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E - The generic type for the de-serialized objects stored as the value
under the key in the index.public interface ITupleCursor<E>
Interface for sequential and random-access cursor-based ITuple
operations on an index or index partition. The interface extends the standard
Iterator for forward sequential scans and also provides symmetric
methods for reverse sequential scans using hasPrior() and
prior(). Random access is supported using seek(byte[]).
This interface is intentionally kept small and does not include methods such as
first() or last() whose semantics would be misleading when applied to an
index partition vs a partitioned index.
Note: Normally ITupleCursors are provisioned such that deleted
tuples are not visited (they are skipped over if delete markers are used by
the index). This corresponds to the most common application requirement.
However, cursors MAY be provisioned using IRangeQuery.DELETED to
visit deleted tuples for indices that maintain delete markers.
| Method Summary | |
|---|---|
IIndex |
getIndex()
The backing index being traversed by the ITupleCursor. |
boolean |
hasNext()
Return true if there is another tuple that orders after
the current cursor position in the natural order of the index and that
lies within the optional constraints key-range on the cursor or on the
index partition. |
boolean |
hasPrior()
Return true if there is another tuple that orders before
the current cursor position in the natural order of the index and that
lies within the optional key-range constraints on the cursor or on the
index partition. |
ITuple<E> |
next()
Position the cursor on the next tuple in the natural key order of the index. |
ITuple<E> |
prior()
Position the cursor on the first visitable tuple ordered less than the current cursor position in the natural key order of the index and return that tuple. |
void |
remove()
Removes the tuple (if any) from the index corresponding to the current cursor position. |
ITuple<E> |
seek(byte[] key)
Positions the cursor on the specified key. |
ITuple<E> |
seek(Object key)
Variant that first encodes the key using the object returned by IndexMetadata.getTupleSerializer() for the backing index. |
| Method Detail |
|---|
IIndex getIndex()
ITupleCursor.
ITuple<E> seek(byte[] key)
If there is a corresponding visitable tuple in the index then it is returned.
If there is no visitable tuple in the index for that key then
null is returned. You can use prior() or
next() to locate the first visitable tuple to either side of the
cursor position.
The cursor position is updated to the specified key regardless of whether there is a visitable tuple in the index for that key.
key - The key (required).
null otherwise.
IllegalArgumentException - if the key is null.
KeyOutOfRangeException - if the key lies outside of the optional constrain on the
ITupleCursor.
KeyOutOfRangeException - if the key lies outside of the key-range constraint on an
index partition.ITuple<E> seek(Object key)
IndexMetadata.getTupleSerializer() for the backing index.
key - The key (required).
null otherwise.
IllegalArgumentException - if the encoded key lies outside of the optional key-range
constraint on the cursor or on the index partition.boolean hasNext()
true if there is another tuple that orders after
the current cursor position in the natural order of the index and that
lies within the optional constraints key-range on the cursor or on the
index partition.
Note: in order to maintain standard iterator semantics, this method will
return true if the current cursor position is undefined
and #first() would report the existence of a visitable tuple.
hasNext in interface Iterator<ITuple<E>>ITuple<E> next()
Note: in order to maintain standard iterator semantics, this method will
visit the #first() visitable tuple if the current cursor position
is undefined.
next in interface Iterator<ITuple<E>>next in interface ITupleIterator<E>ITuple containing the data and metadata for the
current index entry.
NoSuchElementException - if hasNext() would return false.boolean hasPrior()
true if there is another tuple that orders before
the current cursor position in the natural order of the index and that
lies within the optional key-range constraints on the cursor or on the
index partition.
Note: in order to maintain semantics parallel to standard iterator
semantics, this method will return true if the current
cursor position is undefined and #last() would report the
existence of a visitable tuple.
ITuple<E> prior()
Note: in order to maintain semantics parallel to standard iterator
semantics, this method will visit the #last() visitable tuple if
the current cursor position is undefined.
NoSuchElementException - if hasPrior() would return false.void remove()
ITupleCursor2.tuple() will return
null to indicate that there is no tuple in the index
corresponding to the deleted tuple. (When delete markers are enabled and
deleted tuples are being visited, then ITupleCursor2.tuple() will
return the new state of the tuple with its delete marker set.)
remove in interface Iterator<ITuple<E>>IllegalStateException - if the cursor position is not defined.
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