Method GetBlockIterator

catboost/libs/data/external_columns.cpp:26–59

    }

    IDynamicBlockIteratorBasePtr TExternalFloatValuesHolder::GetBlockIterator(ui32 offset) const {
        const auto floatFeatureIdx = QuantizedFeaturesInfo->GetPerTypeFeatureIdx<EFeatureType::Float>(*this);
        const auto nanMode = QuantizedFeaturesInfo->GetNanMode(floatFeatureIdx);

        // it's ok even if it is learn data, for learn nans are checked at CalcBordersAndNanMode stage
        bool allowNans = (nanMode != ENanMode::Forbidden) ||
            QuantizedFeaturesInfo->GetFloatFeaturesAllowNansInTestOnly();
        auto featureIdx = GetId();

         auto transformer = [
            allowNans, nanMode, featureIdx,
            bordersArrRef = MakeArrayRef(QuantizedFeaturesInfo->GetBorders(floatFeatureIdx))
        ] (TConstArrayRef<float> src, auto& dst) {
            QuantizeBlock(
                src,
                allowNans,
                nanMode,
                featureIdx,
                bordersArrRef,
                MakeArrayRef(dst)
            );
        };
        if (QuantizedFeaturesInfo->GetBorders(floatFeatureIdx).size() < 256) {
            return MakeBlockTransformerIterator<ui8>(
                SrcData->GetBlockIterator(offset),
                std::move(transformer)
            );
        } else {
            return MakeBlockTransformerIterator<ui16>(
                SrcData->GetBlockIterator(offset),
                std::move(transformer)
            );
        }
    }


    THolder<IFeatureValuesHolder> TExternalCatValuesHolder::CloneWithNewSubsetIndexing(