**Use case**
`SELECT POSITION('/' IN s) FROM (SELECT 'Hello/World' AS s);`

The same as `position(s, '/')`

{
    const char * function_name = nullptr;
    ASTPtr timestamp_node;
    ASTPtr offset_node;
    if (ParserKeyword("DATEADD").ignore(pos, expected) || ParserKeyword("DATE_ADD").ignore(pos, expected)
        || ParserKeyword("TIMESTAMPADD").ignore(pos, expected) || ParserKeyword("TIMESTAMP_ADD").ignore(pos, expected))
        function_name = "plus";
    else if (ParserKeyword("DATESUB").ignore(pos, expected) || ParserKeyword("DATE_SUB").ignore(pos, expected)
        || ParserKeyword("TIMESTAMPSUB").ignore(pos, expected) || ParserKeyword("TIMESTAMP_SUB").ignore(pos, expected))
        function_name = "minus";
    else
        return false;
    if (pos->type != TokenType::OpeningRoundBracket)
        return false;
    ++pos;
    IntervalKind interval_kind;
    ASTPtr interval_func_node;