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use super::*;
impl<P: PageStore> BTree<P> {
pub fn has_retirement_readers(&self) -> bool {
Arc::strong_count(&self.retirement_pin) != 1
}
/// Enumerate a retired generation before changing the allocator. Never
/// follow leaf sibling links as additional ownership edges: interior
/// children already own every leaf. Validate overflow chains as well.
pub fn retired_pages(&self) -> BTreeResult<Vec<u32>> {
let mut pending = vec![self.root_page_id()];
let mut seen = std::collections::HashSet::new();
let mut pages = Vec::new();
let page_count = self.pager.page_count()?;
while let Some(id) = pending.pop() {
if id == 0 {
continue;
}
if id >= page_count || !seen.insert(id) {
return Err(BTreeError::Corrupted(
"invalid retired tree page ownership".into(),
));
}
let page = self.pager.read_page(id)?;
match page.page_type()? {
PageType::BTreeInterior => {
let (_, children) = read_interior_keys_children(&page)?;
pending.extend(children);
}
PageType::BTreeLeaf => {
for index in 0..usize::from(page.cell_count()) {
let (_, stored) = read_leaf_cell(&page, index)?;
if let Some(head) = value_layout::pointer_head(&stored) {
pending.push(head);
}
}
}
PageType::Overflow => {
let content = page.content();
let next = u32::from_le_bytes(content[..4].try_into().expect("chain header"));
let len = u32::from_le_bytes(content[4..8].try_into().expect("chain length"));
if len as usize > crate::storage::overflow::OVERFLOW_PAYLOAD_PER_PAGE {
return Err(BTreeError::Corrupted(
"invalid retired overflow length".into(),
));
}
pending.push(next);
}
_ => {
return Err(BTreeError::Corrupted(
"unexpected retired tree page type".into(),
))
}
}
pages.push(id);
}
Ok(pages)
}
/// Stream the verified leaves of a damaged tree. Only checksum failures at
/// the proven leaf depth may be skipped. The caller must separately prove
/// that no allocated pages remain unowned before publishing any output.
pub fn visit_recoverable_leaves<C, R>(
&self,
mut claim: C,
mut record: R,
) -> BTreeResult<Vec<u32>>
where
C: FnMut(u32) -> BTreeResult<()>,
R: FnMut(Vec<u8>, Vec<u8>) -> BTreeResult<()>,
{
struct Work {
id: u32,
depth: usize,
low: Option<Vec<u8>>,
high: Option<Vec<u8>>,
}
let mut pending = vec![Work {
id: self.root_page_id(),
depth: 0,
low: None,
high: None,
}];
let mut seen = std::collections::HashSet::new();
let count = self.pager.page_count()?;
let mut leaves: Vec<(u32, Option<u32>)> = Vec::new();
let mut skipped = Vec::new();
let mut leaf_depth = None;
let mut skipped_depths = Vec::new();
let mut previous: Option<Vec<u8>> = None;
while let Some(work) = pending.pop() {
if work.id == 0 || work.id >= count || work.depth > 64 || !seen.insert(work.id) {
return Err(BTreeError::Corrupted(
"invalid recovery tree ownership".into(),
));
}
claim(work.id)?;
let page = match self.pager.read_page(work.id) {
Ok(page) => page,
Err(PagerError::Page(super::super::page::PageError::ChecksumMismatch {
..
})) if work.depth > 0 => {
skipped.push(work.id);
skipped_depths.push(work.depth);
leaves.push((work.id, None));
continue;
}
Err(error) => return Err(error.into()),
};
match page.page_type()? {
PageType::BTreeInterior => {
let (keys, children) = read_interior_keys_children(&page)?;
if children.len() != keys.len() + 1
|| children.contains(&0)
|| keys.windows(2).any(|pair| pair[0] >= pair[1])
|| keys.iter().any(|key| {
work.low.as_ref().is_some_and(|low| key < low)
|| work.high.as_ref().is_some_and(|high| key >= high)
})
{
return Err(BTreeError::Corrupted(
"invalid recovery interior bounds".into(),
));
}
for i in (0..children.len()).rev() {
pending.push(Work {
id: children[i],
depth: work.depth + 1,
low: if i == 0 {
work.low.clone()
} else {
Some(keys[i - 1].clone())
},
high: if i == keys.len() {
work.high.clone()
} else {
Some(keys[i].clone())
},
});
}
}
PageType::BTreeLeaf => {
if leaf_depth.is_some_and(|depth| depth != work.depth) {
return Err(BTreeError::Corrupted(
"inconsistent recovery leaf depth".into(),
));
}
leaf_depth = Some(work.depth);
let bytes = page.content();
let next = u32::from_le_bytes(bytes[4..8].try_into().expect("leaf header"));
leaves.push((work.id, Some(next)));
for index in 0..usize::from(page.cell_count()) {
let (key, stored) = read_leaf_cell(&page, index)?;
if work.low.as_ref().is_some_and(|low| &key < low)
|| work.high.as_ref().is_some_and(|high| &key >= high)
|| previous.as_ref().is_some_and(|old| old >= &key)
{
return Err(BTreeError::Corrupted(
"invalid recovery leaf ordering".into(),
));
}
previous = Some(key.clone());
if let Some(mut overflow) = value_layout::pointer_head(&stored) {
while overflow != 0 {
if overflow >= count || !seen.insert(overflow) {
return Err(BTreeError::Corrupted(
"invalid recovery overflow ownership".into(),
));
}
claim(overflow)?;
let page = self.pager.read_page(overflow)?;
if page.page_type()? != PageType::Overflow {
return Err(BTreeError::Corrupted(
"invalid recovery overflow page".into(),
));
}
let bytes = page.content();
let length = u32::from_le_bytes(
bytes[4..8].try_into().expect("overflow header"),
);
if length as usize
> crate::storage::overflow::OVERFLOW_PAYLOAD_PER_PAGE
{
return Err(BTreeError::Corrupted(
"invalid recovery overflow length".into(),
));
}
overflow = u32::from_le_bytes(
bytes[..4].try_into().expect("overflow header"),
);
}
}
record(
key,
value_layout::decode_with_budget(
self.pager.as_ref(),
&stored,
32 * 1024 * 1024,
)?,
)?;
}
}
_ => {
return Err(BTreeError::Corrupted(
"invalid recovery tree page type".into(),
))
}
}
}
if leaf_depth.is_none()
|| skipped_depths
.iter()
.any(|depth| Some(*depth) != leaf_depth)
{
return Err(BTreeError::Corrupted(
"damaged page is not at proven leaf depth".into(),
));
}
for (i, (_, next)) in leaves.iter().enumerate() {
if next.is_some_and(|id| id != leaves.get(i + 1).map_or(0, |leaf| leaf.0)) {
return Err(BTreeError::Corrupted(
"invalid recovery forward leaf chain".into(),
));
}
}
Ok(skipped)
}
}