Iterators

Iterators can be used to traverse over Key-Value pairs in the database. An iterator provides few basic functions:

• void Seek(Slice key) to seek cursor to a given key
• void SeekToFirst() to seek to first key in database
• void SeekToLast() to seek to last key in database
• void Next() move to next entry from current cursor position
• void Prev() move to previous entry from current cursor position
• bool Valid() returns true if the cursor is at a valid position, false otherwise
• Slice Key() reads key slice from current cursor position
• Slice Value() reads value slice from current cursor position

One can create a new cursor by calling DB.NewIterator(ReadOptions readOptions) method. Here is an example:

using (var itr = db.NewIterator(new ReadOptions()))
{
    itr.Seek(Slice.FromString("foo"));
    while (itr.Valid())
    {
        byte[] key = itr.Key().ToByteArray();
        byte[] val = itr.Value().ToByteArray();
        itr.Next();
    }
}

Iterators can be over a snapshot:

using (var snapshot = db.NewSnapshot())
using (var itr = db.NewIterator(new ReadOptions({ Snapshot = snapshot })))
{
  // use itr
}

An iterator can iterate in reverse order as well ?(Prev() method) but that is usually slower than forward iteration, so it's highly recommended avoid it as much as possible.