Add UT for list struct based executors

[SeaRise]

Enhancement

While tidb currently uses tree struct base executor, older versions of tidb and tispark still use list struct base executors.

The difference is that the list struct base executors does not have an executor_id and the list struct base executors is held by DAGRequest.executors.

tiflash/dbms/src/Flash/Coprocessor/DAGQueryBlock.cpp

Lines 170 to 232 in 0bafed9

	/// construct DAGQueryBlock from a list struct based executors, which is the
	/// format before supporting join in dag request
	DAGQueryBlock::DAGQueryBlock(UInt32 id_, const ::google::protobuf::RepeatedPtrField<tipb::Executor> & executors)
	: id(id_)
	, root(nullptr)
	, qb_column_prefix("__QB_" + std::to_string(id_) + "_")
	{
	for (int i = executors.size() - 1; i >= 0; i--)
	{
	switch (executors[i].tp())
	{
	case tipb::ExecType::TypeTableScan:
	GET_METRIC(tiflash_coprocessor_executor_count, type_ts).Increment();
	assignOrThrowException(&source, &executors[i], SOURCE_NAME);
	/// use index as the prefix for executor name so when we sort by
	/// the executor name, it will result in the same order as it is
	/// in the dag_request, this is needed when filling execution_summary
	/// in DAGDriver
	if (executors[i].has_executor_id())
	source_name = executors[i].executor_id();
	else
	source_name = std::to_string(i) + "_tablescan";
	break;
	case tipb::ExecType::TypeSelection:
	GET_METRIC(tiflash_coprocessor_executor_count, type_sel).Increment();
	assignOrThrowException(&selection, &executors[i], SEL_NAME);
	if (executors[i].has_executor_id())
	selection_name = executors[i].executor_id();
	else
	selection_name = std::to_string(i) + "_selection";
	break;
	case tipb::ExecType::TypeStreamAgg:
	case tipb::ExecType::TypeAggregation:
	GET_METRIC(tiflash_coprocessor_executor_count, type_agg).Increment();
	assignOrThrowException(&aggregation, &executors[i], AGG_NAME);
	if (executors[i].has_executor_id())
	aggregation_name = executors[i].executor_id();
	else
	aggregation_name = std::to_string(i) + "_aggregation";
	break;
	case tipb::ExecType::TypeTopN:
	GET_METRIC(tiflash_coprocessor_executor_count, type_topn).Increment();
	assignOrThrowException(&limit_or_topn, &executors[i], TOPN_NAME);
	if (executors[i].has_executor_id())
	limit_or_topn_name = executors[i].executor_id();
	else
	limit_or_topn_name = std::to_string(i) + "_limitOrTopN";
	break;
	case tipb::ExecType::TypeLimit:
	GET_METRIC(tiflash_coprocessor_executor_count, type_limit).Increment();
	assignOrThrowException(&limit_or_topn, &executors[i], LIMIT_NAME);
	if (executors[i].has_executor_id())
	limit_or_topn_name = executors[i].executor_id();
	else
	limit_or_topn_name = std::to_string(i) + "_limitOrTopN";
	break;
	default:
	throw TiFlashException(
	"Unsupported executor in DAG request: " + executors[i].DebugString(),
	Errors::Coprocessor::Unimplemented);
	}
	}
	}

Currently, ExecutorTestUtils only supports tree struct base executor, and we need to find a way to add UTs for list struct base executor.

related issue: #4609