lidavidm commented on a change in pull request #138:
URL: https://github.com/apache/arrow-cookbook/pull/138#discussion_r811211116
##########
File path: java/source/dataset.rst
##########
@@ -0,0 +1,297 @@
+.. _arrow-dataset:
+
+=======
+Dataset
+=======
+
+* `Arrow Java Dataset`_: Java implementation of Arrow Datasets library.
Implement Dataset Java API by JNI to C++.
+
+.. contents::
+
+Constructing Datasets
+=====================
+
+We can construct a dataset with an auto-inferred schema.
+
+.. testcode::
+
+ import org.apache.arrow.dataset.file.FileFormat;
+ import org.apache.arrow.dataset.file.FileSystemDatasetFactory;
+ import org.apache.arrow.dataset.jni.NativeMemoryPool;
+ import org.apache.arrow.dataset.scanner.ScanOptions;
+ import org.apache.arrow.dataset.scanner.Scanner;
+ import org.apache.arrow.dataset.source.Dataset;
+ import org.apache.arrow.dataset.source.DatasetFactory;
+ import org.apache.arrow.memory.RootAllocator;
+ import java.util.stream.StreamSupport;
+
+ try (RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE)) {
+ String uri = "file:" + System.getProperty("user.dir") +
"/thirdpartydeps/parquetfiles/data1.parquet";
+ try (DatasetFactory datasetFactory = new
FileSystemDatasetFactory(rootAllocator, NativeMemoryPool.getDefault(),
FileFormat.PARQUET, uri)) {
+ try(Dataset dataset = datasetFactory.finish()){
+ ScanOptions options = new ScanOptions(/*batchSize*/ 100);
+ try(Scanner scanner = dataset.newScan(options)){
+
System.out.println(StreamSupport.stream(scanner.scan().spliterator(),
false).count());
+ }
+ }
+ }
+ }
+
+.. testoutput::
+
+ 1
+
+Let construct our dataset with predefined schema.
+
+.. testcode::
+
+ import org.apache.arrow.dataset.file.FileFormat;
+ import org.apache.arrow.dataset.file.FileSystemDatasetFactory;
+ import org.apache.arrow.dataset.jni.NativeMemoryPool;
+ import org.apache.arrow.dataset.scanner.ScanOptions;
+ import org.apache.arrow.dataset.scanner.Scanner;
+ import org.apache.arrow.dataset.source.Dataset;
+ import org.apache.arrow.dataset.source.DatasetFactory;
+ import org.apache.arrow.memory.RootAllocator;
+ import java.util.stream.StreamSupport;
+
+ String uri = "file:" + System.getProperty("user.dir") +
"/thirdpartydeps/parquetfiles/data1.parquet";
+ try (RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE)) {
+ try (DatasetFactory datasetFactory = new
FileSystemDatasetFactory(rootAllocator, NativeMemoryPool.getDefault(),
FileFormat.PARQUET, uri)) {
+ try(Dataset dataset =
datasetFactory.finish(datasetFactory.inspect())){
+ ScanOptions options = new ScanOptions(/*batchSize*/ 100);
+ try(Scanner scanner = dataset.newScan(options)){
+
System.out.println(StreamSupport.stream(scanner.scan().spliterator(),
false).count());
+ }
+ }
+ }
+ }
+
+.. testoutput::
+
+ 1
+
+Getting the Schema
+==================
+
+During Dataset Construction
+***************************
+
+.. testcode::
+
+ import org.apache.arrow.dataset.file.FileFormat;
+ import org.apache.arrow.dataset.file.FileSystemDatasetFactory;
+ import org.apache.arrow.dataset.jni.NativeMemoryPool;
+ import org.apache.arrow.dataset.source.DatasetFactory;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.types.pojo.Schema;
+
+ String uri = "file:" + System.getProperty("user.dir") +
"/thirdpartydeps/parquetfiles/data1.parquet";
+ try(RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE)){
+ try(DatasetFactory datasetFactory = new
FileSystemDatasetFactory(rootAllocator, NativeMemoryPool.getDefault(),
FileFormat.PARQUET, uri)){
+ Schema schema = datasetFactory.inspect();
