allisonwang-db opened a new pull request #32179:
URL: https://github.com/apache/spark/pull/32179
### What changes were proposed in this pull request?
This PR updated the `foundNonEqualCorrelatedPred` logic for correlated
subqueries in `CheckAnalysis` to only allow correlated equality predicates that
guarantee one-to-one mapping between inner and outer attributes, instead of all
equality predicates.
### Why are the changes needed?
To fix correctness bugs. Before this fix Spark can give wrong results for
certain correlated subqueries that pass CheckAnalysis:
Example 1:
```sql
create or replace view t1(c) as values ('a'), ('b')
create or replace view t2(c) as values ('ab'), ('abc'), ('bc')
select c, (select count(*) from t2 where t1.c = substring(t2.c, 1, 1)) from
t1
```
Correct results: [(a, 2), (b, 1)]
Spark results:
```
+---+-----------------+
|c |scalarsubquery(c)|
+---+-----------------+
|a |1 |
|a |1 |
|b |1 |
+---+-----------------+
```
Example 2:
```sql
create or replace view t1(a, b) as values (0, 6), (1, 5), (2, 4), (3, 3);
create or replace view t2(c) as values (6);
select c, (select count(*) from t1 where a + b = c) from t2;
```
Correct results: [(6, 4)]
Spark results:
```
+---+-----------------+
|c |scalarsubquery(c)|
+---+-----------------+
|6 |1 |
|6 |1 |
|6 |1 |
|6 |1 |
+---+-----------------+
```
### Does this PR introduce _any_ user-facing change?
Yes. Users will not be able to run queries that contain unsupported
correlated equality predicates.
### How was this patch tested?
Added unit tests.
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