feat: add btree deletion

Author: peeeuzin

.gitignore

@@ -6,3 +6,4 @@ Cargo.lock
 
 # Test folders
 /test_data
+/example

Cargo.toml

@@ -25,7 +25,6 @@ serde = { version = "1.0", features = ["derive"] }
 bloomfilter = "1.0"
 fs2 = "0.4.3"
 bincode = "1.3.3"
-rand = "0.8.5"
 
 [build-dependencies]
 hooky-rs = "1.0.0"

src/btree/mod.rs

@@ -248,16 +248,19 @@ impl<
 
         let mut results = Vec::new();
 
-        for index in 0..=node.page.len() {
+        for index in 0..node.page.len() {
             let child = node.child(index)?;
 
-            if node.page.len() / 2 == index {
-                results.extend(node.page.values()?);
-            }
-
             if let Some(child) = child {
                 results.extend(self.cells_from_subtree(child)?)
             }
+
+            results.extend(node.page.read(index)?);
+        }
+
+        let right = node.child(node.page.len())?;
+        if let Some(right) = right {
+            results.extend(self.cells_from_subtree(right)?)
         }
 
         Ok(results)
@@ -290,10 +293,10 @@ impl<
         let page = node.page.compact()?;
 
         self.io
-            .write_page(page_number.into(), &page)
+            .write_page(search.page.into(), &page)
             .map_err(Error::IoError)?;
 
-        self.borrow_if_needed(page_number, parents, key)
+        self.borrow_if_needed(search.page, parents, key)
     }
 
     fn borrow_if_needed(
@@ -326,42 +329,56 @@ impl<
             Either::Left(index) => index,
             Either::Right(index) => index,
         };
+        let sibling_index = match index > 0 {
+            false => index + 1,
+            true => index - 1,
+        };
 
-        let sibling_index = if index > 0 { index - 1 } else { index + 1 };
-        let mut cell = parent.page.read(sibling_index)?.unwrap();
+        let sibling_page_index = parent.child(sibling_index)?.unwrap();
 
         let sibling: BTreeNode<K, V> = self
             .io
-            .read_page(cell.left_child.unwrap().into())
+            .read_page(sibling_page_index.into())
             .map_err(Error::IoError)?
             .try_into()?;
-        let merged_node_idx = cmp::min(index, sibling_index);
-
-        let mut merged_node = node.merge(sibling)?;
 
-        cell.left_child = merged_node.header.right_child;
+        let merged_node_idx = cmp::min(index, sibling_index);
 
-        parent.page.delete(sibling_index)?;
+        let cell = parent.page.read(merged_node_idx)?.unwrap();
+        parent.page.delete(merged_node_idx)?;
         let mut parent: BTreeNode<K, V> = parent.page.compact()?.try_into()?;
 
-        merged_node.page.insert(merged_node_idx, cell)?;
+        let mut merged_node = node.merge(sibling, cell)?;
 
         let merged_page_index = self
             .io
             .write_new_page(&merged_node.page)
             .map_err(Error::IoError)?;
 
-        if parent.header.kind == PageType::Root && parent.page.is_empty() {
+        if parent.is_root() && parent.page.is_empty() {
+            merged_node.header.kind = PageType::Root;
+            merged_node
+                .page
+                .write_special(&merged_node.header.to_bytes())?;
+
+            self.io
+                .write_page(merged_page_index.into(), &merged_node.page)
+                .map_err(Error::IoError)?;
+
             self.root = merged_page_index
         } else {
-            parent.set_child(sibling_index, merged_page_index)?;
+            parent.set_child(merged_node_idx, merged_page_index)?;
         }
 
         self.io
             .write_page(parent_index.into(), &parent.page)
             .map_err(Error::IoError)?;
 
-        self.borrow_if_needed(parents.pop().unwrap(), parents, key)
+        if let Some(parent) = parents.pop() {
+            self.borrow_if_needed(parent, parents, key)?;
+        }
+
+        Ok(())
     }
 }
 

src/btree/node.rs

@@ -37,6 +37,10 @@ impl<
         }
     }
 
+    pub fn is_root(&self) -> bool {
+        self.header.kind == PageType::Root
+    }
+
     pub fn split(mut self, b: u16) -> Result<BTreeNodeSplited<K, V>> {
         // split page cells at the middle
         let mut sibling_cells = self.page.split_off(b - 1)?;
@@ -94,15 +98,52 @@ impl<
         Ok(())
     }
 
-    pub fn merge(mut self, mut node: Self) -> Result<Self> {
-        let node_values = node.page.values()?;
-        self.page.write_all(node_values)?;
+    pub fn max_key(&mut self) -> Result<Option<K>> {
+        if self.page.is_empty() {
+            return Ok(None);
+        }
+
+        Ok(self.page.read(self.page.len() - 1)?.map(|e| e.key))
+    }
+
+    pub fn min_key(&mut self) -> Result<Option<K>> {
+        if self.page.is_empty() {
+            return Ok(None);
+        }
+
+        Ok(self.page.read(0)?.map(|e| e.key))
+    }
+
+    pub fn merge(mut self, mut other: Self, mut cell: BTreeCell<K, V>) -> Result<Self> {
+        let new_page_header = BTreePageHeader::new(self.header.kind, None);
+        match self.min_key()? >= other.min_key()? {
+            // merge with left sibling node
+            true => {
+                cell.left_child = other.header.right_child;
+            }
+            // merge with right sibling node
+            false => {
+                cell.left_child = self.header.right_child;
+                self.header.right_child = other.header.right_child
+            }
+        };
+
+        let node_values = self.page.values()?.into_iter();
+        let other_values = other.page.values()?.into_iter();
+
+        let mut merged_values = node_values
+            .chain(other_values)
+            .collect::<Vec<BTreeCell<K, V>>>();
+
+        merged_values.push(cell);
 
-        self.header.right_child = node.header.right_child;
+        merged_values.sort_by(|a, b| a.key.cmp(&b.key));
 
-        self.page.write_special(&self.header.to_bytes())?;
+        let mut page: Page<BTreeCell<K, V>> = Page::create(self.page.special_size())?;
+        page.write_all(merged_values)?;
+        page.write_special(&new_page_header.to_bytes())?;
 
-        Ok(self)
+        page.try_into()
     }
 }
 

src/btree/spec.rs

@@ -11,13 +11,13 @@ pub struct BTreeCell<K, V> {
 
 pub const BTREE_PAGE_HEADER_SIZE: u16 = 9;
 
-#[derive(Serialize, Deserialize, Debug)]
+#[derive(Serialize, Deserialize, Debug, PartialEq, PartialOrd)]
 pub struct BTreePageHeader {
     pub kind: PageType,
     pub right_child: Option<PageNumber>,
 }
 
-#[derive(Debug, PartialEq, Eq, Serialize, Deserialize, Copy, Clone)]
+#[derive(Debug, PartialEq, Eq, Serialize, Deserialize, Copy, Clone, PartialOrd, Ord)]
 pub enum PageType {
     Leaf = 0,
     Internal = 1,

src/page.rs

@@ -437,7 +437,7 @@ impl<T: Serialize + DeserializeOwned + PartialOrd + Ord + Clone> Page<T> {
         PAGE_HEADER_SIZE
     }
 
-    fn special_size(&self) -> u16 {
+    pub fn special_size(&self) -> u16 {
         PAGE_SIZE - self.header.special
     }