Function extractValuesFixedString

src/DataTypes/DataTypeMapHelpers.cpp:336–370

Specialized value extractor for ColumnFixedString, with optional Nullable support.

/// Specialized value extractor for ColumnFixedString, with optional Nullable support.
void extractValuesFixedString(
    const ColumnFixedString & values_column,
    ColumnFixedString & result,
    const PaddedPODArray<size_t> & matched_positions,
    const NullMap * src_null_map = nullptr,
    NullMap * dst_null_map = nullptr)
{
    size_t n = values_column.getN();
    const auto & src_chars = values_column.getChars();
    auto & dst_chars = result.getChars();
    size_t num_rows = matched_positions.size();

    size_t old_chars_size = dst_chars.size();
    size_t old_num_rows = old_chars_size / n;
    dst_chars.resize(old_chars_size + num_rows * n);
    if (dst_null_map)
        dst_null_map->resize(old_num_rows + num_rows);

    for (size_t i = 0; i < num_rows; ++i)
    {
        size_t pos = matched_positions[i];
        if (pos != KEY_NOT_FOUND)
        {
            memcpy(&dst_chars[old_chars_size + i * n], &src_chars[pos * n], n);
            if (dst_null_map)
                (*dst_null_map)[old_num_rows + i] = (*src_null_map)[pos];
        }
        else
        {
            memset(&dst_chars[old_chars_size + i * n], 0, n);
            if (dst_null_map)
                (*dst_null_map)[old_num_rows + i] = static_cast<UInt8>(1);
        }
    }
}

/// Dispatches to the appropriate specialized value extractor based on the value column type.
/// For Nullable columns, unwraps to the nested column and passes null map pointers