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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2022/02/05 17:47:27 UTC
[GitHub] [arrow-cookbook] lidavidm commented on a change in pull request #136: [Java]: Java cookbook for create arrow read/write IPC format
lidavidm commented on a change in pull request #136:
URL: https://github.com/apache/arrow-cookbook/pull/136#discussion_r800081630
##########
File path: java/source/io.rst
##########
@@ -0,0 +1,578 @@
+.. _arrow-io:
+
+========================
+Reading and writing data
+========================
+
+Recipes related to reading and writing data from disk using Apache Arrow.
+
+Arrow defines two types of binary formats for serializing record batches `IPC <https://arrow.apache.org/docs/java/ipc.html>`_: Streaming format / File or Random Access format
+
+Arrow vectors can be serialized to disk as the Arrow IPC format. Such files can be directly memory-mapped when read.
+
+.. contents::
+
+Writing
+=======
+
+Both libraries writing random access file and streaming format offer the same API
Review comment:
"Both writing file and streaming formats use the same API."
##########
File path: java/source/io.rst
##########
@@ -0,0 +1,578 @@
+.. _arrow-io:
+
+========================
+Reading and writing data
+========================
+
+Recipes related to reading and writing data from disk using Apache Arrow.
+
+Arrow defines two types of binary formats for serializing record batches `IPC <https://arrow.apache.org/docs/java/ipc.html>`_: Streaming format / File or Random Access format
+
+Arrow vectors can be serialized to disk as the Arrow IPC format. Such files can be directly memory-mapped when read.
+
+.. contents::
+
+Writing
+=======
+
+Both libraries writing random access file and streaming format offer the same API
+
+Writing Random Access Files
+***************************
+
+Write - Out to File
+-------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import java.io.File;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
Review comment:
Hmm, should we try to always close allocators, roots, etc. to make sure we always show the "right" way to do things? It does make things a little more verbose, though.
##########
File path: java/source/io.rst
##########
@@ -0,0 +1,578 @@
+.. _arrow-io:
+
+========================
+Reading and writing data
+========================
+
+Recipes related to reading and writing data from disk using Apache Arrow.
+
+Arrow defines two types of binary formats for serializing record batches `IPC <https://arrow.apache.org/docs/java/ipc.html>`_: Streaming format / File or Random Access format
+
+Arrow vectors can be serialized to disk as the Arrow IPC format. Such files can be directly memory-mapped when read.
+
+.. contents::
+
+Writing
+=======
+
+Both libraries writing random access file and streaming format offer the same API
+
+Writing Random Access Files
+***************************
+
+Write - Out to File
+-------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import java.io.File;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ File file = new File("randon_access_to_file.arrow");
+ try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/fileOutputStream.getChannel())
+ ){
+ writer.start();
+ for (int i=0; i<10; i++){
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.getRecordBlocks().size());
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ 10
+
+Write - Out to Buffer
+---------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+
+ import java.io.ByteArrayOutputStream;
+ import java.io.FileNotFoundException;
+ import java.io.IOException;
+ import java.nio.channels.Channels;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ try (ByteArrayOutputStream out = new ByteArrayOutputStream();
+ ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/Channels.newChannel(out)))
+ {
+ writer.start();
+ for (int i=0; i<10; i++){
+ // Generate data or modify the root or use a VectorLoader to get fresh data from somewhere else
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.getRecordBlocks().size());
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ 10
+
+Writing Streaming Format
+************************
+
+Write - Out to File
+-------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowStreamWriter;
+ import java.io.File;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ File file = new File("streaming_to_file.arrow");
+ try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowStreamWriter writer = new ArrowStreamWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/fileOutputStream.getChannel())
+ ){
+ writer.start();
+ for (int i=0; i<10; i++){
+ // Generate data or modify the root or use a VectorLoader to get fresh data from somewhere else
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.bytesWritten());
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ 2936
+
+Write - Out to Buffer
+---------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.ipc.ArrowStreamWriter;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+
+ import java.io.ByteArrayOutputStream;
+ import java.io.FileNotFoundException;
+ import java.io.IOException;
+ import java.nio.channels.Channels;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ try (ByteArrayOutputStream out = new ByteArrayOutputStream();
+ ArrowStreamWriter writer = new ArrowStreamWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/Channels.newChannel(out))
+ ){
+ writer.start();
+ for (int i=0; i<10; i++){
+ // Generate data or modify the root or use a VectorLoader to get fresh data from somewhere else
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.bytesWritten());
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ 2936
+
+Reading
+=======
+
+Both libraries writing random access file and streaming format offer the same API
+with the difference that random acces file offer access to the entire payload and
+we could move where do we need to go
+
+Reading Random Access Files
+***************************
+
+Read - From File
+----------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.ipc.message.ArrowBlock;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import java.io.File;
+ import java.io.FileInputStream;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+ import org.apache.arrow.vector.ipc.ArrowFileReader;
+
+ // Read data
Review comment:
nit: the comment here is misleading/doesn't offer much clarity
##########
File path: java/source/io.rst
##########
@@ -0,0 +1,578 @@
+.. _arrow-io:
+
+========================
+Reading and writing data
+========================
+
+Recipes related to reading and writing data from disk using Apache Arrow.
