/** * Update a {@link Dataset} for the given dataset or view URI. * * <p>You can add columns, remove columns, or change the data type of columns in your dataset, * provided you don't attempt a change that is incompatible with written data. Avro defines rules * for compatible schema evolution. See <a * href="http://kitesdk.org/docs/current/Schema-Evolution.html">Schema Evolution</a>. * * <p>This method updates the dataset descriptor, so you can also add or change properties. * * <p>The recommended way to update a dataset descriptor is to build it based on an existing * descriptor. Use {@link DatasetDescriptor.Builder(DatasetDescriptor)} to build a * DatasetDescriptor based on an existing instance. * * <p>You cannot change a dataset format or partition strategy. * * <p>URIs must begin with {@code dataset:}. The remainder of the URI is implementation specific, * depending on the dataset scheme. * * @param uri a {@code Dataset} URI * @param type a Java class that represents an entity in the dataset * @param <E> the type used for readers and writers created by this {@code Dataset} * @param <D> the type of {@code Dataset} expected * @return a {@code Dataset} for the given URI * @throws NullPointerException if {@code uri}, {@code descriptor}, or {@code type} is {@code * null} * @throws IllegalArgumentException if {@code uri} is not a dataset URI * @throws DatasetNotFoundException if there is no dataset for the given URI * @throws UnsupportedOperationException if descriptor updates are not supported by the * implementation * @throws ConcurrentSchemaModificationException if the {@code Dataset} schema is updated * concurrently * @throws IncompatibleSchemaException if the schema is not compatible with previous schemas, or * with existing datasets with shared storage (for example, in the same HBase table) */ @SuppressWarnings("unchecked") public static <E, D extends Dataset<E>> D update( URI uri, DatasetDescriptor descriptor, Class<E> type) { Preconditions.checkArgument( URIBuilder.DATASET_SCHEME.equals(uri.getScheme()), "Not a dataset or view URI: " + uri); Preconditions.checkNotNull( type, "The entity type can't be null, use Object.class to have the type" + " determined by the schema."); Pair<DatasetRepository, Map<String, String>> pair = Registration.lookupDatasetUri(URI.create(uri.getRawSchemeSpecificPart())); DatasetRepository repo = pair.first(); Map<String, String> uriOptions = pair.second(); return (D) repo.update( uriOptions.get(URIBuilder.NAMESPACE_OPTION), uriOptions.get(URIBuilder.DATASET_NAME_OPTION), descriptor, type); }