pratham76 commented on code in PR #58656:
URL: https://github.com/apache/spark/pull/58656#discussion_r4274304907
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/subquery.scala:
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@@ -398,62 +406,476 @@ object RewritePredicateSubquery extends
Rule[LogicalPlan] with PredicateHelper {
(newExpr, newPlan)
}
+ /**
+ * Same as [[rewriteExistentialExpr]], but it also returns the newly
introduced attributes, and
+ * it only rewrites the existential sub-queries for which `canRewrite`
returns true. A sub-query
+ * that is not rewritten stays in the returned expression as it is, and is
not descended into:
+ * rewriting an existential sub-query nested in its join condition would
graft an existence join
+ * onto the plan for an `exists` reference that the sub-query left in place
may never evaluate.
+ */
private def rewriteExistentialExprWithAttrs(
exprs: Seq[Expression],
- plan: LogicalPlan): (Option[Expression], LogicalPlan, Seq[Attribute]) = {
+ plan: LogicalPlan,
+ canRewrite: Expression => Boolean = _ => true): (Option[Expression],
LogicalPlan,
+ Seq[Attribute]) = {
var newPlan = plan
val introducedAttrs = ArrayBuffer.empty[Attribute]
- val newExprs = exprs.map { e =>
- e.transformDownWithPruning(_.containsAnyPattern(EXISTS_SUBQUERY,
IN_SUBQUERY)) {
- case Exists(sub, _, _, conditions, subHint) =>
- val exists = AttributeReference("exists", BooleanType, nullable =
false)()
- val existenceJoin = ExistenceJoin(exists)
- val newCondition = conditions.reduceLeftOption(And)
- newPlan =
- buildJoin(newPlan, rewriteDomainJoinsIfPresent(newPlan, sub,
newCondition),
- existenceJoin, newCondition, subHint)
- introducedAttrs += exists
- exists
- case Not(InSubquery(values, ListQuery(sub, _, _, _, conditions,
subHint))) =>
- val exists = AttributeReference("exists", BooleanType, nullable =
false)()
- // Deduplicate conflicting attributes if any.
- val newSub = dedupSubqueryOnSelfJoin(newPlan, sub, Some(values))
- val inConditions = values.zip(newSub.output).map(EqualTo.tupled)
- // To handle a null-aware predicate not-in-subquery in nested
conditions
- // (e.g., `v > 0 OR t1.id NOT IN (SELECT id FROM t2)`), we transform
- // `inCondition` (t1.id=t2.id) into `(inCondition) OR
ISNULL(inCondition)`.
- //
- // For example, `SELECT * FROM t1 WHERE v > 0 OR t1.id NOT IN
(SELECT id FROM t2)`
- // is transformed into a plan below;
- // == Optimized Logical Plan ==
- // Project [id#78, v#79]
- // +- Filter ((v#79 > 0) OR NOT exists#83)
- // +- Join ExistenceJoin(exists#83), ((id#78 = id#80) OR
isnull((id#78 = id#80)))
- // :- Relation[id#78,v#79] parquet
- // +- Relation[id#80] parquet
- val nullAwareJoinConds = inConditions.map(c => Or(c, IsNull(c)))
- val finalJoinCond = (nullAwareJoinConds ++
conditions).reduceLeft(And)
- val joinHint = JoinHint(None, subHint)
- newPlan = Join(newPlan,
- rewriteDomainJoinsIfPresent(newPlan, newSub, Some(finalJoinCond)),
- ExistenceJoin(exists), Some(finalJoinCond), joinHint)
- introducedAttrs += exists
- Not(exists)
- case InSubquery(values, ListQuery(sub, _, _, _, conditions, subHint))
=>
- val exists = AttributeReference("exists", BooleanType, nullable =
false)()
- // Deduplicate conflicting attributes if any.
- val newSub = dedupSubqueryOnSelfJoin(newPlan, sub, Some(values))
- val inConditions = values.zip(newSub.output).map(EqualTo.tupled)
- val newConditions = (inConditions ++
conditions).reduceLeftOption(And)
- val joinHint = JoinHint(None, subHint)
- newPlan = Join(newPlan, rewriteDomainJoinsIfPresent(newPlan, newSub,
newConditions),
- ExistenceJoin(exists), newConditions, joinHint)
- introducedAttrs += exists
- exists
+ // Builds the replacement of a sub-query expression under that
expression's origin and with
+ // its tags, as TreeNode.transformDownWithPruning does for the nodes a
rule replaces. Without
+ // it every node built below, the `exists` attribute and the join
conditions included, would
+ // take the origin of the enclosing operator, and a runtime error raised
from the rewritten
+ // condition would quote that operator rather than the sub-query fragment.
