dbms: implemented LEFT ARRAY JOIN [#METR-17474].

dbms/include/DB/Interpreters/ExpressionActions.h

@@ -66,6 +66,7 @@ public:
 
 	/// Для ARRAY_JOIN
 	NameSet array_joined_columns;
+	bool array_join_is_left;
 
 	/// Для JOIN
 	const Join * join = nullptr;
@@ -122,13 +123,14 @@ public:
 		return a;
 	}
 
-	static ExpressionAction arrayJoin(const NameSet & array_joined_columns)
+	static ExpressionAction arrayJoin(const NameSet & array_joined_columns, bool array_join_is_left)
 	{
 		if (array_joined_columns.empty())
 			throw Exception("No arrays to join", ErrorCodes::LOGICAL_ERROR);
 		ExpressionAction a;
 		a.type = ARRAY_JOIN;
 		a.array_joined_columns = array_joined_columns;
+		a.array_join_is_left = array_join_is_left;
 		return a;
 	}
 

dbms/include/DB/Parsers/ASTSelectQuery.h

@@ -50,6 +50,7 @@ public:
 	ASTPtr select_expression_list;
 	ASTPtr database;
 	ASTPtr table;	/// Идентификатор, табличная функция или подзапрос (рекурсивно ASTSelectQuery)
+	bool array_join_is_left = false;	/// LEFT ARRAY JOIN
 	ASTPtr array_join_expression_list;	/// ARRAY JOIN
 	ASTPtr join;						/// Обычный (не ARRAY) JOIN.
 	bool final = false;

dbms/src/Interpreters/ExpressionActions.cpp

@@ -6,6 +6,7 @@
 #include <DB/DataTypes/DataTypeNested.h>
 #include <DB/DataTypes/DataTypeArray.h>
 #include <DB/Functions/IFunction.h>
+#include <DB/Functions/FunctionsArray.h>
 #include <set>
 
 
@@ -268,6 +269,24 @@ void ExpressionAction::execute(Block & block) const
 			if (!any_array)
 				throw Exception("ARRAY JOIN of not array: " + *array_joined_columns.begin(), ErrorCodes::TYPE_MISMATCH);
 
+			/// Если LEFT ARRAY JOIN, то создаём столбцы, в которых пустые массивы заменены на массивы с одним элементом - значением по-умолчанию.
+			std::map<String, ColumnPtr> non_empty_array_columns;
+			if (array_join_is_left)
+			{
+				for (const auto & name : array_joined_columns)
+				{
+					auto src_col = block.getByName(name);
+
+					Block tmp_block{src_col, {{}, src_col.type, {}}};
+
+					FunctionEmptyArrayToSingle().execute(tmp_block, {0}, 1);
+					non_empty_array_columns[name] = tmp_block.getByPosition(1).column;
+				}
+
+				any_array_ptr = non_empty_array_columns.begin()->second;
+				any_array = typeid_cast<const ColumnArray *>(&*any_array_ptr);
+			}
+
 			size_t columns = block.columns();
 			for (size_t i = 0; i < columns; ++i)
 			{
@@ -278,7 +297,8 @@ void ExpressionAction::execute(Block & block) const
 					if (!typeid_cast<const DataTypeArray *>(&*current.type))
 						throw Exception("ARRAY JOIN of not array: " + current.name, ErrorCodes::TYPE_MISMATCH);
 
-					ColumnPtr array_ptr = current.column;
+					ColumnPtr array_ptr = array_join_is_left ? non_empty_array_columns[current.name] : current.column;
+
 					if (array_ptr->isConst())
 						array_ptr = dynamic_cast<const IColumnConst &>(*array_ptr).convertToFullColumn();
 
@@ -379,7 +399,7 @@ std::string ExpressionAction::toString() const
 			break;
 
 		case ARRAY_JOIN:
-			ss << "ARRAY JOIN ";
+			ss << (array_join_is_left ? "LEFT " : "") << "ARRAY JOIN ";
 			for (NameSet::const_iterator it = array_joined_columns.begin(); it != array_joined_columns.end(); ++it)
 			{
 				if (it != array_joined_columns.begin())
@@ -761,7 +781,7 @@ std::string ExpressionActions::getID() const
 			ss << actions[i].result_name;
 		if (actions[i].type == ExpressionAction::ARRAY_JOIN)
 		{
-			ss << "{";
+			ss << (actions[i].array_join_is_left ? "LEFT ARRAY JOIN" : "ARRAY JOIN") << "{";
 			for (NameSet::const_iterator it = actions[i].array_joined_columns.begin();
 				 it != actions[i].array_joined_columns.end(); ++it)
 			{

dbms/src/Interpreters/ExpressionAnalyzer.cpp

@@ -1369,7 +1369,7 @@ void ExpressionAnalyzer::getActionsImpl(ASTPtr ast, bool no_subqueries, bool onl
 				actions_stack.addAction(ExpressionAction::copyColumn(arg->getColumnName(), result_name));
 				NameSet joined_columns;
 				joined_columns.insert(result_name);
-				actions_stack.addAction(ExpressionAction::arrayJoin(joined_columns));
+				actions_stack.addAction(ExpressionAction::arrayJoin(joined_columns, false));
 			}
 
 			return;
@@ -1666,7 +1666,7 @@ void ExpressionAnalyzer::addMultipleArrayJoinAction(ExpressionActionsPtr & actio
 		result_columns.insert(result_source.first);
 	}
 
