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new 48cc4c8af3 Optimize planning for projected nested union (#18713)
48cc4c8af3 is described below
commit 48cc4c8af3a5ad500a44c8625ea44d6b4827af1e
Author: Vedic Chawla <[email protected]>
AuthorDate: Tue Nov 25 19:39:26 2025 +0530
Optimize planning for projected nested union (#18713)
## Which issue does this PR close?
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- part of #17261.
## Rationale for this change
as explained in
https://github.com/apache/datafusion/issues/17261#issuecomment-3529432027
and discussion in the above mentioned issue
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in the issue then this section is not needed.
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## What changes are included in this PR?
Projected Nested Union are now merged with their parent union.
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PR.
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## Are these changes tested?
Tested it by Github CI. Works for the scenario discussed in the above
mentioned issue.
```
> explain analyze (SELECT c0, 1 as c1, 2 as c2, 3 as c3, 4 as c4, 5 as c5,
6 as c6, 7 as c7, 8 as c8, 9 as c9 FROM t1 ORDER BY c0)
UNION ALL
(SELECT 0 as c0, c1, 2 as c2, 3 as c3, 4 as c4, 5 as c5, 6 as c6, 7 as c7,
8 as c8, 9 as c9 FROM t1 ORDER BY c1)
UNION ALL
(SELECT 0 as c0, 1 as c1, c2, 3 as c3, 4 as c4, 5 as c5, 6 as c6, 7 as c7,
8 as c8, 9 as c9 FROM t1 ORDER BY c2)
UNION ALL
(SELECT 0 as c0, 1 as c1, 2 as c2, c3, 4 as c4, 5 as c5, 6 as c6, 7 as c7,
8 as c8, 9 as c9 FROM t1 ORDER BY c3)
UNION ALL
(SELECT 0 as c0, 1 as c1, 2 as c2, 3 as c3, c4, 5 as c5, 6 as c6, 7 as c7,
8 as c8, 9 as c9 FROM t1 ORDER BY c4)
UNION ALL
(SELECT 0 as c0, 1 as c1, 2 as c2, 3 as c3, 4 as c4, c5, 6 as c6, 7 as c7,
8 as c8, 9 as c9 FROM t1 ORDER BY c5)
UNION ALL
(SELECT 0 as c0, 1 as c1, 2 as c2, 3 as c3, 4 as c4, 5 as c5, c6, 7 as c7,
8 as c8, 9 as c9 FROM t1 ORDER BY c6)
UNION ALL
(SELECT 0 as c0, 1 as c1, 2 as c2, 3 as c3, 4 as c4, 5 as c5, 6 as c6, c7,
8 as c8, 9 as c9 FROM t1 ORDER BY c7)
UNION ALL
(SELECT 0 as c0, 1 as c1, 2 as c2, 3 as c3, 4 as c4, 5 as c5, 6 as c6, 7 as
c7, c8, 9 as c9 FROM t1 ORDER BY c8)
UNION ALL
(SELECT 0 as c0, 1 as c1, 2 as c2, 3 as c3, 4 as c4, 5 as c5, 6 as c6, 7 as
c7, 8 as c8, c9 FROM t1 ORDER BY c9)
ORDER BY c0, c1, c2, c3, c4, c5, c6, c7, c8, c9;
+-------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
[...]
| plan_type | plan
[...]
+-------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
[...]
| Plan with Metrics | SortPreservingMergeExec: [c0@0 ASC NULLS LAST, c1@1
ASC NULLS LAST, c2@2 ASC NULLS LAST, c3@3 ASC NULLS LAST, c4@4 ASC NULLS LAST,
c5@5 ASC NULLS LAST, c6@6 ASC NULLS LAST, c7@7 ASC NULLS LAST, c8@8 ASC NULLS
LAST, c9@9 ASC NULLS LAST], metrics=[output_rows=0, elapsed_compute=3.817µs,
output_bytes=0.0 B, output_batches=0]
[...]
| | UnionExec, metrics=[output_rows=0,
elapsed_compute=345.775µs, output_bytes=0.0 B, output_batches=0]
[...]
| | SortExec: expr=[c0@0 ASC NULLS LAST],
preserve_partitioning=[false], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_batches=0, spill_count=0, spilled_bytes=0.0 B,
spilled_rows=0, batches_split=0]
[...]
