Reject CREATE TABLE ... CLONE AS SELECT / table function

tuanpach · tuanpach · commit ae90c08aff79 · 2026-05-15T08:43:37.000Z
The parser accepted CREATE TABLE t CLONE AS SELECT ... and CREATE TABLE t CLONE AS <table_function>, but neither shape has partitions to attach, so the CLONE keyword was silently ignored and the table was created as a plain CREATE ... AS SELECT. Reject these shapes early in getTablePropertiesAndNormalizeCreateQuery with BAD_ARGUMENTS instead. Also fix ASTCreateQuery::formatQueryImpl: the `if (select)` branch did not emit CLONE, so an AST round-trip silently dropped the keyword. Add add_clone_if_needed alongside the existing add_empty_if_needed call so CLONE survives reformatting. After this, the randomized-settings injection in clickhouse-test round-trips CLONE faithfully and the interpreter check above catches the rewritten query. Fixes #104994
diff --git a/src/Interpreters/InterpreterCreateQuery.cpp b/src/Interpreters/InterpreterCreateQuery.cpp
@@ -735,6 +735,13 @@ ConstraintsDescription InterpreterCreateQuery::getConstraintsDescription(
 InterpreterCreateQuery::TableProperties InterpreterCreateQuery::getTablePropertiesAndNormalizeCreateQuery(
     ASTCreateQuery & create, LoadingStrictnessLevel mode)
 {
+    /// CLONE AS requires a source table (the partition-attach step needs a real table on disk).
+    /// The parser also accepts CLONE AS SELECT ... / CLONE AS <table_function>, but neither has
+    /// partitions to clone, so reject these forms early instead of silently ignoring CLONE.
+    if (create.is_clone_as && create.as_table.empty())
+        throw Exception(ErrorCodes::BAD_ARGUMENTS,
+            "CLONE AS requires a source table name, not a SELECT query or table function");
+
     /// Set the table engine if it was not specified explicitly.
     setEngine(create);
 
diff --git a/src/Parsers/ASTCreateQuery.cpp b/src/Parsers/ASTCreateQuery.cpp
@@ -593,6 +593,11 @@ void ASTCreateQuery::formatQueryImpl(WriteBuffer & ostr, const FormatSettings &
         ostr << " POPULATE";
 
     add_empty_if_needed();
+    /// Mirrors `add_empty_if_needed` above: the `if (!as_table.empty())` and `if (as_table_function)`
+    /// branches earlier consume CLONE for the table / table-function shapes; this call covers the
+    /// `CLONE AS SELECT` shape so the keyword survives an AST format round-trip. The interpreter
+    /// still rejects `CLONE AS SELECT` at execution, but the formatter must not silently drop CLONE.
+    add_clone_if_needed();
 
     if (sql_security && supportSQLSecurity() && sql_security->as<ASTSQLSecurity &>().type.has_value())
     {
diff --git a/tests/queries/0_stateless/04238_clone_as_select_rejected.reference b/tests/queries/0_stateless/04238_clone_as_select_rejected.reference
@@ -0,0 +1,3 @@
+1
+2
+3
diff --git a/tests/queries/0_stateless/04238_clone_as_select_rejected.sql b/tests/queries/0_stateless/04238_clone_as_select_rejected.sql
@@ -0,0 +1,33 @@
+-- Tags: no-replicated-database
+-- Tag no-replicated-database: Unsupported type of CREATE TABLE ... CLONE AS ... query
+
+-- Regression test for: `CLONE AS SELECT` silently ignores `CLONE` keyword instead of throwing.
+-- See https://github.com/ClickHouse/ClickHouse/issues/104994
+--
+-- `CLONE AS` only makes sense when the source is a real table on disk (the partition-attach
+-- step needs partitions). `CLONE AS SELECT ...` and `CLONE AS <table_function>` are accepted
+-- by the parser but used to silently fall back to plain `CREATE ... AS SELECT`. Both forms
+-- must now be rejected with `BAD_ARGUMENTS`.
+
+DROP TABLE IF EXISTS clone_src;
+DROP TABLE IF EXISTS clone_dst;
+
+CREATE TABLE clone_src (x Int32) ENGINE = MergeTree ORDER BY x;
+INSERT INTO clone_src VALUES (1), (2), (3);
+
+-- Sanity: regular CLONE AS <table> still works.
+CREATE TABLE clone_dst CLONE AS clone_src;
+SELECT * FROM clone_dst ORDER BY x;
+DROP TABLE clone_dst;
+
+-- CLONE AS SELECT must be rejected.
+CREATE TABLE clone_dst CLONE AS SELECT x * 2 AS doubled FROM clone_src; -- { serverError BAD_ARGUMENTS }
+
+-- CLONE AS SELECT with an explicit column list + engine must also be rejected.
+-- (The parser only attempts SELECT in this branch when a storage clause is present, so include ENGINE.)
+CREATE TABLE clone_dst (doubled Int64) ENGINE = MergeTree ORDER BY doubled CLONE AS SELECT x * 2 AS doubled FROM clone_src; -- { serverError BAD_ARGUMENTS }
+
+-- CLONE AS <table_function> must be rejected.
+CREATE TABLE clone_dst CLONE AS numbers(10); -- { serverError BAD_ARGUMENTS }
+
+DROP TABLE clone_src;