+ def replacing(sq: Expression)(replacement: => Expression): Expression = {
+ val newExpr = CurrentOrigin.withOrigin(sq.origin)(replacement)
+ newExpr.copyTagsFrom(sq)
+ newExpr
+ }
+ def rewrite(expr: Expression): Expression = {
+ if (!expr.containsAnyPattern(EXISTS_SUBQUERY, IN_SUBQUERY)) {
+ return expr
+ }
+ expr match {
+ case sq @ Exists(sub, _, _, conditions, subHint) if canRewrite(sq) =>
+ replacing(sq) {
+ val exists = AttributeReference("exists", BooleanType, nullable =
false)()
+ val existenceJoin = ExistenceJoin(exists)
+ val newCondition = conditions.reduceLeftOption(And)
+ newPlan =
+ buildJoin(newPlan, rewriteDomainJoinsIfPresent(newPlan, sub,
newCondition),
+ existenceJoin, newCondition, subHint)
+ introducedAttrs += exists
+ exists
+ }
+ case sq @ Not(InSubquery(values, ListQuery(sub, _, _, _, conditions,
subHint)))
+ if canRewrite(sq) =>
+ replacing(sq) {
+ val exists = AttributeReference("exists", BooleanType, nullable =
false)()
+ // Deduplicate conflicting attributes if any.
+ val newSub = dedupSubqueryOnSelfJoin(newPlan, sub, Some(values))
+ val inConditions = values.zip(newSub.output).map(EqualTo.tupled)
+ // To handle a null-aware predicate not-in-subquery in nested
conditions
+ // (e.g., `v > 0 OR t1.id NOT IN (SELECT id FROM t2)`), we
transform
+ // `inCondition` (t1.id=t2.id) into `(inCondition) OR
ISNULL(inCondition)`.
+ //
+ // For example, `SELECT * FROM t1 WHERE v > 0 OR t1.id NOT IN
(SELECT id FROM t2)`
+ // is transformed into a plan below;
+ // == Optimized Logical Plan ==
+ // Project [id#78, v#79]
+ // +- Filter ((v#79 > 0) OR NOT exists#83)
+ // +- Join ExistenceJoin(exists#83), ((id#78 = id#80) OR
isnull((id#78 = id#80)))
+ // :- Relation[id#78,v#79] parquet
+ // +- Relation[id#80] parquet
+ val nullAwareJoinConds = inConditions.map(c => Or(c, IsNull(c)))
+ val finalJoinCond = (nullAwareJoinConds ++
conditions).reduceLeft(And)
+ val joinHint = JoinHint(None, subHint)
+ newPlan = Join(newPlan,
+ rewriteDomainJoinsIfPresent(newPlan, newSub,
Some(finalJoinCond)),
+ ExistenceJoin(exists), Some(finalJoinCond), joinHint)
+ introducedAttrs += exists
+ Not(exists)
+ }
+ case sq @ InSubquery(values, ListQuery(sub, _, _, _, conditions,
subHint))
+ if canRewrite(sq) =>
+ replacing(sq) {
+ val exists = AttributeReference("exists", BooleanType, nullable =
false)()
+ // Deduplicate conflicting attributes if any.
+ val newSub = dedupSubqueryOnSelfJoin(newPlan, sub, Some(values))
+ val inConditions = values.zip(newSub.output).map(EqualTo.tupled)
+ val newConditions = (inConditions ++
conditions).reduceLeftOption(And)
+ val joinHint = JoinHint(None, subHint)
+ newPlan = Join(newPlan, rewriteDomainJoinsIfPresent(newPlan,
newSub, newConditions),
+ ExistenceJoin(exists), newConditions, joinHint)
+ introducedAttrs += exists
+ exists
+ }
+ // A sub-query that `canRewrite` declined is left as it is, children
included.
