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| <section id="quick-start-guide"> |
| <h1>Quick Start Guide<a class="headerlink" href="#quick-start-guide" title="Link to this heading">¶</a></h1> |
| <p>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.</p> |
| <section id="create-a-valuevector"> |
| <h2>Create a ValueVector<a class="headerlink" href="#create-a-valuevector" title="Link to this heading">¶</a></h2> |
| <p><strong>ValueVectors</strong> represent a sequence of values of the same type. |
| They are also known as “arrays” in the columnar format.</p> |
| <p>Example: create a vector of 32-bit integers representing <code class="docutils literal notranslate"><span class="pre">[1,</span> <span class="pre">null,</span> <span class="pre">2]</span></code>:</p> |
| <div class="highlight-Java notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.memory.BufferAllocator</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.memory.RootAllocator</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.IntVector</span><span class="p">;</span> |
| |
| <span class="k">try</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">BufferAllocator</span><span class="w"> </span><span class="n">allocator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RootAllocator</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">IntVector</span><span class="w"> </span><span class="n">intVector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IntVector</span><span class="p">(</span><span class="s">"fixed-size-primitive-layout"</span><span class="p">,</span><span class="w"> </span><span class="n">allocator</span><span class="p">);</span> |
| <span class="p">){</span> |
| <span class="w"> </span><span class="n">intVector</span><span class="p">.</span><span class="na">allocateNew</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">intVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">intVector</span><span class="p">.</span><span class="na">setNull</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">intVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">2</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">intVector</span><span class="p">.</span><span class="na">setValueCount</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"Vector created in memory: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">intVector</span><span class="p">);</span> |
| <span class="p">}</span> |
| </pre></div> |
| </div> |
| <div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>Vector<span class="w"> </span>created<span class="w"> </span><span class="k">in</span><span class="w"> </span>memory:<span class="w"> </span><span class="o">[</span><span class="m">1</span>,<span class="w"> </span>null,<span class="w"> </span><span class="m">2</span><span class="o">]</span> |
| </pre></div> |
| </div> |
| <p>Example: create a vector of UTF-8 encoded strings representing <code class="docutils literal notranslate"><span class="pre">["one",</span> <span class="pre">"two",</span> <span class="pre">"three"]</span></code>:</p> |
| <div class="highlight-Java notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.memory.BufferAllocator</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.memory.RootAllocator</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.VarCharVector</span><span class="p">;</span> |
| |
| <span class="k">try</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">BufferAllocator</span><span class="w"> </span><span class="n">allocator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RootAllocator</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">VarCharVector</span><span class="w"> </span><span class="n">varCharVector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">VarCharVector</span><span class="p">(</span><span class="s">"variable-size-primitive-layout"</span><span class="p">,</span><span class="w"> </span><span class="n">allocator</span><span class="p">);</span> |
| <span class="p">){</span> |
| <span class="w"> </span><span class="n">varCharVector</span><span class="p">.</span><span class="na">allocateNew</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">varCharVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="s">"one"</span><span class="p">.</span><span class="na">getBytes</span><span class="p">());</span> |
| <span class="w"> </span><span class="n">varCharVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="s">"two"</span><span class="p">.</span><span class="na">getBytes</span><span class="p">());</span> |
| <span class="w"> </span><span class="n">varCharVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="s">"three"</span><span class="p">.</span><span class="na">getBytes</span><span class="p">());</span> |
| <span class="w"> </span><span class="n">varCharVector</span><span class="p">.</span><span class="na">setValueCount</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"Vector created in memory: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">varCharVector</span><span class="p">);</span> |
| <span class="p">}</span> |
| </pre></div> |
| </div> |
| <div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>Vector<span class="w"> </span>created<span class="w"> </span><span class="k">in</span><span class="w"> </span>memory:<span class="w"> </span><span class="o">[</span>one,<span class="w"> </span>two,<span class="w"> </span>three<span class="o">]</span> |
| </pre></div> |
| </div> |
| </section> |
| <section id="create-a-field"> |
| <h2>Create a Field<a class="headerlink" href="#create-a-field" title="Link to this heading">¶</a></h2> |
| <p><strong>Fields</strong> 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.</p> |
| <p>Example: create a field named “document” of string type:</p> |
| <div class="highlight-Java notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.ArrowType</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.Field</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.FieldType</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.util.HashMap</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.util.Map</span><span class="p">;</span> |
| |
| <span class="n">Map</span><span class="o"><</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">metadata</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o"><></span><span class="p">();</span> |
| <span class="n">metadata</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">"A"</span><span class="p">,</span><span class="w"> </span><span class="s">"Id card"</span><span class="p">);</span> |
