do nested collapsing of AND when collapsing ANDNOT

this is needed since the AND getting the extra AND as a child has
already been processed for the optimize pass that performs AND
collapsing.

2 files changed, 24 insertions, 1 deletions

diff --git a/searchlib/src/tests/queryeval/blueprint/intermediate_blueprints_test.cpp b/searchlib/src/tests/queryeval/blueprint/intermediate_blueprints_test.cpp
index e24e91c2f1d..53803c9c9e7 100644
--- a/searchlib/src/tests/queryeval/blueprint/intermediate_blueprints_test.cpp
+++ b/searchlib/src/tests/queryeval/blueprint/intermediate_blueprints_test.cpp
@@ -716,6 +716,22 @@ TEST("AND_NOT AND AND_NOT collapsing") {
     optimize_and_compare(std::move(top), std::move(expect));
 }
 
+TEST("AND_NOT AND AND_NOT AND nested collapsing") {
+    Blueprint::UP top = make::ANDNOT()
+        .add(make::AND()
+             .add(make::ANDNOT()
+                  .add(make::AND().leafs({1,2}))
+                  .leafs({5,6}))
+             .add(make::ANDNOT()
+                  .add(make::AND().leafs({3,4}))
+                  .leafs({8,9})))
+        .leaf(7);
+    Blueprint::UP expect = make::ANDNOT()
+        .add(make::AND().leafs({1,2,3,4}))
+        .leafs({9,8,7,6,5});
+    optimize_and_compare(std::move(top), std::move(expect));
+}
+
 TEST("AND_NOT AND AND_NOT collapsing into full source blender optimization") {
     InvalidSelector sel;
     Blueprint::UP top =
diff --git a/searchlib/src/vespa/searchlib/queryeval/intermediate_blueprints.cpp b/searchlib/src/vespa/searchlib/queryeval/intermediate_blueprints.cpp
index c43335a6fdf..364602cba03 100644
--- a/searchlib/src/vespa/searchlib/queryeval/intermediate_blueprints.cpp
+++ b/searchlib/src/vespa/searchlib/queryeval/intermediate_blueprints.cpp
@@ -133,7 +133,14 @@ AndNotBlueprint::optimize_self(OptimizePass pass)
                     while (grand_child->childCnt() > 1) {
                         addChild(grand_child->removeLastChild());
                     }
-                    child->addChild(grand_child->removeChild(0));
+                    auto orphan = grand_child->removeChild(0);
+                    if (auto *orphan_and = orphan->asAnd()) {
+                        while (orphan_and->childCnt() > 0) {
+                            child->addChild(orphan_and->removeLastChild());
+                        }
+                    } else {
+                        child->addChild(std::move(orphan));
+                    }
                     child->removeChild(i--);
                 }
             }