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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2022/04/01 16:27:38 UTC
[GitHub] [arrow] lidavidm commented on a change in pull request #12739: ARROW-15972: [Java][Doc] Getting Started Section - Landing Page
lidavidm commented on a change in pull request #12739:
URL: https://github.com/apache/arrow/pull/12739#discussion_r840742654
##########
File path: docs/source/java/vector_schema_root.rst
##########
@@ -15,9 +15,6 @@
.. specific language governing permissions and limitations
.. under the License.
-.. default-domain:: java
-.. highlight:: java
-
Review comment:
Did you mean to remove this?
##########
File path: docs/source/java/overview.rst
##########
@@ -0,0 +1,203 @@
+.. Licensed to the Apache Software Foundation (ASF) under one
+.. or more contributor license agreements. See the NOTICE file
+.. distributed with this work for additional information
+.. regarding copyright ownership. The ASF licenses this file
+.. to you under the Apache License, Version 2.0 (the
+.. "License"); you may not use this file except in compliance
+.. with the License. You may obtain a copy of the License at
+
+.. http://www.apache.org/licenses/LICENSE-2.0
+
+.. Unless required by applicable law or agreed to in writing,
+.. software distributed under the License is distributed on an
+.. "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+.. KIND, either express or implied. See the License for the
+.. specific language governing permissions and limitations
+.. under the License.
+
+===================
+High-Level Overview
+===================
+
+.. contents::
+
+The Apache Arrow Java modules implement various specifications including the
+columnar format and IPC. Most modules are native Java implementations,
+but some modules are JNI bindings to the C++ library.
+
+.. list-table:: Arrow Java Modules
+ :widths: 25 50 25
+ :header-rows: 1
+
+ * - Module
+ - Description
+ - Implementation
+ * - arrow-format
+ - Generated Java files from the IPC Flatbuffer definitions.
+ - Native
+ * - arrow-memory-core
+ - Core off-heap memory management libraries for Arrow ValueVectors.
+ - Native
+ * - arrow-memory-unsafe
+ - Memory management implementation based on sun.misc.Unsafe.
+ - Native
+ * - arrow-memory-netty
+ - Memory management implementation based on Netty.
+ - Native
+ * - arrow-vector
+ - An off-heap reference implementation for Arrow columnar data format.
+ - Native
+ * - arrow-tools
+ - Java applications for working with Arrow ValueVectors.
+ - Native
+ * - arrow-jdbc
+ - (Experimental) A library for converting JDBC data to Arrow data.
+ - Native
+ * - arrow-plasma
+ - (Experimental) Java client for the Plasma object store.
+ - Native
+ * - flight-core
+ - (Experimental) An RPC mechanism for transferring ValueVectors.
+ - Native
+ * - flight-grpc
+ - (Experimental) Contains utility class to expose Flight gRPC service and client.
Review comment:
```suggestion
- (Experimental) Contains utility classes to expose Flight gRPC service and client.
```
##########
File path: docs/source/java/overview.rst
##########
@@ -0,0 +1,203 @@
+.. Licensed to the Apache Software Foundation (ASF) under one
+.. or more contributor license agreements. See the NOTICE file
+.. distributed with this work for additional information
+.. regarding copyright ownership. The ASF licenses this file
+.. to you under the Apache License, Version 2.0 (the
+.. "License"); you may not use this file except in compliance
+.. with the License. You may obtain a copy of the License at
+
+.. http://www.apache.org/licenses/LICENSE-2.0
+
+.. Unless required by applicable law or agreed to in writing,
+.. software distributed under the License is distributed on an
+.. "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+.. KIND, either express or implied. See the License for the
+.. specific language governing permissions and limitations
+.. under the License.
+
+===================
+High-Level Overview
+===================
+
+.. contents::
+
+The Apache Arrow Java modules implement various specifications including the
+columnar format and IPC. Most modules are native Java implementations,
+but some modules are JNI bindings to the C++ library.