| <span class="n">metadata</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">"B"</span><span class="p">,</span><span class="w"> </span><span class="s">"Passport"</span><span class="p">);</span> |
| <span class="n">metadata</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">"C"</span><span class="p">,</span><span class="w"> </span><span class="s">"Visa"</span><span class="p">);</span> |
| <span class="n">Field</span><span class="w"> </span><span class="n">document</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Field</span><span class="p">(</span><span class="s">"document"</span><span class="p">,</span> |
| <span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FieldType</span><span class="p">(</span><span class="kc">true</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">Utf8</span><span class="p">(),</span><span class="w"> </span><span class="cm">/*dictionary*/</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">metadata</span><span class="p">),</span> |
| <span class="w"> </span><span class="cm">/*children*/</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span> |
| <span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"Field created: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">document</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">", Metadata: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">document</span><span class="p">.</span><span class="na">getMetadata</span><span class="p">());</span> |
| </pre></div> |
| </div> |
| <div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>Field<span class="w"> </span>created:<span class="w"> </span>document:<span class="w"> </span>Utf8,<span class="w"> </span>Metadata:<span class="w"> </span><span class="o">{</span><span class="nv">A</span><span class="o">=</span>Id<span class="w"> </span>card,<span class="w"> </span><span class="nv">B</span><span class="o">=</span>Passport,<span class="w"> </span><span class="nv">C</span><span class="o">=</span>Visa<span class="o">}</span> |
| </pre></div> |
| </div> |
| </section> |
| <section id="create-a-schema"> |
| <h2>Create a Schema<a class="headerlink" href="#create-a-schema" title="Link to this heading">¶</a></h2> |
| <p><strong>Schemas</strong> hold a sequence of fields together with some optional metadata.</p> |
| <p>Example: Create a schema describing datasets with two columns: |
| an int32 column “A” and a UTF8-encoded string column “B”</p> |
| <div class="highlight-Java notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.ArrowType</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.Field</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.FieldType</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.Schema</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.util.HashMap</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.util.Map</span><span class="p">;</span> |
| <span class="kn">import static</span><span class="w"> </span><span class="nn">java.util.Arrays.asList</span><span class="p">;</span> |
| |
| <span class="n">Map</span><span class="o"><</span><span class="n">String</span><span class="p">,</span><span class="w"> </span><span class="n">String</span><span class="o">></span><span class="w"> </span><span class="n">metadata</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">HashMap</span><span class="o"><></span><span class="p">();</span> |
| <span class="n">metadata</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">"K1"</span><span class="p">,</span><span class="w"> </span><span class="s">"V1"</span><span class="p">);</span> |
| <span class="n">metadata</span><span class="p">.</span><span class="na">put</span><span class="p">(</span><span class="s">"K2"</span><span class="p">,</span><span class="w"> </span><span class="s">"V2"</span><span class="p">);</span> |
| <span class="n">Field</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Field</span><span class="p">(</span><span class="s">"A"</span><span class="p">,</span><span class="w"> </span><span class="n">FieldType</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">Int</span><span class="p">(</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">)),</span><span class="w"> </span><span class="cm">/*children*/</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span> |
| <span class="n">Field</span><span class="w"> </span><span class="n">b</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Field</span><span class="p">(</span><span class="s">"B"</span><span class="p">,</span><span class="w"> </span><span class="n">FieldType</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">Utf8</span><span class="p">()),</span><span class="w"> </span><span class="cm">/*children*/</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span> |
| <span class="n">Schema</span><span class="w"> </span><span class="n">schema</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Schema</span><span class="p">(</span><span class="n">asList</span><span class="p">(</span><span class="n">a</span><span class="p">,</span><span class="w"> </span><span class="n">b</span><span class="p">),</span><span class="w"> </span><span class="n">metadata</span><span class="p">);</span> |
| <span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"Schema created: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">schema</span><span class="p">);</span> |
| </pre></div> |
| </div> |
| <div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>Schema<span class="w"> </span>created:<span class="w"> </span>Schema<A:<span class="w"> </span>Int<span class="o">(</span><span class="m">32</span>,<span class="w"> </span><span class="nb">true</span><span class="o">)</span>,<span class="w"> </span>B:<span class="w"> </span>Utf8><span class="o">(</span>metadata:<span class="w"> </span><span class="o">{</span><span class="nv">K1</span><span class="o">=</span>V1,<span class="w"> </span><span class="nv">K2</span><span class="o">=</span>V2<span class="o">})</span> |
| </pre></div> |
| </div> |
| </section> |
| <section id="create-a-vectorschemaroot"> |
| <h2>Create a VectorSchemaRoot<a class="headerlink" href="#create-a-vectorschemaroot" title="Link to this heading">¶</a></h2> |
| <p>A <strong>VectorSchemaRoot</strong> combines ValueVectors with a Schema to represent tabular data.</p> |
| <p>Example: Create a dataset of names (strings) and ages (32-bit signed integers).</p> |
