function_array_flatten.cpp

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// to you under the Apache License, Version 2.0 (the
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//
//   http://www.apache.org/licenses/LICENSE-2.0
//
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#include "common/status.h"
#include "core/assert_cast.h"
#include "core/block/block.h"
#include "core/block/column_numbers.h"
#include "core/block/column_with_type_and_name.h"
#include "core/column/column.h"
#include "core/column/column_array.h"
#include "core/column/column_nullable.h"
#include "core/data_type/data_type.h"
#include "core/data_type/data_type_array.h"
#include "core/types.h"
#include "exprs/aggregate/aggregate_function.h"
#include "exprs/function/function.h"
#include "exprs/function/simple_function_factory.h"

namespace doris {
#include "common/compile_check_begin.h"

class FunctionArrayFlatten : public IFunction {
public:
    static constexpr auto name = "array_flatten";
    static FunctionPtr create() { return std::make_shared<FunctionArrayFlatten>(); }

    /// Get function name.
    String get_name() const override { return name; }

    size_t get_number_of_arguments() const override { return 1; }

    DataTypePtr get_return_type_impl(const DataTypes& arguments) const override {
        DataTypePtr arg = arguments[0];
        while (arg->get_primitive_type() == TYPE_ARRAY) {
            arg = remove_nullable(assert_cast<const DataTypeArray*>(arg.get())->get_nested_type());
        }
        return std::make_shared<DataTypeArray>(make_nullable(arg));
    }

    Status execute_impl(FunctionContext* context, Block& block, const ColumnNumbers& arguments,
                        uint32_t result, size_t input_rows_count) const override {
        auto src_column =
                block.get_by_position(arguments[0]).column->convert_to_full_column_if_const();
        auto* src_column_array_ptr =
                assert_cast<const ColumnArray*>(remove_nullable(src_column).get());
        ColumnPtr nested_src_column_array = remove_nullable(src_column);

        DataTypePtr src_data_type = block.get_by_position(arguments[0]).type;
        auto* src_data_type_array =
                assert_cast<const DataTypeArray*>(remove_nullable(src_data_type).get());

        auto result_column_offsets = src_column_array_ptr->get_offsets_column().clone();
        auto* offsets = assert_cast<ColumnArray::ColumnOffsets*>(result_column_offsets.get())
                                ->get_data()
                                .data();

        while (src_data_type_array->get_nested_type()->get_primitive_type() == TYPE_ARRAY) {
            const auto* nullable =
                    check_and_get_column<ColumnNullable>(src_column_array_ptr->get_data());
            auto nested_array = remove_nullable(src_column_array_ptr->get_data_ptr());
            const auto& array = assert_cast<const ColumnArray&>(*nested_array);

            // IF can leave [101, 102] beneath a NULL subarray. Remove that range before
            // composing offsets, so [NULL, [9]] flattens to [9] at every nesting level.
            if (nullable && nullable->has_null()) {
                auto data = array.get_data().clone_empty();
                auto nested_offsets = ColumnArray::ColumnOffsets::create();
                auto& nested_offsets_data = nested_offsets->get_data();
                nested_offsets_data.reserve(array.size());
                for (size_t i = 0; i < array.size(); ++i) {
                    // NULL subarrays may own nonempty ranges; their children are invisible.
                    if (!nullable->is_null_at(i)) {
                        data->insert_range_from(array.get_data(), array.offset_at(i),
                                                array.size_at(i));
                    }
                    nested_offsets_data.push_back(data->size());
                }
                nested_array = ColumnArray::create(std::move(data), std::move(nested_offsets));
            }
            const auto& nested_array_offsets =
                    assert_cast<const ColumnArray&>(*nested_array).get_offsets();

            for (size_t i = 0; i < input_rows_count; ++i) {
                offsets[i] = nested_array_offsets[offsets[i] - 1];
            }
            nested_src_column_array = std::move(nested_array);
            src_column_array_ptr = assert_cast<const ColumnArray*>(nested_src_column_array.get());
            src_data_type_array = assert_cast<const DataTypeArray*>(
                    remove_nullable(src_data_type_array->get_nested_type()).get());
        }

        block.replace_by_position(result, ColumnArray::create(src_column_array_ptr->get_data_ptr(),
                                                              std::move(result_column_offsets)));
        return Status::OK();
    }
};

void register_function_array_flatten(SimpleFunctionFactory& factory) {
    factory.register_function<FunctionArrayFlatten>();
}

} // namespace doris