/**
* Returns an object containing basic information about the execution of the query that created
* this cursor This creates a <code>DBObject</code> with the key/value pairs: "cursor" : cursor
* type "nScanned" : number of records examined by the database for this query "n" : the number of
* records that the database returned "millis" : how long it took the database to execute the
* query
*
* @return a <code>DBObject</code>
* @dochub explain
*/
public DBObject explain() {
DBCursor c = copy();
c._explain = true;
if (c._limit > 0) {
// need to pass a negative batchSize as limit for explain
c._batchSize = c._limit * -1;
c._limit = 0;
}
return c.next();
}
/**
* Creates a copy of an existing database cursor. The new cursor is an iterator, even if the
* original was an array.
*
* @return the new cursor
*/
public DBCursor copy() {
DBCursor c = new DBCursor(_collection, _query, _keysWanted, _readPref);
c._orderBy = _orderBy;
c._hint = _hint;
c._hintDBObj = _hintDBObj;
c._limit = _limit;
c._skip = _skip;
c._options = _options;
c._batchSize = _batchSize;
c._snapshot = _snapshot;
c._explain = _explain;
if (_specialFields != null) c._specialFields = new BasicDBObject(_specialFields.toMap());
return c;
}