| <div class="highlight-Java notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.memory.BufferAllocator</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.memory.RootAllocator</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.IntVector</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.VarCharVector</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.VectorSchemaRoot</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.ArrowType</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.Field</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.FieldType</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.Schema</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.nio.charset.StandardCharsets</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.util.HashMap</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.util.Map</span><span class="p">;</span> |
| <span class="kn">import static</span><span class="w"> </span><span class="nn">java.util.Arrays.asList</span><span class="p">;</span> |
| |
| <span class="n">Field</span><span class="w"> </span><span class="n">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Field</span><span class="p">(</span><span class="s">"age"</span><span class="p">,</span> |
| <span class="w"> </span><span class="n">FieldType</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">Int</span><span class="p">(</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">)),</span> |
| <span class="w"> </span><span class="cm">/*children*/</span><span class="kc">null</span> |
| <span class="p">);</span> |
| <span class="n">Field</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Field</span><span class="p">(</span><span class="s">"name"</span><span class="p">,</span> |
| <span class="w"> </span><span class="n">FieldType</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">Utf8</span><span class="p">()),</span> |
| <span class="w"> </span><span class="cm">/*children*/</span><span class="kc">null</span> |
| <span class="p">);</span> |
| <span class="n">Schema</span><span class="w"> </span><span class="n">schema</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Schema</span><span class="p">(</span><span class="n">asList</span><span class="p">(</span><span class="n">age</span><span class="p">,</span><span class="w"> </span><span class="n">name</span><span class="p">),</span><span class="w"> </span><span class="cm">/*metadata*/</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span> |
| <span class="k">try</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">BufferAllocator</span><span class="w"> </span><span class="n">allocator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RootAllocator</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">VectorSchemaRoot</span><span class="w"> </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">VectorSchemaRoot</span><span class="p">.</span><span class="na">create</span><span class="p">(</span><span class="n">schema</span><span class="p">,</span><span class="w"> </span><span class="n">allocator</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">IntVector</span><span class="w"> </span><span class="n">ageVector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">IntVector</span><span class="p">)</span><span class="w"> </span><span class="n">root</span><span class="p">.</span><span class="na">getVector</span><span class="p">(</span><span class="s">"age"</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">VarCharVector</span><span class="w"> </span><span class="n">nameVector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">VarCharVector</span><span class="p">)</span><span class="w"> </span><span class="n">root</span><span class="p">.</span><span class="na">getVector</span><span class="p">(</span><span class="s">"name"</span><span class="p">);</span> |
| <span class="p">){</span> |
| <span class="w"> </span><span class="n">ageVector</span><span class="p">.</span><span class="na">allocateNew</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">ageVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">ageVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">20</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">ageVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">nameVector</span><span class="p">.</span><span class="na">allocateNew</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">nameVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="s">"Dave"</span><span class="p">.</span><span class="na">getBytes</span><span class="p">(</span><span class="n">StandardCharsets</span><span class="p">.</span><span class="na">UTF_8</span><span class="p">));</span> |
| <span class="w"> </span><span class="n">nameVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="s">"Peter"</span><span class="p">.</span><span class="na">getBytes</span><span class="p">(</span><span class="n">StandardCharsets</span><span class="p">.</span><span class="na">UTF_8</span><span class="p">));</span> |
| <span class="w"> </span><span class="n">nameVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="s">"Mary"</span><span class="p">.</span><span class="na">getBytes</span><span class="p">(</span><span class="n">StandardCharsets</span><span class="p">.</span><span class="na">UTF_8</span><span class="p">));</span> |
| <span class="w"> </span><span class="n">root</span><span class="p">.</span><span class="na">setRowCount</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"VectorSchemaRoot created: \n"</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">root</span><span class="p">.</span><span class="na">contentToTSVString</span><span class="p">());</span> |
| <span class="p">}</span> |
| </pre></div> |
| </div> |
| <div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>VectorSchemaRoot<span class="w"> </span>created: |
| age<span class="w"> </span>name |
| <span class="m">10</span><span class="w"> </span>Dave |
| <span class="m">20</span><span class="w"> </span>Peter |
| <span class="m">30</span><span class="w"> </span>Mary |
| </pre></div> |
| </div> |
| </section> |
| <section id="interprocess-communication-ipc"> |
| <h2>Interprocess Communication (IPC)<a class="headerlink" href="#interprocess-communication-ipc" title="Link to this heading">¶</a></h2> |
| <p>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.</p> |
| <p><strong>Write data to an arrow file</strong></p> |
