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https://github.com/aljazceru/turso.git
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Larger compiler directive. Addresses https://github.com/tursodatabase/limbo/pull/1600#discussion_r2115820195
this commit places all pointer map functionality within a module called ptrmap guarded by a compiler directive
This commit is contained in:
Zaid Humayun
@@ -22,6 +22,9 @@ use super::btree::BTreePage;
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use super::page_cache::{CacheError, CacheResizeResult, DumbLruPageCache, PageCacheKey};
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use super::wal::{CheckpointMode, CheckpointStatus};
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#[cfg(not(feature = "omit_autovacuum"))]
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use ptrmap::*;
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pub struct PageInner {
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pub flags: AtomicUsize,
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pub contents: Option<PageContent>,
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@@ -1042,148 +1045,154 @@ impl CreateBTreeFlags {
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** PTRMAP_BTREE: The database page is a non-root btree page. The page number
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** identifies the parent page in the btree.
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*/
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#[cfg(not(feature = "omit_autovacuum"))]
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mod ptrmap {
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use crate::{LimboError, Result};
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// Constants
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pub const PTRMAP_ENTRY_SIZE: usize = 5;
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/// Page 1 is the schema page which contains the database header.
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/// Page 2 is the first pointer map page if the database has any pointer map pages.
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pub const FIRST_PTRMAP_PAGE_NO: u32 = 2;
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// Constants
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pub const PTRMAP_ENTRY_SIZE: usize = 5;
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/// Page 1 is the schema page which contains the database header.
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/// Page 2 is the first pointer map page if the database has any pointer map pages.
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pub const FIRST_PTRMAP_PAGE_NO: u32 = 2;
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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#[repr(u8)]
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pub enum PtrmapType {
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RootPage = 1,
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FreePage = 2,
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Overflow1 = 3,
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Overflow2 = 4,
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BTreeNode = 5,
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}
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#[derive(Debug, Clone, Copy, PartialEq, Eq)]
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#[repr(u8)]
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pub enum PtrmapType {
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RootPage = 1,
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FreePage = 2,
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Overflow1 = 3,
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Overflow2 = 4,
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BTreeNode = 5,
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}
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impl PtrmapType {
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pub fn from_u8(value: u8) -> Option<Self> {
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match value {
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1 => Some(PtrmapType::RootPage),
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2 => Some(PtrmapType::FreePage),
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3 => Some(PtrmapType::Overflow1),
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4 => Some(PtrmapType::Overflow2),
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5 => Some(PtrmapType::BTreeNode),
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_ => None,
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impl PtrmapType {
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pub fn from_u8(value: u8) -> Option<Self> {
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match value {
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1 => Some(PtrmapType::RootPage),
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2 => Some(PtrmapType::FreePage),
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3 => Some(PtrmapType::Overflow1),
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4 => Some(PtrmapType::Overflow2),
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5 => Some(PtrmapType::BTreeNode),
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_ => None,
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}
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}
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}
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}
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#[derive(Debug, Clone, Copy)]
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pub struct PtrmapEntry {
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pub entry_type: PtrmapType,
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pub parent_page_no: u32,
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}
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#[derive(Debug, Clone, Copy)]
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pub struct PtrmapEntry {
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pub entry_type: PtrmapType,
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pub parent_page_no: u32,
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}
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impl PtrmapEntry {
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pub fn serialize(&self, buffer: &mut [u8]) -> Result<()> {
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if buffer.len() < PTRMAP_ENTRY_SIZE {
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return Err(LimboError::InternalError(format!(
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impl PtrmapEntry {
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pub fn serialize(&self, buffer: &mut [u8]) -> Result<()> {
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if buffer.len() < PTRMAP_ENTRY_SIZE {
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return Err(LimboError::InternalError(format!(
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"Buffer too small to serialize ptrmap entry. Expected at least {} bytes, got {}",
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PTRMAP_ENTRY_SIZE,
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buffer.len()
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)));
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}
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buffer[0] = self.entry_type as u8;
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buffer[1..5].copy_from_slice(&self.parent_page_no.to_be_bytes());
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Ok(())
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}
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buffer[0] = self.entry_type as u8;
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buffer[1..5].copy_from_slice(&self.parent_page_no.to_be_bytes());
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Ok(())
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}
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pub fn deserialize(buffer: &[u8]) -> Option<Self> {
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if buffer.len() < PTRMAP_ENTRY_SIZE {
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return None;
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pub fn deserialize(buffer: &[u8]) -> Option<Self> {
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if buffer.len() < PTRMAP_ENTRY_SIZE {
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return None;
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}
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let entry_type_u8 = buffer[0];
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let parent_bytes_slice = buffer.get(1..5)?;
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let parent_page_no = u32::from_be_bytes(parent_bytes_slice.try_into().ok()?);
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PtrmapType::from_u8(entry_type_u8).map(|entry_type| PtrmapEntry {
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entry_type,
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parent_page_no,
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})
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}
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let entry_type_u8 = buffer[0];
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let parent_bytes_slice = buffer.get(1..5)?;
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let parent_page_no = u32::from_be_bytes(parent_bytes_slice.try_into().ok()?);
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PtrmapType::from_u8(entry_type_u8).map(|entry_type| PtrmapEntry {
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entry_type,
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parent_page_no,
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})
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}
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}
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/// Calculates how many database pages are mapped by a single pointer map page.