+
+ System.out.println(schema);
+ }
+ }
+
+.. testoutput::
+
+ Schema<id: Int(32, true), name: Utf8>(metadata:
{parquet.avro.schema={"type":"record","name":"User","namespace":"org.apache.arrow.dataset","fields":[{"name":"id","type":["int","null"]},{"name":"name","type":["string","null"]}]},
writer.model.name=avro})
+
+From a Dataset
+**************
+
+.. testcode::
+
+ import org.apache.arrow.dataset.file.FileFormat;
+ import org.apache.arrow.dataset.file.FileSystemDatasetFactory;
+ import org.apache.arrow.dataset.jni.NativeMemoryPool;
+ import org.apache.arrow.dataset.scanner.ScanOptions;
+ import org.apache.arrow.dataset.scanner.Scanner;
+ import org.apache.arrow.dataset.source.Dataset;
+ import org.apache.arrow.dataset.source.DatasetFactory;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.types.pojo.Schema;
+
+ String uri = "file:" + System.getProperty("user.dir") +
"/thirdpartydeps/parquetfiles/data1.parquet";
+ try(RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE)){
+ try(DatasetFactory datasetFactory = new
FileSystemDatasetFactory(rootAllocator, NativeMemoryPool.getDefault(),
FileFormat.PARQUET, uri)){
+ ScanOptions options = new ScanOptions(/*batchSize*/ 1);
+ try(Dataset dataset = datasetFactory.finish()){
+ try(Scanner scanner = dataset.newScan(options)){
+ Schema schema = scanner.schema();
+
+ System.out.println(schema);
+ }
+ }
+ }
+ }
+
+.. testoutput::
+
+ Schema<id: Int(32, true), name: Utf8>(metadata:
{parquet.avro.schema={"type":"record","name":"User","namespace":"org.apache.arrow.dataset","fields":[{"name":"id","type":["int","null"]},{"name":"name","type":["string","null"]}]},
writer.model.name=avro})
+
+Query Parquet File
+==================
+
+Let query information for a parquet file.
+
+Query Data Content For File
+***************************
+
+.. testcode::
+
+ import com.google.common.collect.Streams;
+ import org.apache.arrow.dataset.file.FileFormat;
+ import org.apache.arrow.dataset.file.FileSystemDatasetFactory;
+ import org.apache.arrow.dataset.jni.NativeMemoryPool;
+ import org.apache.arrow.dataset.scanner.ScanOptions;
+ import org.apache.arrow.dataset.scanner.Scanner;
+ import org.apache.arrow.dataset.source.Dataset;
+ import org.apache.arrow.dataset.source.DatasetFactory;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VectorLoader;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import org.apache.arrow.vector.ipc.message.ArrowRecordBatch;
+
+ import java.util.stream.Stream;
+
+ String uri = "file:" + System.getProperty("user.dir") +
"/thirdpartydeps/parquetfiles/data1.parquet";
+ try(RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ DatasetFactory datasetFactory = new
FileSystemDatasetFactory(rootAllocator, NativeMemoryPool.getDefault(),
FileFormat.PARQUET, uri);
+ Dataset dataset = datasetFactory.finish()){
+ ScanOptions options = new ScanOptions(/*batchSize*/ 100);
+ try(Scanner scanner = dataset.newScan(options);
+ VectorSchemaRoot vsr = VectorSchemaRoot.create(scanner.schema(),
rootAllocator)){
+ scanner.scan().forEach(scanTask-> {
+ Stream<ArrowRecordBatch> stream =
Streams.stream(scanTask.execute());
+ VectorLoader loader = new VectorLoader(vsr);
+ stream.forEach(arrowRecordBatch -> {
+ loader.load(arrowRecordBatch);
+ System.out.print(vsr.contentToTSVString());
+ arrowRecordBatch.close();
+ });
+ });
+ }
+ }
+
+.. testoutput::
+
+ id name
+ 1 David
+ 2 Gladis
+ 3 Juan
+
+Query Data Content For Directory
+********************************
+
+Consider that we have these files: data1: 3 rows, data2: 3 rows and data3: 250
rows.
