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Return enum instead of bool for better documentation

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This commit is contained in:
jussisaurio
2024-08-25 11:15:47 +03:00
parent d653f550e2
commit d1059da9f1
2 changed files with 52 additions and 31 deletions
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82
core/translate/optimizer.rs
View File

@@ -16,8 +16,9 @@ pub fn optimize_plan(mut select_plan: Plan) -> Result<Plan> {
&mut select_plan.root_operator,
&select_plan.referenced_tables,
)?;
let viable_plan = eliminate_constants(&mut select_plan.root_operator)?;
if !viable_plan {
if eliminate_constants(&mut select_plan.root_operator)?
== ConstantConditionEliminationResult::ImpossibleCondition
{
return Ok(Plan {
root_operator: Operator::Nothing,
referenced_tables: vec![],
@@ -122,9 +123,15 @@ fn use_indexes(
}
}
#[derive(Debug, PartialEq, Clone)]
enum ConstantConditionEliminationResult {
Continue,
ImpossibleCondition,
}
// removes predicates that are always true
// returns false if there is an impossible predicate that is always false
fn eliminate_constants(operator: &mut Operator) -> Result<bool> {
// returns a ConstantEliminationResult indicating whether any predicates are always false
fn eliminate_constants(operator: &mut Operator) -> Result<ConstantConditionEliminationResult> {
match operator {
Operator::Filter {
source, predicates, ..
@@ -135,7 +142,7 @@ fn eliminate_constants(operator: &mut Operator) -> Result<bool> {
if predicate.is_always_true()? {
predicates.remove(i);
} else if predicate.is_always_false()? {
return Ok(false);
return Ok(ConstantConditionEliminationResult::ImpossibleCondition);
} else {
i += 1;
}
@@ -148,7 +155,7 @@ fn eliminate_constants(operator: &mut Operator) -> Result<bool> {
eliminate_constants(source)?;
}
return Ok(true);
return Ok(ConstantConditionEliminationResult::Continue);
}
Operator::Join {
left,
@@ -157,15 +164,19 @@ fn eliminate_constants(operator: &mut Operator) -> Result<bool> {
outer,
..
} => {
if !eliminate_constants(left)? {
return Ok(false);
if eliminate_constants(left)? == ConstantConditionEliminationResult::ImpossibleCondition
{
return Ok(ConstantConditionEliminationResult::ImpossibleCondition);
}
if !eliminate_constants(right)? && !*outer {
return Ok(false);
if eliminate_constants(right)?
== ConstantConditionEliminationResult::ImpossibleCondition
&& !*outer
{
return Ok(ConstantConditionEliminationResult::ImpossibleCondition);
}
if predicates.is_none() {
return Ok(true);
return Ok(ConstantConditionEliminationResult::Continue);
}
let predicates = predicates.as_mut().unwrap();
@@ -176,20 +187,22 @@ fn eliminate_constants(operator: &mut Operator) -> Result<bool> {
if predicate.is_always_true()? {
predicates.remove(i);
} else if predicate.is_always_false()? && !*outer {
return Ok(false);
return Ok(ConstantConditionEliminationResult::ImpossibleCondition);
} else {
i += 1;
}
}
return Ok(true);
return Ok(ConstantConditionEliminationResult::Continue);
}
Operator::Aggregate { source, .. } => {
let ok = eliminate_constants(source)?;
if !ok {
if eliminate_constants(source)?
== ConstantConditionEliminationResult::ImpossibleCondition
{
*source = Box::new(Operator::Nothing);
}
return Ok(ok);
// Aggregation operator can return a row even if the source is empty e.g. count(1) from users where 0
return Ok(ConstantConditionEliminationResult::Continue);
}
Operator::SeekRowid {
rowid_predicate,
@@ -203,7 +216,7 @@ fn eliminate_constants(operator: &mut Operator) -> Result<bool> {
if predicate.is_always_true()? {
predicates.remove(i);
} else if predicate.is_always_false()? {
return Ok(false);
return Ok(ConstantConditionEliminationResult::ImpossibleCondition);
} else {
i += 1;
}
@@ -211,31 +224,38 @@ fn eliminate_constants(operator: &mut Operator) -> Result<bool> {
}
if rowid_predicate.is_always_false()? {
return Ok(false);
return Ok(ConstantConditionEliminationResult::ImpossibleCondition);
}
return Ok(true);
return Ok(ConstantConditionEliminationResult::Continue);
}
Operator::Limit { source, .. } => {
let ok = eliminate_constants(source)?;
if !ok {
let constant_elimination_result = eliminate_constants(source)?;
if constant_elimination_result
== ConstantConditionEliminationResult::ImpossibleCondition
{
*operator = Operator::Nothing;
}
return Ok(ok);
return Ok(constant_elimination_result);
}
Operator::Order { source, .. } => {
let ok = eliminate_constants(source)?;
if !ok {
if eliminate_constants(source)?
== ConstantConditionEliminationResult::ImpossibleCondition
{
*operator = Operator::Nothing;
return Ok(ConstantConditionEliminationResult::ImpossibleCondition);
}
return Ok(true);
return Ok(ConstantConditionEliminationResult::Continue);
}
Operator::Projection { source, .. } => {
let ok = eliminate_constants(source)?;
if !ok {
if eliminate_constants(source)?
== ConstantConditionEliminationResult::ImpossibleCondition
{
*operator = Operator::Nothing;
return Ok(ConstantConditionEliminationResult::ImpossibleCondition);
}
return Ok(ok);
return Ok(ConstantConditionEliminationResult::Continue);
}
Operator::Scan { predicates, .. } => {
if let Some(ps) = predicates {
@@ -245,7 +265,7 @@ fn eliminate_constants(operator: &mut Operator) -> Result<bool> {
if predicate.is_always_true()? {
ps.remove(i);
} else if predicate.is_always_false()? {
return Ok(false);
return Ok(ConstantConditionEliminationResult::ImpossibleCondition);
} else {
i += 1;
}
@@ -255,9 +275,9 @@ fn eliminate_constants(operator: &mut Operator) -> Result<bool> {
*predicates = None;
}
}
return Ok(true);
return Ok(ConstantConditionEliminationResult::Continue);
}
Operator::Nothing => return Ok(true),
Operator::Nothing => return Ok(ConstantConditionEliminationResult::Continue),
}
}

1
core/translate/plan.rs
View File

@@ -8,6 +8,7 @@ use sqlite3_parser::ast;
use crate::{function::AggFunc, schema::BTreeTable, util::normalize_ident, Result};
#[derive(Debug)]
pub struct Plan {
pub root_operator: Operator,
pub referenced_tables: Vec<(Rc<BTreeTable>, String)>,