aljaz/turso
1
0
Fork 0
mirror of https://github.com/aljazceru/turso.git synced 2026-02-22 00:15:20 +01:00
Code Issues Packages Projects Releases Wiki Activity

use_indexes: comments

Browse Source
This commit is contained in:
Jussi Saurio
2025-05-10 15:46:29 +03:00
parent e53ab385d7
commit d8218483a2
1 changed files with 18 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
core/translate/optimizer/mod.rs
View File

@@ -119,6 +119,17 @@ fn optimize_subqueries(plan: &mut SelectPlan, schema: &Schema) -> Result<()> {
Ok(())
}
/// Optimize the join order and index selection for a query.
///
/// This function does the following:
/// - Computes a set of [Constraint]s for each table.
/// - Using those constraints, computes the best join order for the list of [TableReference]s
/// and selects the best [crate::translate::optimizer::access_method::AccessMethod] for each table in the join order.
/// - Mutates the [Operation]s in `table_references` to use the selected access methods.
/// - Removes predicates from the `where_clause` that are now redundant due to the selected access methods.
/// - Removes sorting operations if the selected join order and access methods satisfy the [crate::translate::optimizer::order::OrderTarget].
///
/// Returns the join order if it was optimized, or None if the default join order was considered best.
fn use_indexes(
table_references: &mut [TableReference],
available_indexes: &HashMap<String, Vec<Arc<Index>>>,
@@ -145,6 +156,8 @@ fn use_indexes(
best_ordered_plan,
} = best_join_order_result;
// See if best_ordered_plan is better than the overall best_plan if we add a sorting penalty
// to the unordered plan's cost.
let best_plan = if let Some(best_ordered_plan) = best_ordered_plan {
let best_unordered_plan_cost = best_plan.cost;
let best_ordered_plan_cost = best_ordered_plan.cost;
@@ -160,6 +173,7 @@ fn use_indexes(
best_plan
};
// Eliminate sorting if possible.
if let Some(order_target) = maybe_order_target {
let satisfies_order_target = plan_satisfies_order_target(
&best_plan,
@@ -197,6 +211,8 @@ fn use_indexes(
})
.collect();
let mut to_remove_from_where_clause = vec![];
// Mutate the Operations in `table_references` to use the selected access methods.
for (i, join_order_member) in best_join_order.iter().enumerate() {
let table_number = join_order_member.table_no;
let access_method_kind = access_methods_arena.borrow()[best_access_methods[i]]
@@ -220,7 +236,8 @@ fn use_indexes(
if index.is_some() || i == 0 {
Operation::Scan { iter_dir, index }
} else {
// Try to construct ephemeral index since it's going to be better than a scan for non-outermost tables.
// This branch means we have a full table scan for a non-outermost table.
// Try to construct an ephemeral index since it's going to be better than a scan.
let table_constraints = constraints_per_table
.iter()
.find(|c| c.table_no == table_number);