wangyum commented on a change in pull request #27518:
URL: https://github.com/apache/spark/pull/27518#discussion_r484167230
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/QueryPlanConstraints.scala
##########
@@ -78,6 +91,72 @@ trait ConstraintHelper {
inferredConstraints -- constraints
}
+ /**
+ * Infers an additional set of constraints from a given set of inequality
constraints.
+ * For e.g., if an operator has constraints of the form (`a > b`, `b > 5`),
this returns an
+ * additional constraint of the form `a > 5`.
+ */
+ def inferInequalityConstraints(constraints: Set[Expression]):
Set[Expression] = {
+ val binaryComparisons = constraints.filter {
+ case _: GreaterThan => true
+ case _: GreaterThanOrEqual => true
+ case _: LessThan => true
+ case _: LessThanOrEqual => true
+ case _: EqualTo => true
+ case _ => false
+ }
+
+ val greaterThans = binaryComparisons.map {
+ case EqualTo(l, r) if l.foldable => EqualTo(r, l)
+ case LessThan(l, r) => GreaterThan(r, l)
+ case LessThanOrEqual(l, r) => GreaterThanOrEqual(r, l)
+ case other => other
+ }
+
+ val lessThans = binaryComparisons.map {
+ case EqualTo(l, r) if l.foldable => EqualTo(r, l)
+ case GreaterThan(l, r) => LessThan(r, l)
+ case GreaterThanOrEqual(l, r) => LessThanOrEqual(r, l)
+ case other => other
+ }
+
+ var inferredConstraints = Set.empty[Expression]
+ greaterThans.foreach {
+ case op @ BinaryComparison(source: Attribute, destination: Expression)
+ if destination.foldable =>
Review comment:
To avoid generating too many constraints. For example: `a > b > c > 1`.
The expected inferred constraints are: `a > 1 and b > 1`. ` a > c` is useless.
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