LuciferYang commented on code in PR #12756: URL: https://github.com/apache/gluten/pull/12756#discussion_r3821016426
########## backends-velox/src/main/scala/org/apache/gluten/extension/RewriteSelfJoinInequalityToAggregate.scala: ########## @@ -0,0 +1,722 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.gluten.extension + +import org.apache.gluten.config.VeloxConfig + +import org.apache.spark.internal.Logging +import org.apache.spark.sql.SparkSession +import org.apache.spark.sql.catalyst.expressions._ +import org.apache.spark.sql.catalyst.expressions.RowOrdering +import org.apache.spark.sql.catalyst.expressions.aggregate._ +import org.apache.spark.sql.catalyst.plans._ +import org.apache.spark.sql.catalyst.plans.logical._ +import org.apache.spark.sql.catalyst.rules.Rule +import org.apache.spark.sql.types.LongType + +/** + * Rewrites self-join with inequality into GROUP BY + HAVING COUNT(DISTINCT) > 1. + * + * Targets three patterns; all require an existence-only context (LeftSemi/LeftAnti join, or + * InSubquery/Exists expression) so that row-count multiplicity from the self-join cross-product + * does not affect semantics. + * + * - Pattern A' (InSubquery/Exists primary): InSubquery/Exists whose subquery top-level join is a + * direct self-join. The primary path for TPC-DS Q95. + * - Pattern A2 (nested): InSubquery/Exists whose subquery contains an outer InnerJoin that has a + * self-join child. Only the self-join child is replaced with Aggregate; the outer join is + * preserved. + * - Pattern A (LeftSemi/LeftAnti): LeftSemi/LeftAnti whose right child is an Inner self-join + * (possibly wrapped in Project). Matches semi/anti joins that already exist in the input -- + * e.g. from an explicit `LEFT SEMI JOIN` clause. Note: this rule is injected via + * `injectOptimizerRule`, which places it in the operator-optimization batch that runs BEFORE + * `RewritePredicateSubquery`; A is NOT a post-subquery-rewrite fallback for A'. + * + * Correlated subqueries (outer references / joinCond in ListQuery/Exists) are fail-closed at the + * entry expression, since our ExprId canonicalization does not remap those predicates. + * + * All three share: + * - [[buildAggregateHavingDistinctGt1]] to construct `Filter(cnt > 1, Aggregate)` + * - [[canonicalizeWrapper]] to rebuild a wrapping Project so every equi-key reference points to + * the sjLeft-side attribute, with **fresh exprIds** (Spark's SPARK-21835 style -- no reuse of + * original exprIds), returning an old->new attribute remap for downstream rewrite. + * + * Controlled by `spark.gluten.sql.rewrite.selfJoinInequality` (default false, opt-in). + */ +case class RewriteSelfJoinInequalityToAggregate(spark: SparkSession) + extends Rule[LogicalPlan] + with PredicateHelper + with Logging { + + private val CountDistinctAliasName = "_gluten_rw_selfjoin_cnt_distinct" + + override def apply(plan: LogicalPlan): LogicalPlan = { + if (!VeloxConfig.get.enableRewriteSelfJoinInequality) { + logDebug("RewriteSelfJoinInequalityToAggregate: disabled via config, skipping") + return plan + } + + // Pattern A: rewrite LeftSemi/LeftAnti whose right child is an Inner self-join. + val afterOps = plan.transformUp { + case j: Join + if (j.joinType == LeftSemi || j.joinType == LeftAnti) && + j.condition.isDefined && + isInnerJoinShape(j.right) => + tryRewriteSemiWithSelfJoinChild(j).getOrElse(j) + case other => other + } + + // Pattern A' / A2: rewrite subquery plans embedded in InSubquery/Exists. + // Type-based matching (`x: T`) + named-argument copy keeps this portable across + // Spark 3.3/3.4/3.5/4.x where ListQuery/Exists case-class arity has drifted. + // + // Correlated subquery fail-closed: `SubqueryExpression.children.nonEmpty` iff the + // subquery has outer references / correlated join conditions. These predicates + // reference attributes INSIDE the subquery plan by ExprId; our canonicalizeWrapper + // rewrites those ExprIds without remapping the correlated predicates, which would + // leave dangling references after `RewritePredicateSubquery` folds them back into + // the semi-join condition. Target workload (TPC-DS Q95) is uncorrelated, so bail + // on any correlated candidate rather than growing the remap surface. + val rewritten = afterOps.transformAllExpressions { + case in @ InSubquery(_, lq: ListQuery) if lq.children.isEmpty => + rewriteSubqueryPlan(lq.plan) match { + case Some(newSub) => in.copy(query = lq.copy(plan = newSub)) + case None => in + } + case ex: Exists if ex.children.isEmpty => + rewriteSubqueryPlan(ex.plan) match { + case Some(newSub) => ex.copy(plan = newSub) + case None => ex + } + } + if (!