berkaysynnada commented on PR #6273:
URL:
https://github.com/apache/arrow-datafusion/pull/6273#issuecomment-1539944036
> Is there and SQL / plan level test that could be written that would cover
this code? It seems like a neat optimization but I don't fully understand how
to map it to how it would affect queries
This PR optimizes the plan such:
```
query TT
explain
SELECT c1 FROM(
(
SELECT c1 FROM t1
)
UNION ALL
(
SELECT c1a FROM t2
))
ORDER BY c1
----
logical_plan
Sort: t1.c1 ASC NULLS LAST
Union
TableScan: t1 projection=[c1]
Projection: t2.c1a AS t1.c1
TableScan: t2 projection=[c1a]
physical_plan
SortPreservingMergeExec: [c1@0 ASC NULLS LAST]
UnionExec
CsvExec: file_groups={1 group:
[[WORKSPACE_ROOT/testing/data/csv/aggregate_test_100.csv]]}, projection=[c1],
output_ordering=[c1@0 ASC NULLS LAST], has_header=true
ProjectionExec: expr=[c1a@0 as t1.c1]
CsvExec: file_groups={1 group:
[[WORKSPACE_ROOT/testing/data/csv/aggregate_test_100.csv]]}, projection=[c1a],
output_ordering=[c1a@0 ASC NULLS LAST], has_header=true
```
However, the main version results such:
```
logical_plan
Sort: t1.c1 ASC NULLS LAST
Union
TableScan: t1 projection=[c1]
Projection: t2.c1a AS t1.c1
TableScan: t2 projection=[c1a]
physical_plan
SortPreservingMergeExec: [c1@0 ASC NULLS LAST]
UnionExec
CsvExec: file_groups={1 group:
[[WORKSPACE_ROOT/testing/data/csv/aggregate_test_100.csv]]}, projection=[c1],
output_ordering=[c1@0 ASC NULLS LAST], has_header=true
SortExec: expr=[c1@0 ASC NULLS LAST]
ProjectionExec: expr=[c1a@0 as t1.c1]
CsvExec: file_groups={1 group:
[[WORKSPACE_ROOT/testing/data/csv/aggregate_test_100.csv]]}, projection=[c1a],
output_ordering=[c1a@0 ASC NULLS LAST], has_header=true
```
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