Merge 4765fcac38 into 40c7d5fd1a

src/Parsers/Access/ParserCreateUserQuery.cpp

@@ -549,6 +549,8 @@ bool ParserCreateUserQuery::parseImpl(Pos & pos, ASTPtr & node, Expected & expec
     auto names = typeid_cast<std::shared_ptr<ASTUserNamesWithHost>>(names_ast);
     auto names_ref = names->names;
 
+    auto pos_after_parsing_names = pos;
+
     std::optional<String> new_name;
     std::optional<AllowedClientHosts> hosts;
     std::optional<AllowedClientHosts> add_hosts;
@@ -674,6 +676,13 @@ bool ParserCreateUserQuery::parseImpl(Pos & pos, ASTPtr & node, Expected & expec
     else if (alter)
         names->concatParts();
 
+    bool alter_query_with_no_changes = alter && pos_after_parsing_names == pos;
+
+    if (alter_query_with_no_changes)
+    {
+        return false;
+    }
+
     auto query = std::make_shared<ASTCreateUserQuery>();
     node = query;
 

tests/queries/0_stateless/03254_test_alter_user_no_changes.sql

@@ -0,0 +1,5 @@
+-- Tags: no-parallel
+
+create user u_03254_alter_user;
+alter user u_03254_alter_user; -- { clientError SYNTAX_ERROR }
+drop user u_03254_alter_user;