Avoid alias duplicates in PASTE JOIN and fix aliases requirement

src/Analyzer/Passes/QueryAnalysisPass.cpp

@@ -1207,6 +1207,8 @@ class QueryAnalyzer
 
     static void validateJoinTableExpressionWithoutAlias(const QueryTreeNodePtr & join_node, const QueryTreeNodePtr & table_expression_node, IdentifierResolveScope & scope);
 
+    static void checkDuplicateTableNamesOrAlias(const QueryTreeNodePtr & join_node, QueryTreeNodePtr & left_table_expr, QueryTreeNodePtr & right_table_expr, IdentifierResolveScope & scope);
+
     static std::pair<bool, UInt64> recursivelyCollectMaxOrdinaryExpressions(QueryTreeNodePtr & node, QueryTreeNodes & into);
 
     static void expandGroupByAll(QueryNode & query_tree_node_typed);
@@ -2249,7 +2251,13 @@ void QueryAnalyzer::validateJoinTableExpressionWithoutAlias(const QueryTreeNodeP
         return;
 
     auto table_expression_node_type = table_expression_node->getNodeType();
-    if (table_expression_node_type == QueryTreeNodeType::TABLE_FUNCTION ||
+    auto * join_typed = join_node->as<JoinNode>();
+    if (table_expression_node_type == QueryTreeNodeType::QUERY && join_typed->getKind() == JoinKind::Paste)
+    {
+        checkDuplicateTableNamesOrAlias(join_node, join_typed->getLeftTableExpression(), join_typed->getRightTableExpression(), scope);
+        return;
+    }
+    else if (table_expression_node_type == QueryTreeNodeType::TABLE_FUNCTION ||
         table_expression_node_type == QueryTreeNodeType::QUERY ||
         table_expression_node_type == QueryTreeNodeType::UNION)
         throw Exception(ErrorCodes::ALIAS_REQUIRED,
@@ -6777,6 +6785,36 @@ void QueryAnalyzer::resolveArrayJoin(QueryTreeNodePtr & array_join_node, Identif
     }
 }
 
+void QueryAnalyzer::checkDuplicateTableNamesOrAlias(const QueryTreeNodePtr & join_node, QueryTreeNodePtr & left_table_expr, QueryTreeNodePtr & right_table_expr, IdentifierResolveScope & scope)
+{
+    Names column_names;
+    if (!scope.context->getSettingsRef().joined_subquery_requires_alias)
+        return;
+
+    if (join_node->as<JoinNode &>().getKind() != JoinKind::Paste)
+        return;
+
+    auto * left_node = left_table_expr->as<QueryNode>();
+    auto * right_node = right_table_expr->as<QueryNode>();
+
+    if (left_node)
+        for (const auto & name_and_type : left_node->getProjectionColumns())
+            column_names.push_back(name_and_type.name);
+    if (right_node)
+        for (const auto & name_and_type : right_node->getProjectionColumns())
+            column_names.push_back(name_and_type.name);
+
+    if (column_names.empty())
+        throw Exception(ErrorCodes::LOGICAL_ERROR, "Names of projection columns cannot be empty");
+
+    std::sort(column_names.begin(), column_names.end());
+    for (size_t i = 0; i < column_names.size() - 1; i++) // Check if there is not any duplicates because it will lead to broken result
+        if (column_names[i] == column_names[i+1])
+            throw Exception(ErrorCodes::BAD_ARGUMENTS,
+                            "Name of columns and aliases should be unique for this query (you can add/change aliases so they will not be duplicated)"
+                            "While processing '{}'", join_node->formatASTForErrorMessage());
+}
+
 /// Resolve join node in scope
 void QueryAnalyzer::resolveJoin(QueryTreeNodePtr & join_node, IdentifierResolveScope & scope, QueryExpressionsAliasVisitor & expressions_visitor)
 {
@@ -7130,6 +7168,7 @@ void QueryAnalyzer::resolveQuery(const QueryTreeNodePtr & query_node, Identifier
         initializeQueryJoinTreeNode(query_node_typed.getJoinTree(), scope);
         scope.alias_name_to_table_expression_node.clear();
 
+        Names column_names;
         resolveQueryJoinTreeNode(query_node_typed.getJoinTree(), scope, visitor);
     }
 

src/Parsers/ExpressionElementParsers.cpp

@@ -1451,6 +1451,7 @@ const char * ParserAlias::restricted_keywords[] =
     "ASOF",
     "BETWEEN",
     "CROSS",
+    "PASTE",
     "FINAL",
     "FORMAT",
     "FROM",

tests/queries/0_stateless/02933_paste_join.reference

@@ -82,3 +82,22 @@ UInt64
 7	2
 8	1
 9	0
+0	0
+1	1
+2	2
+3	3
+4	4
+5	5
+0	0
+1	1
+2	2
+3	3
+4	4
+5	5
+0	0
+1	1
+2	2
+3	3
+4	4
+5	5
+1	2	3

tests/queries/0_stateless/02933_paste_join.sql

@@ -1,6 +1,6 @@
 select * from (SELECT number as a FROM numbers(10)) t1 PASTE JOIN (select number as a from numbers(10)) t2;
 select * from (SELECT number as a FROM numbers(10)) t1 PASTE JOIN (select number as a from numbers(10) order by a desc) t2;
-create table if not exists test (num UInt64) engine=Memory;
+create table if not exists test (number UInt64) engine=Memory;
 insert into test select number from numbers(6);
 insert into test select number from numbers(5);
 SELECT * FROM (SELECT 1) t1 PASTE JOIN (SELECT 2) SETTINGS joined_subquery_requires_alias=0;
@@ -35,3 +35,11 @@ SET max_threads = 2;
 select * from (SELECT number as a FROM numbers_mt(10)) t1 PASTE JOIN (select number as a from numbers(10) ORDER BY a DESC) t2 SETTINGS max_block_size=10;
 select * from (SELECT number as a FROM numbers(10)) t1 ANY PASTE JOIN (select number as a from numbers(10)) t2; -- { clientError SYNTAX_ERROR }
 select * from (SELECT number as a FROM numbers(10)) t1 ALL PASTE JOIN (select number as a from numbers(10)) t2; -- { clientError SYNTAX_ERROR }
+
+TRUNCATE TABLE test;
+INSERT INTO test SELECT number from numbers(6);
+SELECT * FROM (SELECT number FROM test) PASTE JOIN (SELECT number FROM numbers(6) ORDER BY number) SETTINGS joined_subquery_requires_alias = 0;
+SELECT * FROM (SELECT number FROM test PASTE JOIN (Select number FROM numbers(7))) PASTE JOIN (SELECT number FROM numbers(6) PASTE JOIN (SELECT number FROM test)) SETTINGS joined_subquery_requires_alias = 0;
+SELECT * FROM (SELECT number FROM test PASTE JOIN (SELECT number FROM test PASTE JOIN (Select number FROM numbers(7)))) PASTE JOIN (SELECT number FROM numbers(6) PASTE JOIN (SELECT number FROM test)) SETTINGS joined_subquery_requires_alias = 0;
+SELECT * FROM (SELECT 1 AS a) PASTE JOIN (SELECT 2 AS b) PASTE JOIN (SELECT 3 AS c) SETTINGS allow_experimental_analyzer = 1;
+SELECT * FROM (SELECT 1 AS a) PASTE JOIN (SELECT 2 AS b) PASTE JOIN (SELECT 3 AS a) SETTINGS allow_experimental_analyzer = 1; -- { serverError AMBIGUOUS_COLUMN_NAME }