From eac9f3c33713a3e85e78a16c9babf2fbfb75cbb5 Mon Sep 17 00:00:00 2001
From: Michael Kolupaev <mkolupaev@yandex-team.ru>
Date: Mon, 11 Feb 2013 17:30:09 +0000
Subject: [PATCH] clickhouse: fixed some alias issues [#CONV-2944].

---
 dbms/include/DB/Core/ErrorCodes.h    |  3 +-
 dbms/src/Interpreters/Expression.cpp | 68 ++++++++++++++++++++++------
 2 files changed, 57 insertions(+), 14 deletions(-)

diff --git a/dbms/include/DB/Core/ErrorCodes.h b/dbms/include/DB/Core/ErrorCodes.h
index 8adf18aedbe..2285599bbde 100644
--- a/dbms/include/DB/Core/ErrorCodes.h
+++ b/dbms/include/DB/Core/ErrorCodes.h
@@ -184,7 +184,8 @@ namespace ErrorCodes
 		NEGATIVE_REFCOUNT,
 		CHUNK_NOT_FOUND,
 		DUPLICATE_CHUNK_NAME,
-		NO_SUCH_TABLE,
+		MULTIPLE_ALIASES_FOR_EXPRESSION,
+		MULTIPLE_EXPRESSIONS_FOR_ALIAS,
 
 		POCO_EXCEPTION = 1000,
 		STD_EXCEPTION,
diff --git a/dbms/src/Interpreters/Expression.cpp b/dbms/src/Interpreters/Expression.cpp
index 2475054925d..63a6379b827 100644
--- a/dbms/src/Interpreters/Expression.cpp
+++ b/dbms/src/Interpreters/Expression.cpp
@@ -32,6 +32,27 @@ NamesAndTypesList::const_iterator Expression::findColumn(const String & name)
 }
 
 
+static std::string * GetAlias(ASTPtr & ast)
+{
+	if (ASTFunction * node = dynamic_cast<ASTFunction *>(&*ast))
+	{
+		return &node->alias;
+	}
+	else if (ASTIdentifier * node = dynamic_cast<ASTIdentifier *>(&*ast))
+	{
+		return &node->alias;
+	}
+	else if (ASTLiteral * node = dynamic_cast<ASTLiteral *>(&*ast))
+	{
+		return &node->alias;
+	}
+	else
+	{
+		return NULL;
+	}
+}
+
+
 void Expression::createAliasesDict(ASTPtr & ast)
 {
 	/// Обход снизу-вверх. Не опускаемся в подзапросы.
@@ -39,20 +60,17 @@ void Expression::createAliasesDict(ASTPtr & ast)
 		if (!dynamic_cast<ASTSelectQuery *>(&**it))
 			createAliasesDict(*it);
 	
-	if (ASTFunction * node = dynamic_cast<ASTFunction *>(&*ast))
+	std::string * alias = GetAlias(ast);
+	if (alias)
 	{
-		if (!node->alias.empty())
-			aliases[node->alias] = ast;
-	}
-	else if (ASTIdentifier * node = dynamic_cast<ASTIdentifier *>(&*ast))
-	{
-		if (!node->alias.empty())
-			aliases[node->alias] = ast;
-	}
-	else if (ASTLiteral * node = dynamic_cast<ASTLiteral *>(&*ast))
-	{
-		if (!node->alias.empty())
-			aliases[node->alias] = ast;
+		if (aliases.count(*alias))
+		{
+			throw Exception("Multiple expressions with the same alias", ErrorCodes::MULTIPLE_EXPRESSIONS_FOR_ALIAS);
+		}
+		else
+		{
+			aliases[*alias] = ast;
+		}
 	}
 }
 
@@ -245,9 +263,33 @@ void Expression::glueTreeImpl(ASTPtr ast, Subtrees & subtrees)
 		{
 			String tree_id = (*it)->getTreeID();
 			if (subtrees.end() == subtrees.find(tree_id))
+			{
 				subtrees[tree_id] = *it;
+			}
 			else
+			{
+				/// Перед заменой поддерева запомним алиас.
+				std::string * alias_ptr = GetAlias(*it);
+				std::string initial_alias;
+				if (alias_ptr)
+					initial_alias = *alias_ptr;
+				
 				*it = subtrees[tree_id];
+				
+				/// Объединим два алиаса.
+				alias_ptr = GetAlias(*it);
+				if (alias_ptr)
+				{
+					if (alias_ptr->empty())
+					{
+						*alias_ptr = initial_alias;
+					}
+					else if (!initial_alias.empty())
+					{
+						throw Exception("Multiple aliases for the same expression", ErrorCodes::MULTIPLE_ALIASES_FOR_EXPRESSION);
+					}
+				}
+			}
 		}
 	}
 }