+ case sq @ (_: Exists | Not(_: InSubquery) | _: InSubquery) => sq
+ case other => other.mapChildren(rewrite)
}
}
+ val newExprs = exprs.map(rewrite)
(newExprs.reduceOption(And), newPlan, introducedAttrs.toSeq)
}
+
+ /**
+ * Returns true if `e` references any of the attributes produced by `plan`.
+ */
+ private def referencesPlan(e: Expression, plan: LogicalPlan): Boolean = {
+ // Iterates the references and probes the output set, rather than
materialising the
+ // intersection: AttributeSet.intersect builds a set from its argument, so
the operand order
+ // there would decide whether this walks the references or the whole
output of `plan`. The
+ // membership probes still construct wrappers, so this is cheaper, not
allocation-free.
+ e.references.exists(plan.outputSet.contains)
+ }
+
+ /**
+ * Returns true if `e` effectively references any of the attributes produced
by `plan`, see
+ * [[effectiveReferences]].
+ */
+ private def effectivelyReferencesPlan(e: Expression, plan: LogicalPlan):
Boolean = {
+ effectiveReferences(e).exists(plan.outputSet.contains)
+ }
+
+ /**
+ * Which of an outer plan and a sub-query plan a set of references can be
evaluated by, as
+ * [[planReferences]] determines it.
+ */
+ private case class PlanReferences(subPlanOnly: Boolean, bothPlans: Boolean)
+
+ /**
+ * Classifies `references` against `outerPlan` and `subPlan` in a single
pass: whether they can
+ * only be evaluated by `subPlan`, and whether they need both plans.
+ *
+ * An attribute that both plans produce is attributed to `subPlan` rather
than to `outerPlan`,
+ * which is what the `subPlan` probe coming first does. The two plans share
no ExprId in any
+ * shape reached by the suite: `DeduplicateRelations` has given the
sub-query its own, and the
+ * EXISTS arms classify against the raw sub-query plan while the IN arms
classify against the
+ * plan `dedupSubqueryOnSelfJoin` has already separated from the outer plan.
The order is
+ * therefore defensive rather than something a query exercises, and it is
the safe one: a
+ * nested sub-query resolves in the scope of the sub-query it is nested in,
so an attribute
+ * both plans produce is one of that sub-query's own, and attributing it to
`outerPlan` instead
+ * would let a single shared attribute satisfy both sides of the
classification and have a
+ * nested sub-query referencing only the inner query rejected as referencing
both.
+ *
+ * An attribute neither plan produces leaves both answers false, which
declines the rewrite
+ * without rejecting the sub-query, as a sub-query referencing neither plan
can be left in the
+ * join condition unharmed.
+ */
+ private def planReferences(
+ references: AttributeSet,
+ outerPlan: LogicalPlan,
+ subPlan: LogicalPlan): PlanReferences = {
+ var subPlanReference = false
+ var outerPlanOnlyReference = false
+ val attrs = references.iterator
+ // Stops as soon as both plans are known to be referenced, which is all
the two answers need.
+ while (attrs.hasNext && !(subPlanReference && outerPlanOnlyReference)) {
+ val attr = attrs.next()
+ if (subPlan.outputSet.contains(attr)) {
+ subPlanReference = true
+ } else if (outerPlan.outputSet.contains(attr)) {
+ outerPlanOnlyReference = true
+ }
+ }
+ PlanReferences(
+ subPlanOnly = subPlanReference && !outerPlanOnlyReference,
+ bothPlans = subPlanReference && outerPlanOnlyReference)
+ }
+
+ /**
+ * The attributes that `e` references and can still evaluate. For an
existential sub-query
+ * expression these are the ones of the values it compares and of the
correlated condition that
+ * [[PullupCorrelatedPredicates]] hoisted into it, rather than the ones of
`references`, which
+ * also include the outer attributes the pull-up retains for idempotency.
Those outlive the
+ * condition that referenced them once BooleanSimplification has eliminated
it, as in
+ * `a IN (SELECT col1 FROM t3 WHERE false AND col1 = c1)`, which keeps `c1`
as an outer
+ * attribute of a sub-query that no longer reads it, and which must still be
rewritten against
+ * the outer plan rather than treated as referencing the sub-query plan.
