Fix Sorted constraint for UnionMerge when the one of inputs is empty

commit_hash:1a6c8ea1c65a438f8801f4f71f6d1bcb15a95c81

2 files changed, 31 insertions, 2 deletions

diff --git a/yql/essentials/ast/yql_constraint.cpp b/yql/essentials/ast/yql_constraint.cpp
index 54ef1f44916..b19bf96c98a 100644
--- a/yql/essentials/ast/yql_constraint.cpp
+++ b/yql/essentials/ast/yql_constraint.cpp
@@ -444,7 +444,9 @@ const TSortedConstraintNode* TSortedConstraintNode::MakeCommon(const std::vector
 
     std::optional<TContainerType> content;
     for (size_t i = 0U; i < constraints.size(); ++i) {
-        if (const auto sort = constraints[i]->GetConstraint<TSortedConstraintNode>()) {
+        if (constraints[i]->GetConstraint<TEmptyConstraintNode>()) {
+            ; // just ignore this input with any other constraints
+        } else if (const auto sort = constraints[i]->GetConstraint<TSortedConstraintNode>()) {
             const auto& nextContent = sort->GetContent();
             if (content) {
                 const auto size = std::min(content->size(), nextContent.size());
@@ -466,7 +468,7 @@ const TSortedConstraintNode* TSortedConstraintNode::MakeCommon(const std::vector
             } else {
                 content = nextContent;
             }
-        } else if (!constraints[i]->GetConstraint<TEmptyConstraintNode>()) {
+        } else {
             content.reset();
             break;
         }
diff --git a/yql/essentials/core/ut/yql_expr_constraint_ut.cpp b/yql/essentials/core/ut/yql_expr_constraint_ut.cpp
index 981776d3ccd..d2fec272397 100644
--- a/yql/essentials/core/ut/yql_expr_constraint_ut.cpp
+++ b/yql/essentials/core/ut/yql_expr_constraint_ut.cpp
@@ -674,6 +674,33 @@ Y_UNIT_TEST_SUITE(TYqlExprConstraints) {
         CheckConstraint<TSortedConstraintNode>(exprRoot, "UnionMerge", "Sorted(key[desc])");
     }
 
+    Y_UNIT_TEST(UnionMergeWithEmptyDiffSort) {
+        const auto s = R"((
+            (let res (DataSink 'result))
+            (let list1 (AsList
+                (AsStruct '('key (String '4)) '('subkey (String 'c)) '('value (String 'v)))
+                (AsStruct '('key (String '1)) '('subkey (String 'd)) '('value (String 'v)))
+                (AsStruct '('key (String '3)) '('subkey (String 'b)) '('value (String 'v)))
+            ))
+            (let list2 (AsList
+                (AsStruct '('key (String '4)) '('subkey (Utf8 'c)) '('value (String 'v)))
+                (AsStruct '('key (String '1)) '('subkey (Utf8 'd)) '('value (String 'v)))
+                (AsStruct '('key (String '3)) '('subkey (Utf8 'b)) '('value (String 'v)))
+            ))
+            (let sorted1 (Sort list1 (Bool 'True) (lambda '(item) (Member item 'key))))
+            (let sorted2 (Sort list2 (Bool 'True) (lambda '(item) (Member item 'value))))
+            (let sorted2 (Take sorted2 (Uint64 '0)))
+            (let merged (UnionMerge sorted1 sorted2))
+            (let world (Write! world res (Key) merged '()))
+            (let world (Commit! world res))
+            (return world)
+        ))";
+
+        TExprContext exprCtx;
+        const auto exprRoot = ParseAndAnnotate(s, exprCtx);
+        CheckConstraint<TSortedConstraintNode>(exprRoot, "UnionMerge", "Sorted(key[asc])");
+    }
+
     Y_UNIT_TEST(ExtractMembersKey) {
         const auto s = R"((
             (let res (DataSink 'result))