+
+Arrow defines two types of binary formats for serializing record batches `IPC <https://arrow.apache.org/docs/java/ipc.html>`_: Streaming format / File or Random Access format
+
+Arrow vectors can be serialized to disk as the Arrow IPC format. Such files can be directly memory-mapped when read.
Review comment:
I think we can consolidate this section, or we can just leave it out in favor of linking to the Arrow documentation.
Perhaps something like this:
```
The `Arrow IPC format <https://arrow.apache.org/docs/java/ipc.html>`_ defines two types of binary formats for serializing Arrow data: the streaming format and the file format (or random access format). Such files can be directly memory-mapped when read.
```
##########
File path: java/source/io.rst
##########
@@ -0,0 +1,578 @@
+.. _arrow-io:
+
+========================
+Reading and writing data
+========================
+
+Recipes related to reading and writing data from disk using Apache Arrow.
+
+Arrow defines two types of binary formats for serializing record batches `IPC <https://arrow.apache.org/docs/java/ipc.html>`_: Streaming format / File or Random Access format
+
+Arrow vectors can be serialized to disk as the Arrow IPC format. Such files can be directly memory-mapped when read.
+
+.. contents::
+
+Writing
+=======
+
+Both libraries writing random access file and streaming format offer the same API
+
+Writing Random Access Files
+***************************
+
+Write - Out to File
+-------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import java.io.File;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
Review comment:
nit, but `VectorSchemaRoot.setRowCount` sets the vector's row counts, if we want to be a little more terse
##########
File path: java/source/io.rst
##########
@@ -0,0 +1,578 @@
+.. _arrow-io:
+
+========================
+Reading and writing data
+========================
+
+Recipes related to reading and writing data from disk using Apache Arrow.
+
+Arrow defines two types of binary formats for serializing record batches `IPC <https://arrow.apache.org/docs/java/ipc.html>`_: Streaming format / File or Random Access format
+
+Arrow vectors can be serialized to disk as the Arrow IPC format. Such files can be directly memory-mapped when read.
+
+.. contents::
+
+Writing
+=======
+
+Both libraries writing random access file and streaming format offer the same API
+
+Writing Random Access Files
+***************************
+
+Write - Out to File
+-------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import java.io.File;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ File file = new File("randon_access_to_file.arrow");
+ try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/fileOutputStream.getChannel())
+ ){
+ writer.start();
+ for (int i=0; i<10; i++){
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.getRecordBlocks().size());
Review comment:
```suggestion
System.out.println("Record batches written: " + writer.getRecordBlocks().size());
```
##########
File path: java/source/io.rst
##########
@@ -0,0 +1,578 @@
+.. _arrow-io:
+
+========================
+Reading and writing data
+========================
+
+Recipes related to reading and writing data from disk using Apache Arrow.
+
+Arrow defines two types of binary formats for serializing record batches `IPC <https://arrow.apache.org/docs/java/ipc.html>`_: Streaming format / File or Random Access format
+
+Arrow vectors can be serialized to disk as the Arrow IPC format. Such files can be directly memory-mapped when read.
