refactor: make join projection pushdown schema-aware via ColumnIndex/… (#23185)

## Which issue does this PR close?

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- Closes #23010 

## Rationale for this change

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in the issue then this section is not needed.
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your changes and offer better suggestions for fixes.
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`try_pushdown_through_join`
(`datafusion/physical-plan/src/projection.rs`)
decided whether each projected join-output column belonged to the left
or right
child by comparing its output index against the left child's field count
(`join_table_borders`) — i.e. it assumed the join output is a plain
`left ++ right` concatenation.

That assumption does not hold for all join types. A `LeftMark` /
`RightMark`
join appends a synthetic `mark` boolean column that has `JoinSide::None`
and
originates from neither child, so reasoning from output position can
route the
`mark` column to the wrong child. This is the panic that #22902 worked
around by
**disabling** projection pushdown for `LeftMark` / `RightMark` in
`HashJoinExec`
and `NestedLoopJoinExec` — correct, but it left the helper reasoning
from output
position rather than from the join's actual output-origin contract.


## What changes are included in this PR?

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is sometimes worth providing a summary of the individual changes in this
PR.
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- Thread the join's output-origin metadata (`&[ColumnIndex]`, already
computed by
  `build_join_schema`) into `try_pushdown_through_join`.
- Replace the output-position split (`join_table_borders` +
  `index < left_field_count`) with grouping by `ColumnIndex.side`:
- `Left` / `Right` columns are collected per child using the
child-relative
    `ColumnIndex.index`;
- a `JoinSide::None` (synthetic, e.g. `mark`) column makes the pushdown
decline
(`Ok(None)`), so the projection is embedded into the join instead — no
panic,
    no mis-routing.
- Remove the `LeftMark | RightMark` bypass from
  `HashJoinExec::try_swapping_with_projection` and
  `NestedLoopJoinExec::try_swapping_with_projection`; they now call
  `try_pushdown_through_join` uniformly.
- The shared helpers used by cross / symmetric-hash / sort-merge join
pushdown
  (`new_join_children`, `join_table_borders`, `join_allows_pushdown`,
`update_join_on`, `update_join_filter`) keep their signatures. The
side-grouped
  path uses a new private `new_join_children_from_groups` and reuses
`update_join_on` / `update_join_filter` with a zero column-index offset
(the
  groups already carry child-relative indices).

## Are these changes tested?

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Yes.

- New `subquery.slt` cases place a subset/reordering projection over a
mark join
— hash `LeftMark` (`IN` under `OR`), negated mark (`NOT EXISTS` under
`OR`),
and nested-loop mark (non-equi correlated) — asserting both the query
result
  and the `EXPLAIN` plan shape.
- Existing coverage is preserved: `cargo test -p
datafusion-physical-plan
projection` (incl. the filter-pushdown and `join_table_borders` unit
tests),
  the join `*.slt` suite, and `subquery.slt` all pass.
- `cargo clippy -p datafusion-physical-plan -- -D warnings` and `cargo
fmt --all`
  are clean.

## Are there any user-facing changes?

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updated before approving the PR.
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change` label.
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No behavior change: the produced physical plans are unchanged for the
supported
cases (mark joins keep falling back to the same embedded-projection plan
as
before, regular joins push down as before).

One signature change to a `pub` helper: `try_pushdown_through_join`
gains a
`column_indices: &[ColumnIndex]` parameter (all in-tree callers are
updated). If
the project treats this helper as part of the public API surface, please
add the
`api change` label.

---------

Signed-off-by: Jiawei Zhao <Phoenix500526@163.com>
Co-authored-by: Andrew Lamb <andrew@nerdnetworks.org>

Author: Phoenix500526

datafusion/physical-plan/src/joins/hash_join/exec.rs

@@ -49,7 +49,7 @@ use crate::joins::{JoinOn, JoinOnRef, PartitionMode, SharedBitmapBuilder};
 use crate::metrics::{Count, MetricBuilder, MetricCategory};
 use crate::projection::{
     EmbeddedProjection, JoinData, ProjectionExec, try_embed_projection,
-    try_pushdown_through_join,
+    try_pushdown_through_join_with_column_indices,
 };
 use crate::repartition::REPARTITION_RANDOM_STATE;
 use crate::statistics::{ChildStats, StatisticsArgs};
@@ -1564,23 +1564,21 @@ impl ExecutionPlan for HashJoinExec {
             return Ok(None);
         }
 
-        // TODO: split by `col`/`JoinSide` instead so mark joins can also push down to children.
         let schema = self.schema();
-        if !matches!(self.join_type(), JoinType::LeftMark | JoinType::RightMark)
-            && let Some(JoinData {
-                projected_left_child,
-                projected_right_child,
-                join_filter,
-                join_on,
-            }) = try_pushdown_through_join(
-                projection,
-                self.left(),
-                self.right(),
-                self.on(),
-                &schema,
-                self.filter(),
-            )?
-        {
+        if let Some(JoinData {
+            projected_left_child,
+            projected_right_child,
+            join_filter,
+            join_on,
+        }) = try_pushdown_through_join_with_column_indices(
+            projection,
+            self.left(),
+            self.right(),
+            self.on(),
+            &schema,
+            self.filter(),
+            self.column_indices.as_slice(),
+        )? {
             self.builder()
                 .with_new_children(vec![
                     Arc::new(projected_left_child),

datafusion/physical-plan/src/joins/nested_loop_join.rs

@@ -40,7 +40,7 @@ use crate::metrics::{
 };
 use crate::projection::{
     EmbeddedProjection, JoinData, ProjectionExec, try_embed_projection,
-    try_pushdown_through_join,
+    try_pushdown_through_join_with_column_indices,
 };
 use crate::statistics::{ChildStats, StatisticsArgs};
 use crate::{
@@ -741,23 +741,21 @@ impl ExecutionPlan for NestedLoopJoinExec {
             return Ok(None);
         }
 
