bustubx 0.3.0

A simple relational database written in Rust
Documentation
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use std::collections::VecDeque;
use std::ops::{Bound, RangeBounds};
use std::sync::atomic::Ordering;
use std::sync::Arc;

use crate::buffer::{AtomicPageId, PageId, PageRef, INVALID_PAGE_ID};
use crate::catalog::SchemaRef;
use crate::common::util::page_bytes_to_array;
use crate::storage::codec::{
    BPlusTreeInternalPageCodec, BPlusTreeLeafPageCodec, BPlusTreePageCodec,
};
use crate::storage::{InternalKV, LeafKV};
use crate::{
    buffer::BufferPoolManager,
    storage::{BPlusTreeInternalPage, BPlusTreeLeafPage, BPlusTreePage, RecordId},
    BustubxError, BustubxResult,
};

use super::tuple::Tuple;

struct Context {
    pub root_page_id: PageId,
    pub write_set: VecDeque<PageId>,
    pub read_set: VecDeque<PageId>,
}
impl Context {
    pub fn new(root_page_id: PageId) -> Self {
        Self {
            root_page_id,
            write_set: VecDeque::new(),
            read_set: VecDeque::new(),
        }
    }
}

// B+树索引
#[derive(Debug)]
pub struct BPlusTreeIndex {
    pub key_schema: SchemaRef,
    pub buffer_pool: Arc<BufferPoolManager>,
    pub internal_max_size: u32,
    pub leaf_max_size: u32,
    pub root_page_id: AtomicPageId,
}

impl BPlusTreeIndex {
    pub fn new(
        key_schema: SchemaRef,
        buffer_pool: Arc<BufferPoolManager>,
        internal_max_size: u32,
        leaf_max_size: u32,
    ) -> Self {
        Self {
            key_schema,
            buffer_pool,
            internal_max_size,
            leaf_max_size,
            root_page_id: AtomicPageId::new(INVALID_PAGE_ID),
        }
    }

    pub fn is_empty(&self) -> bool {
        self.root_page_id.load(Ordering::SeqCst) == INVALID_PAGE_ID
    }

    pub fn insert(&self, key: &Tuple, rid: RecordId) -> BustubxResult<()> {
        if self.is_empty() {
            self.start_new_tree(key, rid)?;
            return Ok(());
        }
        let mut context = Context::new(self.root_page_id.load(Ordering::SeqCst));
        // 找到leaf page
        let Some(leaf_page) = self.find_leaf_page(key, &mut context)? else {
            return Err(BustubxError::Storage(
                "Cannot find leaf page to insert".to_string(),
            ));
        };

        let (mut leaf_tree_page, _) = BPlusTreeLeafPageCodec::decode(
            leaf_page.read().unwrap().data(),
            self.key_schema.clone(),
        )?;
        leaf_tree_page.insert(key.clone(), rid);

        let mut curr_page = leaf_page;
        let mut curr_tree_page = BPlusTreePage::Leaf(leaf_tree_page);

        // leaf page已满则分裂
        while curr_tree_page.is_full() {
            // 向右分裂出一个新page
            let internalkv = self.split(&mut curr_tree_page)?;

            curr_page
                .write()
                .unwrap()
                .set_data(page_bytes_to_array(&BPlusTreePageCodec::encode(
                    &curr_tree_page,
                )));

            let curr_page_id = curr_page.read().unwrap().page_id;
            if let Some(parent_page_id) = context.read_set.pop_back() {
                // 更新父节点
                let (parent_page, mut parent_tree_page) = self
                    .buffer_pool
                    .fetch_tree_page(parent_page_id, self.key_schema.clone())?;
                parent_tree_page.insert_internalkv(internalkv);

                curr_page = parent_page;
                curr_tree_page = parent_tree_page;
            } else if curr_page_id == self.root_page_id.load(Ordering::SeqCst) {
                // new 一个新的root page
                let new_root_page = self.buffer_pool.new_page()?;
                let new_root_page_id = new_root_page.read().unwrap().page_id;
                let mut new_root_internal_page =
                    BPlusTreeInternalPage::new(self.key_schema.clone(), self.internal_max_size);

                // internal page第一个kv对的key为空
                new_root_internal_page.insert(
                    Tuple::empty(self.key_schema.clone()),
                    self.root_page_id.load(Ordering::SeqCst),
                );
                new_root_internal_page.insert(internalkv.0, internalkv.1);

                new_root_page.write().unwrap().set_data(page_bytes_to_array(
                    &BPlusTreeInternalPageCodec::encode(&new_root_internal_page),
                ));

