```
DROP TABLE IF EXISTS foo;

CREATE TABLE foo (timestamp DateTime, x UInt64)
ENGINE = MergeTree PARTITION BY toYYYYMMDD(timestamp)
ORDER BY (timestamp);

INSERT INTO foo (timestamp, x) SELECT toDateTime('2020-01-01 00:05:00'), number from system.numbers_mt LIMIT 100;

SELECT count() FROM system.mutations; -- ok

ALTER TABLE foo UPDATE x = 1 WHERE x = (SELECT x from foo WHERE x = 1);

SELECT count() FROM system.mutations; -- stuck

```
#pragma once
#include <Core/Block.h>
#include <Core/NamesAndTypes.h>
#include <Interpreters/Aliases.h>
#include <Interpreters/Context_fwd.h>
#include <Interpreters/DatabaseAndTableWithAlias.h>
#include <Interpreters/SelectQueryOptions.h>
#include <Storages/IStorage_fwd.h>
namespace DB
{
class ASTFunction;
struct ASTTablesInSelectQueryElement;
class TableJoin;