| <p>Example: Write the dataset from the previous example to an Arrow IPC file (random-access).</p> |
| <div class="highlight-Java notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.memory.BufferAllocator</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.memory.RootAllocator</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.IntVector</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.VarCharVector</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.VectorSchemaRoot</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.ipc.ArrowFileWriter</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.ArrowType</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.Field</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.FieldType</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.Schema</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.io.File</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.io.FileOutputStream</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.io.IOException</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.nio.charset.StandardCharsets</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.util.HashMap</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.util.Map</span><span class="p">;</span> |
| <span class="kn">import static</span><span class="w"> </span><span class="nn">java.util.Arrays.asList</span><span class="p">;</span> |
| |
| <span class="n">Field</span><span class="w"> </span><span class="n">age</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Field</span><span class="p">(</span><span class="s">"age"</span><span class="p">,</span> |
| <span class="w"> </span><span class="n">FieldType</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">Int</span><span class="p">(</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">)),</span> |
| <span class="w"> </span><span class="cm">/*children*/</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span> |
| <span class="n">Field</span><span class="w"> </span><span class="n">name</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Field</span><span class="p">(</span><span class="s">"name"</span><span class="p">,</span> |
| <span class="w"> </span><span class="n">FieldType</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">Utf8</span><span class="p">()),</span> |
| <span class="w"> </span><span class="cm">/*children*/</span><span class="w"> </span><span class="kc">null</span><span class="p">);</span> |
| <span class="n">Schema</span><span class="w"> </span><span class="n">schema</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Schema</span><span class="p">(</span><span class="n">asList</span><span class="p">(</span><span class="n">age</span><span class="p">,</span><span class="w"> </span><span class="n">name</span><span class="p">));</span> |
| <span class="k">try</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">BufferAllocator</span><span class="w"> </span><span class="n">allocator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RootAllocator</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">VectorSchemaRoot</span><span class="w"> </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">VectorSchemaRoot</span><span class="p">.</span><span class="na">create</span><span class="p">(</span><span class="n">schema</span><span class="p">,</span><span class="w"> </span><span class="n">allocator</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">IntVector</span><span class="w"> </span><span class="n">ageVector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">IntVector</span><span class="p">)</span><span class="w"> </span><span class="n">root</span><span class="p">.</span><span class="na">getVector</span><span class="p">(</span><span class="s">"age"</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">VarCharVector</span><span class="w"> </span><span class="n">nameVector</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">VarCharVector</span><span class="p">)</span><span class="w"> </span><span class="n">root</span><span class="p">.</span><span class="na">getVector</span><span class="p">(</span><span class="s">"name"</span><span class="p">);</span> |
| <span class="p">){</span> |
| <span class="w"> </span><span class="n">ageVector</span><span class="p">.</span><span class="na">allocateNew</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">ageVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">ageVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">20</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">ageVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">30</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">nameVector</span><span class="p">.</span><span class="na">allocateNew</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">nameVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="s">"Dave"</span><span class="p">.</span><span class="na">getBytes</span><span class="p">(</span><span class="n">StandardCharsets</span><span class="p">.</span><span class="na">UTF_8</span><span class="p">));</span> |
| <span class="w"> </span><span class="n">nameVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="s">"Peter"</span><span class="p">.</span><span class="na">getBytes</span><span class="p">(</span><span class="n">StandardCharsets</span><span class="p">.</span><span class="na">UTF_8</span><span class="p">));</span> |
| <span class="w"> </span><span class="n">nameVector</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="s">"Mary"</span><span class="p">.</span><span class="na">getBytes</span><span class="p">(</span><span class="n">StandardCharsets</span><span class="p">.</span><span class="na">UTF_8</span><span class="p">));</span> |
| <span class="w"> </span><span class="n">root</span><span class="p">.</span><span class="na">setRowCount</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">File</span><span class="w"> </span><span class="n">file</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="s">"random_access_file.arrow"</span><span class="p">);</span> |
| <span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">(</span> |