                // 更新root page id
                self.root_page_id.store(new_root_page_id, Ordering::SeqCst);

                curr_page = new_root_page;
                curr_tree_page = BPlusTreePage::Internal(new_root_internal_page);
            }
        }

        curr_page
            .write()
            .unwrap()
            .set_data(page_bytes_to_array(&BPlusTreePageCodec::encode(
                &curr_tree_page,
            )));

        Ok(())
    }

    pub fn delete(&self, key: &Tuple) -> BustubxResult<()> {
        if self.is_empty() {
            return Ok(());
        }
        let mut context = Context::new(self.root_page_id.load(Ordering::SeqCst));
        // 找到leaf page
        let Some(leaf_page) = self.find_leaf_page(key, &mut context)? else {
            return Err(BustubxError::Storage(
                "Cannot find leaf page to delete".to_string(),
            ));
        };
        let (mut leaf_tree_page, _) = BPlusTreeLeafPageCodec::decode(
            leaf_page.read().unwrap().data(),
            self.key_schema.clone(),
        )?;
        leaf_tree_page.delete(key);
        leaf_page
            .write()
            .unwrap()
            .set_data(page_bytes_to_array(&BPlusTreeLeafPageCodec::encode(
                &leaf_tree_page,
            )));

        let mut curr_tree_page = BPlusTreePage::Leaf(leaf_tree_page);
        let mut curr_page_id = leaf_page.read().unwrap().page_id;

        // leaf page未达到半满则从兄弟节点借一个或合并
        while curr_tree_page.is_underflow(self.root_page_id.load(Ordering::SeqCst) == curr_page_id)
        {
            let Some(parent_page_id) = context.read_set.pop_back() else {
                return Err(BustubxError::Storage("Cannot find parent page".to_string()));
            };
            let (left_sibling_page_id, right_sibling_page_id) =
                self.find_sibling_pages(parent_page_id, curr_page_id)?;

            // 尝试从左兄弟借一个
            if let Some(left_sibling_page_id) = left_sibling_page_id {
                if self.borrow_max_kv(parent_page_id, curr_page_id, left_sibling_page_id)? {
                    break;
                }
            }

            // 尝试从右兄弟借一个
            if let Some(right_sibling_page_id) = right_sibling_page_id {
                if self.borrow_min_kv(parent_page_id, curr_page_id, right_sibling_page_id)? {
                    break;
                }
            }

            let new_parent_page_id = if let Some(left_sibling_page_id) = left_sibling_page_id {
                // 跟左兄弟合并
                self.merge(parent_page_id, left_sibling_page_id, curr_page_id)?
            } else if let Some(right_sibling_page_id) = right_sibling_page_id {
                // 跟右兄弟合并
                self.merge(parent_page_id, curr_page_id, right_sibling_page_id)?
            } else {
                return Err(BustubxError::Storage(
                    "Cannot process index page borrow or merge".to_string(),
                ));
            };
            let (_, new_parent_tree_page) = self
                .buffer_pool
                .fetch_tree_page(new_parent_page_id, self.key_schema.clone())?;

            curr_page_id = new_parent_page_id;
            curr_tree_page = new_parent_tree_page;
        }

        Ok(())
    }

    fn start_new_tree(&self, key: &Tuple, rid: RecordId) -> BustubxResult<()> {
        let new_page = self.buffer_pool.new_page()?;
        let new_page_id = new_page.read().unwrap().page_id;

        let mut leaf_page = BPlusTreeLeafPage::new(self.key_schema.clone(), self.leaf_max_size);
        leaf_page.insert(key.clone(), rid);

        new_page
            .write()
            .unwrap()
            .set_data(page_bytes_to_array(&BPlusTreeLeafPageCodec::encode(
                &leaf_page,
            )));

        // 更新root page id
        self.root_page_id.store(new_page_id, Ordering::SeqCst);

        Ok(())
    }

    // 找到叶子节点上对应的Value
    pub fn get(&self, key: &Tuple) -> BustubxResult<Option<RecordId>> {
        if self.is_empty() {
            return Ok(None);
        }

        // 找到leaf page
        let mut context = Context::new(self.root_page_id.load(Ordering::SeqCst));
        let Some(leaf_page) = self.find_leaf_page(key, &mut context)? else {
            return Ok(None);
        };
        let (leaf_tree_page, _) = BPlusTreeLeafPageCodec::decode(
            leaf_page.read().unwrap().data(),
            self.key_schema.clone(),
        )?;
        let result = leaf_tree_page.look_up(key);
        Ok(result)
    }

    fn find_leaf_page(&self, key: &Tuple, context: &mut Context) -> BustubxResult<Option<PageRef>> {
        if self.is_empty() {
            return Ok(None);
        }
        let (mut curr_page, mut curr_tree_page) = self.buffer_pool.fetch_tree_page(
            self.root_page_id.load(Ordering::SeqCst),
            self.key_schema.clone(),
        )?;

