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AsOF Join #63

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5398171
asof first iteration
jonathanc-n Jun 24, 2026
573c191
fix
jonathanc-n Jun 24, 2026
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321 changes: 272 additions & 49 deletions datafusion/physical-optimizer/src/join_selection.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -28,14 +28,16 @@ use datafusion_common::config::ConfigOptions;
use datafusion_common::error::Result;
use datafusion_common::tree_node::{Transformed, TransformedResult, TreeNode};
use datafusion_common::{internal_err, JoinSide, JoinType};
use datafusion_expr::Operator;
use datafusion_expr_common::sort_properties::SortProperties;
use datafusion_physical_expr::expressions::Column;
use datafusion_physical_expr::expressions::{BinaryExpr, Column};
use datafusion_physical_expr::LexOrdering;
use datafusion_physical_expr::PhysicalExprRef;
use datafusion_physical_plan::execution_plan::EmissionType;
use datafusion_physical_plan::joins::utils::ColumnIndex;
use datafusion_physical_plan::joins::utils::{ColumnIndex, JoinFilter, JoinOn};
use datafusion_physical_plan::joins::{
CrossJoinExec, HashJoinExec, NestedLoopJoinExec, PartitionMode,
StreamJoinPartitionMode, SymmetricHashJoinExec,
AsOfJoinCondition, AsOfJoinExec, CrossJoinExec, HashJoinExec, NestedLoopJoinExec,
PartitionMode, StreamJoinPartitionMode, SymmetricHashJoinExec,
};
use datafusion_physical_plan::{ExecutionPlan, ExecutionPlanProperties};
use std::sync::Arc;
Expand Down Expand Up @@ -256,59 +258,60 @@ fn statistical_join_selection_subrule(
collect_threshold_byte_size: usize,
collect_threshold_num_rows: usize,
) -> Result<Transformed<Arc<dyn ExecutionPlan>>> {
let transformed =
if let Some(hash_join) = plan.as_any().downcast_ref::<HashJoinExec>() {
match hash_join.partition_mode() {
PartitionMode::Auto => try_collect_left(
hash_join,
false,
collect_threshold_byte_size,
collect_threshold_num_rows,
)?
let transformed = if let Some(asof_join) = try_asof_join(&plan)? {
Some(asof_join)
} else if let Some(hash_join) = plan.as_any().downcast_ref::<HashJoinExec>() {
match hash_join.partition_mode() {
PartitionMode::Auto => try_collect_left(
hash_join,
false,
collect_threshold_byte_size,
collect_threshold_num_rows,
)?
.map_or_else(
|| partitioned_hash_join(hash_join).map(Some),
|v| Ok(Some(v)),
)?,
PartitionMode::CollectLeft => try_collect_left(hash_join, true, 0, 0)?
.map_or_else(
|| partitioned_hash_join(hash_join).map(Some),
|v| Ok(Some(v)),
)?,
PartitionMode::CollectLeft => try_collect_left(hash_join, true, 0, 0)?
.map_or_else(
|| partitioned_hash_join(hash_join).map(Some),
|v| Ok(Some(v)),
)?,
PartitionMode::Partitioned => {
let left = hash_join.left();
let right = hash_join.right();
if hash_join.join_type().supports_swap()
&& should_swap_join_order(&**left, &**right)?
{
hash_join
.swap_inputs(PartitionMode::Partitioned)
.map(Some)?
} else {
None
}
PartitionMode::Partitioned => {
let left = hash_join.left();
let right = hash_join.right();
if hash_join.join_type().supports_swap()
&& should_swap_join_order(&**left, &**right)?
{
hash_join
.swap_inputs(PartitionMode::Partitioned)
.map(Some)?
} else {
None
}
}
} else if let Some(cross_join) = plan.as_any().downcast_ref::<CrossJoinExec>() {
let left = cross_join.left();
let right = cross_join.right();
if should_swap_join_order(&**left, &**right)? {
cross_join.swap_inputs().map(Some)?
} else {
None
}
} else if let Some(nl_join) = plan.as_any().downcast_ref::<NestedLoopJoinExec>() {
let left = nl_join.left();
let right = nl_join.right();
if nl_join.join_type().supports_swap()
&& should_swap_join_order(&**left, &**right)?
{
nl_join.swap_inputs().map(Some)?
} else {
None
}
}
} else if let Some(cross_join) = plan.as_any().downcast_ref::<CrossJoinExec>() {
let left = cross_join.left();
let right = cross_join.right();
if should_swap_join_order(&**left, &**right)? {
cross_join.swap_inputs().map(Some)?
} else {
None
};
}
} else if let Some(nl_join) = plan.as_any().downcast_ref::<NestedLoopJoinExec>() {
let left = nl_join.left();
let right = nl_join.right();
if nl_join.join_type().supports_swap()
&& should_swap_join_order(&**left, &**right)?
{
nl_join.swap_inputs().map(Some)?
} else {
None
}
} else {
None
};

