iterator issue about badger HOT 5 CLOSED

Hi!

i think you used the for-loop in a "wrong" way. You put a Next()-call at the initializing position. Looking at the godoc for the NewIterator-function, it says

for it.Rewind(); it.Valid(); it.Next() {
...
}

So you can just put the Rewind()-call inside the head of the for-loop.

Still wondering, why a new created iterator must be rewinded, following does not work too, if the Rewind()-call is missing:

it.Rewind()
for it.Valid() {
	kvItem = it.Item()
	fmt.Println("k", string(kvItem.Key()), "v", string(kvItem.Value()), "c", kvItem.Counter())
	it.Next()
}

I would expect a new iterator is just usable after creating it.

from badger.

The reason Rewind must be called, is because we need to know where to start prefetching from. One could use Seek instead of Rewind. In that case, if we automatically start prefetching from the beginning, all that work would need to be abandoned and would cause delays in doing the Seek call.

In short, the reason to specify the initial point is that we do extra work in the background; and we need to know where to begin.

Hope that answers your query.

from badger.

Well, the idea was to implement a custom Seek but as far as I understood it's not possible without calling Rewind.

from badger.

You can call Seek directly, then you don't need to call Rewind.

from badger.

Yes, but you can't build a Seek like Seek([]byte("contains")). You can only seek the whole key and that's my issue. I thought it would be possible to build a custom seek without Rewind.

from badger.