Java RethinkDB Expected type DATUM but found SELECTION

问题

I'm using RethinkDB driver for Java. I want to filter the rows without field endedAt in table jam like this:

public List<Jam> getCurrent(){
        Cursor cursor = r.table("jam")
                .filter(row -> row.hasFields("endedAt")).not()
                .run(conn);
        List<Map<String,Object>> list=cursor.toList();
        return list.stream().map(item->JamRepository.toJam(item)).collect(Collectors.toList());
    }

And I've got this error Expected type DATUM but found SELECTION Java

I have another filter function in another class:

public List<Speedlog> getByTime(long time){
        Cursor cursor = r.table("speedlog")
                .filter(row -> row.g("createdAt").eq(time))
                .run(conn);
        List<Map<String,Object>> list=cursor.toList();
        return list.stream().map(item->SpeedlogRepository.toSpeedlog(item)).collect(Collectors.toList());
    }

This function works properly

Could anyone please explain what makes the difference between these two? Why does getCurrent function get that error? What is its meaning and how to fix? Thank you

回答1:

not() should be right after row.hasFields("endedAt"). For now you are trying to call not() on the result of filter function. So, correct code:

public List<Jam> getCurrent(){
        Cursor cursor = r.table("jam")
                .filter(row -> row.hasFields("endedAt").not())
                .run(conn);
        List<Map<String,Object>> list=cursor.toList();
        return list.stream().map(item->JamRepository.toJam(item)).collect(Collectors.toList());
}

来源：https://stackoverflow.com/questions/40206697/java-rethinkdb-expected-type-datum-but-found-selection