        // 找到leaf page
        loop {
            match curr_tree_page {
                BPlusTreePage::Internal(internal_page) => {
                    context
                        .read_set
                        .push_back(curr_page.read().unwrap().page_id);
                    // 查找下一页
                    let next_page_id = internal_page.look_up(key);
                    let (next_page, next_tree_page) = self
                        .buffer_pool
                        .fetch_tree_page(next_page_id, self.key_schema.clone())?;
                    curr_page = next_page;
                    curr_tree_page = next_tree_page;
                }
                BPlusTreePage::Leaf(_leaf_page) => {
                    return Ok(Some(curr_page));
                }
            }
        }
    }

    // 分裂page
    fn split(&self, tree_page: &mut BPlusTreePage) -> BustubxResult<InternalKV> {
        let new_page = self.buffer_pool.new_page()?;
        let new_page_id = new_page.read().unwrap().page_id;

        match tree_page {
            BPlusTreePage::Leaf(leaf_page) => {
                // 拆分kv对
                let mut new_leaf_page =
                    BPlusTreeLeafPage::new(self.key_schema.clone(), self.leaf_max_size);
                new_leaf_page
                    .batch_insert(leaf_page.split_off(leaf_page.header.current_size as usize / 2));

                // 更新next page id
                new_leaf_page.header.next_page_id = leaf_page.header.next_page_id;
                leaf_page.header.next_page_id = new_page.read().unwrap().page_id;

                new_page.write().unwrap().set_data(page_bytes_to_array(
                    &BPlusTreeLeafPageCodec::encode(&new_leaf_page),
                ));

                Ok((new_leaf_page.key_at(0).clone(), new_page_id))
            }
            BPlusTreePage::Internal(internal_page) => {
                // 拆分kv对
                let mut new_internal_page =
                    BPlusTreeInternalPage::new(self.key_schema.clone(), self.internal_max_size);
                new_internal_page.batch_insert(
                    internal_page.split_off(internal_page.header.current_size as usize / 2),
                );

                new_page.write().unwrap().set_data(page_bytes_to_array(
                    &BPlusTreeInternalPageCodec::encode(&new_internal_page),
                ));

                let min_leafkv = self.find_subtree_min_leafkv(new_page_id)?;
                Ok((min_leafkv.0, new_page_id))
            }
        }
    }

    fn borrow_min_kv(
        &self,
        parent_page_id: PageId,
        page_id: PageId,
        borrowed_page_id: PageId,
    ) -> BustubxResult<bool> {
        self.borrow(parent_page_id, page_id, borrowed_page_id, true)
    }

    fn borrow_max_kv(
        &self,
        parent_page_id: PageId,
        page_id: PageId,
        borrowed_page_id: PageId,
    ) -> BustubxResult<bool> {
        self.borrow(parent_page_id, page_id, borrowed_page_id, false)
    }

    fn borrow(
        &self,
        parent_page_id: PageId,
        page_id: PageId,
        borrowed_page_id: PageId,
        min_max: bool,
    ) -> BustubxResult<bool> {
        let (borrowed_page, mut borrowed_tree_page) = self
            .buffer_pool
            .fetch_tree_page(borrowed_page_id, self.key_schema.clone())?;
        if !borrowed_tree_page.can_borrow() {
            return Ok(false);
        }

        let (page, mut tree_page) = self
            .buffer_pool
            .fetch_tree_page(page_id, self.key_schema.clone())?;

