Sort order of cartesian product join children

ad-freiburg · Feb 26, 2025 · 7f8f88c · 7f8f88c
1 parent 8fe0642
commit 7f8f88c
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diff --git a/src/engine/QueryPlanner.cpp b/src/engine/QueryPlanner.cpp
@@ -1553,6 +1553,9 @@ vector<vector<QueryPlanner::SubtreePlan>> QueryPlanner::fillDpTab(
         textLimitIds |= plan.idsOfIncludedTextLimits_;
         subtrees.push_back(std::move(plan._qet));
       });
+  // Ensure estimated largest tree is on the right side.
+  ql::ranges::sort(subtrees, {},
+                   [](const auto& tree) { return tree->getSizeEstimate(); });
   result.at(0).push_back(
       makeSubtreePlan<CartesianProductJoin>(_qec, std::move(subtrees)));
   auto& plan = result.at(0).back();

diff --git a/test/QueryPlannerTest.cpp b/test/QueryPlannerTest.cpp
@@ -2981,3 +2981,32 @@ TEST(QueryPlanner, Exists) {
       "GRAPH ?g { ?u ?v ?c}}}",
       filter);
 }
+
+// _____________________________________________________________________________
+TEST(QueryPlanner, CartesianProductJoinChildrenAreOrdered) {
+  auto qp = makeQueryPlanner();
+  {
+    auto query =
+        SparqlParser::parseQuery("SELECT * { VALUES ?x {1} VALUES ?y {2 3} }");
+    auto qet = qp.createExecutionTree(query);
+    EXPECT_TRUE(std::dynamic_pointer_cast<CartesianProductJoin>(
+        qet.getRootOperation()));
+    ASSERT_EQ(qet.getRootOperation()->getChildren().size(), 2);
+    EXPECT_EQ(qet.getRootOperation()->getChildren().at(0)->getCacheKey(),
+              "VALUES (?x) { (1) }");
+    EXPECT_EQ(qet.getRootOperation()->getChildren().at(1)->getCacheKey(),
+              "VALUES (?y) { (2) (3) }");
+  }
+  {
+    auto query =
+        SparqlParser::parseQuery("SELECT * { VALUES ?y {2 3} VALUES ?x {1} }");
+    auto qet = qp.createExecutionTree(query);
+    EXPECT_TRUE(std::dynamic_pointer_cast<CartesianProductJoin>(
+        qet.getRootOperation()));
+    ASSERT_EQ(qet.getRootOperation()->getChildren().size(), 2);
+    EXPECT_EQ(qet.getRootOperation()->getChildren().at(0)->getCacheKey(),
+              "VALUES (?x) { (1) }");
+    EXPECT_EQ(qet.getRootOperation()->getChildren().at(1)->getCacheKey(),
+              "VALUES (?y) { (2) (3) }");
+  }
+}