+
+.. list-table:: Arrow Java Modules
+ :widths: 25 50 25
+ :header-rows: 1
+
+ * - Module
+ - Description
+ - Implementation
+ * - arrow-format
+ - Generated Java files from the IPC Flatbuffer definitions.
+ - Native
+ * - arrow-memory-core
+ - Core off-heap memory management libraries for Arrow ValueVectors.
+ - Native
+ * - arrow-memory-unsafe
+ - Memory management implementation based on sun.misc.Unsafe.
+ - Native
+ * - arrow-memory-netty
+ - Memory management implementation based on Netty.
+ - Native
+ * - arrow-vector
+ - An off-heap reference implementation for Arrow columnar data format.
+ - Native
+ * - arrow-tools
+ - Java applications for working with Arrow ValueVectors.
+ - Native
+ * - arrow-jdbc
+ - (Experimental) A library for converting JDBC data to Arrow data.
+ - Native
+ * - arrow-plasma
+ - (Experimental) Java client for the Plasma object store.
+ - Native
+ * - flight-core
+ - (Experimental) An RPC mechanism for transferring ValueVectors.
+ - Native
+ * - flight-grpc
+ - (Experimental) Contains utility class to expose Flight gRPC service and client.
+ - Native
+ * - flight-sql
+ - (Experimental) Contains utility classes to expose Flight SQL semantics for clients and servers over Arrow Flight.
Review comment:
```suggestion
- (Experimental) Implements SQL semantics for clients and servers over Arrow Flight.
```
##########
File path: docs/source/java/overview.rst
##########
@@ -0,0 +1,203 @@
+.. Licensed to the Apache Software Foundation (ASF) under one
+.. or more contributor license agreements. See the NOTICE file
+.. distributed with this work for additional information
+.. regarding copyright ownership. The ASF licenses this file
+.. to you under the Apache License, Version 2.0 (the
+.. "License"); you may not use this file except in compliance
+.. with the License. You may obtain a copy of the License at
+
+.. http://www.apache.org/licenses/LICENSE-2.0
+
+.. Unless required by applicable law or agreed to in writing,
+.. software distributed under the License is distributed on an
+.. "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+.. KIND, either express or implied. See the License for the
+.. specific language governing permissions and limitations
+.. under the License.
+
+===================
+High-Level Overview
+===================
+
+.. contents::
+
+The Apache Arrow Java modules implement various specifications including the
+columnar format and IPC. Most modules are native Java implementations,
+but some modules are JNI bindings to the C++ library.
+
+.. list-table:: Arrow Java Modules
+ :widths: 25 50 25
+ :header-rows: 1
+
+ * - Module
+ - Description
+ - Implementation
+ * - arrow-format
+ - Generated Java files from the IPC Flatbuffer definitions.
+ - Native
+ * - arrow-memory-core
+ - Core off-heap memory management libraries for Arrow ValueVectors.
+ - Native
+ * - arrow-memory-unsafe
+ - Memory management implementation based on sun.misc.Unsafe.
+ - Native
+ * - arrow-memory-netty
+ - Memory management implementation based on Netty.
+ - Native
+ * - arrow-vector
+ - An off-heap reference implementation for Arrow columnar data format.
+ - Native
+ * - arrow-tools
+ - Java applications for working with Arrow ValueVectors.
+ - Native
+ * - arrow-jdbc
+ - (Experimental) A library for converting JDBC data to Arrow data.
+ - Native
+ * - arrow-plasma
+ - (Experimental) Java client for the Plasma object store.
+ - Native
+ * - flight-core
+ - (Experimental) An RPC mechanism for transferring ValueVectors.
+ - Native
+ * - flight-grpc
+ - (Experimental) Contains utility class to expose Flight gRPC service and client.
+ - Native
+ * - flight-sql
+ - (Experimental) Contains utility classes to expose Flight SQL semantics for clients and servers over Arrow Flight.
+ - Native
+ * - flight-integration-tests
+ - Integration tests for Flight RPC.
