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use std::collections::{HashMap, hash_map};
use by_address::ByAddress;
use toasty_core::{schema::db::Index, stmt};
use crate::engine::index::PartitionCtx;
#[derive(Debug)]
pub(super) struct IndexMatch<'stmt> {
/// The index in question
pub(super) index: &'stmt Index,
/// Restriction matches for each column
pub(super) columns: Vec<IndexColumnMatch<'stmt>>,
}
#[derive(Debug)]
pub(super) struct IndexColumnMatch<'stmt> {
pub(super) exprs: HashMap<ByAddress<&'stmt stmt::Expr>, ExprMatch>,
}
#[derive(Debug, Copy, Clone)]
pub(super) struct ExprMatch {
pub(super) eq: bool,
}
type ExprPair = (stmt::Expr, stmt::Expr);
impl<'stmt> IndexMatch<'stmt> {
pub(super) fn match_restriction(
&mut self,
cx: &stmt::ExprContext<'_>,
expr: &'stmt stmt::Expr,
) -> bool {
use stmt::Expr::*;
match expr {
BinaryOp(e) => match (&*e.lhs, &*e.rhs) {
(stmt::Expr::Reference(lhs @ stmt::ExprReference::Column(_)), rhs) => {
assert!(
!rhs.is_expr_reference(),
"TODO: handle ExprReference on both sides"
);
self.match_expr_binary_op_column(cx, lhs, expr, e.op)
}
(_, stmt::Expr::Reference(rhs @ stmt::ExprReference::Column(_))) => {
self.match_expr_binary_op_column(cx, rhs, expr, e.op.commute())
}
_ => todo!("expr={:#?}", expr),
},
InList(e) => self.match_expr_in_list(cx, &e.expr, expr),
IsNull(e) => match &*e.expr {
stmt::Expr::Reference(expr_column @ stmt::ExprReference::Column(_)) => {
self.match_expr_binary_op_column(cx, expr_column, expr, stmt::BinaryOp::Eq)
}
_ => todo!("expr={:#?}", expr),
},
And(and_exprs) => {
let matched = self.match_all_restrictions(cx, and_exprs);
if matched {
// Union all matched columns for each operand
for column in &mut self.columns {
for and_expr in and_exprs {
if let Some(operand_match) =
column.exprs.get(&ByAddress(and_expr)).copied()
{
match column.exprs.entry(ByAddress(expr)) {
hash_map::Entry::Vacant(e) => {
e.insert(ExprMatch {
eq: operand_match.eq,
});
}
hash_map::Entry::Occupied(mut e) if operand_match.eq => {
e.get_mut().eq = true;
}
_ => continue,
}
if operand_match.eq {
break;
}
}
}
}
}
matched
}
Or(or_exprs) => {
let matched_any_expr = self.match_all_restrictions(cx, or_exprs);
let mut matched_operand = false;
// For OR expressions, we need to ensure that the index match is
// balanced for each column. To do this, if operand matched, then
// we do a deeper search to see if any index column matched with
// *all* or branches.
if matched_any_expr {
'columns: for column in &mut self.columns {
let mut eq = true;
for or_expr in or_exprs {
if let Some(operand_match) = column.exprs.get(&ByAddress(or_expr)) {
eq &= operand_match.eq;
} else {
continue 'columns;
}
}
// At this point, we verified *each* operand matched a
// column, so we can consider the entire expression as
// having matched that column.
column.exprs.insert(ByAddress(expr), ExprMatch { eq });
matched_operand = true;
}
}
matched_operand
}
Any(expr_any) => {
// Any operates on a Map expression that evaluates to bools.
// It's similar to a dynamic OR expression. If the map expression
// matches an index, the Any expression matches as well.
// We don't need the "balanced" check like OR because each
// evaluation of the map will have the same structure.
let stmt::Expr::Map(expr_map) = &*expr_any.expr else {
todo!("expr_any.expr={:#?}", expr_any.expr);
};
// Try to match the map expression (the predicate applied to each element)
if self.match_restriction(cx, &expr_map.map) {
// If the map expression matched, propagate that match to this Any expression
for column in &mut self.columns {
if let Some(operand_match) =
column.exprs.get(&ByAddress(&*expr_map.map)).copied()
{
column.exprs.insert(
ByAddress(expr),
ExprMatch {
eq: operand_match.eq,
},
);
}
}
true
} else {
false
}
}
_ => {
// Unsupported expression type for index matching - return false
// to indicate this expression cannot be matched against an index
false
}
}
}
/// Returns true if **any** expression in the provided list match with
/// **any** index column.
fn match_all_restrictions(
&mut self,
cx: &stmt::ExprContext<'_>,
exprs: &'stmt [stmt::Expr],
) -> bool {
let mut matched = false;
for expr in exprs {
matched |= self.match_restriction(cx, expr);
}
matched
}
fn match_expr_in_list(
&mut self,
cx: &stmt::ExprContext<'_>,
lhs: &'stmt stmt::Expr,
expr: &'stmt stmt::Expr,
) -> bool {
match lhs {
stmt::Expr::Reference(expr_column @ stmt::ExprReference::Column(_)) => {
self.match_expr_binary_op_column(cx, expr_column, expr, stmt::BinaryOp::Eq)
}
stmt::Expr::Record(expr_record) => {
let mut matched = false;
for sub_expr in expr_record {
let stmt::Expr::Reference(expr_column @ stmt::ExprReference::Column(_)) =
sub_expr
else {
todo!()
};
matched |= self.match_expr_binary_op_column(
cx,
expr_column,
sub_expr,
stmt::BinaryOp::Eq,
);
}
if matched {
for column in &mut self.columns {
for sub_expr in expr_record {
if column.exprs.contains_key(&ByAddress(sub_expr)) {
column.exprs.insert(ByAddress(expr), ExprMatch { eq: true });
break;
}
}
}
}
matched
}
_ => todo!("expr={:#?}", expr),
}
}
fn match_expr_binary_op_column(
&mut self,
cx: &stmt::ExprContext<'_>,
expr_ref: &stmt::ExprReference,
expr: &'stmt stmt::Expr,
op: stmt::BinaryOp,
) -> bool {
let mut matched = false;
for (i, index_column) in self.index.columns.iter().enumerate() {
// Check that the path matches an index column
if cx.resolve_expr_reference(expr_ref).as_column_unwrap().id != index_column.column {
continue;
}
// If the index column is scoped as a partition key, then only
// equality predicates are supported.