+ *
+ * The sets are merged with `AttributeSet.fromAttributeSets` rather than
built from a flattened
+ * sequence of attributes: `AttributeSet.apply` would take one allocation
per attribute of a
+ * sequence as long as the total number of references, which a row-valued IN
over a wide row
+ * makes unnecessarily large.
+ */
+ private def effectiveReferences(e: Expression): AttributeSet = e match {
+ case Exists(_, _, _, joinCond, _) =>
+ AttributeSet.fromAttributeSets(joinCond.map(_.references))
+ case Not(in: InSubquery) => effectiveReferences(in)
+ case InSubquery(values, ListQuery(_, _, _, _, joinCond, _)) =>
+ AttributeSet.fromAttributeSets(values.map(_.references) ++
joinCond.map(_.references))
+ case _ => e.references
+ }
+
+ /**
+ * Rewrites the existential sub-queries that are nested in the correlated
predicates which
+ * [[PullupCorrelatedPredicates]] hoisted out of a predicate sub-query, and
which therefore end
+ * up in the condition of the semi/anti join that replaces that sub-query.
+ *
+ * A hoisted predicate can carry a nested existential sub-query out of the
sub-query plan,
+ * because a correlated predicate is hoisted as a whole when it is a
disjunction. For example
+ *
+ * SELECT * FROM t1 WHERE EXISTS (
+ * SELECT 1 FROM t2 WHERE t1.a = t2.c1 OR t2.c1 IN (SELECT col1 FROM t3))
+ *
+ * hoists `a = c1 OR c1 IN (SELECT col1 FROM t3)` into the join condition.
Such a nested
+ * sub-query must be rewritten against the plan that produces the attributes
it references:
+ * the one above references `c1`, which is produced by the sub-query plan
and not by the outer
+ * plan, so its existence join has to be built on top of the sub-query plan.
Building it on top
+ * of the outer plan instead yields a join whose condition references an
attribute that neither
+ * of its children can produce (SPARK-59351).
+ *
+ * A nested sub-query that references both plans cannot be rewritten into an
existence join on
+ * either side, since neither alone can evaluate it, so it has to stay in
the join condition,
+ * where both plans are in scope. Leaving it there is only correct while it
is uncorrelated: the
+ * join condition of a correlated one is dropped when it is planned as an
in-subquery filter,
+ * which would silently change the result, so a correlated one is reported
as unsupported
+ * instead. Note that such a sub-query can be
+ * correlated only to the sub-query plan, as being correlated to the outer
plan as well would
+ * require two levels of correlation, which the Analyzer rejects.
+ *
+ * A sub-query left here is further subject to the rewrite of predicate
sub-queries in join
+ * conditions, which rejects one referencing both plans under the default
configuration. It
+ * survives that rewrite when
+ *
`spark.sql.optimizer.decorrelatePredicateSubqueriesInJoinPredicate.enabled` is
disabled, and
+ * also when it is an uncorrelated IN sub-query and
+ *
`spark.sql.optimizer.optimizeUncorrelatedInSubqueriesInJoinCondition.enabled`
is disabled,
+ * since it is then not among the sub-queries that rewrite considers.
+ *
+ * An existence join yields only whether a row matched, so its `exists`
attribute cannot tell
+ * FALSE from unknown, while `IN` is three-valued. The two are
indistinguishable while the value
+ * only feeds a predicate, which is what a hoisted condition normally does,
but not when it
+ * reaches something else, e.g. `(c1 IN (SELECT col1 FROM t3)) <=> false`,
which is FALSE for a
+ * NULL that matches nothing and TRUE for the `exists` attribute. An IN
sub-query whose row
+ * comparison can evaluate to unknown is therefore rejected in that position
rather than
+ * rewritten. NOT IN is rewritten with a null-aware join condition of its
own, which is equally
+ * two-valued, so it is rejected there too.
+ *
+ * Returns the rewritten condition along with the updated outer and
sub-query plans.
+ */
+ private def rewriteExistentialExprInJoinCondition(
+ conditions: Seq[Expression],
+ outerPlan: LogicalPlan,
+ subPlan: LogicalPlan): (Option[Expression], LogicalPlan, LogicalPlan) = {
+ val (subCond, newSubPlan) =
+ rewriteExistentialExprInSubqueryPlan(conditions, outerPlan, subPlan)
+ // The sub-queries that do not reference the sub-query plan are rewritten
against the outer
+ // plan, as they only reference attributes of the outer plan, if any. This
accepts on the
+ // negation of the test above rather than on a positive one, which rests
on the invariant that
+ // `effectiveReferences` sees every attribute the rewrite can put in a
join condition: one it
+ // cannot see would be rewritten here and end up in a condition the outer
plan cannot evaluate.
