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feat: use covering indexes #592

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feat: use covering indexes #592

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8065f2b
feat: use covering indexes
KKould Jan 1, 2025
84106d0
chore: codefmt
KKould Jan 1, 2025
7fb87bb
fix: special mapping of row ids
KKould Jan 2, 2025
7e023e8
fix: remove row_id unwrap
KKould Jan 2, 2025
8683df7
rebase
KKould Jan 2, 2025
3637a82
refactor: simplify index cover implementation
KKould Jan 17, 2025
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39 changes: 32 additions & 7 deletions core/schema.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -458,6 +458,7 @@ pub struct Index {
pub root_page: usize,
pub columns: Vec<IndexColumn>,
pub unique: bool,
pub index_cover_mapping: HashMap<usize, usize>,
}

#[allow(dead_code)]
Expand All @@ -474,7 +475,11 @@ pub enum Order {
}

impl Index {
pub fn from_sql(sql: &str, root_page: usize) -> Result<Index> {
pub fn from_sql(
sql: &str,
tables: &HashMap<String, Rc<BTreeTable>>,
root_page: usize,
) -> Result<Index> {
let mut parser = Parser::new(sql.as_bytes());
let cmd = parser.next()?;
match cmd {
Expand All @@ -485,24 +490,44 @@ impl Index {
unique,
..
})) => {
let table_name = normalize_ident(&tbl_name.0);
let Some((_, table)) = tables.iter().find(|(t_name, _)| t_name == &&table_name)
else {
crate::bail_corrupt_error!("Parse error: no such table: {}", tbl_name);
};
let mut index_cover_mapping = HashMap::with_capacity(columns.len());
let index_name = normalize_ident(&idx_name.name.0);
let index_columns = columns
.into_iter()
.map(|col| IndexColumn {
name: normalize_ident(&col.expr.to_string()),

let mut index_columns = Vec::with_capacity(columns.len());

for (i, col) in columns.into_iter().enumerate() {
let column_name = normalize_ident(&col.expr.to_string());
// SAFETY: the column in the index must exist in the table
let (pos, _) = table.get_column(&column_name).unwrap();
index_cover_mapping.insert(pos, i);
index_columns.push(IndexColumn {
name: column_name,
order: match col.order {
Some(sqlite3_parser::ast::SortOrder::Asc) => Order::Ascending,
Some(sqlite3_parser::ast::SortOrder::Desc) => Order::Descending,
None => Order::Ascending,
},
})
.collect();
}
if let Some(pos) = table
.columns
.iter()
.position(|column| column.is_rowid_alias)
{
index_cover_mapping.insert(pos, index_cover_mapping.len());
}
Ok(Index {
name: index_name,
table_name: normalize_ident(&tbl_name.0),
table_name,
root_page,
columns: index_columns,
unique,
index_cover_mapping,
})
}
_ => todo!("Expected create index statement"),
Expand Down
105 changes: 74 additions & 31 deletions core/translate/emitter.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -664,34 +664,26 @@ fn init_source(
search,
..
} => {
let table_cursor_id = program.alloc_cursor_id(
Some(table_reference.table_identifier.clone()),
Some(table_reference.table.clone()),
);
let mut is_cover = false;

match mode {
OperationMode::SELECT => {
program.emit_insn(Insn::OpenReadAsync {
cursor_id: table_cursor_id,
root_page: table_reference.table.get_root_page(),
});
program.emit_insn(Insn::OpenReadAwait {});
}
OperationMode::DELETE => {
program.emit_insn(Insn::OpenWriteAsync {
cursor_id: table_cursor_id,
root_page: table_reference.table.get_root_page(),
});
program.emit_insn(Insn::OpenWriteAwait {});
}
_ => {
unimplemented!()
}
}

if let Search::IndexSearch { index, .. } = search {
let index_cursor_id = program
.alloc_cursor_id(Some(index.name.clone()), Some(Table::Index(index.clone())));
if let Search::IndexSearch {
index,
cover_mapping,
..
} = search
{
let index_cursor_id = if cover_mapping.is_some() {
is_cover = true;
program.alloc_cursor_id(
Some(table_reference.table_identifier.clone()),
Some(Table::Index(index.clone())),
)
} else {
program.alloc_cursor_id(
Some(index.name.clone()),
Some(Table::Index(index.clone())),
)
};