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/// This is based on the total page size, as ptrmap pages are filled with entries.
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fn entries_per_ptrmap_page(page_size: usize) -> usize {
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if page_size < PTRMAP_ENTRY_SIZE {
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0
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} else {
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page_size / PTRMAP_ENTRY_SIZE
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}
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}
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/// Calculates the cycle length of pointer map pages
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/// The cycle length is the number of database pages that are mapped by a single pointer map page.
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fn ptrmap_page_cycle_length(page_size: usize) -> usize {
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if page_size < PTRMAP_ENTRY_SIZE {
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0
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} else {
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(page_size / PTRMAP_ENTRY_SIZE) + 1
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}
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}
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/// Determines if a given page number `db_page_no` (1-indexed) is a pointer map page in a database with autovacuum enabled
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pub fn is_ptrmap_page(db_page_no: u32, page_size: usize) -> bool {
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// The first page cannot be a ptrmap page because its for the schema
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if db_page_no == 1 {
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return false;
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}
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if db_page_no == FIRST_PTRMAP_PAGE_NO {
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return true;
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}
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return get_ptrmap_page_no_for_db_page(db_page_no, page_size) == db_page_no;
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}
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/// Calculates which pointer map page (1-indexed) contains the entry for `db_page_no_to_query` (1-indexed).
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/// `db_page_no_to_query` is the page whose ptrmap entry we are interested in.
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pub fn get_ptrmap_page_no_for_db_page(db_page_no_to_query: u32, page_size: usize) -> u32 {
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let group_size = ptrmap_page_cycle_length(page_size) as u32;
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if group_size == 0 {
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panic!("Page size too small, a ptrmap page cannot map any db pages.");
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}
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let effective_page_index = db_page_no_to_query - FIRST_PTRMAP_PAGE_NO;
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let group_idx = effective_page_index / group_size;
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(group_idx * group_size) + FIRST_PTRMAP_PAGE_NO
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}
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/// Calculates the byte offset of the entry for `db_page_no_to_query` (1-indexed)
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/// within its pointer map page (`ptrmap_page_no`, 1-indexed).
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pub fn get_ptrmap_offset_in_page(
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db_page_no_to_query: u32,
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ptrmap_page_no: u32,
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page_size: usize,
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) -> Result<usize> {
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// The data pages mapped by `ptrmap_page_no` are:
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// `ptrmap_page_no + 1`, `ptrmap_page_no + 2`, ..., up to `ptrmap_page_no + n_data_pages_per_group`.
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// `db_page_no_to_query` must be one of these.
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// The 0-indexed position of `db_page_no_to_query` within this sequence of data pages is:
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// `db_page_no_to_query - (ptrmap_page_no + 1)`.
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let n_data_pages_per_group = entries_per_ptrmap_page(page_size);
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let first_data_page_mapped = ptrmap_page_no + 1;
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let last_data_page_mapped = ptrmap_page_no + n_data_pages_per_group as u32;
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if db_page_no_to_query < first_data_page_mapped || db_page_no_to_query > last_data_page_mapped {
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return Err(LimboError::InternalError(format!(
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"Page {} is not mapped by the data page range [{}, {}] of ptrmap page {}",
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db_page_no_to_query, first_data_page_mapped, last_data_page_mapped, ptrmap_page_no
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)));
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}
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if is_ptrmap_page(db_page_no_to_query, page_size) {
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return Err(LimboError::InternalError(format!(
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"Page {} is a pointer map page and should not have an entry calculated this way.",
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db_page_no_to_query
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)));
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/// Calculates how many database pages are mapped by a single pointer map page.
