wangyum commented on a change in pull request #27252: [SPARK-29231][SQL]
Constraints should be inferred from cast equality constraint
URL: https://github.com/apache/spark/pull/27252#discussion_r378248376
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/QueryPlanConstraints.scala
##########
@@ -62,11 +62,17 @@ trait ConstraintHelper {
*/
def inferAdditionalConstraints(constraints: Set[Expression]):
Set[Expression] = {
var inferredConstraints = Set.empty[Expression]
- constraints.foreach {
+ // IsNotNull should be constructed by `constructIsNotNullConstraints`.
+ val predicates = constraints.filterNot(_.isInstanceOf[IsNotNull])
+ predicates.foreach {
case eq @ EqualTo(l: Attribute, r: Attribute) =>
- val candidateConstraints = constraints - eq
+ val candidateConstraints = predicates - eq
inferredConstraints ++= replaceConstraints(candidateConstraints, l, r)
inferredConstraints ++= replaceConstraints(candidateConstraints, r, l)
+ case eq @ EqualTo(l @ Cast(_: Attribute, _, _), r: Attribute) =>
+ inferredConstraints ++= replaceConstraints(predicates - eq, r, l)
Review comment:
@cloud-fan This PR support `cast(1, dt) = b` before:
https://github.com/apache/spark/compare/048a0ecc65763c6feaa939938e2dec6f4040d939..7dcfe915087dbe274b470928600197745a645f5e
I removed it because:
1. It may be broken the plan. [This
is](https://github.com/apache/spark/compare/048a0ecc65763c6feaa939938e2dec6f4040d939..7dcfe915087dbe274b470928600197745a645f5e#diff-b40fcb6ac9b2e94b410f39a94a97e822R91-R93)
how I handled it before.
2. For `cast(a, dt) = b`, we support inferring many predicates, for example:
`a > 1`, `a < 1`, `a in (2, 3)`. I'm not sure if it's safe.
How about only supporting `cast(a, dt) = 1` now?
@peter-toth I'd like to support these cases in
https://github.com/apache/spark/pull/27518:
```
a < b && b < c infer a < c
a < b && b <= c infer a < c
a < b && b = c infer a < c
...
```
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