Ok(if let Some(transformed) = transformed {
Transformed::yes(transformed)
Expand All @@ -317,6 +320,226 @@ fn statistical_join_selection_subrule(
})
}

fn try_asof_join(
plan: &Arc<dyn ExecutionPlan>,
) -> Result<Option<Arc<dyn ExecutionPlan>>> {
if let Some(hash_join) = plan.as_any().downcast_ref::<HashJoinExec>() {
if !matches!(hash_join.join_type(), JoinType::Inner | JoinType::Left) {
return Ok(None);
}

let Some(filter) = hash_join.filter() else {
return Ok(None);
};
let Some((filter_on, asof_condition)) =
extract_asof_join_predicates(filter, hash_join.left(), hash_join.right())?
else {
return Ok(None);
};

let mut on = hash_join.on().to_vec();
on.extend(filter_on);

return Ok(Some(Arc::new(AsOfJoinExec::try_new(
Arc::clone(hash_join.left()),
Arc::clone(hash_join.right()),
on,
asof_condition,
*hash_join.join_type(),
hash_join.projection.clone(),
hash_join.null_equality(),
)?)));
}

if let Some(nl_join) = plan.as_any().downcast_ref::<NestedLoopJoinExec>() {
if !matches!(nl_join.join_type(), JoinType::Inner | JoinType::Left) {
return Ok(None);
}

let Some(filter) = nl_join.filter() else {
return Ok(None);
};
let Some((on, asof_condition)) =
extract_asof_join_predicates(filter, nl_join.left(), nl_join.right())?
else {
return Ok(None);
};

return Ok(Some(Arc::new(AsOfJoinExec::try_new(
Arc::clone(nl_join.left()),
Arc::clone(nl_join.right()),
on,
asof_condition,
*nl_join.join_type(),
nl_join.projection().cloned(),
datafusion_common::NullEquality::NullEqualsNothing,
)?)));
}

Ok(None)
}

fn extract_asof_join_predicates(
filter: &JoinFilter,
left: &Arc<dyn ExecutionPlan>,
right: &Arc<dyn ExecutionPlan>,
) -> Result<Option<(JoinOn, AsOfJoinCondition)>> {
let mut visitor = AsOfPredicateVisitor {
filter,
left,
right,
on: vec![],
asof_condition: None,
inequality_count: 0,
unsupported: false,
};
visitor.visit(filter.expression())?;

if visitor.unsupported || visitor.inequality_count != 1 {
return Ok(None);
}

Ok(visitor
.asof_condition
.map(|asof_condition| (visitor.on, asof_condition)))
}

struct AsOfPredicateVisitor<'a> {
filter: &'a JoinFilter,
left: &'a Arc<dyn ExecutionPlan>,
right: &'a Arc<dyn ExecutionPlan>,
on: JoinOn,
asof_condition: Option<AsOfJoinCondition>,
inequality_count: usize,
unsupported: bool,
}