+ - Native
+ * - arrow-performance
+ - JMH benchmarks for the Arrow libraries.
+ - Native
+ * - arrow-algorithm
+ - (Experimental) A collection of algorithms for working with ValueVectors.
+ - Native
+ * - arrow-avro
+ - (Experimental) A library for converting Avro data to Arrow data.
+ - Native
+ * - arrow-compression
+ - (Experimental) A library for working with compression/decompression of Arrow data.
+ - Native
+ * - arrow-c-data
+ - Java implementation of `C Data Interface`_
+ - JNI
+ * - arrow-orc
+ - (Experimental) A JNI wrapper for the C++ ORC reader implementation.
+ - JNI
+ * - arrow-gandiva
+ - Java wrappers around the native Gandiva SQL expression compiler.
+ - JNI
+ * - arrow-dataset
+ - Java bindings to the Arrow Datasets library.
+ - JNI
+
+Arrow Java modules support working with data (1) in-memory, (2) at rest, and (3) on-the-wire.
+
+For more detail about how to install this modules please review `Installing Java Modules`.
+
+Arrow Java In-Memory (The Physical Layer)
Review comment:
I think we can just keep the table and we don't need the rest of this file. Most of this content is already present in other documentation.
##########
File path: docs/source/java/overview.rst
##########
@@ -0,0 +1,203 @@
+.. Licensed to the Apache Software Foundation (ASF) under one
+.. or more contributor license agreements. See the NOTICE file
+.. distributed with this work for additional information
+.. regarding copyright ownership. The ASF licenses this file
+.. to you under the Apache License, Version 2.0 (the
+.. "License"); you may not use this file except in compliance
+.. with the License. You may obtain a copy of the License at
+
+.. http://www.apache.org/licenses/LICENSE-2.0
+
+.. Unless required by applicable law or agreed to in writing,
+.. software distributed under the License is distributed on an
+.. "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+.. KIND, either express or implied. See the License for the
+.. specific language governing permissions and limitations
+.. under the License.
+
+===================
+High-Level Overview
+===================
+
+.. contents::
+
+The Apache Arrow Java modules implement various specifications including the
+columnar format and IPC. Most modules are native Java implementations,
+but some modules are JNI bindings to the C++ library.
+
+.. list-table:: Arrow Java Modules
+ :widths: 25 50 25
+ :header-rows: 1
+
+ * - Module
+ - Description
+ - Implementation
+ * - arrow-format
+ - Generated Java files from the IPC Flatbuffer definitions.
+ - Native
+ * - arrow-memory-core
+ - Core off-heap memory management libraries for Arrow ValueVectors.
+ - Native
+ * - arrow-memory-unsafe
+ - Memory management implementation based on sun.misc.Unsafe.
+ - Native
+ * - arrow-memory-netty
+ - Memory management implementation based on Netty.
+ - Native
+ * - arrow-vector
+ - An off-heap reference implementation for Arrow columnar data format.
+ - Native
+ * - arrow-tools
+ - Java applications for working with Arrow ValueVectors.
+ - Native
+ * - arrow-jdbc
+ - (Experimental) A library for converting JDBC data to Arrow data.
+ - Native
+ * - arrow-plasma
+ - (Experimental) Java client for the Plasma object store.
+ - Native
+ * - flight-core
+ - (Experimental) An RPC mechanism for transferring ValueVectors.
+ - Native
+ * - flight-grpc
+ - (Experimental) Contains utility class to expose Flight gRPC service and client.
+ - Native
+ * - flight-sql
+ - (Experimental) Contains utility classes to expose Flight SQL semantics for clients and servers over Arrow Flight.
+ - Native
+ * - flight-integration-tests
+ - Integration tests for Flight RPC.
+ - Native
+ * - arrow-performance
+ - JMH benchmarks for the Arrow libraries.
+ - Native
+ * - arrow-algorithm
+ - (Experimental) A collection of algorithms for working with ValueVectors.