-	actions->add(ExpressionAction::arrayJoin(result_columns));
+	actions->add(ExpressionAction::arrayJoin(result_columns, select_query->array_join_is_left));
 }
 
 bool ExpressionAnalyzer::appendArrayJoin(ExpressionActionsChain & chain, bool only_types)

dbms/src/Parsers/ParserSelectQuery.cpp

@@ -23,6 +23,7 @@ bool ParserSelectQuery::parseImpl(Pos & pos, Pos end, ASTPtr & node, Pos & max_p
 	ParserString s_select("SELECT", true, true);
 	ParserString s_distinct("DISTINCT", true, true);
 	ParserString s_from("FROM", true, true);
+	ParserString s_left("LEFT", true, true);
 	ParserString s_array("ARRAY", true, true);
 	ParserString s_join("JOIN", true, true);
 	ParserString s_using("USING", true, true);
@@ -166,8 +167,22 @@ bool ParserSelectQuery::parseImpl(Pos & pos, Pos end, ASTPtr & node, Pos & max_p
 	if (!parse_final_and_sample())
 		return false;
 
-	/// ARRAY JOIN expr list
-	if (s_array.ignore(pos, end, max_parsed_pos, expected))
+	/// [LEFT] ARRAY JOIN expr list
+	Pos saved_pos = pos;
+	bool has_array_join = false;
+	if (s_left.ignore(pos, end, max_parsed_pos, expected) && ws.ignore(pos, end) && s_array.ignore(pos, end, max_parsed_pos, expected))
+	{
+		select_query->array_join_is_left = true;
+		has_array_join = true;
+	}
+	else
+	{
+		pos = saved_pos;
+		if (s_array.ignore(pos, end, max_parsed_pos, expected))
+			has_array_join = true;
+	}
+
+	if (has_array_join)
 	{
 		ws.ignore(pos, end);
 
@@ -182,7 +197,7 @@ bool ParserSelectQuery::parseImpl(Pos & pos, Pos end, ASTPtr & node, Pos & max_p
 		ws.ignore(pos, end);
 	}
 
-	/// [GLOBAL] ANY|ALL INNER|LEFT JOIN (subquery) USING tuple
+	/// [GLOBAL] [ANY|ALL] INNER|LEFT|RIGHT|FULL|CROSS [OUTER] JOIN (subquery)|table_name USING tuple
 	join.parse(pos, end, select_query->join, max_parsed_pos, expected);
 
 	if (!parse_final_and_sample())

dbms/src/Parsers/formatAST.cpp

@@ -163,7 +163,9 @@ void formatAST(const ASTSelectQuery 		& ast, std::ostream & s, size_t indent, bo
 
 	if (ast.array_join_expression_list)
 	{
-		s << (hilite ? hilite_keyword : "") << nl_or_ws << indent_str << "ARRAY JOIN " << (hilite ? hilite_none : "");
+		s << (hilite ? hilite_keyword : "") << nl_or_ws << indent_str
+			<< (ast.array_join_is_left ? "LEFT " : "") << "ARRAY JOIN " << (hilite ? hilite_none : "");
+
 		one_line
 			? formatAST(*ast.array_join_expression_list, s, indent, hilite, one_line)
 			: formatExpressionListMultiline(typeid_cast<const ASTExpressionList &>(*ast.array_join_expression_list), s, indent, hilite);

dbms/tests/queries/0_stateless/00207_left_array_join.reference

+0
+1
+2
+2
+3
+4
+5
+5
+6
+7
+0	[]	0
+1	[0]	0
+2	[0,1]	0
+2	[0,1]	1
+3	[]	0
+4	[0]	0
+5	[0,1]	0
+5	[0,1]	1
+6	[]	0
+7	[0]	0
+8	[0,1]	0
+8	[0,1]	1
+9	[]	0

dbms/tests/queries/0_stateless/00207_left_array_join.sql

+SELECT number FROM system.numbers LEFT ARRAY JOIN range(number % 3) AS arr LIMIT 10;
+SELECT number, arr, x FROM (SELECT number, range(number % 3) AS arr FROM system.numbers LIMIT 10) LEFT ARRAY JOIN arr AS x;