+ // A positive test is not available without also refusing the sub-queries
whose retained outer
+ // attributes no longer correspond to a condition, which must keep being
rewritten here.
+ val (newCond, newOuterPlan, _) = rewriteExistentialExprWithAttrs(
+ subCond.toSeq, outerPlan, e => !effectivelyReferencesPlan(e, subPlan))
+ (newCond, newOuterPlan, newSubPlan)
+ }
+
+ /**
+ * Rewrites the existential sub-queries in `conditions` that can only be
evaluated by the
+ * sub-query plan, that is those referencing the sub-query plan but not the
outer plan, into
+ * existence joins on top of the sub-query plan. See
+ * [[rewriteExistentialExprInJoinCondition]] for details.
+ *
+ * Returns the rewritten condition along with the updated sub-query plan.
+ */
+ private def rewriteExistentialExprInSubqueryPlan(
+ conditions: Seq[Expression],
+ outerPlan: LogicalPlan,
+ subPlan: LogicalPlan): (Option[Expression], LogicalPlan) = {
+ // The rejection collector below is a plain `collect`, which visits every
node of the hoisted
+ // conditions whether or not it can hold a sub-query, so skip the
classification entirely when
+ // they hold none at all, which is the common case for a correlated EXISTS
or IN.
+ // [[collectUnknownSensitiveInSubqueries]] prunes subquery-free subtrees
on its own, so this
+ // guard only saves it the top-level call.
+ if (!conditions.exists(_.containsAnyPattern(EXISTS_SUBQUERY,
IN_SUBQUERY))) {
+ return (conditions.reduceOption(And), subPlan)
+ }
+ // A sub-query left in the join condition loses its own join condition
when it is planned
+ // there, so a correlated one would silently return a wrong result: reject
it instead. The
+ // same holds for a correlated sub-query nested below one that is left
there, since the
+ // rewrite leaves a declined sub-query whole, children included, and
nothing else will reach
+ // it: see carriesCorrelatedSubquery. Note that this walks the whole
expression, including the
+ // join condition of a sub-query the rewrite declines to descend into,
which is deliberate for
+ // the same reason.
+ //
+ // Which plan a candidate references is asked of it up to three times
below, once for the
+ // rejection of a sub-query referencing both plans, once to keep only the
unknown-sensitive
+ // ones the sub-query plan owns, and once more by the rewrite itself. Both
answers come from
+ // the same reference set in a single pass over it, and the result is
memoised per candidate,
+ // so neither the set nor the scan is repeated. The memo is keyed by
identity: the candidates
+ // are nodes of the expressions being classified, and comparing two of
them structurally would
+ // compare the sub-query plans they hold.
+ val classified = new java.util.IdentityHashMap[Expression,
PlanReferences]()
+ def classify(sq: Expression): PlanReferences = {
+ var references = classified.get(sq)
+ if (references == null) {
+ references = planReferences(effectiveReferences(sq), outerPlan,
subPlan)
+ classified.put(sq, references)
+ }
+ references
+ }
+ def ownedBySubPlan(sq: Expression): Boolean = classify(sq).subPlanOnly
+ def referencesBothPlans(sq: Expression): Boolean = classify(sq).bothPlans
+ val referencingBothPlans = conditions.flatMap(_.collect {
+ case sq @ (_: Exists | _: InSubquery)
+ if referencesBothPlans(sq) &&
+ (hasCorrelatedCondition(sq) || carriesCorrelatedSubquery(sq)) => sq
+ })
+ if (referencingBothPlans.nonEmpty) {
+ throw
QueryCompilationErrors.nestedSubqueryReferencingOuterAndInnerQueryError(
+ referencingBothPlans)
+ }
+ // An IN sub-query whose result can be unknown cannot be represented by
the `exists` attribute
+ // of an existence join once that result is observable, see above.