+
+.. contents::
+
+Writing
+=======
+
+Both libraries writing random access file and streaming format offer the same API
+
+Writing Random Access Files
+***************************
+
+Write - Out to File
+-------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import java.io.File;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ File file = new File("randon_access_to_file.arrow");
+ try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/fileOutputStream.getChannel())
+ ){
+ writer.start();
+ for (int i=0; i<10; i++){
+ writer.writeBatch();
Review comment:
We should clearly note (either as a comment, or in the prose) that this will write the same batch 10 times, because it implicitly writes the current contents of the associated VectorSchemaRoot as a single record batch
##########
File path: java/source/io.rst
##########
@@ -0,0 +1,578 @@
+.. _arrow-io:
+
+========================
+Reading and writing data
+========================
+
+Recipes related to reading and writing data from disk using Apache Arrow.
+
+Arrow defines two types of binary formats for serializing record batches `IPC <https://arrow.apache.org/docs/java/ipc.html>`_: Streaming format / File or Random Access format
+
+Arrow vectors can be serialized to disk as the Arrow IPC format. Such files can be directly memory-mapped when read.
+
+.. contents::
+
+Writing
+=======
+
+Both libraries writing random access file and streaming format offer the same API
+
+Writing Random Access Files
+***************************
+
+Write - Out to File
+-------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import java.io.File;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ File file = new File("randon_access_to_file.arrow");
+ try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/fileOutputStream.getChannel())
Review comment:
nit, but for this sort of thing, I think it would be clearer if the parameter-comment was on the `null` and not on the channel
##########
File path: java/source/io.rst
##########
@@ -0,0 +1,578 @@
+.. _arrow-io:
+
+========================
+Reading and writing data
+========================
+
+Recipes related to reading and writing data from disk using Apache Arrow.
+
+Arrow defines two types of binary formats for serializing record batches `IPC <https://arrow.apache.org/docs/java/ipc.html>`_: Streaming format / File or Random Access format
+
+Arrow vectors can be serialized to disk as the Arrow IPC format. Such files can be directly memory-mapped when read.
+
+.. contents::
+
+Writing
+=======
+
+Both libraries writing random access file and streaming format offer the same API
+
+Writing Random Access Files
+***************************
+
+Write - Out to File
+-------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import java.io.File;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ File file = new File("randon_access_to_file.arrow");
+ try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/fileOutputStream.getChannel())
+ ){
+ writer.start();
+ for (int i=0; i<10; i++){
+ writer.writeBatch();
+ }
+ writer.end();
Review comment:
Doesn't ArrowFileWriter's AutoCloseable implementation call `end`?
##########
File path: java/source/io.rst
##########
@@ -0,0 +1,578 @@
+.. _arrow-io:
+
+========================
+Reading and writing data
+========================
+
+Recipes related to reading and writing data from disk using Apache Arrow.
+
+Arrow defines two types of binary formats for serializing record batches `IPC <https://arrow.apache.org/docs/java/ipc.html>`_: Streaming format / File or Random Access format
+
+Arrow vectors can be serialized to disk as the Arrow IPC format. Such files can be directly memory-mapped when read.
+
+.. contents::
+
+Writing
+=======
+
+Both libraries writing random access file and streaming format offer the same API
+
+Writing Random Access Files
+***************************
+
+Write - Out to File
+-------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import java.io.File;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ File file = new File("randon_access_to_file.arrow");
+ try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/fileOutputStream.getChannel())
+ ){
+ writer.start();
+ for (int i=0; i<10; i++){
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.getRecordBlocks().size());
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ 10
+
+Write - Out to Buffer
+---------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+
+ import java.io.ByteArrayOutputStream;
+ import java.io.FileNotFoundException;
+ import java.io.IOException;
+ import java.nio.channels.Channels;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ try (ByteArrayOutputStream out = new ByteArrayOutputStream();
+ ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/Channels.newChannel(out)))
+ {
+ writer.start();
+ for (int i=0; i<10; i++){
+ // Generate data or modify the root or use a VectorLoader to get fresh data from somewhere else
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.getRecordBlocks().size());
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ 10
+
+Writing Streaming Format
+************************
+
+Write - Out to File
+-------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowStreamWriter;
+ import java.io.File;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ File file = new File("streaming_to_file.arrow");
+ try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowStreamWriter writer = new ArrowStreamWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/fileOutputStream.getChannel())
+ ){
+ writer.start();
+ for (int i=0; i<10; i++){
+ // Generate data or modify the root or use a VectorLoader to get fresh data from somewhere else
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.bytesWritten());
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ 2936
+
+Write - Out to Buffer
+---------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.ipc.ArrowStreamWriter;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+
+ import java.io.ByteArrayOutputStream;
+ import java.io.FileNotFoundException;
+ import java.io.IOException;
+ import java.nio.channels.Channels;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ try (ByteArrayOutputStream out = new ByteArrayOutputStream();
+ ArrowStreamWriter writer = new ArrowStreamWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/Channels.newChannel(out))
+ ){
+ writer.start();
+ for (int i=0; i<10; i++){
+ // Generate data or modify the root or use a VectorLoader to get fresh data from somewhere else
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.bytesWritten());
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ 2936
+
+Reading
+=======
+
+Both libraries writing random access file and streaming format offer the same API
+with the difference that random acces file offer access to the entire payload and
+we could move where do we need to go
Review comment:
```suggestion
Reading the random access format and streaming format both offer the same API,
with the difference that random access files also offer access to any record batch by index.