(rewritten eq plan)) { + logDebug( + "RewriteSelfJoinInequalityToAggregate: rewrote self-join to " + + "GROUP BY + HAVING COUNT(DISTINCT) > 1") + } + rewritten + } + + // ============================================================================ + // Shared helpers + // ============================================================================ + + private def isInnerJoinShape(plan: LogicalPlan): Boolean = plan match { + case Project(_, j: Join) if j.joinType == Inner && j.condition.isDefined => true + case j: Join if j.joinType == Inner && j.condition.isDefined => true + case _ => false + } + + /** + * Build `Filter(cnt > 1, Aggregate(equiKeys, [equiKeys, cnt_alias], Filter(IsNotNull(equiKeys), + * child)))`. Returns the Filter node whose output is `equiKeys ++ [count_alias_attr]`. + * + * The extra `IsNotNull(equiKeys)` filter is essential to preserve the original equi-join's NULL + * semantics. Under SQL 3VL, `left.k = right.k` never matches when either side is NULL, so the + * original self-join drops rows with NULL equi-keys. Aggregate, in contrast, groups NULL keys + * together into a single "NULL group" -- if that group has >= 2 distinct non-null neq values, + * COUNT(DISTINCT) > 1 fires and injects NULL into the subquery output. That leaked NULL then + * turns `NOT IN` into a spurious empty result (Spark's null-aware anti-join uses + * `Or(equi, IsNull(equi))` which any NULL sub-row satisfies) and can flip EXISTS/IN outcomes. The + * neq column needs no such filter: `COUNT(DISTINCT col)` already ignores NULL. + */ + private def buildAggregateHavingDistinctGt1( + equiKeys: Seq[Attribute], + neqCol: Attribute, + child: LogicalPlan): LogicalPlan = { + val countExpr = AggregateExpression( + Count(Seq(neqCol)), + mode = Complete, + isDistinct = true, + filter = None, + NamedExpression.newExprId) + val countAlias = Alias(countExpr, CountDistinctAliasName)() + // Seq[Attribute] is a Seq[NamedExpression] via covariance; no cast needed. + val aggExprs: Seq[NamedExpression] = equiKeys :+ countAlias + val nonNullChild = equiKeys + .map(a => IsNotNull(a): Expression) + .reduceOption(And) + .map(Filter(_, child)) + .getOrElse(child) + val agg = Aggregate(equiKeys, aggExprs, nonNullChild) + Filter(GreaterThan(countAlias.toAttribute, Literal(1L, LongType)), agg) + } + + /** + * Canonicalize a Project so every equi-key reference points at the sjLeft-side attribute (both + * sides of a valid self-join share names, so this substitution is semantically safe). Uses + * **fresh exprIds** (no reuse of original wrapper output exprIds) -- the same technique Spark's + * own `dedupSubqueryOnSelfJoin` uses when it needs to change subquery output. + * + * Returns the rebuilt Project and a map `oldWrapperOutputExprId -> newWrapperOutputAttr`, so + * downstream references (outer join condition, top-level Project) can be updated consistently. + * + * `equiPairs` provides the definitive ExprId-based lookup: `equiPair (l, r)` binds + * `l.exprId -> l` (identity) and `r.exprId -> l` (sjRight -> sjLeft). Attribute identity in + * Catalyst is ExprId, not name; two columns can share a name with distinct ExprIds. Name-based + * lookup would silently drop such entries via `.toMap`. + * + * Fails (returns None) when a projectList entry is neither an equi-key Attribute (by ExprId) nor + * `Alias(equi-key Attribute, _)`. Fail-closed. + */ + private def canonicalizeWrapper( + projectList: Seq[NamedExpression], + equiPairs: Seq[(Attribute, Attribute)], + newChild: LogicalPlan): Option[(Project, Map[ExprId, Attribute])] = { + // ExprId-based canonical map: any equi-key attribute (either side) -> sjLeft attribute. + val exprIdToLeft: Map[ExprId, Attribute] = + equiPairs.flatMap { case (l, r) => Seq(l.exprId -> l, r.exprId -> l) }.toMap + val oldOutput: Seq[Attribute] = projectList.map(_.toAttribute) + val mapped: Seq[Option[NamedExpression]] = projectList.map { + case a: Attribute if exprIdToLeft.contains(a.exprId) => + // Wrap every rewritten output slot in a fresh Alias. + // + // When a wrapper reprojects BOTH sides of the same equi pair (e.g. + // `SELECT s1.k, s2.k FROM T s1 JOIN T s2 ON s1.k = s2.k AND s1.v <> s2.v`), + // both entries collapse to the same sjLeft Attribute after the self-join is + // rewritten. Duplicate output ExprIds are not illegal in Spark (`SELECT a, a` + // is a valid Project), but fresh Aliases give each output slot an independent + // identity, which keeps the `oldOutput -> newOutput` remap 1-to-1 and lets + // downstream references (outer join condition, top-level Project) be updated + // unambiguously via ExprId. + // + // The fresh ExprId is on the Alias ITSELF; the referenced child keeps its + // original ExprId. Spark's logical-plan integrity checks reject reusing a + // referenced ExprId as the Alias's own ExprId, not duplication across slots. + Some(Alias(exprIdToLeft(a.exprId), a.name)(): NamedExpression) + case al @ Alias(a: Attribute, _) if exprIdToLeft.contains(a.exprId) => + // Fresh exprId; do NOT reuse `al.exprId`. Reusing another expression's exprId + // is the pattern that Spark 3.3 flags via structural-integrity checks. + Some(Alias(exprIdToLeft(a.exprId), al.name)(): NamedExpression) + case _ => None Review Comment: The common `EXISTS (SELECT 1 FROM t1 JOIN t2 ...)` shape is analyzed as `Project(Literal(1), Join(...))`, but `canonicalizeWrapper` falls through to `case _ => None` for that projection, so the A' rewrite is skipped. The config and PR description advertise `Exists` support, yet this form still materializes the self-join's O(N²) build side; the current EXISTS test is a single-table correlated subquery and does not exercise it. Please preserve the EXISTS output shape while allowing literal projections, and add an uncorrelated EXISTS regression test that contains the self-join. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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