Consider aliases when checking if sorting order is preserved by

expression

src/Interpreters/ActionsDAG.cpp

@@ -1927,7 +1927,7 @@ ActionsDAGPtr ActionsDAG::cloneActionsForFilterPushDown(
     return actions;
 }
 
-bool ActionsDAG::isSortingPreserved(const Block & header, const SortDescription & sort_description) const
+bool ActionsDAG::isSortingPreserved(const Block & input_header, const SortDescription & sort_description) const
 {
     if (sort_description.empty())
         return true;
@@ -1935,12 +1935,40 @@ bool ActionsDAG::isSortingPreserved(const Block & header, const SortDescription
     if (hasArrayJoin())
         return false;
 
-    const Block & output_header = updateHeader(header);
+    /// build reversed aliases, use it later to find out if some aliases refer to sorted columns
+    std::unordered_map<std::string_view, const String &> reversed_aliases;
+    for (const Node * node : index)
+    {
+        if (node->type == ActionType::ALIAS)
+        {
+            reversed_aliases.emplace(node->children.front()->result_name, node->result_name);
+        }
+    }
+
+    const Block & output_header = updateHeader(input_header);
     for (const auto & desc : sort_description)
     {
+        /// check if column is part of output header
+        /// if not, check if aliases in output header refers to the column
         if (!output_header.findByName(desc.column_name))
+        {
+            const auto it = reversed_aliases.find(desc.column_name);
+            if (it == reversed_aliases.end())
+                return false;
+
+            /// check if alias to sorted column is in output header
+            if (!output_header.findByName(it->second))
                 return false;
         }
+
+        /// check that found colunm is not an alias
+        for (const Node * node : index)
+        {
+            if (node->type == ActionType::ALIAS && node->result_name == desc.column_name)
+                return false;
+        }
+    }
+
     return true;
 }
 

src/Interpreters/ActionsDAG.h

@@ -303,7 +303,7 @@ public:
         const Names & available_inputs,
         const ColumnsWithTypeAndName & all_inputs);
 
-    bool isSortingPreserved(const Block & header, const SortDescription & sort_description) const;
+    bool isSortingPreserved(const Block & input_header, const SortDescription & sort_description) const;
 
 private:
     Node & addNode(Node node);

src/Processors/QueryPlan/FilterStep.cpp

@@ -14,7 +14,7 @@ static ITransformingStep::Traits getTraits(const ActionsDAGPtr & expression, con
     bool preserves_sorting = expression->isSortingPreserved(header, sort_description);
     if (remove_filter_column)
     {
-        preserves_sorting = find_if(
+        preserves_sorting &= find_if(
                                  begin(sort_description),
                                  end(sort_description),
                                  [&](const auto & column_desc) { return column_desc.column_name == filter_column_name; })

tests/queries/0_stateless/02377_optimize_sorting_for_input_stream_explain.reference

@@ -24,3 +24,15 @@ Sort Mode: Chunk: a ASC
 Sort Mode: None
 Sort Mode: None
 Sort Mode: Chunk: a ASC
+-- PLAN: aliases break sorting order
+Sort Mode: Stream: a ASC
+Sort Mode: Stream: a ASC
+Sort Mode: None
+Sort Mode: Stream: a ASC
+Sort Mode: Port: a ASC
+Sort Mode: Port: a ASC
+-- PLAN: aliases DONT break sorting order
+Sort Mode: Stream: x ASC, y ASC
+Sort Mode: Stream: x ASC, y ASC
+Sort Mode: Chunk: a ASC, b ASC
+Sort Mode: Chunk: a ASC, b ASC

tests/queries/0_stateless/02377_optimize_sorting_for_input_stream_explain.sh

@@ -37,3 +37,13 @@ $CLICKHOUSE_CLIENT -nq "EXPLAIN PLAN sortmode=1 SELECT a FROM optimize_sorting W
 
 $CLICKHOUSE_CLIENT -q "select '-- PLAN: FilterStep breaks sort mode'"
 $CLICKHOUSE_CLIENT -nq "EXPLAIN PLAN sortmode=1 SELECT a > 0 FROM optimize_sorting WHERE a > 0" | eval $FIND_SORTMODE
+
+$CLICKHOUSE_CLIENT -q "select '-- PLAN: aliases break sorting order'"
+$CLICKHOUSE_CLIENT -nq "EXPLAIN PLAN sortmode=1 SELECT a FROM (SELECT sipHash64(a) AS a FROM (SELECT a FROM optimize_sorting ORDER BY a)) ORDER BY a" | eval $FIND_SORTMODE
+
+# FIXME: we still do full sort here, - it's because, for most inner subqueury, sorting description contains original column names but header contains only aliases on those columns:
+#|     Header: x Int32                                                 │
+#│             y Int32                                                 │
+#│     Sort Mode: Chunk: a ASC, b ASC                                  │
+$CLICKHOUSE_CLIENT -q "select '-- PLAN: aliases DONT break sorting order'"
+$CLICKHOUSE_CLIENT -nq "EXPLAIN PLAN sortmode=1 SELECT a, b FROM (SELECT x AS a, y AS b FROM (SELECT a AS x, b AS y FROM optimize_sorting) ORDER BY x, y)" | eval $FIND_SORTMODE