if index_column.scope.is_partition() && !op.is_eq() {
continue;
}
self.columns[i]
.exprs
.insert(ByAddress(expr), ExprMatch { eq: op.is_eq() });
matched = true;
}
matched
}
/// Copute the cost of using this index match to execute the query.
pub(super) fn compute_cost(&self, filter: &stmt::Expr) -> usize {
if self.index.unique {
let mut cost = 0;
for column in &self.columns {
let Some(expr_match) = column.exprs.get(&ByAddress(filter)) else {
break;
};
if expr_match.eq {
cost += 1;
} else {
cost += 10;
}
}
cost
} else {
// Arbitrary
10
}
}
pub(super) fn partition_filter(
&self,
ctx: &mut PartitionCtx<'_>,
expr: &stmt::Expr,
) -> ExprPair {
use stmt::Expr::*;
match expr {
InList(_) | IsNull(_) | Not(_) => {
if self
.columns
.iter()
.any(|f| f.exprs.contains_key(&ByAddress(expr)))
{
(expr.clone(), true.into())
} else {
(true.into(), expr.clone())
}
}
BinaryOp(binary_op) => {
if self
.columns
.iter()
.any(|f| f.exprs.contains_key(&ByAddress(expr)))
{
if binary_op.op.is_ne() && !ctx.capability.primary_key_ne_predicate {
ctx.apply_result_filter_on_results = true;
return (true.into(), true.into());
}
// Normalize the expression to include the column on the LHS
let expr = match (&*binary_op.lhs, &*binary_op.rhs) {
(stmt::Expr::Reference(stmt::ExprReference::Column(_)), _) => expr.clone(),
(
lhs,
stmt::Expr::Reference(column_ref @ stmt::ExprReference::Column(_)),
) => stmt::ExprBinaryOp {
lhs: Box::new(stmt::Expr::Reference(*column_ref)),
rhs: Box::new(lhs.clone()),
op: binary_op.op.commute(),
}
.into(),
_ => todo!("binary_op={binary_op:#?}"),
};
(expr, true.into())
} else {
(true.into(), expr.clone())
}
}
And(expr_and) => {
let mut index_filter_operands = vec![];
let mut result_filter_operands = vec![];
for operand in &expr_and.operands {
let (index_filter, result_filter) = self.partition_filter(ctx, operand);
if !index_filter.is_true() {
index_filter_operands.push(index_filter);
}
if !result_filter.is_true() {
result_filter_operands.push(result_filter);
}
}
let index_filter = match index_filter_operands.len() {
0 => true.into(),
1 => index_filter_operands.into_iter().next().unwrap(),
_ => stmt::ExprAnd {
operands: index_filter_operands,
}
.into(),
};
let result_filter = match result_filter_operands.len() {
0 => true.into(),
1 => result_filter_operands.into_iter().next().unwrap(),
_ => stmt::ExprAnd {
operands: result_filter_operands,
}
.into(),
};
(index_filter, result_filter)
}
Or(expr_or) => {
let mut index_filter_operands = vec![];
let mut result_filter_operands = vec![];
for operand in &expr_or.operands {
let (index_filter, result_filter) = self.partition_filter(ctx, operand);
if !index_filter.is_true() && !result_filter.is_true() {
todo!("expr_or={:#?}", expr_or);
}
if !index_filter.is_true() {
assert!(result_filter_operands.is_empty());
index_filter_operands.push(index_filter);
} else if !result_filter.is_true() {
assert!(index_filter_operands.is_empty());
result_filter_operands.push(result_filter);
} else {
todo!()
}
}
if !index_filter_operands.is_empty() {
(
stmt::ExprOr {
operands: index_filter_operands,
}
.into(),
true.into(),
)
} else {
(
true.into(),
stmt::ExprOr {
operands: result_filter_operands,
}
.into(),
)
}
}
Any(expr_any) => {
// For Any expressions, partition the inner map expression
let stmt::Expr::Map(expr_map) = &*expr_any.expr else {
todo!("expr_any.expr={:#?}", expr_any.expr);
};
let (index_filter, result_filter) = self.partition_filter(ctx, &expr_map.map);
// If the map expression can be used as an index filter, reconstruct
// the Any with the index filter version
if !index_filter.is_true() {
let index_any = stmt::ExprAny {
expr: Box::new(stmt::Expr::Map(stmt::ExprMap {
base: expr_map.base.clone(),
map: Box::new(index_filter),
})),
};
(index_any.into(), true.into())
} else if !result_filter.is_true() {
let result_any = stmt::ExprAny {
expr: Box::new(stmt::Expr::Map(stmt::ExprMap {
base: expr_map.base.clone(),
map: Box::new(result_filter),
})),
};
(true.into(), result_any.into())
} else {
(true.into(), true.into())
}
}
_ => todo!("partition_filter={:#?}", expr),
}
}
}