hareshkh opened a new pull request, #18077:
URL: https://github.com/apache/datafusion/pull/18077
## Which issue does this PR close?
Related to #18072
Related to #17294
## Rationale for this change
Fix ambiguous column names in substrait conversion as a result of literals
before and after a join being assigned the same name.
More information in the issue, but say you have a NULL literal before a join
called "column1" and then you create a new NULL column after the join called
column2, you would get an ambiguous column name errors like.
```
Error: SchemaError(AmbiguousReference { field: Column { relation: Some(Bare
{ table: "left" }), name: "UTF8(NULL)" } }, Some(""))
```
## What changes are included in this PR?
Simply alias all literals as they're converted to have a UUID name.
## Are these changes tested?
Yes.
Tested by using substrait-java with this query
```
./isthmus-cli/build/graal/isthmus --create "create table A (a int); create
table B (a int, c int); create table C (a int, d int)" "select t.*, C.d,
CAST(NULL AS VARCHAR) as e from (select a, CAST(NULL AS VARCHAR) as c from A
UNION ALL select a, c from B) t LEFT JOIN C ON t.a = C.a"
```
## Are there any user-facing changes?
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