| <span class="w"> </span><span class="n">FileOutputStream</span><span class="w"> </span><span class="n">fileOutputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileOutputStream</span><span class="p">(</span><span class="n">file</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">ArrowFileWriter</span><span class="w"> </span><span class="n">writer</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrowFileWriter</span><span class="p">(</span><span class="n">root</span><span class="p">,</span><span class="w"> </span><span class="cm">/*provider*/</span><span class="w"> </span><span class="kc">null</span><span class="p">,</span><span class="w"> </span><span class="n">fileOutputStream</span><span class="p">.</span><span class="na">getChannel</span><span class="p">());</span> |
| <span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="n">writer</span><span class="p">.</span><span class="na">start</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">writer</span><span class="p">.</span><span class="na">writeBatch</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">writer</span><span class="p">.</span><span class="na">end</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"Record batches written: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">writer</span><span class="p">.</span><span class="na">getRecordBlocks</span><span class="p">().</span><span class="na">size</span><span class="p">()</span> |
| <span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="s">". Number of rows written: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">root</span><span class="p">.</span><span class="na">getRowCount</span><span class="p">());</span> |
| <span class="w"> </span><span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span> |
| <span class="w"> </span><span class="p">}</span> |
| <span class="p">}</span> |
| </pre></div> |
| </div> |
| <div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>Record<span class="w"> </span>batches<span class="w"> </span>written:<span class="w"> </span><span class="m">1</span>.<span class="w"> </span>Number<span class="w"> </span>of<span class="w"> </span>rows<span class="w"> </span>written:<span class="w"> </span><span class="m">3</span> |
| </pre></div> |
| </div> |
| <p><strong>Read data from an arrow file</strong></p> |
| <p>Example: Read the dataset from the previous example from an Arrow IPC file (random-access).</p> |
| <div class="highlight-Java notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.memory.RootAllocator</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.ipc.ArrowFileReader</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.ipc.message.ArrowBlock</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.VectorSchemaRoot</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.io.File</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.io.FileInputStream</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.io.FileOutputStream</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">java.io.IOException</span><span class="p">;</span> |
| |
| <span class="k">try</span><span class="p">(</span> |
| <span class="w"> </span><span class="n">BufferAllocator</span><span class="w"> </span><span class="n">allocator</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">RootAllocator</span><span class="p">(</span><span class="n">Long</span><span class="p">.</span><span class="na">MAX_VALUE</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">FileInputStream</span><span class="w"> </span><span class="n">fileInputStream</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">FileInputStream</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">File</span><span class="p">(</span><span class="s">"random_access_file.arrow"</span><span class="p">));</span> |
| <span class="w"> </span><span class="n">ArrowFileReader</span><span class="w"> </span><span class="n">reader</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrowFileReader</span><span class="p">(</span><span class="n">fileInputStream</span><span class="p">.</span><span class="na">getChannel</span><span class="p">(),</span><span class="w"> </span><span class="n">allocator</span><span class="p">);</span> |
| <span class="p">){</span> |
| <span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"Record batches in file: "</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="na">getRecordBlocks</span><span class="p">().</span><span class="na">size</span><span class="p">());</span> |
| <span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">ArrowBlock</span><span class="w"> </span><span class="n">arrowBlock</span><span class="w"> </span><span class="p">:</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="na">getRecordBlocks</span><span class="p">())</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="na">loadRecordBatch</span><span class="p">(</span><span class="n">arrowBlock</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">VectorSchemaRoot</span><span class="w"> </span><span class="n">root</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">reader</span><span class="p">.</span><span class="na">getVectorSchemaRoot</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">System</span><span class="p">.</span><span class="na">out</span><span class="p">.</span><span class="na">println</span><span class="p">(</span><span class="s">"VectorSchemaRoot read: \n"</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">root</span><span class="p">.</span><span class="na">contentToTSVString</span><span class="p">());</span> |
| <span class="w"> </span><span class="p">}</span> |
| <span class="p">}</span><span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">IOException</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="n">e</span><span class="p">.</span><span class="na">printStackTrace</span><span class="p">();</span> |
| <span class="p">}</span> |
| </pre></div> |
| </div> |
| <div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>Record<span class="w"> </span>batches<span class="w"> </span><span class="k">in</span><span class="w"> </span>file:<span class="w"> </span><span class="m">1</span> |
| VectorSchemaRoot<span class="w"> </span>read: |
| age<span class="w"> </span>name |
| <span class="m">10</span><span class="w"> </span>Dave |
| <span class="m">20</span><span class="w"> </span>Peter |
| <span class="m">30</span><span class="w"> </span>Mary |
| </pre></div> |
| </div> |
| <p>More examples available at <a class="reference external" href="https://arrow.apache.org/cookbook/java">Arrow Java Cookbook</a>.</p> |
| </section> |
| </section> |
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| <li><a class="reference internal" href="#">Quick Start Guide</a><ul> |
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