`SELECT ... WHERE match(key, '^prefix...')`
should use index similarly to
`SELECT ... WHERE key LIKE 'prefix%'`
{
    String res;
    for (size_t i = 0; i < rpn.size(); ++i)
    {
        if (i)
            res += ", ";
        res += rpn[i].toString();
    }
    return res;
}
KeyCondition::Description KeyCondition::getDescription() const
{
    
    
    Description description;
    
    
    struct Node
    {
        enum class Type