+ val unknownResult = conditions
+ .flatMap(unknownSensitiveInSubqueries(_, truthOnly = true))
+ .filter(ownedBySubPlan)
+ if (unknownResult.nonEmpty) {
+ throw
QueryCompilationErrors.nestedInSubqueryWithUnknownResultError(unknownResult)
+ }
+ val (newCond, newSubPlan, _) =
+ rewriteExistentialExprWithAttrs(conditions, subPlan, ownedBySubPlan)
+ (newCond, newSubPlan)
+ }
+
+ /**
+ * Collects the IN sub-queries in `expr` whose result can be unknown and
whose value is observed
+ * beyond being TRUE, so that rewriting them into an existence join, whose
`exists` attribute is
+ * FALSE where IN is unknown, would be observable. See
[[rewriteExistentialExprInJoinCondition]].
+ *
+ * `truthOnly` states whether the value of `expr` is only ever tested for
being TRUE, which is
+ * where unknown and FALSE cannot be told apart. That holds for the operands
of AND and OR within
+ * a condition that ends up in a Filter or a join condition, and for the
positions
+ * [[ReplaceNullWithFalseInPredicate]] rewrites for the same reason: the
operand of an
+ * `EqualNullSafe` against TRUE, and the predicate of an `If` or of a
`CaseWhen` branch. The
+ * result branches of a conditional are consumed wherever the conditional
itself is, so they
+ * inherit its context rather than being value positions of their own.
+ *
+ * It does not hold under NOT, where `NOT FALSE` is TRUE while `NOT unknown`
is unknown. A NOT
+ * directly over an IN sub-query is still safe, but for another reason: it
is rewritten with a
+ * null-aware join condition of its own, which is TRUE where the comparison
is unknown, so the
+ * negation of its `exists` attribute is FALSE there, as SQL requires.
+ */
+ private def unknownSensitiveInSubqueries(
+ expr: Expression,
+ truthOnly: Boolean): Seq[Expression] = {
+ val reported = ArrayBuffer.empty[Expression]
+ collectUnknownSensitiveInSubqueries(expr, truthOnly, reported)
+ reported.toSeq
+ }
+
+ /**
+ * Appends what [[unknownSensitiveInSubqueries]] reports to `reported`, in
the order the
+ * expression is walked. The results are accumulated rather than
concatenated on the way back up,
+ * so a condition with many reportable sub-queries does not copy the prefix
at every node.
+ */
+ private def collectUnknownSensitiveInSubqueries(
+ expr: Expression,
+ truthOnly: Boolean,
+ reported: ArrayBuffer[Expression]): Unit = expr match {
+ case _ if !expr.containsAnyPattern(EXISTS_SUBQUERY, IN_SUBQUERY) =>
+ case And(left, right) =>
+ collectUnknownSensitiveInSubqueries(left, truthOnly, reported)
+ collectUnknownSensitiveInSubqueries(right, truthOnly, reported)
+ case Or(left, right) =>
+ collectUnknownSensitiveInSubqueries(left, truthOnly, reported)
+ collectUnknownSensitiveInSubqueries(right, truthOnly, reported)
+ // `null <=> true` and `false <=> true` are both FALSE, so only truth is
observed here whatever
+ // consumes the comparison.
+ case EqualNullSafe(left, Literal.TrueLiteral) =>
+ collectUnknownSensitiveInSubqueries(left, truthOnly = true, reported)
+ case EqualNullSafe(Literal.TrueLiteral, right) =>
+ collectUnknownSensitiveInSubqueries(right, truthOnly = true, reported)
+ // COALESCE(x, false) maps both unknown and FALSE to FALSE, so only truth
is observed. A
+ // different default does not: COALESCE(x, true) is TRUE where x is
unknown and FALSE where x
+ // is FALSE.
+ case Coalesce(child +: rest) if
rest.headOption.contains(Literal.FalseLiteral) =>
+ collectUnknownSensitiveInSubqueries(child, truthOnly = true, reported)
+ case If(predicate, trueValue, falseValue) =>
+ collectUnknownSensitiveInSubqueries(predicate, truthOnly = true,
reported)
+ collectUnknownSensitiveInSubqueries(trueValue, truthOnly, reported)
+ collectUnknownSensitiveInSubqueries(falseValue, truthOnly, reported)
+ case CaseWhen(branches, elseValue) =>
+ branches.foreach { case (condition, value) =>
+ collectUnknownSensitiveInSubqueries(condition, truthOnly = true,
reported)
+ collectUnknownSensitiveInSubqueries(value, truthOnly, reported)
+ }
+ elseValue.foreach(collectUnknownSensitiveInSubqueries(_, truthOnly,
reported))
+ // A NOT directly over an IN sub-query keeps its own null-aware rewrite,
so only its operands
+ // are examined. Under any other NOT, unknown is observable and
`truthOnly` does not carry.