match mode {
OperationMode::SELECT => {
Expand All @@ -714,6 +706,33 @@ fn init_source(
}
}

if !is_cover {
let table_cursor_id = program.alloc_cursor_id(
Some(table_reference.table_identifier.clone()),
Some(table_reference.table.clone()),
);

match mode {
OperationMode::SELECT => {
program.emit_insn(Insn::OpenReadAsync {
cursor_id: table_cursor_id,
root_page: table_reference.table.get_root_page(),
});
program.emit_insn(Insn::OpenReadAwait {});
}
OperationMode::DELETE => {
program.emit_insn(Insn::OpenWriteAsync {
cursor_id: table_cursor_id,
root_page: table_reference.table.get_root_page(),
});
program.emit_insn(Insn::OpenWriteAwait {});
}
_ => {
unimplemented!()
}
}
}

Ok(())
}
SourceOperator::Nothing { .. } => Ok(()),
Expand Down Expand Up @@ -921,6 +940,7 @@ fn open_loop(
predicates,
..
} => {
let mut is_index_cover = false;
let table_cursor_id = program.resolve_cursor_id(&table_reference.table_identifier);
let loop_labels = metadata
.loop_labels
Expand All @@ -929,8 +949,21 @@ fn open_loop(
// Open the loop for the index search.
// Rowid equality point lookups are handled with a SeekRowid instruction which does not loop, since it is a single row lookup.
if !matches!(search, Search::RowidEq { .. }) {
let index_cursor_id = if let Search::IndexSearch { index, .. } = search {
Some(program.resolve_cursor_id(&index.name))
let index_cursor_id = if let Search::IndexSearch {
index,
cover_mapping,
..
} = search
{
if let Some(cover_mapping) = &cover_mapping {
program
.table_remapping_cursors
.insert(table_cursor_id, cover_mapping.clone());
is_index_cover = true;
Some(table_cursor_id)
} else {
Some(program.resolve_cursor_id(&index.name))
}
} else {
None
};
Expand Down Expand Up @@ -1069,7 +1102,7 @@ fn open_loop(
_ => {}
}

if let Some(index_cursor_id) = index_cursor_id {
if let (Some(index_cursor_id), false) = (index_cursor_id, is_index_cover) {
program.emit_insn(Insn::DeferredSeek {
index_cursor_id,
table_cursor_id,
Expand Down Expand Up @@ -1459,7 +1492,17 @@ fn close_loop(
return Ok(());
}
let cursor_id = match search {
Search::IndexSearch { index, .. } => program.resolve_cursor_id(&index.name),
Search::IndexSearch {
index,
cover_mapping,
..
} => {
if cover_mapping.is_some() {
program.resolve_cursor_id(&table_reference.table_identifier)
} else {
program.resolve_cursor_id(&index.name)
}
}
Search::RowidSearch { .. } => {
program.resolve_cursor_id(&table_reference.table_identifier)
}
Expand Down
10 changes: 9 additions & 1 deletion core/translate/expr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1967,7 +1967,14 @@ pub fn translate_expr(
// the table and read the column from the cursor.
TableReferenceType::BTreeTable => {
let cursor_id = program.resolve_cursor_id(&tbl_ref.table_identifier);
if *is_rowid_alias {
if let Some(columns_mapping) = program.table_remapping_cursors.get(&cursor_id) {
// FIXME: row_id is displayed as `column` in explain
program.emit_insn(Insn::Column {
cursor_id,
column: columns_mapping[column],
dest: target_register,
});
} else if *is_rowid_alias {
program.emit_insn(Insn::RowId {
cursor_id,
dest: target_register,
Expand All @@ -1979,6 +1986,7 @@ pub fn translate_expr(
dest: target_register,
});
}

let column = tbl_ref.table.get_column_at(*column);
maybe_apply_affinity(column.ty, target_register, program);
Ok(target_register)
Expand Down
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