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For now always calculate post-balance seek key

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This commit is contained in:
Jussi Saurio 2025-06-10 11:26:39 +03:00
parent 976c2f72ef
commit d827eeade0
1 changed files with 63 additions and 26 deletions
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89
core/storage/btree.rs
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@ -165,19 +165,27 @@ enum DeleteSavepoint {
#[derive(Debug, Clone)]
enum DeleteState {
Start,
LoadPage,
FindCell,
DeterminePostBalancingSeekKey,
LoadPage {
post_balancing_seek_key: Option<DeleteSavepoint>,
},
FindCell {
post_balancing_seek_key: Option<DeleteSavepoint>,
},
ClearOverflowPages {
cell_idx: usize,
cell: BTreeCell,
original_child_pointer: Option<u32>,
post_balancing_seek_key: Option<DeleteSavepoint>,
},
InteriorNodeReplacement {
cell_idx: usize,
original_child_pointer: Option<u32>,
post_balancing_seek_key: Option<DeleteSavepoint>,
},
CheckNeedsBalancing {
rightmost_cell_was_dropped: bool,
post_balancing_seek_key: Option<DeleteSavepoint>,
},
WaitForBalancingToComplete {
target_key: DeleteSavepoint,
@ -4164,14 +4172,15 @@ impl BTreeCursor {
/// Delete state machine flow:
/// 1. Start -> check if the rowid to be delete is present in the page or not. If not we early return
/// 2. LoadPage -> load the page.
/// 3. FindCell -> find the cell to be deleted in the page.
/// 4. ClearOverflowPages -> Clear the overflow pages if there are any before dropping the cell, then if we are in a leaf page we just drop the cell in place.
/// 2. DeterminePostBalancingSeekKey -> determine the key to seek to after balancing.
/// 3. LoadPage -> load the page.
/// 4. FindCell -> find the cell to be deleted in the page.
/// 5. ClearOverflowPages -> Clear the overflow pages if there are any before dropping the cell, then if we are in a leaf page we just drop the cell in place.
/// if we are in interior page, we need to rotate keys in order to replace current cell (InteriorNodeReplacement).
/// 5. InteriorNodeReplacement -> we copy the left subtree leaf node into the deleted interior node's place.
/// 6. WaitForBalancingToComplete -> perform balancing
/// 7. SeekAfterBalancing -> adjust the cursor to a node that is closer to the deleted value. go to Finish
/// 8. Finish -> Delete operation is done. Return CursorResult(Ok())
/// 6. InteriorNodeReplacement -> we copy the left subtree leaf node into the deleted interior node's place.
/// 7. WaitForBalancingToComplete -> perform balancing
/// 8. SeekAfterBalancing -> adjust the cursor to a node that is closer to the deleted value. go to Finish
/// 9. Finish -> Delete operation is done. Return CursorResult(Ok())
pub fn delete(&mut self) -> Result<CursorResult<()>> {
assert!(self.mv_cursor.is_none());
@ -4213,18 +4222,49 @@ impl BTreeCursor {
}
let delete_info = self.state.mut_delete_info().unwrap();
delete_info.state = DeleteState::LoadPage;
delete_info.state = DeleteState::DeterminePostBalancingSeekKey;
}
DeleteState::LoadPage => {
DeleteState::DeterminePostBalancingSeekKey => {
// FIXME: skip this work if we determine deletion wont result in balancing
// Right now we calculate the key every time for simplicity/debugging
// since it won't affect correctness which is more important
let page = self.stack.top();
return_if_locked_maybe_load!(self.pager, page);
let target_key = if page.get().is_index() {
let record = match return_if_io!(self.record()) {
Some(record) => record.clone(),
None => unreachable!("there should've been a record"),
};
DeleteSavepoint::Payload(record)
} else {
let Some(rowid) = return_if_io!(self.rowid()) else {
panic!("cursor should be pointing to a record with a rowid");
};
DeleteSavepoint::Rowid(rowid)
};
let delete_info = self.state.mut_delete_info().unwrap();
delete_info.state = DeleteState::LoadPage {
post_balancing_seek_key: Some(target_key),
};
}
DeleteState::LoadPage {
post_balancing_seek_key,
} => {
let page = self.stack.top();
return_if_locked_maybe_load!(self.pager, page);
let delete_info = self.state.mut_delete_info().unwrap();
delete_info.state = DeleteState::FindCell;
delete_info.state = DeleteState::FindCell {
post_balancing_seek_key,
};
}
DeleteState::FindCell => {
DeleteState::FindCell {
post_balancing_seek_key,
} => {
let page = self.stack.top();
let cell_idx = self.stack.current_cell_index() as usize;
@ -4268,6 +4308,7 @@ impl BTreeCursor {
cell_idx,
cell,
original_child_pointer,
post_balancing_seek_key,
};
}
@ -4275,6 +4316,7 @@ impl BTreeCursor {
cell_idx,
cell,
original_child_pointer,
post_balancing_seek_key,
} => {
return_if_io!(self.clear_overflow_pages(&cell));
@ -4289,6 +4331,7 @@ impl BTreeCursor {
delete_info.state = DeleteState::InteriorNodeReplacement {
cell_idx,
original_child_pointer,
post_balancing_seek_key,
};
} else {
let contents = page.get().contents.as_mut().unwrap();
@ -4297,6 +4340,7 @@ impl BTreeCursor {
let delete_info = self.state.mut_delete_info().unwrap();
delete_info.state = DeleteState::CheckNeedsBalancing {
rightmost_cell_was_dropped: is_last_cell,
post_balancing_seek_key,
};
}
}
@ -4304,6 +4348,7 @@ impl BTreeCursor {
DeleteState::InteriorNodeReplacement {
cell_idx,
original_child_pointer,
post_balancing_seek_key,
} => {
// This is an interior node, we need to handle deletion differently
// For interior nodes:
@ -4381,11 +4426,13 @@ impl BTreeCursor {
let delete_info = self.state.mut_delete_info().unwrap();
delete_info.state = DeleteState::CheckNeedsBalancing {
rightmost_cell_was_dropped: false, // TODO: when is this true?
post_balancing_seek_key,
};
}
DeleteState::CheckNeedsBalancing {
rightmost_cell_was_dropped,
post_balancing_seek_key,
} => {
let page = self.stack.top();
return_if_locked_maybe_load!(self.pager, page);
@ -4406,25 +4453,15 @@ impl BTreeCursor {
}
if needs_balancing {
let target_key = if page.is_index() {
let record = match return_if_io!(self.record()) {
Some(record) => record.clone(),
None => unreachable!("there should've been a record"),
};
DeleteSavepoint::Payload(record)
} else {
let Some(rowid) = return_if_io!(self.rowid()) else {
panic!("cursor should be pointing to a record with a rowid");
};
DeleteSavepoint::Rowid(rowid)
};
let delete_info = self.state.mut_delete_info().unwrap();
if delete_info.balance_write_info.is_none() {
let mut write_info = WriteInfo::new();
write_info.state = WriteState::BalanceStart;
delete_info.balance_write_info = Some(write_info);
}
delete_info.state = DeleteState::WaitForBalancingToComplete { target_key }
delete_info.state = DeleteState::WaitForBalancingToComplete {
target_key: post_balancing_seek_key.unwrap(),
}
} else {
self.stack.retreat();
self.state = CursorState::None;