| | ProjectionExec: expr=[CAST(c0@0 AS
Decimal128(20, 0)) as c0, CAST(1 AS Decimal128(20, 0)) as c1, CAST(2 AS
Decimal128(20, 0)) as c2, CAST(3 AS Decimal128(20, 0)) as c3, CAST(4 AS
Decimal128(20, 0)) as c4, CAST(5 AS Decimal128(20, 0)) as c5, CAST(6 AS
Decimal128(20, 0)) as c6, CAST(7 AS Decimal128(20, 0)) as c7, CAST(8 AS
Decimal128(20, 0)) as c8, CAST(9 AS Decimal128(20, 0)) as c9],
metrics=[output_rows=0, elapsed_compute=1ns, output_bytes=0.0 B, output_bat
[...]
| | DataSourceExec: partitions=1,
partition_sizes=[0], metrics=[]
[...]
| | SortExec: expr=[c1@1 ASC NULLS LAST],
preserve_partitioning=[false], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_batches=0, spill_count=0, spilled_bytes=0.0 B,
spilled_rows=0, batches_split=0]
[...]
| | ProjectionExec: expr=[CAST(0 AS Decimal128(20,
0)) as c0, CAST(c1@0 AS Decimal128(20, 0)) as c1, CAST(2 AS Decimal128(20, 0))
as c2, CAST(3 AS Decimal128(20, 0)) as c3, CAST(4 AS Decimal128(20, 0)) as c4,
CAST(5 AS Decimal128(20, 0)) as c5, CAST(6 AS Decimal128(20, 0)) as c6, CAST(7
AS Decimal128(20, 0)) as c7, CAST(8 AS Decimal128(20, 0)) as c8, CAST(9 AS
Decimal128(20, 0)) as c9], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_bat [...]
| | DataSourceExec: partitions=1,
partition_sizes=[0], metrics=[]
[...]
| | SortExec: expr=[c2@2 ASC NULLS LAST],
preserve_partitioning=[false], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_batches=0, spill_count=0, spilled_bytes=0.0 B,
spilled_rows=0, batches_split=0]
[...]
| | ProjectionExec: expr=[CAST(0 AS Decimal128(20,
0)) as c0, CAST(1 AS Decimal128(20, 0)) as c1, CAST(c2@0 AS Decimal128(20, 0))
as c2, CAST(3 AS Decimal128(20, 0)) as c3, CAST(4 AS Decimal128(20, 0)) as c4,
CAST(5 AS Decimal128(20, 0)) as c5, CAST(6 AS Decimal128(20, 0)) as c6, CAST(7
AS Decimal128(20, 0)) as c7, CAST(8 AS Decimal128(20, 0)) as c8, CAST(9 AS
Decimal128(20, 0)) as c9], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_bat [...]
| | DataSourceExec: partitions=1,
partition_sizes=[0], metrics=[]
[...]
| | SortExec: expr=[c3@3 ASC NULLS LAST],
preserve_partitioning=[false], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_batches=0, spill_count=0, spilled_bytes=0.0 B,
spilled_rows=0, batches_split=0]
[...]
| | ProjectionExec: expr=[CAST(0 AS Decimal128(20,
0)) as c0, CAST(1 AS Decimal128(20, 0)) as c1, CAST(2 AS Decimal128(20, 0)) as
c2, CAST(c3@0 AS Decimal128(20, 0)) as c3, CAST(4 AS Decimal128(20, 0)) as c4,
CAST(5 AS Decimal128(20, 0)) as c5, CAST(6 AS Decimal128(20, 0)) as c6, CAST(7
AS Decimal128(20, 0)) as c7, CAST(8 AS Decimal128(20, 0)) as c8, CAST(9 AS
Decimal128(20, 0)) as c9], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_bat [...]
| | DataSourceExec: partitions=1,
partition_sizes=[0], metrics=[]
[...]
| | SortExec: expr=[c4@4 ASC NULLS LAST],
preserve_partitioning=[false], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_batches=0, spill_count=0, spilled_bytes=0.0 B,
spilled_rows=0, batches_split=0]
[...]
| | ProjectionExec: expr=[CAST(0 AS Decimal128(20,
0)) as c0, CAST(1 AS Decimal128(20, 0)) as c1, CAST(2 AS Decimal128(20, 0)) as
c2, CAST(3 AS Decimal128(20, 0)) as c3, CAST(c4@0 AS Decimal128(20, 0)) as c4,
CAST(5 AS Decimal128(20, 0)) as c5, CAST(6 AS Decimal128(20, 0)) as c6, CAST(7
AS Decimal128(20, 0)) as c7, CAST(8 AS Decimal128(20, 0)) as c8, CAST(9 AS
Decimal128(20, 0)) as c9], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_bat [...]