+
+.. testcode::
+
+ import com.google.common.collect.Streams;
+ import org.apache.arrow.dataset.file.FileFormat;
+ import org.apache.arrow.dataset.file.FileSystemDatasetFactory;
+ import org.apache.arrow.dataset.jni.NativeMemoryPool;
+ import org.apache.arrow.dataset.scanner.ScanOptions;
+ import org.apache.arrow.dataset.scanner.Scanner;
+ import org.apache.arrow.dataset.source.Dataset;
+ import org.apache.arrow.dataset.source.DatasetFactory;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.util.AutoCloseables;
+ import org.apache.arrow.vector.FieldVector;
+ import org.apache.arrow.vector.VectorLoader;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import org.apache.arrow.vector.ipc.message.ArrowRecordBatch;
+ import org.apache.arrow.vector.types.pojo.Schema;
+
+ import java.util.List;
+ import java.util.stream.Collectors;
+ import java.util.stream.StreamSupport;
+
+ String uri = "file:" + System.getProperty("user.dir") +
"/thirdpartydeps/parquetfiles/";
+ try(RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ DatasetFactory datasetFactory = new
FileSystemDatasetFactory(rootAllocator, NativeMemoryPool.getDefault(),
FileFormat.PARQUET, uri);
+ Dataset dataset = datasetFactory.finish()){
+ ScanOptions options = new ScanOptions(/*batchSize*/ 100);
+ try(Scanner scanner = dataset.newScan(options);
+ VectorSchemaRoot vsr = VectorSchemaRoot.create(scanner.schema(),
rootAllocator)){
+ scanner.scan().forEach(scanTask-> {
+ Stream<ArrowRecordBatch> stream =
Streams.stream(scanTask.execute());
Review comment:
Just wondering, why can't we use a foreach loop instead of using streams
in these recipes? Streams are a bit incidental/cluttered here
##########
File path: java/source/dataset.rst
##########
@@ -0,0 +1,297 @@
+.. _arrow-dataset:
+
+=======
+Dataset
+=======
+
+* `Arrow Java Dataset`_: Java implementation of Arrow Datasets library.
Implement Dataset Java API by JNI to C++.
+
+.. contents::
+
+Constructing Datasets
+=====================
+
+We can construct a dataset with an auto-inferred schema.
+
+.. testcode::
+
+ import org.apache.arrow.dataset.file.FileFormat;
+ import org.apache.arrow.dataset.file.FileSystemDatasetFactory;
+ import org.apache.arrow.dataset.jni.NativeMemoryPool;
+ import org.apache.arrow.dataset.scanner.ScanOptions;
+ import org.apache.arrow.dataset.scanner.Scanner;
+ import org.apache.arrow.dataset.source.Dataset;
+ import org.apache.arrow.dataset.source.DatasetFactory;
+ import org.apache.arrow.memory.RootAllocator;
+ import java.util.stream.StreamSupport;
+
+ try (RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE)) {
+ String uri = "file:" + System.getProperty("user.dir") +
"/thirdpartydeps/parquetfiles/data1.parquet";
+ try (DatasetFactory datasetFactory = new
FileSystemDatasetFactory(rootAllocator, NativeMemoryPool.getDefault(),
FileFormat.PARQUET, uri)) {
+ try(Dataset dataset = datasetFactory.finish()){
+ ScanOptions options = new ScanOptions(/*batchSize*/ 100);
+ try(Scanner scanner = dataset.newScan(options)){
+
System.out.println(StreamSupport.stream(scanner.scan().spliterator(),
false).count());
+ }
+ }
+ }
+ }
+
+.. testoutput::
+
+ 1
+
+Let construct our dataset with predefined schema.
