Merge pull request #37161 from vespa-engine/havardpe/fix-equiv-children-flow-stats

calculate flow stats for full children trees, not just one level

Author: arnej27959

searchlib/src/tests/queryeval/blueprint/intermediate_blueprints_test.cpp

@@ -1095,6 +1095,29 @@ TEST(IntermediateBlueprintsTest, require_that_replaced_blueprints_retain_source_
     EXPECT_EQ(42u, top2_up->getSourceId());
 }
 
+TEST(IntermediateBlueprintsTest, equiv_flow_stats_reach_into_intermediate_term_subtrees) {
+    // Equiv terms are not part of the optimize tree, so EquivBlueprint must
+    // update flow stats on the full subtree of each term — not just the term
+    // itself. Otherwise an IntermediateBlueprint sitting between Equiv and
+    // its real leaves (e.g. a SourceBlender wrapped around a term in proton)
+    // sees zero-initialized child stats, propagates estimate=0/cost=0 up to
+    // Equiv, and zeroes out the planner cost for everything that follows
+    // Equiv in an AND.
+    FieldSpecBaseList fields;
+    fields.add(FieldSpecBase(1, 1));
+    auto equiv = std::make_unique<EquivBlueprint>(fields, EquivBlueprint::allocate_outside_equiv_tag{});
+    for (uint32_t i = 0; i < 3; ++i) {
+        auto wrap = std::make_unique<OrBlueprint>();
+        wrap->addChild(ap(MyLeafSpec(40).addField(1, 2 + i * 2).create()));
+        wrap->addChild(ap(MyLeafSpec(40).addField(1, 3 + i * 2).create()));
+        equiv->addTerm(std::move(wrap), 1.0);
+    }
+    equiv->basic_plan(false, 1000);
+    EXPECT_GT(equiv->estimate(), 0.0);
+    EXPECT_GT(equiv->cost(), 0.0);
+    EXPECT_GT(equiv->strict_cost(), 0.0);
+}
+
 TEST(IntermediateBlueprintsTest, test_Equiv_Blueprint) {
     FieldSpecBaseList            fields;
     search::fef::MatchDataLayout subLayout;

searchlib/src/vespa/searchlib/queryeval/equiv_blueprint.cpp

@@ -57,8 +57,9 @@ void EquivBlueprint::sort(InFlow in_flow) {
 }
 
 FlowStats EquivBlueprint::calculate_flow_stats(uint32_t docid_limit) const {
+    auto update = [docid_limit](Blueprint& bp) { bp.update_flow_stats(docid_limit); };
     for (auto& term : _terms) {
-        term->update_flow_stats(docid_limit);
+        term->each_node_post_order(update);
     }
     double est = OrFlow::estimate_of(_terms);
     return {est, OrFlow::cost_of(_terms, false), OrFlow::cost_of(_terms, true) + flow::heap_cost(est, _terms.size())};