```
##########
File path: java/source/io.rst
##########
@@ -0,0 +1,578 @@
+.. _arrow-io:
+
+========================
+Reading and writing data
+========================
+
+Recipes related to reading and writing data from disk using Apache Arrow.
+
+Arrow defines two types of binary formats for serializing record batches `IPC <https://arrow.apache.org/docs/java/ipc.html>`_: Streaming format / File or Random Access format
+
+Arrow vectors can be serialized to disk as the Arrow IPC format. Such files can be directly memory-mapped when read.
+
+.. contents::
+
+Writing
+=======
+
+Both libraries writing random access file and streaming format offer the same API
+
+Writing Random Access Files
+***************************
+
+Write - Out to File
+-------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import java.io.File;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ File file = new File("randon_access_to_file.arrow");
+ try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/fileOutputStream.getChannel())
+ ){
+ writer.start();
+ for (int i=0; i<10; i++){
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.getRecordBlocks().size());
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ 10
+
+Write - Out to Buffer
+---------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+
+ import java.io.ByteArrayOutputStream;
+ import java.io.FileNotFoundException;
+ import java.io.IOException;
+ import java.nio.channels.Channels;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ try (ByteArrayOutputStream out = new ByteArrayOutputStream();
+ ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/Channels.newChannel(out)))
+ {
+ writer.start();
+ for (int i=0; i<10; i++){
+ // Generate data or modify the root or use a VectorLoader to get fresh data from somewhere else
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.getRecordBlocks().size());
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ 10
+
+Writing Streaming Format
+************************
+
+Write - Out to File
+-------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowStreamWriter;
+ import java.io.File;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ File file = new File("streaming_to_file.arrow");
+ try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowStreamWriter writer = new ArrowStreamWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/fileOutputStream.getChannel())
+ ){
+ writer.start();
+ for (int i=0; i<10; i++){
+ // Generate data or modify the root or use a VectorLoader to get fresh data from somewhere else
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.bytesWritten());
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ 2936
+
+Write - Out to Buffer
+---------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.ipc.ArrowStreamWriter;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+
+ import java.io.ByteArrayOutputStream;
+ import java.io.FileNotFoundException;
+ import java.io.IOException;
+ import java.nio.channels.Channels;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ try (ByteArrayOutputStream out = new ByteArrayOutputStream();
+ ArrowStreamWriter writer = new ArrowStreamWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/Channels.newChannel(out))
+ ){
+ writer.start();
+ for (int i=0; i<10; i++){
+ // Generate data or modify the root or use a VectorLoader to get fresh data from somewhere else
+ writer.writeBatch();
+ }
+ writer.end();
+ System.out.println(writer.bytesWritten());
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ 2936
+
+Reading
+=======
+
+Both libraries writing random access file and streaming format offer the same API
+with the difference that random acces file offer access to the entire payload and
+we could move where do we need to go
+
+Reading Random Access Files
+***************************
+
+Read - From File
+----------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.ipc.message.ArrowBlock;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import java.io.File;
+ import java.io.FileInputStream;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+ import org.apache.arrow.vector.ipc.ArrowFileReader;
+
+ // Read data
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ File file = new File("randon_access_to_file.arrow");
+ try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/fileOutputStream.getChannel())
+ ){
+ // write
+ writer.start();
+ for (int i=0; i<10; i++){
