aljaz/turso
1
0
Fork 0
mirror of https://github.com/aljazceru/turso.git synced 2026-01-15 06:04:19 +01:00
Code Issues Packages Projects Releases Wiki Activity

core/mvcc/cursor: rewind with btree

Browse Source
This commit is contained in:
Pere Diaz Bou
2025-10-24 13:01:27 +02:00
parent a7614267af
commit 724bc94f96
1 changed files with 63 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files

101
core/mvcc/cursor.rs
View File

@@ -131,6 +131,52 @@ impl<Clock: LogicalClock + 'static> MvccLazyCursor<Clock> {
fn get_current_pos(&self) -> CursorPosition {
*self.current_pos.borrow()
}
/// Returns the new position of the cursor based on the new position in MVCC and the current rowid in BTree.
/// If the new position in MVCC is less than the current rowid in BTree, the cursor will be set to the new position in MVCC.
fn get_new_position_from_mvcc_and_btree(
&mut self,
new_position_in_mvcc: &Option<i64>,
current_rowid_in_btree: &Option<i64>,
) -> CursorPosition {
let new_position = match (new_position_in_mvcc, current_rowid_in_btree) {
(Some(mvcc_rowid), Some(btree_rowid)) => {
if mvcc_rowid < btree_rowid {
CursorPosition::Loaded {
row_id: RowID {
table_id: self.table_id,
row_id: *mvcc_rowid,
},
in_btree: false,
}
} else {
CursorPosition::Loaded {
row_id: RowID {
table_id: self.table_id,
row_id: *btree_rowid,
},
in_btree: true,
}
}
}
(None, Some(btree_rowid)) => CursorPosition::Loaded {
row_id: RowID {
table_id: self.table_id,
row_id: *btree_rowid,
},
in_btree: true,
},
(Some(mvcc_rowid), None) => CursorPosition::Loaded {
row_id: RowID {
table_id: self.table_id,
row_id: *mvcc_rowid,
},
in_btree: false,
},
(None, None) => CursorPosition::End,
};
new_position
}
}
impl<Clock: LogicalClock + 'static> CursorTrait for MvccLazyCursor<Clock> {
@@ -220,42 +266,8 @@ impl<Clock: LogicalClock + 'static> CursorTrait for MvccLazyCursor<Clock> {
} else {
None
};
let new_position = match (new_position_in_mvcc, current_rowid_in_btree) {
(Some(mvcc_rowid), Some(btree_rowid)) => {
if mvcc_rowid < btree_rowid {
CursorPosition::Loaded {
row_id: RowID {
table_id: self.table_id,
row_id: mvcc_rowid,
},
in_btree: false,
}
} else {
CursorPosition::Loaded {
row_id: RowID {
table_id: self.table_id,
row_id: btree_rowid,
},
in_btree: true,
}
}
}
(None, Some(btree_rowid)) => CursorPosition::Loaded {
row_id: RowID {
table_id: self.table_id,
row_id: btree_rowid,
},
in_btree: true,
},
(Some(mvcc_rowid), None) => CursorPosition::Loaded {
row_id: RowID {
table_id: self.table_id,
row_id: mvcc_rowid,
},
in_btree: false,
},
(None, None) => CursorPosition::End,
};
let new_position = self
.get_new_position_from_mvcc_and_btree(&new_position_in_mvcc, &current_rowid_in_btree);
self.current_pos.replace(new_position);
self.invalidate_record();
self.state.replace(None);
@@ -473,12 +485,25 @@ impl<Clock: LogicalClock + 'static> CursorTrait for MvccLazyCursor<Clock> {
}
fn rewind(&mut self) -> Result<IOResult<()>> {
// First run btree_cursor rewind so that we don't need a explicit state machine.
return_if_io!(self.btree_cursor.rewind());
self.invalidate_record();
if !matches!(self.get_current_pos(), CursorPosition::BeforeFirst) {
self.current_pos.replace(CursorPosition::BeforeFirst);
}
// Next will set cursor position to a valid position if it exists, otherwise it will set it to one that doesn't exist.
let _ = return_if_io!(self.next());
let new_position_in_mvcc = self
.db
.get_next_row_id_for_table(self.table_id, i64::MIN, self.tx_id)
.map(|id| id.row_id);
let IOResult::Done(maybe_rowid_in_btree) = self.btree_cursor.rowid()? else {
panic!("BTree should have returned rowid after next");
};
let new_position =
self.get_new_position_from_mvcc_and_btree(&new_position_in_mvcc, &maybe_rowid_in_btree);
self.current_pos.replace(new_position);
Ok(IOResult::Done(()))
}