer.retain(|layer_key, layer| {
     468         5336 :             match layer {
     469         4848 :                 Some(l) => {
     470         4848 :                     self.layers.insert(layer_key.clone(), l.clone());
     471         4848 :                 }
     472          488 :                 None => {
     473          488 :                     self.layers.remove(layer_key);
     474          488 :                 }
     475              :             };
     476         5336 :             false
     477         5336 :         });
     478         1366 : 
     479         1366 :         // Rebuild
     480         1366 :         let mut num_inserted = 0;
     481         1366 :         self.historic_coverage.trim(&rebuild_since);
     482         5038 :         for (layer_key, layer) in self.layers.range(
     483         1366 :             LayerKey {
     484         1366 :                 lsn: rebuild_since..0,
     485         1366 :                 key: 0..0,
     486         1366 :                 is_image: false,
     487         1366 :             }..,
     488         5038 :         ) {
     489         5038 :             self.historic_coverage
     490         5038 :                 .insert(layer_key.clone(), layer.clone());
     491         5038 :             num_inserted += 1;
     492         5038 :         }
     493              : 
     494              :         // TODO maybe only warn if ratio is at least 10
     495         1366 :         info!(
     496            0 :             "Rebuilt layer map. Did {} insertions to process a batch of {} updates.",
     497              :             num_inserted, num_updates,
     498              :         )
     499         1900 :     }
     500              : 
     501              :     /// Iterate all the layers
     502         3480 :     pub fn iter(&self) -> impl '_ + Iterator<Item = Value> {
     503         3480 :         // NOTE we can actually perform this without rebuilding,
     504         3480 :         //      but it's not necessary for now.
     505         3480 :         if !self.buffer.is_empty() {
     506            0 :             panic!("rebuild pls")
     507         3480 :         }
     508         3480 : 
     509         3480 :         self.layers.values().cloned()
     510         3480 :     }
     511              : 
     512              :     /// Return a reference to a queryable map, assuming all updates
     513              :     /// have already been processed using self.rebuild()
     514       542919 :     pub fn get(&self) -> anyhow::Result<&HistoricLayerCoverage<Value>> {
     515       542919 :         // NOTE we error here instead of implicitly rebuilding because
     516       542919 :         //      rebuilding is somewhat expensive.
     517       542919 :         // TODO maybe implicitly rebuild and log/sentry an error?
     518       542919 :         if !self.buffer.is_empty() {
     519            0 :             anyhow::bail!("rebuild required")
     520       542919 :         }
     521       542919 : 
     522       542919 :         Ok(&self.historic_coverage)
     523       542919 :     }
     524              : 
     525          404 :     pub(crate) fn len(&self) -> usize {
     526          404 :         self.layers.len()
     527          404 :     }
     528              : }
     529              : 
     530              : #[test]
     531            2 : fn test_retroactive_regression_1() {
     532            2 :     let mut map = BufferedHistoricLayerCoverage::new();
     533            2 : 
     534            2 :     map.insert(
     535            2 :         LayerKey {
     536            2 :             key: 0..21267647932558653966460912964485513215,
     537            2 :             lsn: 23761336..23761457,
     538            2 :             is_image: false,
     539            2 :         },
     540            2 :         "sdfsdfs".to_string(),
     541            2 :     );
     542            2 : 
     543            2 :     map.rebuild();
     544            2 : 
     545            2 :     let version = map.get().unwrap().get_version(23761457).unwrap();
     546            2 :     assert_eq!(
     547            2 :         version.delta_coverage.query(100),
     548            2 :         Some("sdfsdfs".to_string())
     549            2 :     );
     550            2 : }
     551              : 
     552              : #[test]
     553            2 : fn test_retroactive_simple() {
     554            2 :     let mut map = BufferedHistoricLayerCoverage::new();
     555            2 : 
     556            2 :     // Append some images in increasing LSN order
     557            2 :     map.insert(
     558            2 :         LayerKey {
     559            2 :             key: 0..5,
     560            2 :             lsn: 100..101,
     561            2 :             is_image: true,
     562            2 :         },
     563            2 :         "Image 1".to_string(),
     564            2 :     );
     565            2 :     map.insert(
     566            2 :         LayerKey {
     567            2 :             key: 3..9,
     568            2 :             lsn: 110..111,
     569            2 :             is_image: true,
     570            2 :         },
     571            2 :         "Image 2".to_string(),
     572            2 :     );
     573            2 :     map.insert(
     574            2 :         LayerKey {
     575            2 :             key: 4..6,
     576            2 :             lsn: 120..121,
     577            2 :             is_image: true,
     578            2 :         },
     579            2 :         "Image 3".to_string(),
     580            2 :     );
     581            2 :     map.insert(
     582            2 :         LayerKey {
     583            2 :             key: 8..9,
     584            2 :             lsn: 120..121,
     585            2 :             is_image: true,
     586            2 :         },
     587            2 :         "Image 4".to_string(),
     588            2 :     );
     589            2 : 
     590            2 :     // Add a delta layer out of order
     591            2 :     map.insert(
     592            2 :         LayerKey {
     593            2 :             key: 2..5,
     594            2 :             lsn: 105..106,
     595            2 :             is_image: false,
     596            2 :         },
     597            2 :         "Delta 1".to_string(),
     598            2 :     );
     599            2 : 
     600            2 :     // Rebuild so we can start querying
     601            2 :     map.rebuild();
     602            2 : 
     603            2 :     {
     604            2 :         let map = map.get().expect("rebuilt");
     605            2 : 
     606            2 :         let version = map.get_version(90);
     607            2 :         assert!(version.is_none());
     608            2 :         let version = map.get_version(102).unwrap();
     609            2 :         assert_eq!(version.image_coverage.query(4), Some("Image 1".to_string()));
     610              : 
     611            2 :         let version = map.get_version(107).unwrap();
     612            2 :         assert_eq!(version.image_coverage.query(4), Some("Image 1".to_string()));
     613            2 :         assert_eq!(version.delta_coverage.query(4), Some("Delta 1".to_string()));
     614              : 
     615            2 :         let version = map.get_version(115).unwrap();
     616            2 :         assert_eq!(version.image_coverage.query(4), Some("Image 2".to_string()));
     617              : 
     618            2 :         let version = map.get_version(125).unwrap();
     619            2 :         assert_eq!(version.image_coverage.query(4), Some("Image 3".to_string()));
     620              :     }
     621              : 
     622              :     // Remove Image 3
     623            2 :     map.remove(LayerKey {
     624            2 :         key: 4..6,
     625            2 :         lsn: 120..121,
     626            2 :         is_image: true,
     627            2 :     });
     628            2 :     map.rebuild();
     629            2 : 
     630            2 :     {
     631            2 :         // Check deletion worked
     632            2 :         let map = map.get().expect("rebuilt");
     633            2 :         let version = map.get_version(125).unwrap();
     634            2 :         assert_eq!(version.image_coverage.query(4), Some("Image 2".to_string()));
     635            2 :         assert_eq!(version.image_coverage.query(8), Some("Image 4".to_string()));
     636              :     }
     637            2 : }
        

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