```
SELECT version()
─version()─┐
│ 21.8.5.7  │
└───────────┘
```
We have a request, as a result of which we get an array.
When getting an item using a computed value, there is no value
```
SELECT
    arrayMap(x -> x, [[1], [2], [3]]) AS x,
    toTypeName(x),
    x[3 - 2] AS y,
    x[toInt64(1)] AS yy,
    x[toUInt8(1)] AS yyy

┌─x─────────────┬─toTypeName(arrayMap(lambda(tuple(x), x), [[1], [2], [3]]))─┬─y──┬─yy─┬─yyy─┐
│ [[1],[2],[3]] │ Array(Array(UInt8))                                        │ [] │ [] │ [1] │
└───────────────┴────────────────────────────────────────────────────────────┴────┴────┴─────┘
```
However, when the array is explicitly specified, the value is present.
The types are the same.
```
SELECT
    [[1], [2], [3]] AS x,
    toTypeName(x),
    x[3 - 2] AS y,
    x[toInt64(1)] AS yy,
    x[toInt8(1)] AS yyy

┌─x─────────────┬─toTypeName([[1], [2], [3]])─┬─y───┬─yy──┬─yyy─┐
│ [[1],[2],[3]] │ Array(Array(UInt8))         │ [1] │ [1] │ [1] │
└───────────────┴─────────────────────────────┴─────┴─────┴─────┘
```


const IColumn & data, const Offsets & offsets,
    const Field & index, PaddedPODArray<UInt64> & matched_idxs)
{
    return castColumnNumeric(&data, [&](const auto & data_column)
    {
        using DataType = typename std::decay_t<decltype(data_column)>::ValueType;
        std::optional<DataType> index_as_integer;
        Field::dispatch([&](const auto & value)
        {
            using FieldType = std::decay_t<decltype(value)>;
            if constexpr (areConvertibleTypes<FieldType, DataType>)
                index_as_integer = static_cast<DataType>(value);
        }, index);
        if (!index_as_integer)
            return false;
        MatcherNumberConst<DataType> matcher{data_column.getData(), *index_as_integer};
        executeMatchKeyToIndex(offsets, matched_idxs, matcher);
        return true;
    });
}
bool FunctionArrayElement::matchKeyToIndexNumber(