ClickHouse/src/Interpreters/DictionaryReader.cpp

#include <Interpreters/DictionaryReader.h>
#include <Interpreters/Context.h>
#include <Common/typeid_cast.h>
#include <Columns/ColumnString.h>
#include <Columns/ColumnConst.h>
#include <DataTypes/DataTypeNullable.h>
#include <DataTypes/DataTypeString.h>
#include <DataTypes/DataTypesNumber.h>
#include <Functions/FunctionFactory.h>

namespace DB
{

namespace ErrorCodes
{
    extern const int NUMBER_OF_COLUMNS_DOESNT_MATCH;
    extern const int TYPE_MISMATCH;
}


DictionaryReader::FunctionWrapper::FunctionWrapper(FunctionOverloadResolverPtr resolver, const ColumnsWithTypeAndName & arguments,
                                                   Block & block, const ColumnNumbers & arg_positions_, const String & column_name,
                                                   TypeIndex expected_type)
    : arg_positions(arg_positions_)
    , result_pos(block.columns())
{
    FunctionBasePtr prepared_function = resolver->build(arguments);

    ColumnWithTypeAndName result;
    result.name = "get_" + column_name;
    result.type = prepared_function->getReturnType();
    if (result.type->getTypeId() != expected_type)
        throw Exception("Type mismatch in dictionary reader for: " + column_name, ErrorCodes::TYPE_MISMATCH);
    block.insert(result);

    function = prepared_function->prepare(block, arg_positions, result_pos);
}

static constexpr const size_t key_size = 1;

DictionaryReader::DictionaryReader(const String & dictionary_name, const Names & src_column_names, const NamesAndTypesList & result_columns,
                                   const Context & context)
    : result_header(makeResultBlock(result_columns))
    , key_position(key_size + result_header.columns())
{
    if (src_column_names.size() != result_columns.size())
        throw Exception("Columns number mismatch in dictionary reader", ErrorCodes::NUMBER_OF_COLUMNS_DOESNT_MATCH);

    ColumnWithTypeAndName dict_name;
    ColumnWithTypeAndName key;
    ColumnWithTypeAndName column_name;

    {
        dict_name.name = "dict";
        dict_name.type = std::make_shared<DataTypeString>();
        dict_name.column = dict_name.type->createColumnConst(1, dictionary_name);

        /// TODO: composite key (key_size > 1)
        key.name = "key";
        key.type = std::make_shared<DataTypeUInt64>();

        column_name.name = "column";
        column_name.type = std::make_shared<DataTypeString>();
    }

    /// dictHas('dict_name', id)
    ColumnsWithTypeAndName arguments_has;
    arguments_has.push_back(dict_name);
    arguments_has.push_back(key);

    /// dictGet('dict_name', 'attr_name', id)
    ColumnsWithTypeAndName arguments_get;
    arguments_get.push_back(dict_name);
    arguments_get.push_back(column_name);
    arguments_get.push_back(key);

    sample_block.insert(dict_name);

    for (const auto & columns_name : src_column_names)
    {
        ColumnWithTypeAndName name;
        name.name = "col_" + columns_name;
        name.type = std::make_shared<DataTypeString>();
        name.column = name.type->createColumnConst(1, columns_name);

        sample_block.insert(name);
    }

    sample_block.insert(key);

    ColumnNumbers positions_has{0, key_position};
    function_has = std::make_unique<FunctionWrapper>(FunctionFactory::instance().get("dictHas", context),
                                                        arguments_has, sample_block, positions_has, "has", DataTypeUInt8().getTypeId());
    functions_get.reserve(result_header.columns());

    for (size_t i = 0; i < result_header.columns(); ++i)
    {
        size_t column_name_pos = key_size + i;
        auto & column = result_header.getByPosition(i);
        arguments_get[1].column = DataTypeString().createColumnConst(1, src_column_names[i]);
        ColumnNumbers positions_get{0, column_name_pos, key_position};
        functions_get.emplace_back(
            FunctionWrapper(FunctionFactory::instance().get("dictGet", context),
                            arguments_get, sample_block, positions_get, column.name, column.type->getTypeId()));
    }
}

void DictionaryReader::readKeys(const IColumn & keys, Block & out_block, ColumnVector<UInt8>::Container & found,
                                std::vector<size_t> & positions) const
{
    Block working_block = sample_block;
    size_t has_position = key_position + 1;
    size_t size = keys.size();

    /// set keys for dictHas()
    ColumnWithTypeAndName & key_column = working_block.getByPosition(key_position);
    key_column.column = keys.cloneResized(size); /// just a copy we cannot avoid

    /// calculate and extract dictHas()
    function_has->execute(working_block, size);
    ColumnWithTypeAndName & has_column = working_block.getByPosition(has_position);
    auto mutable_has = (*std::move(has_column.column)).mutate();
    found.swap(typeid_cast<ColumnVector<UInt8> &>(*mutable_has).getData());
    has_column.column = nullptr;

    /// set mapping form source keys to resulting rows in output block
    positions.clear();
    positions.resize(size, 0);
    size_t pos = 0;
    for (size_t i = 0; i < size; ++i)
        if (found[i])
            positions[i] = pos++;

    /// set keys for dictGet(): remove not found keys
    key_column.column = key_column.column->filter(found, -1);
    size_t rows = key_column.column->size();

    /// calculate dictGet()
    for (const auto & func : functions_get)
        func.execute(working_block, rows);

    /// make result: copy header block with correct names and move data columns
    out_block = result_header.cloneEmpty();
    size_t first_get_position = has_position + 1;
    for (size_t i = 0; i < out_block.columns(); ++i)
    {
        auto & src_column = working_block.getByPosition(first_get_position + i);
        auto & dst_column = out_block.getByPosition(i);
        dst_column.column = src_column.column;
        src_column.column = nullptr;
    }
}

Block DictionaryReader::makeResultBlock(const NamesAndTypesList & names)
{
    Block block;
    for (const auto & nm : names)
    {
        ColumnWithTypeAndName column{nullptr, nm.type, nm.name};
        if (column.type->isNullable())
            column.type = typeid_cast<const DataTypeNullable &>(*column.type).getNestedType();
        block.insert(std::move(column));
    }
    return block;
}

}