jonahgao opened a new pull request, #11738:
URL: https://github.com/apache/datafusion/pull/11738
## Which issue does this PR close?
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Closes #11704.
## Rationale for this change
Given an example query:
```sql
CREATE TABLE t1(a INT) AS VALUES(NULL);
CREATE TABLE t2(a INT) AS VALUES(NULL);
SELECT * FROM
(SELECT * FROM t1 CROSS JOIN t2)
WHERE t1.a == t2.a
AND t1.a + t2.a IS NULL;
```
The `push_down_filter` rule will convert the cross join into an inner join.
```sh
| initial_logical_plan | Projection: t1.a, t2.a
|
| | Filter: t1.a = t2.a AND t1.a +
t2.a IS NULL |
| | Projection: t1.a, t2.a
|
| | CrossJoin:
|
| | TableScan: t1
|
| | TableScan: t2
|
| logical_plan after push_down_filter | Projection: t1.a, t2.a
|
| | Projection: t1.a, t2.a
|
| | Inner Join: Filter: t2.a = t1.a
AND t1.a + t2.a IS NULL |
| | TableScan: t1
|
| | TableScan: t2
|
| extract_equijoin_predicate | Inner Join: t1.a = t2.a Filter: t1.a
+ t2.a IS NULL |
| | TableScan: t1 projection=[a]
|
| | TableScan: t2 projection=[a]
|
```
`null_equals_null` is only valid for equijoins, and when applying the
corresponding equality predicate to the cross join, null does not equal null.
So we should set `null_equals_null` to false in order to convert the cross join
to an equivalent equijoin.
## What changes are included in this PR?
<!--
There is no need to duplicate the description in the issue here but it is
sometimes worth providing a summary of the individual changes in this PR.
-->
## Are these changes tested?
Yes
## Are there any user-facing changes?
No
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