mustafasrepo opened a new pull request, #7011:
URL: https://github.com/apache/arrow-datafusion/pull/7011
# Which issue does this PR close?
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Closes #.
# Rationale for this change
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Currently Datafusion can detect ordering equivalent expressions. This
enables us to do additional optimizations during planning.
Consider query below
```sql
SELECT c9, rn1 FROM (SELECT c9,
ROW_NUMBER() OVER(ORDER BY c9 ASC) as rn1
FROM aggregate_test_100
ORDER BY c9 ASC)
ORDER BY rn1
```
It produces the following plan
```
"ProjectionExec: expr=[c9@0 as c9, ROW_NUMBER() ORDER BY
[aggregate_test_100.c9 ASC NULLS LAST] RANGE BETWEEN UNBOUNDED PRECEDING AND
CURRENT ROW@1 as rn1]",
" BoundedWindowAggExec: wdw=[ROW_NUMBER(): Ok(Field { name:
\"ROW_NUMBER()\", data_type: UInt64, nullable: false, dict_id: 0,
dict_is_ordered: false, metadata: {} }), frame: WindowFrame { units: Range,
start_bound: Preceding(UInt32(NULL)), end_bound: CurrentRow }], mode=[Sorted]",
" SortExec: expr=[c9@0 ASC NULLS LAST]",
" CsvExec: files={1 group: [[SOURCE_PATH]]}, has_header=true,
limit=None, projection=[c9]",
```
thanks to `ROW_NUMBER` result is ordered, and it can be detected by
Datafusion (last SortExec is removed since `c9 ASC`, and `rn1 ASC` describes
same ordering.).
When `ROW_NUMBER` window clause contains `PARTITION BY`, `ROW_NUMBER` result
is not globally ordered. Hence we shouldn't add its results to the ordering
equivalences. Currently this check is not done.
The query below
```sql
SELECT c9, rn1 FROM (SELECT c9,
ROW_NUMBER() OVER(PARTITION BY c1 ORDER BY c9 ASC) as rn1
FROM aggregate_test_100
ORDER BY c9 ASC)
ORDER BY rn1
```
still removes last SortExec since it thinks that `c9 ASC`, and `rn1 ASC`
describes same ordering (which is not the case).
This PR adds partition by expression check, to prevent above case hapenning.
Please note that, when different partitions are separated by ordering (all
partition by expressions are set equal with existing ordering expressions), we
can add newly introduced ordering to ordering equivalences.
# What changes are included in this PR?
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# Are these changes tested?
Yes, new tests are added
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# Are there any user-facing changes?
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