+ // Generate data or modify the root or use a VectorLoader to get fresh data from somewhere else
+ writer.writeBatch();
+ }
+ writer.end();
+
+ // read
+ try (FileInputStream fileInputStream = new FileInputStream(file);
+ ArrowFileReader reader = new ArrowFileReader(fileInputStream.getChannel(), rootAllocator)
+ ){
+ // read the 2nd batch or the index that you need according to you write
+ ArrowBlock block = reader.getRecordBlocks().get(1);
+ reader.loadRecordBatch(block);
+ VectorSchemaRoot vectorSchemaRootRecover = reader.getVectorSchemaRoot();
+ System.out.print(vectorSchemaRootRecover.contentToTSVString());
+ }
+
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ name age
+ David 10
+ Gladis 20
+ Juan 30
+
+Read - From Buffer
+------------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.ipc.ArrowFileReader;
+ import org.apache.arrow.vector.ipc.SeekableReadChannel;
+ import org.apache.arrow.vector.ipc.message.ArrowBlock;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import org.apache.arrow.vector.util.ByteArrayReadableSeekableByteChannel;
+
+ import java.io.ByteArrayOutputStream;
+ import java.io.FileNotFoundException;
+ import java.io.IOException;
+ import java.nio.channels.Channels;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ try (ByteArrayOutputStream out = new ByteArrayOutputStream();
+ ArrowFileWriter writer = new ArrowFileWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/Channels.newChannel(out)))
+ {
+ // write
+ writer.start();
+ for (int i=0; i<10; i++){
+ // Generate data or modify the root or use a VectorLoader to get fresh data from somewhere else
+ writer.writeBatch();
+ }
+ writer.end();
+
+ // read
+ try (ArrowFileReader reader = new ArrowFileReader(new SeekableReadChannel(new ByteArrayReadableSeekableByteChannel(out.toByteArray())), rootAllocator)
+ ){
+ // read the 2nd batch or the index that you need according to you write
+ ArrowBlock block = reader.getRecordBlocks().get(1);
+ reader.loadRecordBatch(block);
+ VectorSchemaRoot vectorSchemaRootRecover = reader.getVectorSchemaRoot();
+ System.out.print(vectorSchemaRootRecover.contentToTSVString());
+ }
+ } catch (FileNotFoundException e) {
+ e.printStackTrace();
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. testoutput::
+
+ name age
+ David 10
+ Gladis 20
+ Juan 30
+
+Reading Streaming Format
+************************
+
+Read - From File
+----------------
+
+.. testcode::
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.ipc.ArrowStreamReader;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import static java.util.Arrays.asList;
+ import org.apache.arrow.vector.ipc.ArrowStreamWriter;
+ import java.io.File;
+ import java.io.FileInputStream;
+ import java.io.FileNotFoundException;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ // Create and populate data:
+ Field name = new Field("name", FieldType.nullable(new ArrowType.Utf8()), null);
+ Field age = new Field("age", FieldType.nullable(new ArrowType.Int(32, true)), null);
+ Schema schemaPerson = new Schema(asList(name, age));
+ RootAllocator rootAllocator = new RootAllocator(Long.MAX_VALUE);
+ VectorSchemaRoot vectorSchemaRoot = VectorSchemaRoot.create(schemaPerson, rootAllocator);
+ VarCharVector nameVector = (VarCharVector) vectorSchemaRoot.getVector("name");
+ nameVector.allocateNew(3);
+ nameVector.set(0, "David".getBytes());
+ nameVector.set(1, "Gladis".getBytes());
+ nameVector.set(2, "Juan".getBytes());
+ nameVector.setValueCount(3);
+ IntVector ageVector = (IntVector) vectorSchemaRoot.getVector("age");
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ ageVector.setValueCount(3);
+ vectorSchemaRoot.setRowCount(3);
+ File file = new File("streaming_to_file.arrow");
+ try (FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowStreamWriter writer = new ArrowStreamWriter(vectorSchemaRoot, null, /*WritableByteChannel out*/fileOutputStream.getChannel())
+ ){
+ // write
+ writer.start();
+ for (int i=0; i<10; i++){
+ // Generate data or modify the root or use a VectorLoader to get fresh data from somewhere else
+ writer.writeBatch();
+ }
+ writer.end();
+
+ // read
+ try (FileInputStream fileInputStreamForStream = new FileInputStream(file);
+ ArrowStreamReader reader = new ArrowStreamReader(fileInputStreamForStream, rootAllocator)){
+ // read the batch
+ reader.loadNextBatch();
Review comment:
Can we demonstrate iterating through all batches in the file?
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