Updated UnionNode documentation

src/Analyzer/QueryNode.h

@@ -74,7 +74,7 @@ public:
         return is_subquery;
     }
 
-    /// Set query node is subquery
+    /// Set query node is subquery value
     void setIsSubquery(bool is_subquery_value)
     {
         is_subquery = is_subquery_value;

src/Analyzer/TableNode.h

@@ -16,10 +16,6 @@ namespace DB
 /** Table node represents table in query tree.
   * Example: SELECT a FROM test_table.
   * test_table - is identifier, that during query analysis pass must be resolved into table node.
-  *
-  * During construction table node:
-  * 1. Lock storage for share. Later lock can be moved out of node using `moveTableLock` method.
-  * 2. Take storage snapshot.
   */
 class TableNode;
 using TableNodePtr = std::shared_ptr<TableNode>;

src/Analyzer/UnionNode.cpp

@@ -41,10 +41,12 @@ UnionNode::UnionNode()
 NamesAndTypes UnionNode::computeProjectionColumns() const
 {
     std::vector<NamesAndTypes> projections;
-    const auto & query_nodes = getQueries().getNodes();
 
     NamesAndTypes query_node_projection;
 
+    const auto & query_nodes = getQueries().getNodes();
+    projections.reserve(query_nodes.size());
+
     for (const auto & query_node : query_nodes)
     {
         if (auto * query_node_typed = query_node->as<QueryNode>())
@@ -234,7 +236,7 @@ ASTPtr UnionNode::toASTImpl() const
 
     if (union_mode != SelectUnionMode::UNION_DEFAULT &&
         union_mode != SelectUnionMode::EXCEPT_DEFAULT &&
-        union_mode != SelectUnionMode::EXCEPT_DEFAULT)
+        union_mode != SelectUnionMode::INTERSECT_DEFAULT)
         select_with_union_query->is_normalized = true;
 
     select_with_union_query->list_of_modes = union_modes;

src/Analyzer/UnionNode.h

@@ -19,6 +19,15 @@ namespace ErrorCodes
 }
 
 /** Union node represents union of queries in query tree.
+  *
+  * Example: (SELECT id FROM test_table) UNION ALL (SELECT id FROM test_table_2);
+  * Example: (SELECT id FROM test_table) UNION DISTINCT (SELECT id FROM test_table_2);
+  * Example: (SELECT id FROM test_table) EXCEPT ALL (SELECT id FROM test_table_2);
+  * Example: (SELECT id FROM test_table) EXCEPT DISTINCT (SELECT id FROM test_table_2);
+  * Example: (SELECT id FROM test_table) INTERSECT ALL (SELECT id FROM test_table_2);
+  * Example: (SELECT id FROM test_table) INTERSECT DISTINCT (SELECT id FROM test_table_2);
+  *
+  * During query analysis pass union node queries must be resolved.
   */
 class UnionNode;
 using UnionNodePtr = std::shared_ptr<UnionNode>;
@@ -28,77 +37,91 @@ class UnionNode final : public IQueryTreeNode
 public:
     explicit UnionNode();
 
+    /// Returns true if union node is subquery, false otherwise
     bool isSubquery() const
     {
         return is_subquery;
     }
 
+    /// Set union node is subquery value
     void setIsSubquery(bool is_subquery_value)
     {
         is_subquery = is_subquery_value;
     }
 
+    /// Returns true if union node is CTE, false otherwise
     bool isCTE() const
     {
         return is_cte;
     }
 
+    /// Set union node is CTE
     void setIsCTE(bool is_cte_value)
     {
         is_cte = is_cte_value;
     }
 
+    /// Get union node CTE name
     const std::string & getCTEName() const
     {
         return cte_name;
     }
 
+    /// Set union node CTE name
     void setCTEName(std::string cte_name_value)
     {
         cte_name = std::move(cte_name_value);
     }
 
+    /// Get union mode
     SelectUnionMode getUnionMode() const
     {
         return union_mode;
     }
 
+    /// Set union mode value
     void setUnionMode(SelectUnionMode union_mode_value)
     {
         union_mode = union_mode_value;
     }
 
+    /// Get union modes
     const SelectUnionModes & getUnionModes() const
     {
         return union_modes;
     }
 
+    /// Set union modes value
     void setUnionModes(const SelectUnionModes & union_modes_value)
     {
         union_modes = union_modes_value;
         union_modes_set = SelectUnionModesSet(union_modes.begin(), union_modes.end());
     }
 
-    const QueryTreeNodePtr & getQueriesNode() const
-    {
-        return children[queries_child_index];
-    }
-
-    QueryTreeNodePtr & getQueriesNode()
-    {
-        return children[queries_child_index];
-    }
-
+    /// Get union node queries
     const ListNode & getQueries() const
     {
         return children[queries_child_index]->as<const ListNode &>();
     }
 
+    /// Get union node queries
     ListNode & getQueries()
     {
         return children[queries_child_index]->as<ListNode &>();
     }
 
+    /// Get union node queries node
+    const QueryTreeNodePtr & getQueriesNode() const
+    {
+        return children[queries_child_index];
+    }
+
+    /// Get union node queries node
+    QueryTreeNodePtr & getQueriesNode()
+    {
+        return children[queries_child_index];
+    }
+
     /// Return true if union node has table expression modifiers, false otherwise
     bool hasTableExpressionModifiers() const
     {
@@ -117,8 +140,7 @@ public:
         table_expression_modifiers = std::move(table_expression_modifiers_value);
     }
 
-
-    /// Compute union projection
+    /// Compute union node projection columns
     NamesAndTypes computeProjectionColumns() const;
 
     QueryTreeNodeType getNodeType() const override