From 3a518dd53bb1a4f3f08909ef24a6f3e0c3dda17d Mon Sep 17 00:00:00 2001
From: pineappleBest123 <gaotianyang0222@outlook.com>
Date: Sun, 5 Apr 2026 21:53:38 -0700
Subject: [PATCH] [ASTERIXDB-3021][COMP] Emit cross product warning for
 implicit joins

When a query uses implicit cross join syntax (FROM A, B without a join
condition), SimpleUnnestToProductRule rewrites the unnest pipeline into
an InnerJoinOperator with a constant TRUE condition but never emits a
warning. Explicit JOIN ... ON TRUE already triggers the CROSS_PRODUCT_JOIN
warning via JoinUtils. This change closes that gap.

- Change warnIfCrossProduct() in JoinUtils from private to public
- Call JoinUtils.warnIfCrossProduct() in SimpleUnnestToProductRule
  after the cross product join is constructed
---
 .../algebricks/rewriter/rules/SimpleUnnestToProductRule.java   | 3 +++
 .../org/apache/hyracks/algebricks/rewriter/util/JoinUtils.java | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/SimpleUnnestToProductRule.java b/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/SimpleUnnestToProductRule.java
index 58a15e23e8f..a95f209be9b 100644
--- a/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/SimpleUnnestToProductRule.java
+++ b/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/rules/SimpleUnnestToProductRule.java
@@ -37,6 +37,7 @@
 import org.apache.hyracks.algebricks.core.algebra.operators.logical.visitors.VariableUtilities;
 import org.apache.hyracks.algebricks.core.algebra.util.OperatorPropertiesUtil;
 import org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;
+import org.apache.hyracks.algebricks.rewriter.util.JoinUtils;
 
 public class SimpleUnnestToProductRule implements IAlgebraicRewriteRule {
 
@@ -142,6 +143,8 @@ && descOrSelfIsSourceScan(currentOpRef.getValue())) {
         context.computeAndSetTypeEnvironmentForOperator(boundaryOperator);
         context.computeAndSetTypeEnvironmentForOperator(innerBranchOperator);
         context.computeAndSetTypeEnvironmentForOperator(join);
+        JoinUtils.warnIfCrossProduct(join.getCondition().getValue(),
+                innerBranchOperator.getSourceLocation(), context);
         return true;
     }
 
diff --git a/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/util/JoinUtils.java b/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/util/JoinUtils.java
index 085580f08ea..f4afb6fe5de 100644
--- a/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/util/JoinUtils.java
+++ b/hyracks-fullstack/algebricks/algebricks-rewriter/src/main/java/org/apache/hyracks/algebricks/rewriter/util/JoinUtils.java
@@ -340,7 +340,7 @@ private static BuildSide getHashJoinBuildSide(ILogicalExpression e, List<Logical
         return null;
     }
 
-    private static void warnIfCrossProduct(ILogicalExpression conditionExpr, SourceLocation sourceLoc,
+    public static void warnIfCrossProduct(ILogicalExpression conditionExpr, SourceLocation sourceLoc,
             IOptimizationContext context) {
         if (OperatorPropertiesUtil.isAlwaysTrueCond(conditionExpr) && sourceLoc != null) {
             IWarningCollector warningCollector = context.getWarningCollector();