Jeadie opened a new issue, #24446:
URL: https://github.com/apache/datafusion/issues/24446
### Describe the bug
Consider `a UNION ALL (b UNION a)`, that becomes a plan
```
Union
a
Distinct::All
Union
b
a
```
This will get incorrectly unparsed as `SELECT a UNION SELECT b UNION SELECT
a`.
All union operations are now distinct, instead of correctly preserving the
true per node nature. Root cause: traversing the inner `Distinct::All(Union)`
sets `QueryBuilder::distinct_union = true` globally. All subsequent Unions are
considered distinct during unpausing the query. A single, query-level boolean
is insufficient to track `ast::SetQuantifier` for each UNION operation.
### To Reproduce
Add this example case to `datafusion/sql/tests/cases/plan_to_sql.rs` and
rerun.
```
r#"SELECT j1_string FROM j1 UNION ALL (SELECT j2_string FROM j2 UNION SELECT
j1_string FROM j1)"#,
```
### Expected behavior
**Actual**: the outer ALL is dropped.
```
SELECT a.x FROM a UNION SELECT b.x FROM b UNION SELECT a.x FROM a
```
**Expected**
```
SELECT a.x FROM a UNION ALL (SELECT b.x FROM b UNION SELECT a.x FROM a)
```
### Additional context
_No response_
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