+ - Native
+ * - arrow-avro
+ - (Experimental) A library for converting Avro data to Arrow data.
+ - Native
+ * - arrow-compression
+ - (Experimental) A library for working with compression/decompression of Arrow data.
+ - Native
+ * - arrow-c-data
+ - Java implementation of `C Data Interface`_
+ - JNI
+ * - arrow-orc
+ - (Experimental) A JNI wrapper for the C++ ORC reader implementation.
+ - JNI
+ * - arrow-gandiva
+ - Java wrappers around the native Gandiva SQL expression compiler.
+ - JNI
+ * - arrow-dataset
+ - Java bindings to the Arrow Datasets library.
+ - JNI
+
+Arrow Java modules support working with data (1) in-memory, (2) at rest, and (3) on-the-wire.
+
+For more detail about how to install this modules please review `Installing Java Modules`.
Review comment:
I don't think we need this, don't we have install instructions as one of the sidebar items already?
##########
File path: docs/source/java/index.rst
##########
@@ -18,12 +18,11 @@
Java Implementation
===================
-This is the documentation of the Java API of Apache Arrow. For more details
-on the Arrow format and other language bindings see the :doc:`parent documentation <../index>`.
-
Review comment:
Did you mean to remove this?
##########
File path: docs/source/java/quickstartguide.rst
##########
@@ -0,0 +1,311 @@
+.. Licensed to the Apache Software Foundation (ASF) under one
+.. or more contributor license agreements. See the NOTICE file
+.. distributed with this work for additional information
+.. regarding copyright ownership. The ASF licenses this file
+.. to you under the Apache License, Version 2.0 (the
+.. "License"); you may not use this file except in compliance
+.. with the License. You may obtain a copy of the License at
+
+.. http://www.apache.org/licenses/LICENSE-2.0
+
+.. Unless required by applicable law or agreed to in writing,
+.. software distributed under the License is distributed on an
+.. "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+.. KIND, either express or implied. See the License for the
+.. specific language governing permissions and limitations
+.. under the License.
+
+=================
+Quick Start Guide
+=================
+
+.. contents::
+
+Arrow Java provides several building blocks. Data types describe the types of values;
+ValueVectors are sequences of typed values; fields describe the types of columns in
+tabular data; schemas describe a sequence of columns in tabular data, and
+VectorSchemaRoot represents tabular data. Arrow also provides readers and
+writers for loading data from and persisting data to storage.
+
+Create a ValueVector
+********************
+
+**ValueVectors** represent a sequence of values of the same type.
+They are also known as "arrays" in the columnar format.
+
+Example: create a vector of 32-bit integers representing ``[1, null, 2]``:
+
+.. code-block:: Java
+
+ import org.apache.arrow.memory.BufferAllocator;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.IntVector;
+
+ try(
+ BufferAllocator allocator = new RootAllocator();
+ IntVector intVector = new IntVector("fixed-size-primitive-layout", allocator);
+ ){
+ intVector.allocateNew(3);
+ intVector.set(0,1);
+ intVector.setNull(1);
+ intVector.set(2,2);
+ intVector.setValueCount(3);
+ System.out.println("Vector created in memory: " + intVector);
+ }
+
+.. code-block:: shell
+
+ Vector created in memory: [1, null, 2]
+
+
+Example: create a vector of UTF-8 encoded strings representing ``["one", "two", "three"]``:
+
+.. code-block:: Java
+
+ import org.apache.arrow.memory.BufferAllocator;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.VarCharVector;
+
+ try(
+ BufferAllocator allocator = new RootAllocator();
+ VarCharVector varCharVector = new VarCharVector("variable-size-primitive-layout", allocator);
+ ){
+ varCharVector.allocateNew(3);
+ varCharVector.set(0, "one".getBytes());
+ varCharVector.set(1, "two".getBytes());
+ varCharVector.set(2, "three".getBytes());
+ varCharVector.setValueCount(3);
+ System.out.println("Vector created in memory: " + varCharVector);
+ }
+
+.. code-block:: shell
+
+ Vector created in memory: [one, two, three]
+
+Create a Field
+**************
+
+**Fields** are used to denote the particular columns of tabular data.