| | DataSourceExec: partitions=1,
partition_sizes=[0], metrics=[]
[...]
| | SortExec: expr=[c5@5 ASC NULLS LAST],
preserve_partitioning=[false], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_batches=0, spill_count=0, spilled_bytes=0.0 B,
spilled_rows=0, batches_split=0]
[...]
| | ProjectionExec: expr=[CAST(0 AS Decimal128(20,
0)) as c0, CAST(1 AS Decimal128(20, 0)) as c1, CAST(2 AS Decimal128(20, 0)) as
c2, CAST(3 AS Decimal128(20, 0)) as c3, CAST(4 AS Decimal128(20, 0)) as c4,
CAST(c5@0 AS Decimal128(20, 0)) as c5, CAST(6 AS Decimal128(20, 0)) as c6,
CAST(7 AS Decimal128(20, 0)) as c7, CAST(8 AS Decimal128(20, 0)) as c8, CAST(9
AS Decimal128(20, 0)) as c9], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_bat [...]
| | DataSourceExec: partitions=1,
partition_sizes=[0], metrics=[]
[...]
| | SortExec: expr=[c6@6 ASC NULLS LAST],
preserve_partitioning=[false], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_batches=0, spill_count=0, spilled_bytes=0.0 B,
spilled_rows=0, batches_split=0]
[...]
| | ProjectionExec: expr=[CAST(0 AS Decimal128(20,
0)) as c0, CAST(1 AS Decimal128(20, 0)) as c1, CAST(2 AS Decimal128(20, 0)) as
c2, CAST(3 AS Decimal128(20, 0)) as c3, CAST(4 AS Decimal128(20, 0)) as c4,
CAST(5 AS Decimal128(20, 0)) as c5, CAST(c6@0 AS Decimal128(20, 0)) as c6,
CAST(7 AS Decimal128(20, 0)) as c7, CAST(8 AS Decimal128(20, 0)) as c8, CAST(9
AS Decimal128(20, 0)) as c9], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_bat [...]
| | DataSourceExec: partitions=1,
partition_sizes=[0], metrics=[]
[...]
| | SortExec: expr=[c7@7 ASC NULLS LAST],
preserve_partitioning=[false], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_batches=0, spill_count=0, spilled_bytes=0.0 B,
spilled_rows=0, batches_split=0]
[...]
| | ProjectionExec: expr=[CAST(0 AS Decimal128(20,
0)) as c0, CAST(1 AS Decimal128(20, 0)) as c1, CAST(2 AS Decimal128(20, 0)) as
c2, CAST(3 AS Decimal128(20, 0)) as c3, CAST(4 AS Decimal128(20, 0)) as c4,
CAST(5 AS Decimal128(20, 0)) as c5, CAST(6 AS Decimal128(20, 0)) as c6,
CAST(c7@0 AS Decimal128(20, 0)) as c7, CAST(8 AS Decimal128(20, 0)) as c8,
CAST(9 AS Decimal128(20, 0)) as c9], metrics=[output_rows=0,
elapsed_compute=1ns, output_bytes=0.0 B, output_bat [...]
| | DataSourceExec: partitions=1,
partition_sizes=[0], metrics=[]
[...]
| | SortExec: expr=[c8@8 ASC NULLS LAST],
preserve_partitioning=[false], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_batches=0, spill_count=0, spilled_bytes=0.0 B,
spilled_rows=0, batches_split=0]
[...]
| | ProjectionExec: expr=[CAST(0 AS Decimal128(20,
0)) as c0, CAST(1 AS Decimal128(20, 0)) as c1, CAST(2 AS Decimal128(20, 0)) as
c2, CAST(3 AS Decimal128(20, 0)) as c3, CAST(4 AS Decimal128(20, 0)) as c4,
CAST(5 AS Decimal128(20, 0)) as c5, CAST(6 AS Decimal128(20, 0)) as c6, CAST(7
AS Decimal128(20, 0)) as c7, CAST(c8@0 AS Decimal128(20, 0)) as c8, CAST(9 AS
Decimal128(20, 0)) as c9], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_bat [...]
| | DataSourceExec: partitions=1,
partition_sizes=[0], metrics=[]
[...]
| | SortExec: expr=[c9@9 ASC NULLS LAST],
preserve_partitioning=[false], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_batches=0, spill_count=0, spilled_bytes=0.0 B,
spilled_rows=0, batches_split=0]
[...]
