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Merge 'Fix overwrite cell with size less than cell size' from Pere Diaz Bou

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We cannot simply paste a new payload into a cell with a payload with
less size because we need to track fragmentation + free blocks. Let's
keep it simple by only overwriting if size is the same.
Btw I feel like update is not re-entrant.

Reviewed-by: Preston Thorpe (@PThorpe92)

Closes #1301
This commit is contained in:
Pekka Enberg
2025-04-11 07:17:53 +03:00
parent 17b206297e 745c2b92d0
commit 2f428b7dcc
1 changed files with 6 additions and 47 deletions
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53
core/storage/btree.rs
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@@ -1924,6 +1924,7 @@ impl BTreeCursor {
let mut count_cells_in_old_pages = Vec::new();
let page_type = balance_info.pages_to_balance[0].get_contents().page_type();
tracing::debug!("balance_non_root(page_type={:?})", page_type);
let leaf_data = matches!(page_type, PageType::TableLeaf);
let leaf = matches!(page_type, PageType::TableLeaf | PageType::IndexLeaf);
for (i, old_page) in balance_info.pages_to_balance.iter().enumerate() {
@@ -3859,25 +3860,8 @@ impl BTreeCursor {
};
// if it all fits in local space and old_local_size is enough, do an in-place overwrite
if new_payload.len() <= old_local_size {
self.overwrite_content(
page_ref.clone(),
old_offset,
&new_payload,
0,
new_payload.len(),
)?;
let remaining = old_local_size - new_payload.len();
if remaining > 0 {
// fill the rest with zeros
self.overwrite_content(
page_ref.clone(),
old_offset + new_payload.len(),
&[0; 1],
0,
remaining,
)?;
}
if new_payload.len() == old_local_size {
self.overwrite_content(page_ref.clone(), old_offset, &new_payload)?;
Ok(CursorResult::Ok(()))
} else {
// doesn't fit, drop it and insert a new one
@@ -3901,36 +3885,11 @@ impl BTreeCursor {
page_ref: PageRef,
dest_offset: usize,
new_payload: &[u8],
src_offset: usize,
amount: usize,
) -> Result<CursorResult<()>> {
return_if_locked!(page_ref);
page_ref.set_dirty();
self.pager.add_dirty(page_ref.get().id);
let buf = page_ref.get().contents.as_mut().unwrap().as_ptr();
buf[dest_offset..dest_offset + new_payload.len()].copy_from_slice(&new_payload);
// if new_payload doesn't have enough data, we fill with zeros
let n_data = new_payload.len().saturating_sub(src_offset);
if n_data == 0 {
// everything is zeros
for i in 0..amount {
if buf[dest_offset + i] != 0 {
buf[dest_offset + i] = 0;
}
}
} else {
let copy_len = n_data.min(amount);
// copy the overlapping portion
buf[dest_offset..dest_offset + copy_len]
.copy_from_slice(&new_payload[src_offset..src_offset + copy_len]);
// if copy_len < amount => fill remainder with 0
if copy_len < amount {
for i in copy_len..amount {
buf[dest_offset + i] = 0;
}
}
}
Ok(CursorResult::Ok(()))
}
@@ -4117,7 +4076,7 @@ fn find_free_cell(page_ref: &PageContent, usable_space: u16, amount: usize) -> R
return Ok(0);
}
// Delete the slot from freelist and update the page's fragment count.
page_ref.write_u16(prev_pc, next);
page_ref.write_u16_no_offset(prev_pc, next);
let frag = page_ref.num_frag_free_bytes() + new_size as u8;
page_ref.write_u8(offset::BTREE_FRAGMENTED_BYTES_COUNT, frag);
return Ok(pc);
@@ -4126,7 +4085,7 @@ fn find_free_cell(page_ref: &PageContent, usable_space: u16, amount: usize) -> R
} else {
// Requested amount fits inside the current free slot so we reduce its size
// to account for newly allocated space.
page_ref.write_u16(pc + 2, new_size as u16);
page_ref.write_u16_no_offset(pc + 2, new_size as u16);
return Ok(pc + new_size);
}
}