+ case not @ Not(in: InSubquery) => collectOrDescend(not, in, truthOnly,
reported)
+ case Not(child) =>
+ collectUnknownSensitiveInSubqueries(child, truthOnly = false, reported)
+ case in: InSubquery => collectOrDescend(in, in, truthOnly, reported)
+ case sq: SubqueryExpression =>
+ // Only the hoisted join condition of a sub-query expression is a
predicate, evaluated by
+ // the join it is rewritten into. Its outer attributes are value
expressions.
+ sq.getJoinCond.foreach(
+ collectUnknownSensitiveInSubqueries(_, truthOnly = true, reported))
+ sq.getOuterAttrs.foreach(
+ collectUnknownSensitiveInSubqueries(_, truthOnly = false, reported))
+ case other =>
+ other.children.foreach(
+ collectUnknownSensitiveInSubqueries(_, truthOnly = false, reported))
+ }
+
+ /**
+ * Appends `report` to `reported` if the IN sub-query `in` would lose an
observable unknown, and
+ * otherwise descends into the values it compares and into its list query.
The descent matters
+ * because [[InSubquery]] is a [[Predicate]] rather than a
[[SubqueryExpression]], so an IN
+ * sub-query nested in the values or in the hoisted join condition of
another one is only reached
+ * from here.
+ */
+ private def collectOrDescend(
+ report: Expression,
+ in: InSubquery,
+ truthOnly: Boolean,
+ reported: ArrayBuffer[Expression]): Unit = {
+ if (!truthOnly && inSubqueryMayBeUnknown(in)) {
+ reported += report
+ } else {
+ in.values.foreach(collectUnknownSensitiveInSubqueries(_, truthOnly =
false, reported))
+ collectUnknownSensitiveInSubqueries(in.query, truthOnly, reported)
+ }
+ }
+
+ /**
+ * Returns true if the row comparison of the IN sub-query `in` can evaluate
to unknown, that is
+ * if it can return NULL rather than only TRUE or FALSE. An existence join
cannot represent that
+ * third value, see [[rewriteExistentialExprInJoinCondition]].
+ *
+ * This deliberately does not use `InSubquery.nullable`, which under
+ * `spark.sql.legacy.inSubqueryNullability` (SPARK-43413) reports only the
nullability of the
+ * compared values and ignores that of the list query's columns. What is
protected here is the
+ * three-valued result the rewrite would drop, which does not depend on that
configuration, so
+ * the nullability is re-derived from both sides.
+ */
+ private def inSubqueryMayBeUnknown(in: InSubquery): Boolean = {
+ // Iterators, so a wide row-valued IN stops at the first nullable side
rather than pairing up
+ // the whole arity first.
+ in.values.iterator.zip(in.query.childOutputs.iterator).exists {
Review Comment:
Confirmed — every UNKNOWN-sensitive regression was scalar, so the all-fields
contract was unprotected. Added, in both directions you asked for, with the
nullability isolated to the second pair so the first pair is non-nullable on
both sides:
* **later list output nullable** — `(c1, c2) IN (SELECT col1, col2 FROM
t6)`, where `t2r` is non-nullable and only `t6.col2` is;
* **later compared value nullable** — `(c1, c2n) IN (SELECT col1, col2 FROM
t7)`, where `t7` is non-nullable and only `t2rn.c2n` is.
Both are rejected. And the fully non-nullable row-valued shape, `(c1, c2) IN
(SELECT col1, col2 FROM t7)`, is still rewritten and plan-checked, so the guard
cannot be satisfied by giving up on arity in the other direction.
Checked that they discriminate: replacing the `zip` with `zip(...).take(1)`,
so only the first pair is inspected, leaves both new rejections un-fired and
the test red, while the whole pre-existing suite stays green.
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