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fix: addresses comments https://github.com/tursodatabase/limbo/pull/897#discussion_r1962100891 and https://github.com/tursodatabase/limbo/pull/897#discussion_r1962100299 by @pereman2
this commit introduces the ability of the state machine traversal to handle index interior cell overflow pages. it also makes the state machine states more explicit with match arms.
This commit is contained in:
Zaid Humayun
parent
fdf4166a7c
commit
662b34c8b6
1 changed files with 98 additions and 63 deletions
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@ -2302,41 +2302,52 @@ impl BTreeCursor {
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assert!(page.is_loaded()); // page should be loaded at this time
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let contents = page.get().contents.as_ref().unwrap();
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let cell_idx = self.stack.current_cell_index();
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if cell_idx > contents.cell_count() as i32 {
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// If all the cells in this page have been processed, move state machine to freeing current page
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let destroy_info = self
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.state
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.mut_destroy_info()
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.expect("unable to get a mut reference to destroy state in cursor");
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destroy_info.state = DestroyState::FreePage;
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continue;
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} else if cell_idx == contents.cell_count() as i32 {
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// At the last cell index
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// If interior page, free right page
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if !contents.is_leaf() {
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if let Some(rightmost) = contents.rightmost_pointer() {
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let rightmost_page = self.pager.read_page(rightmost as usize)?;
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self.stack.advance();
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self.stack.push(rightmost_page);
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// If we've processed all cells in this page, figure out what to do with this page
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if cell_idx >= contents.cell_count() as i32 {
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match (contents.is_leaf(), cell_idx) {
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// Leaf pages with all cells processed
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(true, n) if n >= contents.cell_count() as i32 => {
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let destroy_info = self.state.mut_destroy_info().expect(
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"unable to get a mut reference to destroy state in cursor",
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);
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destroy_info.state = DestroyState::LoadPage;
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destroy_info.state = DestroyState::FreePage;
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continue;
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}
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// Non-leaf page which has processed all children but not it's potential right child
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(false, n) if n == contents.cell_count() as i32 => {
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if let Some(rightmost) = contents.rightmost_pointer() {
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let rightmost_page =
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self.pager.read_page(rightmost as usize)?;
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self.stack.advance();
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self.stack.push(rightmost_page);
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let destroy_info = self.state.mut_destroy_info().expect(
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"unable to get a mut reference to destroy state in cursor",
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);
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destroy_info.state = DestroyState::LoadPage;
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} else {
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let destroy_info = self.state.mut_destroy_info().expect(
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"unable to get a mut reference to destroy state in cursor",
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);
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destroy_info.state = DestroyState::FreePage;
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}
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continue;
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}
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// Non-leaf page which has processed all children and it's right child
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(false, n) if n > contents.cell_count() as i32 => {
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let destroy_info = self.state.mut_destroy_info().expect(
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"unable to get a mut reference to destroy state in cursor",
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);
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destroy_info.state = DestroyState::FreePage;
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continue;
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}
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_ => unreachable!("Invalid cell idx state"),
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}
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// If leaf page, free current page
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let destroy_info = self
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.state
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.mut_destroy_info()
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.expect("unable to get a mut reference to destroy state in cursor");
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destroy_info.state = DestroyState::FreePage;
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continue;
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}
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// There are still cells left to process in this page
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// We have not yet processed all cells in this page
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// Get the current cell
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let cell = contents.cell_get(
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cell_idx as usize,
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Rc::clone(&self.pager),
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@ -2344,48 +2355,72 @@ impl BTreeCursor {
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self.payload_overflow_threshold_min(contents.page_type()),
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self.usable_space(),
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)?;
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if !contents.is_leaf() {
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// Load the left child of this interior cell
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let child_page_id = match &cell {
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BTreeCell::TableInteriorCell(cell) => cell._left_child_page,
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BTreeCell::IndexInteriorCell(cell) => cell.left_child_page,
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_ => panic!("expected interior cell"),
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};
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let child_page = self.pager.read_page(child_page_id as usize)?;
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self.stack.advance();
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self.stack.push(child_page);
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let destroy_info = self
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.state
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.mut_destroy_info()
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.expect("unable to get a mut reference to destroy state in cursor");
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destroy_info.state = DestroyState::LoadPage;
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continue;
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} else {
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// Clear the overflow pages for this leaf cell
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let cell = contents.cell_get(
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cell_idx as usize,
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Rc::clone(&self.pager),
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self.payload_overflow_threshold_max(contents.page_type()),
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self.payload_overflow_threshold_min(contents.page_type()),
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self.usable_space(),
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)?;
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let destroy_info = self
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.state
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.mut_destroy_info()
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.expect("unable to get a mut reference to destroy state in cursor");
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destroy_info.state = DestroyState::ClearOverflowPages { cell };
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}
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}
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DestroyState::ClearOverflowPages { cell } => {
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match self.clear_overflow_pages(&cell)? {
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CursorResult::Ok(_) => {
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match contents.is_leaf() {
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// For a leaf cell, clear the overflow pages associated with this cell
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true => {
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let destroy_info = self
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.state
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.mut_destroy_info()
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.expect("unable to get a mut reference to destroy state in cursor");
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destroy_info.state = DestroyState::ProcessPage;
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self.stack.advance();
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destroy_info.state = DestroyState::ClearOverflowPages { cell };
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continue;
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}
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// For interior cells, check the type of cell to determine what to do
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false => match &cell {
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// For index interior cells, remove the overflow pages
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BTreeCell::IndexInteriorCell(_) => {
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let destroy_info = self.state.mut_destroy_info().expect(
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"unable to get a mut reference to destroy state in cursor",
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);
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destroy_info.state = DestroyState::ClearOverflowPages { cell };
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continue;
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}
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// For all other interior cells, load the left child page
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_ => {
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let child_page_id = match &cell {
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BTreeCell::TableInteriorCell(cell) => cell._left_child_page,
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BTreeCell::IndexInteriorCell(cell) => cell.left_child_page,
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_ => panic!("expected interior cell"),
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};
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let child_page = self.pager.read_page(child_page_id as usize)?;
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self.stack.advance();
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self.stack.push(child_page);
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let destroy_info = self.state.mut_destroy_info().expect(
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"unable to get a mut reference to destroy state in cursor",
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);
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destroy_info.state = DestroyState::LoadPage;
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continue;
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}
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},
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}
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}
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DestroyState::ClearOverflowPages { cell } => {
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match self.clear_overflow_pages(&cell)? {
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CursorResult::Ok(_) => match cell {
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// For an index interior cell, clear the left child page now that overflow pages have been cleared
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BTreeCell::IndexInteriorCell(index_int_cell) => {
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let child_page = self
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.pager
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.read_page(index_int_cell.left_child_page as usize)?;
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self.stack.advance();
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self.stack.push(child_page);
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let destroy_info = self.state.mut_destroy_info().expect(
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"unable to get a mut reference to destroy state in cursor",
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);
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destroy_info.state = DestroyState::LoadPage;
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continue;
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}
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// For any leaf cell, advance the index now that overflow pages have been cleared
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BTreeCell::TableLeafCell(_) | BTreeCell::IndexLeafCell(_) => {
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self.stack.advance();
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let destroy_info = self.state.mut_destroy_info().expect(
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"unable to get a mut reference to destroy state in cursor",
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);
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destroy_info.state = DestroyState::LoadPage;
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}
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_ => panic!("unexpected cell type"),
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},
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CursorResult::IO => return Ok(CursorResult::IO),
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}
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}
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