+They consist of a name, a data type, a flag indicating whether the column can have null values,
+and optional key-value metadata.
+
+Example: create a field named "document" of string type:
+
+.. code-block:: Java
+
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import java.util.HashMap;
+ import java.util.Map;
+
+ Map<String, String> metadata = new HashMap<>();
+ metadata.put("A", "Id card");
+ metadata.put("B", "Passport");
+ metadata.put("C", "Visa");
+ Field document = new Field("document",
+ new FieldType(true, new ArrowType.Utf8(), /*dictionary*/ null, metadata),
+ /*children*/ null);
+ System.out.println("Field created: " + document + ", Metadata: " + document.getMetadata());
+
+.. code-block:: shell
+
+ Field created: document: Utf8, Metadata: {A=Id card, B=Passport, C=Visa}
+
+Create a Schema
+***************
+
+**Schemas** hold a sequence of fields together with some optional metadata.
+
+Example: Create a schema describing datasets with two columns:
+an int32 column "A" and a UTF8-encoded string column "B"
+
+.. code-block:: Java
+
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import java.util.HashMap;
+ import java.util.Map;
+ import static java.util.Arrays.asList;
+
+ Map<String, String> metadata = new HashMap<>();
+ metadata.put("K1", "V1");
+ metadata.put("K2", "V2");
+ Field a = new Field("A", FieldType.nullable(new ArrowType.Int(32, true)), /*children*/ null);
+ Field b = new Field("B", FieldType.nullable(new ArrowType.Utf8()), /*children*/ null);
+ Schema schema = new Schema(asList(a, b), metadata);
+ System.out.println("Schema created: " + schema);
+
+.. code-block:: shell
+
+ Schema created: Schema<A: Int(32, true), B: Utf8>(metadata: {K1=V1, K2=V2})
+
+Create a VectorSchemaRoot
+*************************
+
+A **VectorSchemaRoot** combines ValueVectors with a Schema to represent tabular data.
+
+Example: Create a dataset of names (strings) and ages (32-bit signed integers).
+
+.. code-block:: Java
+
+ import org.apache.arrow.memory.BufferAllocator;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import java.nio.charset.StandardCharsets;
+ import java.util.HashMap;
+ import java.util.Map;
+ import static java.util.Arrays.asList;
+
+ Field age = new Field("age",
+ FieldType.nullable(new ArrowType.Int(32, true)),
+ /*children*/null
+ );
+ Field name = new Field("name",
+ FieldType.nullable(new ArrowType.Utf8()),
+ /*children*/null
+ );
+ Schema schema = new Schema(asList(age, name), /*metadata*/ null);
+ try(
+ BufferAllocator allocator = new RootAllocator();
+ VectorSchemaRoot root = VectorSchemaRoot.create(schema, allocator);
+ IntVector ageVector = (IntVector) root.getVector("age");
+ VarCharVector nameVector = (VarCharVector) root.getVector("name");
+ ){
+ root.setRowCount(3);
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ nameVector.allocateNew(3);
+ nameVector.set(0, "Dave".getBytes(StandardCharsets.UTF_8));
+ nameVector.set(1, "Peter".getBytes(StandardCharsets.UTF_8));
+ nameVector.set(2, "Mary".getBytes(StandardCharsets.UTF_8));
+ System.out.println("VectorSchemaRoot created: \n" + root.contentToTSVString());
+ }
+
+.. code-block:: shell
+
+ VectorSchemaRoot created:
+ age name
+ 10 Dave
+ 20 Peter
+ 30 Mary
+
+
+Interprocess Communication (IPC)
+********************************
+
+Arrow data can be written to and read from disk, and both of these can be done in
+a streaming and/or random-access fashion depending on application requirements.
