public interface TupleCursor
TupleList
.
Stops short of the full Iterator
interface. If you want
that, see TupleIterator
.
Modifier and Type | Method and Description |
---|---|
List<Member> |
current()
Returns the tuple that this cursor is positioned on.
|
void |
currentToArray(Member[] members,
int offset)
Writes the member(s) of the next tuple to a given offset in an array.
|
boolean |
forward()
Moves the iterator forward one position.
|
int |
getArity()
Returns the number of members in each tuple.
|
Member |
member(int column) |
void |
setContext(Evaluator evaluator) |
void setContext(Evaluator evaluator)
boolean forward()
Returns false only when end of data has been reached.
Similar to calling the Iterator
methods
Iterator.hasNext()
followed by
Iterator.next()
but
does not construct an object, and is therefore cheaper.
If you want to use an Iterator, see TupleIterator
.
List<Member> current()
This method never returns null, and may safely be called multiple times (or not all) for each position in the iteration.
Invalid to call this method when the cursor is has not been
positioned, for example, if forward()
has not been called or
if the most recent call to forward
returned false
.
int getArity()
Member member(int column)
void currentToArray(Member[] members, int offset)
This method saves the overhead of a memory allocation when the
resulting tuple will be written immediately to an array. The effect of
currentToArray(members, 0)
is the same as calling
current().toArray(members)
.
Before calling this method, you must position the iterator at a valid position. Typically you would call hasNext followed by next; or forward.
members
- Membersoffset
- Offset in the array to write toCopyright © 2019 Hitachi Vantara. All rights reserved.