-        // TODO: split by `col`/`JoinSide` instead so mark joins can also push down to children.
         let schema = self.schema();
-        if !matches!(self.join_type(), JoinType::LeftMark | JoinType::RightMark)
-            && let Some(JoinData {
-                projected_left_child,
-                projected_right_child,
-                join_filter,
-                ..
-            }) = try_pushdown_through_join(
-                projection,
-                self.left(),
-                self.right(),
-                &[],
-                &schema,
-                self.filter(),
-            )?
-        {
+        if let Some(JoinData {
+            projected_left_child,
+            projected_right_child,
+            join_filter,
+            ..
+        }) = try_pushdown_through_join_with_column_indices(
+            projection,
+            self.left(),
+            self.right(),
+            &[],
+            &schema,
+            self.filter(),
+            self.column_indices.as_slice(),
+        )? {
             Ok(Some(Arc::new(NestedLoopJoinExec::try_new(
                 Arc::new(projected_left_child),
                 Arc::new(projected_right_child),

datafusion/physical-plan/src/joins/symmetric_hash_join.rs

@@ -47,8 +47,7 @@ use crate::joins::utils::{
     matchable_join_keys, symmetric_join_output_partitioning, update_hash,
 };
 use crate::projection::{
-    ProjectionExec, join_allows_pushdown, join_table_borders, new_join_children,
-    physical_to_column_exprs, update_join_filter, update_join_on,
+    JoinData, ProjectionExec, try_pushdown_through_join_with_column_indices,
 };
 use crate::stream::EmptyRecordBatchStream;
 use crate::{
@@ -598,69 +597,36 @@ impl ExecutionPlan for SymmetricHashJoinExec {
         &self,
         projection: &ProjectionExec,
     ) -> Result<Option<Arc<dyn ExecutionPlan>>> {
-        // Convert projected PhysicalExpr's to columns. If not possible, we cannot proceed.
-        let Some(projection_as_columns) = physical_to_column_exprs(projection.expr())
-        else {
-            return Ok(None);
-        };
-
-        let (far_right_left_col_ind, far_left_right_col_ind) = join_table_borders(
-            self.left().schema().fields().len(),
-            &projection_as_columns,
-        );
-
-        if !join_allows_pushdown(
-            &projection_as_columns,
-            &self.schema(),
-            far_right_left_col_ind,
-            far_left_right_col_ind,
-        ) {
-            return Ok(None);
-        }
-
-        let Some(new_on) = update_join_on(
-            &projection_as_columns[0..=far_right_left_col_ind as _],
-            &projection_as_columns[far_left_right_col_ind as _..],
-            self.on(),
-            self.left().schema().fields().len(),
-        ) else {
-            return Ok(None);
-        };
-
-        let new_filter = if let Some(filter) = self.filter() {
-            match update_join_filter(
-                &projection_as_columns[0..=far_right_left_col_ind as _],
-                &projection_as_columns[far_left_right_col_ind as _..],
-                filter,
-                self.left().schema().fields().len(),
-            ) {
-                Some(updated_filter) => Some(updated_filter),
-                None => return Ok(None),
-            }
-        } else {
-            None
-        };
-
-        let (new_left, new_right) = new_join_children(
-            &projection_as_columns,
-            far_right_left_col_ind,
-            far_left_right_col_ind,
+        let schema = self.schema();
+        if let Some(JoinData {
+            projected_left_child,
+            projected_right_child,
+            join_filter,
+            join_on,
+        }) = try_pushdown_through_join_with_column_indices(
+            projection,
             self.left(),
             self.right(),
-        )?;
-
-        SymmetricHashJoinExec::try_new(
-            Arc::new(new_left),
-            Arc::new(new_right),
-            new_on,
-            new_filter,
-            self.join_type(),
-            self.null_equality(),
-            self.right().output_ordering().cloned(),
-            self.left().output_ordering().cloned(),
-            self.partition_mode(),
-        )
-        .map(|e| Some(Arc::new(e) as _))
+            self.on(),
+            &schema,
+            self.filter(),
+            self.column_indices.as_slice(),
+        )? {
+            SymmetricHashJoinExec::try_new(
+                Arc::new(projected_left_child),
+                Arc::new(projected_right_child),
+                join_on,
+                join_filter,
+                self.join_type(),
+                self.null_equality(),
+                self.right().output_ordering().cloned(),
+                self.left().output_ordering().cloned(),
+                self.partition_mode(),
+            )
+            .map(|e| Some(Arc::new(e) as _))
+        } else {
+            Ok(None)
+        }
     }
 }