impl AsOfPredicateVisitor<'_> {
fn visit(&mut self, expr: &PhysicalExprRef) -> Result<()> {
let Some(binary) = expr.as_any().downcast_ref::<BinaryExpr>() else {
self.unsupported = true;
return Ok(());
};

if binary.op() == &Operator::And {
self.visit(binary.left())?;
self.visit(binary.right())?;
return Ok(());
}

match binary.op() {
Operator::Eq => {
if let Some((left, right)) =
self.extract_side_pair(binary.left(), binary.right(), *binary.op())?
{
self.on.push((left, right));
} else {
self.unsupported = true;
}
}
Operator::Lt | Operator::LtEq | Operator::Gt | Operator::GtEq => {
self.inequality_count += 1;
if self.inequality_count > 1 {
self.unsupported = true;
return Ok(());
}

if let Some((left, right, op)) =
self.extract_inequality(binary.left(), binary.right(), *binary.op())?
{
self.asof_condition =
Some(AsOfJoinCondition::try_new(left, op, right)?);
} else {
self.unsupported = true;
}
}
_ => self.unsupported = true,
}

Ok(())
}

fn extract_side_pair(
&self,
left_expr: &PhysicalExprRef,
right_expr: &PhysicalExprRef,
op: Operator,
) -> Result<Option<(PhysicalExprRef, PhysicalExprRef)>> {
let Some((left_side, left_expr)) = self.filter_column(left_expr)? else {
return Ok(None);
};
let Some((right_side, right_expr)) = self.filter_column(right_expr)? else {
return Ok(None);
};

match (left_side, right_side, op) {
(JoinSide::Left, JoinSide::Right, Operator::Eq) => {
Ok(Some((left_expr, right_expr)))
}
(JoinSide::Right, JoinSide::Left, Operator::Eq) => {
Ok(Some((right_expr, left_expr)))
}
_ => Ok(None),
}
}

fn extract_inequality(
&self,
left_expr: &PhysicalExprRef,
right_expr: &PhysicalExprRef,
op: Operator,
) -> Result<Option<(PhysicalExprRef, PhysicalExprRef, Operator)>> {
let Some((left_side, left_expr)) = self.filter_column(left_expr)? else {
return Ok(None);
};
let Some((right_side, right_expr)) = self.filter_column(right_expr)? else {
return Ok(None);
};

match (left_side, right_side) {
(JoinSide::Left, JoinSide::Right) => Ok(Some((left_expr, right_expr, op))),
(JoinSide::Right, JoinSide::Left) => {
Ok(Some((right_expr, left_expr, flip_inequality(op)?)))
}
_ => Ok(None),
}
}

fn filter_column(
&self,
expr: &PhysicalExprRef,
) -> Result<Option<(JoinSide, PhysicalExprRef)>> {
let Some(column) = expr.as_any().downcast_ref::<Column>() else {
return Ok(None);
};
let Some(column_index) = self.filter.column_indices().get(column.index()) else {
return Ok(None);
};

let (schema, side) = match column_index.side {
JoinSide::Left => (self.left.schema(), JoinSide::Left),
JoinSide::Right => (self.right.schema(), JoinSide::Right),
JoinSide::None => return Ok(None),
};

let field = schema.field(column_index.index);
Ok(Some((
side,
Arc::new(Column::new(field.name(), column_index.index)) as _,
)))
}
}

fn flip_inequality(op: Operator) -> Result<Operator> {
match op {
Operator::Lt => Ok(Operator::Gt),
Operator::LtEq => Ok(Operator::GtEq),
Operator::Gt => Ok(Operator::Lt),
Operator::GtEq => Ok(Operator::LtEq),
_ => internal_err!("Can not flip non-inequality operator {op}"),
}
}

/// Pipeline-fixing join selection subrule.
pub type PipelineFixerSubrule =
dyn Fn(Arc<dyn ExecutionPlan>, &ConfigOptions) -> Result<Arc<dyn ExecutionPlan>>;
Expand Down
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