FLASH-451: Let qualified column reference not resolve to alias (#209)

* Let qualified column reference not resolve to alias, partial based on ClickHouse #4351

* Add alias test

* Address comments

dbms/src/Interpreters/ExpressionAnalyzer.cpp

@@ -342,6 +342,7 @@ void ExpressionAnalyzer::translateQualifiedNamesImpl(ASTPtr & ast, const String
                     {
                         String node_alias = ast->tryGetAlias();
                         ast = ast->children.back();
+                        static_cast<ASTIdentifier &>(*ast.get()).can_be_alias = false;
                         if (!node_alias.empty())
                             ast->setAlias(node_alias);
                     }
@@ -356,6 +357,7 @@ void ExpressionAnalyzer::translateQualifiedNamesImpl(ASTPtr & ast, const String
                                 new_name += '.';
                             new_name += static_cast<const ASTIdentifier &>(*child.get()).name;
                         }
+                        ident->can_be_alias = false;
                         ident->name = new_name;
                     }
                 }
@@ -1007,7 +1009,7 @@ void ExpressionAnalyzer::normalizeTreeImpl(
     }
     else if ((identifier_node = typeid_cast<ASTIdentifier *>(ast.get())))
     {
-        if (identifier_node->kind == ASTIdentifier::Column)
+        if (identifier_node->kind == ASTIdentifier::Column && identifier_node->can_be_alias)
         {
             /// If it is an alias, but not a parent alias (for constructs like "SELECT column + 1 AS column").
             auto it_alias = aliases.find(identifier_node->name);

dbms/src/Parsers/ASTIdentifier.h

@@ -25,8 +25,11 @@ class ASTIdentifier : public ASTWithAlias
     /// what this identifier identifies
     Kind kind;
 
+    /// if it's a cropped name it could not be an alias
+    bool can_be_alias;
+
     ASTIdentifier(const String & name_, const Kind kind_ = Column)
-        : name(name_), kind(kind_) {}
+        : name(name_), kind(kind_), can_be_alias(true) {}
 
     /** Get the text that identifies this element. */
     String getID() const override { return "Identifier_" + name; }

tests/mutable-test/bugs/flash-451.test

@@ -0,0 +1,17 @@
+>> DBGInvoke __enable_schema_sync_service('false')
+
+# Unqualified identifiers resolve to alias in select list.
+>> select 0 as c, c + 1 as c1 from (select 1 as c) as t where c = 1;
+
+# Qualified identifiers resolve to column in table.
+>> select 0 as c, t.c + 1 as c1 from (select 1 as c) as t where t.c = 1;
+┌─c─┬─c1─┐
+│ 0 │  2 │
+└───┴────┘
+
+# Combine the above two.
+>> select 0 as c, c + 1 as c1 from (select 1 as c) as t where t.c = 1;
+┌─c─┬─c1─┐
+│ 0 │  1 │
+└───┴────┘
+