+
+.. testcode::
+
+ import org.apache.arrow.dataset.file.FileFormat;
+ import org.apache.arrow.dataset.file.FileSystemDatasetFactory;
+ import org.apache.arrow.dataset.jni.NativeMemoryPool;
+ import org.apache.arrow.dataset.scanner.ScanOptions;
+ import org.apache.arrow.dataset.scanner.Scanner;
+ import org.apache.arrow.dataset.source.Dataset;
+ import org.apache.arrow.dataset.source.DatasetFactory;
+ import org.apache.arrow.memory.RootAllocator;
+ import java.util.stream.StreamSupport;
+
+ String uri = "file:" + System.getProperty("user.dir") +
"/thirdpartydeps/parquetfiles/data1.parquet";
+ try (RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE)) {
+ try (DatasetFactory datasetFactory = new
FileSystemDatasetFactory(rootAllocator, NativeMemoryPool.getDefault(),
FileFormat.PARQUET, uri)) {
+ try(Dataset dataset =
datasetFactory.finish(datasetFactory.inspect())){
+ ScanOptions options = new ScanOptions(/*batchSize*/ 100);
+ try(Scanner scanner = dataset.newScan(options)){
+
System.out.println(StreamSupport.stream(scanner.scan().spliterator(),
false).count());
+ }
+ }
+ }
+ }
+
+.. testoutput::
+
+ 1
+
+Getting the Schema
+==================
+
+During Dataset Construction
+***************************
+
+.. testcode::
+
+ import org.apache.arrow.dataset.file.FileFormat;
+ import org.apache.arrow.dataset.file.FileSystemDatasetFactory;
+ import org.apache.arrow.dataset.jni.NativeMemoryPool;
+ import org.apache.arrow.dataset.source.DatasetFactory;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.types.pojo.Schema;
+
+ String uri = "file:" + System.getProperty("user.dir") +
"/thirdpartydeps/parquetfiles/data1.parquet";
+ try(RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE)){
+ try(DatasetFactory datasetFactory = new
FileSystemDatasetFactory(rootAllocator, NativeMemoryPool.getDefault(),
FileFormat.PARQUET, uri)){
+ Schema schema = datasetFactory.inspect();
+
+ System.out.println(schema);
+ }
+ }
+
+.. testoutput::
+
+ Schema<id: Int(32, true), name: Utf8>(metadata:
{parquet.avro.schema={"type":"record","name":"User","namespace":"org.apache.arrow.dataset","fields":[{"name":"id","type":["int","null"]},{"name":"name","type":["string","null"]}]},
writer.model.name=avro})
+
+From a Dataset
+**************
+
+.. testcode::
+
+ import org.apache.arrow.dataset.file.FileFormat;
+ import org.apache.arrow.dataset.file.FileSystemDatasetFactory;
+ import org.apache.arrow.dataset.jni.NativeMemoryPool;
+ import org.apache.arrow.dataset.scanner.ScanOptions;
+ import org.apache.arrow.dataset.scanner.Scanner;
+ import org.apache.arrow.dataset.source.Dataset;
+ import org.apache.arrow.dataset.source.DatasetFactory;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.types.pojo.Schema;
+
+ String uri = "file:" + System.getProperty("user.dir") +
"/thirdpartydeps/parquetfiles/data1.parquet";
+ try(RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE)){
+ try(DatasetFactory datasetFactory = new
FileSystemDatasetFactory(rootAllocator, NativeMemoryPool.getDefault(),
FileFormat.PARQUET, uri)){
+ ScanOptions options = new ScanOptions(/*batchSize*/ 1);
+ try(Dataset dataset = datasetFactory.finish()){
+ try(Scanner scanner = dataset.newScan(options)){
+ Schema schema = scanner.schema();
+
+ System.out.println(schema);
+ }
+ }
+ }
+ }
+
+.. testoutput::
+
+ Schema<id: Int(32, true), name: Utf8>(metadata:
{parquet.avro.schema={"type":"record","name":"User","namespace":"org.apache.arrow.dataset","fields":[{"name":"id","type":["int","null"]},{"name":"name","type":["string","null"]}]},
writer.model.name=avro})
+
+Query Parquet File
+==================
+
+Let query information for a parquet file.
+
+Query Data Content For File
+***************************
+
+.. testcode::
+
+ import com.google.common.collect.Streams;
+ import org.apache.arrow.dataset.file.FileFormat;
+ import org.apache.arrow.dataset.file.FileSystemDatasetFactory;
+ import org.apache.arrow.dataset.jni.NativeMemoryPool;
+ import org.apache.arrow.dataset.scanner.ScanOptions;
+ import org.apache.arrow.dataset.scanner.Scanner;
+ import org.apache.arrow.dataset.source.Dataset;
+ import org.apache.arrow.dataset.source.DatasetFactory;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VectorLoader;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import org.apache.arrow.vector.ipc.message.ArrowRecordBatch;
+
+ import java.util.stream.Stream;
+
+ String uri = "file:" + System.getProperty("user.dir") +
"/thirdpartydeps/parquetfiles/data1.parquet";
+ try(RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ DatasetFactory datasetFactory = new
FileSystemDatasetFactory(rootAllocator, NativeMemoryPool.getDefault(),
FileFormat.PARQUET, uri);
+ Dataset dataset = datasetFactory.finish()){
+ ScanOptions options = new ScanOptions(/*batchSize*/ 100);
+ try(Scanner scanner = dataset.newScan(options);
+ VectorSchemaRoot vsr = VectorSchemaRoot.create(scanner.schema(),
rootAllocator)){
+ scanner.scan().forEach(scanTask-> {
Review comment:
Filed https://issues.apache.org/jira/browse/ARROW-15745
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