        let (old_internal_key, new_internal_key) = match borrowed_tree_page {
            BPlusTreePage::Internal(ref mut borrowed_internal_page) => {
                let BPlusTreePage::Internal(ref mut internal_page) = tree_page else {
                    return Err(BustubxError::Storage(
                        "Leaf page can not borrow from internal page".to_string(),
                    ));
                };
                if min_max {
                    let kv = borrowed_internal_page.reverse_split_off(0).remove(0);
                    internal_page.insert(kv.0.clone(), kv.1);
                    (
                        kv.0,
                        self.find_subtree_min_leafkv(borrowed_internal_page.value_at(0))?
                            .0,
                    )
                } else {
                    let kv = borrowed_internal_page
                        .split_off(borrowed_internal_page.header.current_size as usize - 1)
                        .remove(0);
                    let min_key = internal_page.key_at(0).clone();
                    internal_page.insert(kv.0.clone(), kv.1);
                    (
                        min_key,
                        self.find_subtree_min_leafkv(borrowed_internal_page.value_at(0))?
                            .0,
                    )
                }
            }
            BPlusTreePage::Leaf(ref mut borrowed_leaf_page) => {
                let BPlusTreePage::Leaf(ref mut leaf_page) = tree_page else {
                    return Err(BustubxError::Storage(
                        "Internal page can not borrow from leaf page".to_string(),
                    ));
                };
                if min_max {
                    let kv = borrowed_leaf_page.reverse_split_off(0).remove(0);
                    leaf_page.insert(kv.0.clone(), kv.1);
                    (kv.0, borrowed_leaf_page.key_at(0).clone())
                } else {
                    let kv = borrowed_leaf_page
                        .split_off(borrowed_leaf_page.header.current_size as usize - 1)
                        .remove(0);
                    leaf_page.insert(kv.0.clone(), kv.1);
                    (leaf_page.key_at(1).clone(), leaf_page.key_at(0).clone())
                }
            }
        };

        page.write()
            .unwrap()
            .set_data(page_bytes_to_array(&BPlusTreePageCodec::encode(&tree_page)));

        borrowed_page
            .write()
            .unwrap()
            .set_data(page_bytes_to_array(&BPlusTreePageCodec::encode(
                &borrowed_tree_page,
            )));

        // 更新父节点
        let (parent_page, mut parent_internal_page) = self
            .buffer_pool
            .fetch_tree_internal_page(parent_page_id, self.key_schema.clone())?;
        parent_internal_page.replace_key(&old_internal_key, new_internal_key);

        parent_page.write().unwrap().set_data(page_bytes_to_array(
            &BPlusTreeInternalPageCodec::encode(&parent_internal_page),
        ));
        Ok(true)
    }

    fn find_sibling_pages(
        &self,
        parent_page_id: PageId,
        child_page_id: PageId,
    ) -> BustubxResult<(Option<PageId>, Option<PageId>)> {
        let (_, parent_internal_page) = self
            .buffer_pool
            .fetch_tree_internal_page(parent_page_id, self.key_schema.clone())?;
        Ok(parent_internal_page.sibling_page_ids(child_page_id))
    }

    fn merge(
        &self,
        parent_page_id: PageId,
        left_page_id: PageId,
        right_page_id: PageId,
    ) -> BustubxResult<PageId> {
        let (left_page, mut left_tree_page) = self
            .buffer_pool
            .fetch_tree_page(left_page_id, self.key_schema.clone())?;
        let (_, mut right_tree_page) = self
            .buffer_pool
            .fetch_tree_page(right_page_id, self.key_schema.clone())?;

        // 向左合入
        match left_tree_page {
            BPlusTreePage::Internal(ref mut left_internal_page) => {
                if let BPlusTreePage::Internal(ref mut right_internal_page) = right_tree_page {
                    // 空key处理
                    let mut kvs = right_internal_page.array.clone();
                    let min_leaf_kv =
                        self.find_subtree_min_leafkv(right_internal_page.value_at(0))?;
                    kvs[0].0 = min_leaf_kv.0;
                    left_internal_page.batch_insert(kvs);
                } else {
                    return Err(BustubxError::Storage(
                        "Leaf page can not merge from internal page".to_string(),
                    ));
                }
            }
            BPlusTreePage::Leaf(ref mut left_leaf_page) => {
                if let BPlusTreePage::Leaf(ref mut right_leaf_page) = right_tree_page {
                    left_leaf_page.batch_insert(right_leaf_page.array.clone());
                    // 更新next page id
                    left_leaf_page.header.next_page_id = right_leaf_page.header.next_page_id;
                } else {
                    return Err(BustubxError::Storage(
                        "Internal page can not merge from leaf page".to_string(),
                    ));
                }
            }
        };

        left_page
            .write()
            .unwrap()
            .set_data(page_bytes_to_array(&BPlusTreePageCodec::encode(
                &left_tree_page,
            )));

        // 删除右边页
        self.buffer_pool.delete_page(right_page_id)?;

        // 更新父节点
        let (parent_page, mut parent_internal_page) = self
            .buffer_pool
            .fetch_tree_internal_page(parent_page_id, self.key_schema.clone())?;
        parent_internal_page.delete_page_id(right_page_id);