| | ProjectionExec: expr=[CAST(0 AS Decimal128(20,
0)) as c0, CAST(1 AS Decimal128(20, 0)) as c1, CAST(2 AS Decimal128(20, 0)) as
c2, CAST(3 AS Decimal128(20, 0)) as c3, CAST(4 AS Decimal128(20, 0)) as c4,
CAST(5 AS Decimal128(20, 0)) as c5, CAST(6 AS Decimal128(20, 0)) as c6, CAST(7
AS Decimal128(20, 0)) as c7, CAST(8 AS Decimal128(20, 0)) as c8, CAST(c9@0 AS
Decimal128(20, 0)) as c9], metrics=[output_rows=0, elapsed_compute=1ns,
output_bytes=0.0 B, output_bat [...]
| | DataSourceExec: partitions=1,
partition_sizes=[0], metrics=[]
[...]
| |
[...]
+-------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
[...]
```
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1. Prevent the code from being accidentally broken by subsequent changes
2. Serve as another way to document the expected behavior of the code
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## Are there any user-facing changes?
Yes? logical plans for some queries should be different(and better) now.
No syntax changes.
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updated before approving the PR.
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---
datafusion/optimizer/src/optimize_unions.rs | 55 ++++++++++++++++++++++++++++-
1 file changed, 54 insertions(+), 1 deletion(-)
diff --git a/datafusion/optimizer/src/optimize_unions.rs
b/datafusion/optimizer/src/optimize_unions.rs
index cfabd512b4..23a6fe95e5 100644
--- a/datafusion/optimizer/src/optimize_unions.rs
+++ b/datafusion/optimizer/src/optimize_unions.rs
@@ -21,7 +21,7 @@ use crate::{OptimizerConfig, OptimizerRule};
use datafusion_common::tree_node::Transformed;
use datafusion_common::Result;
use datafusion_expr::expr_rewriter::coerce_plan_expr_for_schema;
-use datafusion_expr::{Distinct, LogicalPlan, Union};
+use datafusion_expr::{Distinct, LogicalPlan, Projection, Union};
use itertools::Itertools;
use std::sync::Arc;
@@ -105,6 +105,38 @@ fn extract_plans_from_union(plan: Arc<LogicalPlan>) ->
Vec<LogicalPlan> {
.into_iter()
.map(Arc::unwrap_or_clone)
.collect::<Vec<_>>(),
+ // While unnesting, unwrap a Projection whose input is a nested Union,
+ // flatten the inner Union, and push the same Projection down onto
+ // each of the nested Union’s children.
+ //
+ // Example:
+ // Union { Projection { Union { plan1, plan2 } }, plan3 }
+ // => Union { Projection { plan1 }, Projection { plan2 }, plan3 }
+ LogicalPlan::Projection(Projection {
+ expr,
+ input,
+ schema,
+ ..
+ }) => match Arc::unwrap_or_clone(input) {
+ LogicalPlan::Union(Union { inputs, .. }) => inputs
+ .into_iter()
+ .map(Arc::unwrap_or_clone)
+ .map(|plan| {
+ LogicalPlan::Projection(
+ Projection::try_new_with_schema(
+ expr.clone(),
+ Arc::new(plan),
+ Arc::clone(&schema),
+ )
+ .unwrap(),
+ )
+ })
+ .collect::<Vec<_>>(),
+
+ plan => vec![LogicalPlan::Projection(
+ Projection::try_new_with_schema(expr, Arc::new(plan),
schema).unwrap(),
+ )],
+ },
plan => vec![plan],
}
}
@@ -331,6 +363,27 @@ mod tests {
")
}
+ #[test]
+ fn eliminate_nested_union_in_projection() -> Result<()> {
+ let plan_builder = table_scan(Some("table"), &schema(), None)?;
+
+ let plan = plan_builder
+ .clone()
+ .union(plan_builder.clone().build()?)?
+ .project(vec![col("id").alias("table_id"), col("key"),
col("value")])?
+ .union(plan_builder.build()?)?
+ .build()?;
+
+ assert_optimized_plan_equal!(plan, @r"
+ Union
+ Projection: id AS table_id, key, value
+ TableScan: table
+ Projection: id AS table_id, key, value
+ TableScan: table
+ TableScan: table
+ ")
+ }
+
#[test]
fn eliminate_nested_union_with_type_cast_projection() -> Result<()> {
let table_1 = table_scan(
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