And waits for them. That's pointless.
BlockInputStreamPtr & input_stream,
    const NameSet & updated_columns,
    const StorageMetadataPtr & metadata_snapshot,
    ContextPtr context,
    const NameSet & materialized_indices,
    const MergeTreeData::DataPartPtr & source_part)
{
    
    const auto & index_factory = MergeTreeIndexFactory::instance();
    std::set<MergeTreeIndexPtr> indices_to_recalc;
    ASTPtr indices_recalc_expr_list = std::make_shared<ASTExpressionList>();
    const auto & indices = metadata_snapshot->getSecondaryIndices();
    for (size_t i = 0; i < indices.size(); ++i)
    {
        const auto & index = indices[i];
        
        if (!source_part->checksums.has(INDEX_FILE_PREFIX + index.name + ".idx") && materialized_indices.count(index.name))
        {
            if (indices_to_recalc.insert(index_factory.get(index)).second)
            {
                ASTPtr expr_list = index.expression_list_ast->clone();