        // 根节点只有一个子节点(叶子)时,则叶子节点成为新的根节点
        if parent_page_id == self.root_page_id.load(Ordering::SeqCst)
            && parent_internal_page.header.current_size == 1
        {
            self.root_page_id.store(left_page_id, Ordering::SeqCst);
            // 删除旧的根节点
            self.buffer_pool.delete_page(parent_page_id)?;
            Ok(left_page_id)
        } else {
            parent_page.write().unwrap().set_data(page_bytes_to_array(
                &BPlusTreeInternalPageCodec::encode(&parent_internal_page),
            ));
            Ok(parent_page_id)
        }
    }

    // 查找子树最小的leafKV
    fn find_subtree_min_leafkv(&self, page_id: PageId) -> BustubxResult<LeafKV> {
        self.find_subtree_leafkv(page_id, true)
    }

    // 查找子树最大的leafKV
    fn find_subtree_max_leafkv(&self, page_id: PageId) -> BustubxResult<LeafKV> {
        self.find_subtree_leafkv(page_id, false)
    }

    fn find_subtree_leafkv(&self, page_id: PageId, min_or_max: bool) -> BustubxResult<LeafKV> {
        let (_, mut curr_tree_page) = self
            .buffer_pool
            .fetch_tree_page(page_id, self.key_schema.clone())?;
        loop {
            match curr_tree_page {
                BPlusTreePage::Internal(internal_page) => {
                    let index = if min_or_max {
                        0
                    } else {
                        internal_page.header.current_size as usize - 1
                    };
                    let next_page_id = internal_page.value_at(index);
                    let (_, next_tree_page) = self
                        .buffer_pool
                        .fetch_tree_page(next_page_id, self.key_schema.clone())?;
                    curr_tree_page = next_tree_page;
                }
                BPlusTreePage::Leaf(leaf_page) => {
                    let index = if min_or_max {
                        0
                    } else {
                        leaf_page.header.current_size as usize - 1
                    };
                    return Ok(leaf_page.kv_at(index).clone());
                }
            }
        }
    }

    pub fn get_first_leaf_page(&self) -> BustubxResult<BPlusTreeLeafPage> {
        let (_, mut curr_tree_page) = self.buffer_pool.fetch_tree_page(
            self.root_page_id.load(Ordering::SeqCst),
            self.key_schema.clone(),
        )?;
        loop {
            match curr_tree_page {
                BPlusTreePage::Internal(internal_page) => {
                    let next_page_id = internal_page.value_at(0);
                    let (_, next_tree_page) = self
                        .buffer_pool
                        .fetch_tree_page(next_page_id, self.key_schema.clone())?;
                    curr_tree_page = next_tree_page;
                }
                BPlusTreePage::Leaf(leaf_page) => {
                    return Ok(leaf_page);
                }
            }
        }
    }
}

#[derive(Debug)]
pub struct TreeIndexIterator {
    index: Arc<BPlusTreeIndex>,
    start_bound: Bound<Tuple>,
    end_bound: Bound<Tuple>,
    leaf_page: BPlusTreeLeafPage,
    cursor: usize,
    started: bool,
}

impl TreeIndexIterator {
    pub fn new<R: RangeBounds<Tuple>>(index: Arc<BPlusTreeIndex>, range: R) -> Self {
        Self {
            index,
            start_bound: range.start_bound().cloned(),
            end_bound: range.end_bound().cloned(),
            leaf_page: BPlusTreeLeafPage::empty(),
            cursor: 0,
            started: false,
        }
    }

    pub fn load_next_leaf_page(&mut self) -> BustubxResult<bool> {
        let next_page_id = self.leaf_page.header.next_page_id;
        if next_page_id == INVALID_PAGE_ID {
            Ok(false)
        } else {
            let (_, next_leaf_page) = self
                .index
                .buffer_pool
                .fetch_tree_leaf_page(next_page_id, self.index.key_schema.clone())?;
            self.leaf_page = next_leaf_page;
            Ok(true)
        }
    }

