E
- The type of entities stored in the Dataset
underlying this
View
.@Immutable public interface View<E>
View
is a subset of a Dataset
.
A View
defines a space of potential storage keys or a partition
space. Views can be created from ranges, partial keys, or the union of other
views.Modifier and Type | Method and Description |
---|---|
boolean |
deleteAll()
Deletes the entities included in this
View or throws an
UnsupportedOperationException . |
Dataset<E> |
getDataset()
Returns the underlying
Dataset for the
View . |
Class<E> |
getType()
Get the runtime type of entities contained in this
View . |
URI |
getUri()
Get a
URI that identifies this View . |
boolean |
includes(E entity)
|
boolean |
isEmpty()
Check whether this
View contains any records. |
DatasetReader<E> |
newReader()
Get an appropriate
DatasetReader implementation based on this
View of the underlying Dataset implementation. |
DatasetWriter<E> |
newWriter()
Get an appropriate
DatasetWriter implementation based on this
View of the underlying Dataset implementation. |
Dataset<E> getDataset()
Dataset
for the
View
.Dataset
DatasetReader<E> newReader()
DatasetReader
implementation based on this
View
of the underlying Dataset
implementation.
Implementations are free to return different types of readers, depending on
the disposition of the data. For example, a partitioned dataset can use a
different reader than that of a non-partitioned dataset. Clients should not
make any assumptions about the returned implementations: implementations
are free to change their internal structure at any time.DatasetException
DatasetWriter<E> newWriter()
DatasetWriter
implementation based on this
View
of the underlying Dataset
implementation.
Implementations are free to return different types of writers depending on
the disposition of the data. For example, a partitioned dataset may use a
different writer than that of a non-partitioned dataset. Clients should not
make any assumptions about the returned implementations: implementations
are free to change their internal structure at any time.DatasetException
boolean includes(E entity)
entity
- an entity Object
entity
is in the partition space of this view.boolean deleteAll()
View
or throws an
UnsupportedOperationException
.
Implementations are allowed to throw UnsupportedOperationException
if the View
could require additional work to delete. For example,
if some but not all of the data in an underlying data file must be removed,
then the implementation is allowed to reject the deletion rather than
copy the remaining records to a new file. Implementations must document
what deletes are supported and under what conditions deletes are rejected.UnsupportedOperationException
- if the requested delete cannot be completed by the implementationDatasetIOException
- if the requested delete failed because of an IOExceptionClass<E> getType()
View
.boolean isEmpty()
View
contains any records.
Implementations should return once a single record in this view is found.
But this might require scanning through large amounts of data sequentially
to determine if there are any records.true
if least one record exists, false
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