YannisSismanis commented on code in PR #41763:
URL: https://github.com/apache/spark/pull/41763#discussion_r1304830952
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala:
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@@ -324,6 +325,124 @@ object LogicalPlanIntegrity {
LogicalPlanIntegrity.hasUniqueExprIdsForOutput(plan))
}
+ /**
+ * This method validates there are no dangling attribute references.
+ * Returns an error message if the check does not pass, or None if it does
pass.
+ */
+ def validateNoDanglingReferences(plan: LogicalPlan): Option[String] = {
+ plan.collectFirst {
+ // DML commands and multi instance relations (like InMemoryRelation
caches)
+ // have different output semantics than typical queries.
+ case _: Command => None
+ case _: MultiInstanceRelation => None
+ case n if canGetOutputAttrs(n) =>
+ val inputExprIds = (n.children.flatMap(c => c.output ++
c.metadataOutput) ++ n.output)
+ .map(_.exprId).toSet
+ val danglingReferences = n.references.filter {
+ a => a.resolved && !inputExprIds.contains(a.exprId)
+ }.map(_.qualifiedName)
+ if (danglingReferences.nonEmpty) {
+ Some(s"Aliases ${danglingReferences.mkString(", ")} are dangling " +
+ s"in the references for plan:\n ${n.treeString}")
+ } else {
+ None
+ }
+ }.flatten
+ }
+
+ /**
+ * Validate that the grouping key types in Aggregate plans are valid.
+ * Returns an error message if the check fails, or None if it succeeds.
+ */
+ def validateGroupByTypes(plan: LogicalPlan): Option[String] = {
+ plan.collectFirst {
+ case a @ Aggregate(groupingExprs, _, _) =>
+ val badExprs =
groupingExprs.filter(_.dataType.isInstanceOf[MapType]).map(_.toString)
+ if (badExprs.nonEmpty) {
+ Some(s"Grouping expressions ${badExprs.mkString(", ")} cannot be of
type Map " +
+ s"for plan:\n ${a.treeString}")
+ } else {
+ None
+ }
+ }.flatten
+ }
+
+ /**
+ * Validate that the aggregation expressions in Aggregate plans are valid.
+ * Returns an error message if the check fails, or None if it succeeds.
+ */
+ def validateAggregateExpressions(plan: LogicalPlan): Option[String] = {
+ /**
+ * Returns true if all the exprIds, referenced in an Expression <subExpr>
+ * (used in the aggregate expressions of an Aggregate),
+ * are either used as measures (under an AggregateFunction) or are
explicitly grouped,
+ * given the <groupingExprIds> of all grouping expressions
+ * (used in the grouping expressions of the same Aggregate)
+
+ * I.e:
+ * <groupingExprIds> can be used "freely" in an AggregateExpressions, all
other exprIds can only
+ * be used under an AggregateFunction (i.e. aggregated).
+ */
+ def isAggregateSubExpressionValid(
+ groupingExpressions: Seq[Expression],
+ groupingExprIds: Set[ExprId],
+ subExpr: Expression): Boolean = {
+ // First collect all non-grouping ExprIds in <subExpr>.
+ val restrictedExprIds = subExpr.collect {
+ case g: Attribute if !groupingExprIds.contains(g.exprId) => g.exprId
+ }.groupBy(identity).mapValues(_.size)
+
+ // Second collect all non-grouping ExprIds under an AggregateFunction in
<subExpr>.
+ val restrictedExprIdsUnderAggregateFunction = subExpr.flatMap {
+ case a: AggregateExpression => a.collect {
+ case g: Attribute if !groupingExprIds.contains(g.exprId) => g.exprId
+ }
+ case _ => Seq.empty
+ }.groupBy(identity).mapValues(_.size)
+
+ // Validate a) that all non-grouping exprIds are used under some
aggregate function,
+ // i.e. all such exprIds are aggregated (measures) OR
+ // b) a grouping expression can be used in sub-expressions
+ // for aggregate expressions of an Aggregate.
+ restrictedExprIds == restrictedExprIdsUnderAggregateFunction ||
+ groupingExpressions.exists(_.semanticEquals(subExpr))
+ }
+
+ def isAggregateExpressionValid(groupingExpressions: Seq[Expression],
+ groupingExprIds: Set[ExprId],
+ expr: Expression): Boolean = {
+ isAggregateSubExpressionValid(groupingExpressions, groupingExprIds,
expr) ||
+ (expr.children.nonEmpty &&
+ expr.children.forall(isAggregateExpressionValid(groupingExpressions,
groupingExprIds, _)))
+ }
+
+ plan.collectFirst {
+ case a @ Aggregate(groupingExprs, aggrExprs, _) =>
+ // Collect all exprIds used in grouping keys that can be used in
aggregate expressions
+ // outside an aggregate function (like sum).
Review Comment:
Grouping expressions can be referenced in aggregate expressions either by
exprid (if the grouping expression corresponds to a named expression) or by
semantic equivalence. Grouping expressions can be used everywhere in aggregate
expressions (they do not need to be below an aggregation function), unlike
non-grouping expressions that can only be used under an aggregation function
(like sum).
In your example, `a`, `c` can be referenced everywhere in aggregate
expressions through exprid and `a+b`, `a*b` can be used everywhere through
semantic equivalence. I.e. something like `select c, (a*b), a+b, sum(c*m) from
... group by a, a+b, a*b as c` is valid. The check for the semantic equivalence
for expressions like (`a+b` or `a*b`) for each of the aggregate expressions
that appear in the select clause happens in line 408 above.
All other expressions (i.e. non-grouping expressions) can only be used under
an aggregation function in aggregate expressions.
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