    pub fn next(&mut self) -> BustubxResult<Option<RecordId>> {
        if self.started {
            match self.end_bound.as_ref() {
                Bound::Included(end_tuple) => {
                    self.cursor += 1;
                    let end_tuple = end_tuple.clone();
                    let kv = if self.cursor >= self.leaf_page.header.current_size as usize {
                        if self.load_next_leaf_page()? {
                            self.cursor = 0;
                            self.leaf_page.array[self.cursor].clone()
                        } else {
                            return Ok(None);
                        }
                    } else {
                        self.leaf_page.array[self.cursor].clone()
                    };
                    if kv.0 <= end_tuple {
                        Ok(Some(kv.1))
                    } else {
                        Ok(None)
                    }
                }
                Bound::Excluded(end_tuple) => {
                    self.cursor += 1;
                    let end_tuple = end_tuple.clone();
                    let kv = if self.cursor >= self.leaf_page.header.current_size as usize {
                        if self.load_next_leaf_page()? {
                            self.cursor = 0;
                            self.leaf_page.array[self.cursor].clone()
                        } else {
                            return Ok(None);
                        }
                    } else {
                        self.leaf_page.array[self.cursor].clone()
                    };
                    if kv.0 < end_tuple {
                        Ok(Some(kv.1))
                    } else {
                        Ok(None)
                    }
                }
                Bound::Unbounded => {
                    self.cursor += 1;
                    if self.cursor >= self.leaf_page.header.current_size as usize {
                        if self.load_next_leaf_page()? {
                            self.cursor = 0;
                            Ok(Some(self.leaf_page.array[self.cursor].1))
                        } else {
                            Ok(None)
                        }
                    } else {
                        Ok(Some(self.leaf_page.array[self.cursor].1))
                    }
                }
            }
        } else {
            self.started = true;
            match self.start_bound.as_ref() {
                Bound::Included(start_tuple) => {
                    let mut context = Context::new(self.index.root_page_id.load(Ordering::SeqCst));
                    let Some(leaf_page) = self.index.find_leaf_page(start_tuple, &mut context)?
                    else {
                        return Ok(None);
                    };
                    self.leaf_page = BPlusTreeLeafPageCodec::decode(
                        leaf_page.read().unwrap().data(),
                        self.index.key_schema.clone(),
                    )?
                    .0;
                    if let Some(idx) = self.leaf_page.next_closest(start_tuple, true) {
                        self.cursor = idx;
                        Ok(Some(self.leaf_page.array[self.cursor].1))
                    } else if self.load_next_leaf_page()? {
                        self.cursor = 0;
                        Ok(Some(self.leaf_page.array[self.cursor].1))
                    } else {
                        Ok(None)
                    }
                }
                Bound::Excluded(start_tuple) => {
                    let mut context = Context::new(self.index.root_page_id.load(Ordering::SeqCst));
                    let Some(leaf_page) = self.index.find_leaf_page(start_tuple, &mut context)?
                    else {
                        return Ok(None);
                    };
                    self.leaf_page = BPlusTreeLeafPageCodec::decode(
                        leaf_page.read().unwrap().data(),
                        self.index.key_schema.clone(),
                    )?
                    .0;
                    if let Some(idx) = self.leaf_page.next_closest(start_tuple, false) {
                        self.cursor = idx;
                        Ok(Some(self.leaf_page.array[self.cursor].1))
                    } else if self.load_next_leaf_page()? {
                        self.cursor = 0;
                        Ok(Some(self.leaf_page.array[self.cursor].1))
                    } else {
                        Ok(None)
                    }
                }
                Bound::Unbounded => {
                    self.leaf_page = self.index.get_first_leaf_page()?;
                    self.cursor = 0;
                    Ok(Some(self.leaf_page.array[self.cursor].1))
                }
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use std::ops::Bound;
    use std::sync::Arc;
    use tempfile::TempDir;

    use crate::catalog::SchemaRef;
    use crate::common::util::pretty_format_index_tree;
    use crate::storage::index::TreeIndexIterator;
    use crate::{
        buffer::BufferPoolManager,
        catalog::{Column, DataType, Schema},
        storage::{DiskManager, RecordId, Tuple},
    };

    use super::BPlusTreeIndex;

    fn build_index() -> (BPlusTreeIndex, SchemaRef) {
        let temp_dir = TempDir::new().unwrap();
        let temp_path = temp_dir.path().join("test.db");

        let key_schema = Arc::new(Schema::new(vec![
            Column::new("a", DataType::Int8, false),
            Column::new("b", DataType::Int16, false),
        ]));
        let disk_manager = DiskManager::try_new(temp_path).unwrap();
        let buffer_pool = Arc::new(BufferPoolManager::new(1000, Arc::new(disk_manager)));
        let index = BPlusTreeIndex::new(key_schema.clone(), buffer_pool, 4, 4);

