```
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

```
plan.addStep(std::make_unique<FilterStep>(plan.getCurrentDataStream(), step->actions(), stage.filter_column_names[i], false));
            }
            else
            {
                
                plan.addStep(std::make_unique<ExpressionStep>(plan.getCurrentDataStream(), step->actions()));
            }
        }
        SubqueriesForSets & subqueries_for_sets = stage.analyzer->getSubqueriesForSets();
        if (!subqueries_for_sets.empty())
        {
            const Settings & settings = context->getSettingsRef();
            SizeLimits network_transfer_limits(
                    settings.max_rows_to_transfer, settings.max_bytes_to_transfer, settings.transfer_overflow_mode);
            addCreatingSetsStep(plan, std::move(subqueries_for_sets), network_transfer_limits, context);
        }
    }
    QueryPlanOptimizationSettings do_not_optimize_plan;
    do_not_optimize_plan.optimize_plan = false;
    auto pipeline = plan.buildQueryPipeline(
        do_not_optimize_plan,
        BuildQueryPipelineSettings::fromContext(context));
    pipeline->addSimpleTransform([&](const Block & header)
    {
        return std::make_shared<MaterializingTransform>(header);
    });
    return pipeline;
}
void MutationsInterpreter::validate()