Performance of PosList pointing into index

benchmark.cpp

 BENCHMARK_F(TPCHDataMicroBenchmarkFixture, BM_TPCHQ6IndexScan)(benchmark::State& state) {
  auto& sm = Hyrise::get().storage_manager;
  auto lineitem_table = sm.get_table("lineitem");

  std::vector<ColumnID> index_column_ids = {ColumnID{10}};
  lineitem_table->create_index<GroupKeyIndex>(index_column_ids);

  // Similar to the less predicate used in tpchq6 on l_shipdate.
  const std::vector<ColumnID> left_column_ids = {ColumnID{10}};
  const std::vector<AllTypeVariant> right_values = {"1995-01-01"};
  for (auto _ : state) {
    const auto table_scan = std::make_shared<IndexScan>(_table_wrapper_map.at("lineitem"), SegmentIndexType::GroupKey,
                                                        left_column_ids, PredicateCondition::LessThan, right_values);
    table_scan->execute();
  }
}

BENCHMARK_F(TPCHDataMicroBenchmarkFixture, BM_TPCHQ6IndexScan_Matches_All_Predicate)(benchmark::State& state) {
  auto& sm = Hyrise::get().storage_manager;
  auto lineitem_table = sm.get_table("lineitem");

  std::vector<ColumnID> index_column_ids = {ColumnID{10}};
  lineitem_table->create_index<GroupKeyIndex>(index_column_ids);
  const std::vector<ColumnID> left_column_ids = {ColumnID{10}};
  const std::vector<AllTypeVariant> right_values = {"1600-01-01"};
  for (auto _ : state) {
    const auto table_scan = std::make_shared<IndexScan>(_table_wrapper_map.at("lineitem"), SegmentIndexType::GroupKey,
                                                        left_column_ids, PredicateCondition::GreaterThan, right_values);
    table_scan->execute();
  }
}

BENCHMARK_F(TPCHDataMicroBenchmarkFixture, BM_TPCHQ6TableScan_After_IndexScan)(benchmark::State& state) {
  auto& sm = Hyrise::get().storage_manager;
  auto lineitem_table = sm.get_table("lineitem");

  std::vector<ColumnID> index_column_ids = {ColumnID{10}};
  lineitem_table->create_index<GroupKeyIndex>(index_column_ids);
  const std::vector<ColumnID> left_column_ids = {ColumnID{10}};
  const std::vector<AllTypeVariant> right_values = {"1995-01-01"};
  const auto index_scan = std::make_shared<IndexScan>(_table_wrapper_map.at("lineitem"), SegmentIndexType::GroupKey,
                                                      left_column_ids, PredicateCondition::LessThan, right_values);
  index_scan->execute();

  const auto scan_result = index_scan->get_output();

  for (auto _ : state) {
    const auto table_scan = std::make_shared<TableScan>(index_scan, _tpchq6_quantity_predicate);
    table_scan->execute();
  }
}

BENCHMARK_F(TPCHDataMicroBenchmarkFixture, BM_TPCHQ6IndexScan_And_TableScan_Together)(benchmark::State& state) {
  auto& sm = Hyrise::get().storage_manager;
  auto lineitem_table = sm.get_table("lineitem");

  std::vector<ColumnID> index_column_ids = {ColumnID{10}};
  lineitem_table->create_index<GroupKeyIndex>(index_column_ids);
  const std::vector<ColumnID> left_column_ids = {ColumnID{10}};
  const std::vector<AllTypeVariant> right_values = {"1995-01-01"};

  for (auto _ : state) {
    const auto index_scan = std::make_shared<IndexScan>(_table_wrapper_map.at("lineitem"), SegmentIndexType::GroupKey,
                                                        left_column_ids, PredicateCondition::LessThan, right_values);
    index_scan->execute();
    const auto table_scan = std::make_shared<TableScan>(index_scan, _tpchq6_quantity_predicate);
    table_scan->execute();
  }
}

Results.txt

PosList pointing into index:
------------------------------------------------------------------------------------------------------------------
Benchmark                                                                        Time             CPU   Iterations
------------------------------------------------------------------------------------------------------------------
TPCHDataMicroBenchmarkFixture/BM_TPCHQ6IndexScan                            182104 ns       182102 ns         3837
TPCHDataMicroBenchmarkFixture/BM_TPCHQ6IndexScan_Matches_All_Predicate      328445 ns       328420 ns         2147
TPCHDataMicroBenchmarkFixture/BM_TPCHQ6TableScan_After_IndexScan          22750846 ns     22750434 ns           28
TPCHDataMicroBenchmarkFixture/BM_TPCHQ6IndexScan_And_TableScan_Together   23127492 ns     23124115 ns           30

normal (RowID) posList:
------------------------------------------------------------------------------------------------------------------
Benchmark                                                                        Time             CPU   Iterations
------------------------------------------------------------------------------------------------------------------
TPCHDataMicroBenchmarkFixture/BM_TPCHQ6IndexScan                           4177652 ns      4177585 ns          166
TPCHDataMicroBenchmarkFixture/BM_TPCHQ6IndexScan_Matches_All_Predicate    11711713 ns     11711153 ns           58
TPCHDataMicroBenchmarkFixture/BM_TPCHQ6TableScan_After_IndexScan          20667343 ns     20666796 ns           34
TPCHDataMicroBenchmarkFixture/BM_TPCHQ6IndexScan_And_TableScan_Together   25021510 ns     25019400 ns           28

I am getting these results for your branch but it is kind of pointless without being able to comparing it to the normal (RowID) PosList.

------------------------------------------------------------------------------------------------------------------
Benchmark                                                                        Time             CPU   Iterations
------------------------------------------------------------------------------------------------------------------
TPCHDataMicroBenchmarkFixture/BM_TPCHQ6IndexScan                            120146 ns       120147 ns         5785
TPCHDataMicroBenchmarkFixture/BM_TPCHQ6IndexScan_Matches_All_Predicate      217132 ns       217134 ns         3220
TPCHDataMicroBenchmarkFixture/BM_TPCHQ6TableScan_After_IndexScan           6973421 ns      6968938 ns           97
TPCHDataMicroBenchmarkFixture/BM_TPCHQ6IndexScan_And_TableScan_Together    7178071 ns      7175552 ns           94