        index
            .insert(
                &Tuple::new(key_schema.clone(), vec![1i8.into(), 1i16.into()]),
                RecordId::new(1, 1),
            )
            .unwrap();
        index
            .insert(
                &Tuple::new(key_schema.clone(), vec![2i8.into(), 2i16.into()]),
                RecordId::new(2, 2),
            )
            .unwrap();
        index
            .insert(
                &Tuple::new(key_schema.clone(), vec![3i8.into(), 3i16.into()]),
                RecordId::new(3, 3),
            )
            .unwrap();
        index
            .insert(
                &Tuple::new(key_schema.clone(), vec![4i8.into(), 4i16.into()]),
                RecordId::new(4, 4),
            )
            .unwrap();
        index
            .insert(
                &Tuple::new(key_schema.clone(), vec![5i8.into(), 5i16.into()]),
                RecordId::new(5, 5),
            )
            .unwrap();
        index
            .insert(
                &Tuple::new(key_schema.clone(), vec![6i8.into(), 6i16.into()]),
                RecordId::new(6, 6),
            )
            .unwrap();
        index
            .insert(
                &Tuple::new(key_schema.clone(), vec![7i8.into(), 7i16.into()]),
                RecordId::new(7, 7),
            )
            .unwrap();
        index
            .insert(
                &Tuple::new(key_schema.clone(), vec![8i8.into(), 8i16.into()]),
                RecordId::new(8, 8),
            )
            .unwrap();
        index
            .insert(
                &Tuple::new(key_schema.clone(), vec![9i8.into(), 9i16.into()]),
                RecordId::new(9, 9),
            )
            .unwrap();
        index
            .insert(
                &Tuple::new(key_schema.clone(), vec![10i8.into(), 10i16.into()]),
                RecordId::new(10, 10),
            )
            .unwrap();
        index
            .insert(
                &Tuple::new(key_schema.clone(), vec![11i8.into(), 11i16.into()]),
                RecordId::new(11, 11),
            )
            .unwrap();
        (index, key_schema)
    }

    #[test]
    pub fn test_index_insert() {
        let (index, _) = build_index();
        let display = pretty_format_index_tree(&index).unwrap();
        println!("{display}");
        assert_eq!(display, "B+ Tree Level No.1:
+-----------------------+
| page_id=13, size: 2/4 |
+-----------------------+
| +------------+------+ |
| | NULL, NULL | 5, 5 | |
| +------------+------+ |
| | 8          | 12   | |
| +------------+------+ |
+-----------------------+
B+ Tree Level No.2:
+-----------------------+------------------------+
| page_id=8, size: 2/4  | page_id=12, size: 3/4  |
+-----------------------+------------------------+
| +------------+------+ | +------+------+------+ |
| | NULL, NULL | 3, 3 | | | 5, 5 | 7, 7 | 9, 9 | |
| +------------+------+ | +------+------+------+ |
| | 6          | 7    | | | 9    | 10   | 11   | |
| +------------+------+ | +------+------+------+ |
+-----------------------+------------------------+
B+ Tree Level No.3:
+--------------------------------------+--------------------------------------+---------------------------------------+----------------------------------------+---------------------------------------+
| page_id=6, size: 2/4, next_page_id=7 | page_id=7, size: 2/4, next_page_id=9 | page_id=9, size: 2/4, next_page_id=10 | page_id=10, size: 2/4, next_page_id=11 | page_id=11, size: 3/4, next_page_id=0 |
+--------------------------------------+--------------------------------------+---------------------------------------+----------------------------------------+---------------------------------------+
| +------+------+                      | +------+------+                      | +------+------+                       | +------+------+                        | +------+--------+--------+            |
| | 1, 1 | 2, 2 |                      | | 3, 3 | 4, 4 |                      | | 5, 5 | 6, 6 |                       | | 7, 7 | 8, 8 |                        | | 9, 9 | 10, 10 | 11, 11 |            |
| +------+------+                      | +------+------+                      | +------+------+                       | +------+------+                        | +------+--------+--------+            |
| | 1-1  | 2-2  |                      | | 3-3  | 4-4  |                      | | 5-5  | 6-6  |                       | | 7-7  | 8-8  |                        | | 9-9  | 10-10  | 11-11  |            |
| +------+------+                      | +------+------+                      | +------+------+                       | +------+------+                        | +------+--------+--------+            |
+--------------------------------------+--------------------------------------+---------------------------------------+----------------------------------------+---------------------------------------+
");
    }