+
+**Write data to an arrow file**
+
+Example: Write the dataset from the previous example to an Arrow random-access file.
+
+.. code-block:: Java
+
+ import org.apache.arrow.memory.BufferAllocator;
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.IntVector;
+ import org.apache.arrow.vector.VarCharVector;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import org.apache.arrow.vector.ipc.ArrowFileWriter;
+ import org.apache.arrow.vector.types.pojo.ArrowType;
+ import org.apache.arrow.vector.types.pojo.Field;
+ import org.apache.arrow.vector.types.pojo.FieldType;
+ import org.apache.arrow.vector.types.pojo.Schema;
+ import java.io.File;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+ import java.nio.charset.StandardCharsets;
+ import java.util.HashMap;
+ import java.util.Map;
+ import static java.util.Arrays.asList;
+
+ Field age = new Field("age",
+ FieldType.nullable(new ArrowType.Int(32, true)),
+ /*children*/ null);
+ Field name = new Field("name",
+ FieldType.nullable(new ArrowType.Utf8()),
+ /*children*/ null);
+ Schema schema = new Schema(asList(age, name));
+ try(
+ BufferAllocator allocator = new RootAllocator();
+ VectorSchemaRoot root = VectorSchemaRoot.create(schema, allocator);
+ IntVector ageVector = (IntVector) root.getVector("age");
+ VarCharVector nameVector = (VarCharVector) root.getVector("name");
+ ){
+ ageVector.allocateNew(3);
+ ageVector.set(0, 10);
+ ageVector.set(1, 20);
+ ageVector.set(2, 30);
+ nameVector.allocateNew(3);
+ nameVector.set(0, "Dave".getBytes(StandardCharsets.UTF_8));
+ nameVector.set(1, "Peter".getBytes(StandardCharsets.UTF_8));
+ nameVector.set(2, "Mary".getBytes(StandardCharsets.UTF_8));
+ root.setRowCount(3);
+ File file = new File("random_access_file.arrow");
+ try (
+ FileOutputStream fileOutputStream = new FileOutputStream(file);
+ ArrowFileWriter writer = new ArrowFileWriter(root, /*provider*/ null, fileOutputStream.getChannel());
+ ) {
+ writer.start();
+ writer.writeBatch();
+ writer.end();
+ System.out.println("Record batches written: " + writer.getRecordBlocks().size()
+ + ". Number of rows written: " + root.getRowCount());
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+ }
+
+.. code-block:: shell
+
+ Record batches written: 1. Number of rows written: 3
+
+**Read data from an arrow file**
+
+Example: Read the dataset from the previous example to an Arrow random-access file.
+
+.. code-block:: Java
+
+ import org.apache.arrow.memory.RootAllocator;
+ import org.apache.arrow.vector.ipc.ArrowFileReader;
+ import org.apache.arrow.vector.ipc.message.ArrowBlock;
+ import org.apache.arrow.vector.VectorSchemaRoot;
+ import java.io.File;
+ import java.io.FileInputStream;
+ import java.io.FileOutputStream;
+ import java.io.IOException;
+
+ try(
+ BufferAllocator allocator = new RootAllocator(Long.MAX_VALUE);
+ FileInputStream fileInputStream = new FileInputStream(new File("random_access_file.arrow"));
+ ArrowFileReader reader = new ArrowFileReader(fileInputStream.getChannel(), allocator);
+ ){
+ System.out.println("Record batches in file: " + reader.getRecordBlocks().size());
+ for (ArrowBlock arrowBlock : reader.getRecordBlocks()) {
+ reader.loadRecordBatch(arrowBlock);
+ VectorSchemaRoot root = reader.getVectorSchemaRoot();
+ System.out.println("VectorSchemaRoot read: \n" + root.contentToTSVString());
+ }
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+
+.. code-block:: shell
+
+ VectorSchemaRoot read:
Review comment:
This output is missing the "Record batches in file" line
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