Phoenix500526 opened a new pull request, #23185:
URL: https://github.com/apache/datafusion/pull/23185
## Which issue does this PR close?
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- Closes #23010
## Rationale for this change
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the issue then this section is not needed.
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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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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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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.
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