    #[test]
    pub fn test_index_delete() {
        let (index, key_schema) = build_index();

        index
            .delete(&Tuple::new(
                key_schema.clone(),
                vec![3i8.into(), 3i16.into()],
            ))
            .unwrap();
        println!("{}", pretty_format_index_tree(&index).unwrap());
        index
            .delete(&Tuple::new(
                key_schema.clone(),
                vec![10i8.into(), 10i16.into()],
            ))
            .unwrap();
        println!("{}", pretty_format_index_tree(&index).unwrap());
        index
            .delete(&Tuple::new(
                key_schema.clone(),
                vec![8i8.into(), 8i16.into()],
            ))
            .unwrap();
        println!("{}", pretty_format_index_tree(&index).unwrap());

        assert_eq!(pretty_format_index_tree(&index).unwrap(),
                   "B+ Tree Level No.1:
+------------------------------+
| page_id=8, size: 3/4         |
+------------------------------+
| +------------+------+------+ |
| | NULL, NULL | 5, 5 | 7, 7 | |
| +------------+------+------+ |
| | 6          | 9    | 10   | |
| +------------+------+------+ |
+------------------------------+
B+ Tree Level No.2:
+--------------------------------------+---------------------------------------+---------------------------------------+
| page_id=6, size: 3/4, next_page_id=9 | page_id=9, size: 2/4, next_page_id=10 | page_id=10, size: 3/4, next_page_id=0 |
+--------------------------------------+---------------------------------------+---------------------------------------+
| +------+------+------+               | +------+------+                       | +------+------+--------+              |
| | 1, 1 | 2, 2 | 4, 4 |               | | 5, 5 | 6, 6 |                       | | 7, 7 | 9, 9 | 11, 11 |              |
| +------+------+------+               | +------+------+                       | +------+------+--------+              |
| | 1-1  | 2-2  | 4-4  |               | | 5-5  | 6-6  |                       | | 7-7  | 9-9  | 11-11  |              |
| +------+------+------+               | +------+------+                       | +------+------+--------+              |
+--------------------------------------+---------------------------------------+---------------------------------------+
");
    }

    #[test]
    pub fn test_index_get() {
        let (index, key_schema) = build_index();
        assert_eq!(
            index
                .get(&Tuple::new(
                    key_schema.clone(),
                    vec![3i8.into(), 3i16.into()],
                ))
                .unwrap(),
            Some(RecordId::new(3, 3))
        );
        assert_eq!(
            index
                .get(&Tuple::new(
                    key_schema.clone(),
                    vec![10i8.into(), 10i16.into()],
                ))
                .unwrap(),
            Some(RecordId::new(10, 10))
        );
    }

    #[test]
    pub fn test_index_iterator() {
        let (index, key_schema) = build_index();
        let index = Arc::new(index);

        let end_tuple1 = Tuple::new(key_schema.clone(), vec![3i8.into(), 3i16.into()]);
        let mut iterator1 = TreeIndexIterator::new(index.clone(), ..end_tuple1);
        assert_eq!(iterator1.next().unwrap(), Some(RecordId::new(1, 1)));
        assert_eq!(iterator1.next().unwrap(), Some(RecordId::new(2, 2)));
        assert_eq!(iterator1.next().unwrap(), None);

        let start_tuple2 = Tuple::new(key_schema.clone(), vec![3i8.into(), 3i16.into()]);
        let end_tuple2 = Tuple::new(key_schema.clone(), vec![5i8.into(), 5i16.into()]);
        let mut iterator2 = TreeIndexIterator::new(index.clone(), start_tuple2..=end_tuple2);
        assert_eq!(iterator2.next().unwrap(), Some(RecordId::new(3, 3)));
        assert_eq!(iterator2.next().unwrap(), Some(RecordId::new(4, 4)));
        assert_eq!(iterator2.next().unwrap(), Some(RecordId::new(5, 5)));
        assert_eq!(iterator2.next().unwrap(), None);

        let start_tuple3 = Tuple::new(key_schema.clone(), vec![6i8.into(), 6i16.into()]);
        let end_tuple3 = Tuple::new(key_schema.clone(), vec![8i8.into(), 8i16.into()]);
        let mut iterator3 = TreeIndexIterator::new(
            index.clone(),
            (Bound::Excluded(start_tuple3), Bound::Excluded(end_tuple3)),
        );
        assert_eq!(iterator3.next().unwrap(), Some(RecordId::new(7, 7)));

        let start_tuple4 = Tuple::new(key_schema.clone(), vec![9i8.into(), 9i16.into()]);
        let mut iterator4 = TreeIndexIterator::new(index.clone(), start_tuple4..);
        assert_eq!(iterator4.next().unwrap(), Some(RecordId::new(9, 9)));
        assert_eq!(iterator4.next().unwrap(), Some(RecordId::new(10, 10)));
        assert_eq!(iterator4.next().unwrap(), Some(RecordId::new(11, 11)));
        assert_eq!(iterator4.next().unwrap(), None);
        assert_eq!(iterator4.next().unwrap(), None);
    }
}