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fix(store::TreeMap): remove of the entry API now correctly updates the tree root when changed #995

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merged 5 commits into from
May 26, 2023
Merged

fix(store::TreeMap): remove of the entry API now correctly updates the tree root when changed #995

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316361b
fix(store::TreeMap): remove of the entry API now correctly updates th…
austinabell Dec 12, 2022
18b5722
add specific assertions for the root value after each operation
austinabell Dec 12, 2022
9bd5084
update fuzz test to include entry functions
austinabell Dec 12, 2022
92a648b
remove bloat from test
austinabell Dec 12, 2022
54881b8
Merge branch 'master' into austin/fix_treemap_entry
ChaoticTempest May 25, 2023
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73 changes: 58 additions & 15 deletions near-sdk/src/store/tree_map/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -667,7 +667,7 @@ where
// - right-most (max) node of the left subtree (containing smaller keys) of node holding `key`
// - or left-most (min) node of the right subtree (containing larger keys) of node holding `key`
//
fn do_remove<Q: ?Sized>(&mut self, key: &Q) -> (Option<FreeListIndex>, Option<K>)
fn do_remove<Q: ?Sized>(&mut self, key: &Q) -> Option<K>
where
K: Borrow<Q>,
Q: BorshSerialize + Eq + PartialOrd,
Expand All @@ -679,15 +679,15 @@ where
.and_then(|root| self.lookup_at(root, key))
{
Some(((l_id, node), r)) => ((l_id, node.clone()), r.map(|(i, n, e)| (i, n.clone(), e))),
None => return (self.root, None), // cannot remove a missing key, no changes to the tree needed
None => return None, // cannot remove a missing key, no changes to the tree needed
};

let lft_opt = r_node.lft;
let rgt_opt = r_node.rgt;

if lft_opt.is_none() && rgt_opt.is_none() {
// Node is leaf, can simply remove and rebalance.
let mut new_id = if let Some((p_id, mut p_node, p_edge)) = remove_parent {
if let Some((p_id, mut p_node, p_edge)) = remove_parent {
match p_edge {
Edge::Right => {
p_node.rgt = None;
Expand All @@ -701,17 +701,15 @@ where
// removing node might have caused a imbalance - balance the tree up to the root,
// starting from lowest affected key - the parent of a leaf node in this case.
// At this point, we can assume there is a root because there is at least the parent
self.root.map(|root| self.check_balance(root, &p_node.key))
} else {
self.root
};
self.root = self.root.map(|root| self.check_balance(root, &p_node.key));
}

let removed = expect(self.nodes.remove(r_id));
if Some(r_id) == self.root {
new_id = None;
self.root = None;
}

(new_id, Some(removed.key))
Some(removed.key)
} else {
// non-leaf node, select subtree to proceed with depending on balance
let b = self.get_balance(&r_node);
Expand Down Expand Up @@ -747,13 +745,13 @@ where

// removing node might have caused an imbalance - balance the tree up to the root,
// starting from the lowest affected key (max key from left subtree in this case)
let new_root = self.root.map(|root| {
self.root = self.root.map(|root| {
self.check_balance(
root,
parent.as_ref().map(|p| &p.1.key).unwrap_or(&r_node.key),
)
});
(new_root, Some(replaced_key))
Some(replaced_key)
} else {
// proceed with right subtree
let rgt = expect(rgt_opt);
Expand Down Expand Up @@ -786,13 +784,13 @@ where

// removing node might have caused an imbalance - balance the tree up to the root,
// starting from the lowest affected key (max key from left subtree in this case)
let new_root = self.root.map(|root| {
self.root = self.root.map(|root| {
self.check_balance(
root,
parent.as_ref().map(|p| &p.1.key).unwrap_or(&r_node.key),
)
});
(new_root, Some(replaced_key))
Some(replaced_key)
}
}
}
Expand Down Expand Up @@ -957,8 +955,7 @@ where
Q: BorshSerialize + ToOwned<Owned = K> + Eq + PartialOrd,
{
self.values.remove(key).map(|removed_value| {
let (new_root, removed) = self.tree.do_remove(key);
self.tree.root = new_root;
let removed = self.tree.do_remove(key);
(expect(removed), removed_value)
})
}
Expand Down Expand Up @@ -2059,6 +2056,8 @@ mod tests {
Flush,
Restore,
Get(u8),
EntryInsert(u8, u8),
EntryRemove(u8),
}

#[test]
Expand Down Expand Up @@ -2100,9 +2099,53 @@ mod tests {
let r2 = hm.get(&k);
assert_eq!(r1, r2)
}
Op::EntryInsert(k, v) => {
let r1 = um.entry(k).or_insert(v);
let r2 = hm.entry(k).or_insert(v);
assert_eq!(r1, r2)
}
Op::EntryRemove(k) => match (um.entry(k), hm.entry(k)) {
(
Entry::Occupied(o1),
std::collections::btree_map::Entry::Occupied(o2),
) => {
let r1 = o1.remove();
let r2 = o2.remove();
assert_eq!(r1, r2)
}
(Entry::Vacant(_), std::collections::btree_map::Entry::Vacant(_)) => {}
_ => panic!("inconsistent entry states"),
},
}
}
}
}
}

#[test]
fn issue993() {
fn swap_set<H>(map: &mut TreeMap<(), (), H>)
where
H: ToKey,
{
match map.entry(()) {
Entry::Occupied(o) => {
o.remove();
}
Entry::Vacant(o) => {
o.insert(());
}
};
}

let mut map = TreeMap::new(b"m");
swap_set(&mut map);
assert_eq!(map.tree.root, Some(FreeListIndex(0)));
swap_set(&mut map);
assert_eq!(map.tree.root, None);
// This line previously panicked because the entry was removed without updating the tree
// root.
swap_set(&mut map);
assert_eq!(map.tree.root, Some(FreeListIndex(0)));
}
}