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/// This is based on the total page size, as ptrmap pages are filled with entries.
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pub fn entries_per_ptrmap_page(page_size: usize) -> usize {
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if page_size < PTRMAP_ENTRY_SIZE {
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0
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} else {
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page_size / PTRMAP_ENTRY_SIZE
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}
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}
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let entry_index_on_page = (db_page_no_to_query - first_data_page_mapped) as usize;
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Ok(entry_index_on_page * PTRMAP_ENTRY_SIZE)
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/// Calculates the cycle length of pointer map pages
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/// The cycle length is the number of database pages that are mapped by a single pointer map page.
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fn ptrmap_page_cycle_length(page_size: usize) -> usize {
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if page_size < PTRMAP_ENTRY_SIZE {
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0
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} else {
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(page_size / PTRMAP_ENTRY_SIZE) + 1
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}
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}
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/// Determines if a given page number `db_page_no` (1-indexed) is a pointer map page in a database with autovacuum enabled
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pub fn is_ptrmap_page(db_page_no: u32, page_size: usize) -> bool {
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// The first page cannot be a ptrmap page because its for the schema
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if db_page_no == 1 {
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return false;
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}
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if db_page_no == FIRST_PTRMAP_PAGE_NO {
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return true;
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}
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return get_ptrmap_page_no_for_db_page(db_page_no, page_size) == db_page_no;
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}
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/// Calculates which pointer map page (1-indexed) contains the entry for `db_page_no_to_query` (1-indexed).
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/// `db_page_no_to_query` is the page whose ptrmap entry we are interested in.
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pub fn get_ptrmap_page_no_for_db_page(db_page_no_to_query: u32, page_size: usize) -> u32 {
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let group_size = ptrmap_page_cycle_length(page_size) as u32;
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if group_size == 0 {
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panic!("Page size too small, a ptrmap page cannot map any db pages.");
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}
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let effective_page_index = db_page_no_to_query - FIRST_PTRMAP_PAGE_NO;
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let group_idx = effective_page_index / group_size;
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(group_idx * group_size) + FIRST_PTRMAP_PAGE_NO
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}
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/// Calculates the byte offset of the entry for `db_page_no_to_query` (1-indexed)
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/// within its pointer map page (`ptrmap_page_no`, 1-indexed).
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pub fn get_ptrmap_offset_in_page(
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db_page_no_to_query: u32,
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ptrmap_page_no: u32,
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page_size: usize,
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) -> Result<usize> {
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// The data pages mapped by `ptrmap_page_no` are:
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// `ptrmap_page_no + 1`, `ptrmap_page_no + 2`, ..., up to `ptrmap_page_no + n_data_pages_per_group`.
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// `db_page_no_to_query` must be one of these.
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// The 0-indexed position of `db_page_no_to_query` within this sequence of data pages is:
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// `db_page_no_to_query - (ptrmap_page_no + 1)`.
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let n_data_pages_per_group = entries_per_ptrmap_page(page_size);
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let first_data_page_mapped = ptrmap_page_no + 1;
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let last_data_page_mapped = ptrmap_page_no + n_data_pages_per_group as u32;
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if db_page_no_to_query < first_data_page_mapped
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|| db_page_no_to_query > last_data_page_mapped
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{
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return Err(LimboError::InternalError(format!(
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"Page {} is not mapped by the data page range [{}, {}] of ptrmap page {}",
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db_page_no_to_query, first_data_page_mapped, last_data_page_mapped, ptrmap_page_no
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)));
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}
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if is_ptrmap_page(db_page_no_to_query, page_size) {
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return Err(LimboError::InternalError(format!(
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"Page {} is a pointer map page and should not have an entry calculated this way.",
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db_page_no_to_query
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)));
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}
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let entry_index_on_page = (db_page_no_to_query - first_data_page_mapped) as usize;
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Ok(entry_index_on_page * PTRMAP_ENTRY_SIZE)
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}
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}
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#[cfg(test)]
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@@ -1219,6 +1228,7 @@ mod tests {
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#[cfg(test)]
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mod ptrmap_tests {
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use super::ptrmap::*;
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use super::*;
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#[cfg(not(feature = "omit_autovacuum"))]
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