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   <section id="reading-and-writing-parquet-files">
 <h1>Reading and writing Parquet files<a class="headerlink" href="#reading-and-writing-parquet-files" title="Permalink to this heading">#</a></h1>
 <div class="admonition seealso">
 <p class="admonition-title">See also</p>
 <p><a class="reference internal" href="api/formats.html#cpp-api-parquet"><span class="std std-ref">Parquet reader and writer API reference</span></a>.</p>
 </div>
 <p>The <a class="reference external" href="https://parquet.apache.org/docs/">Parquet format</a>
 is a space-efficient columnar storage format for complex data.  The Parquet
 C++ implementation is part of the Apache Arrow project and benefits
 from tight integration with the Arrow C++ classes and facilities.</p>
 <section id="reading-parquet-files">
 <h2>Reading Parquet files<a class="headerlink" href="#reading-parquet-files" title="Permalink to this heading">#</a></h2>
 <p>The <a class="reference internal" href="api/formats.html#_CPPv4N7parquet5arrow10FileReaderE" title="parquet::arrow::FileReader"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::FileReader</span></code></a> class reads data into Arrow Tables and Record
 Batches.</p>
 <p>The <a class="reference internal" href="api/formats.html#_CPPv4N7parquet12StreamReaderE" title="parquet::StreamReader"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">StreamReader</span></code></a> class allows for data to be read using a C++ input
 stream approach to read fields column by column and row by row.  This approach
 is offered for ease of use and type-safety.  It is of course also useful when
 data must be streamed as files are read and written incrementally.</p>
 <p>Please note that the performance of the <a class="reference internal" href="api/formats.html#_CPPv4N7parquet12StreamReaderE" title="parquet::StreamReader"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">StreamReader</span></code></a> will not
 be as good due to the type checking and the fact that column values
 are processed one at a time.</p>
 <section id="filereader">
 <h3>FileReader<a class="headerlink" href="#filereader" title="Permalink to this heading">#</a></h3>
 <p>To read Parquet data into Arrow structures, use <a class="reference internal" href="api/formats.html#_CPPv4N7parquet5arrow10FileReaderE" title="parquet::arrow::FileReader"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::FileReader</span></code></a>.
 To construct, it requires a <a class="reference internal" href="api/io.html#_CPPv4N5arrow2io16RandomAccessFileE" title="arrow::io::RandomAccessFile"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">::arrow::io::RandomAccessFile</span></code></a> instance
 representing the input file. To read the whole file at once,
 use <a class="reference internal" href="api/formats.html#_CPPv4N7parquet5arrow10FileReader9ReadTableEPNSt10shared_ptrIN5arrow5TableEEE" title="parquet::arrow::FileReader::ReadTable"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">arrow::FileReader::ReadTable()</span></code></a>:</p>
 <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="c1">// #include &quot;arrow/io/api.h&quot;</span>
 <span class="c1">// #include &quot;arrow/parquet/arrow/reader.h&quot;</span>

 <span class="n">arrow</span><span class="o">::</span><span class="n">MemoryPool</span><span class="o">*</span><span class="w"> </span><span class="n">pool</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arrow</span><span class="o">::</span><span class="n">default_memory_pool</span><span class="p">();</span>
 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">arrow</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">RandomAccessFile</span><span class="o">&gt;</span><span class="w"> </span><span class="n">input</span><span class="p">;</span>
 <span class="n">ARROW_ASSIGN_OR_RAISE</span><span class="p">(</span><span class="n">input</span><span class="p">,</span><span class="w"> </span><span class="n">arrow</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">ReadableFile</span><span class="o">::</span><span class="n">Open</span><span class="p">(</span><span class="n">path_to_file</span><span class="p">));</span>

 <span class="c1">// Open Parquet file reader</span>
 <span class="hll"><span class="n">std</span><span class="o">::</span><span class="n">unique_ptr</span><span class="o">&lt;</span><span class="n">parquet</span><span class="o">::</span><span class="n">arrow</span><span class="o">::</span><span class="n">FileReader</span><span class="o">&gt;</span><span class="w"> </span><span class="n">arrow_reader</span><span class="p">;</span>
 </span><span class="hll"><span class="n">ARROW_RETURN_NOT_OK</span><span class="p">(</span><span class="n">parquet</span><span class="o">::</span><span class="n">arrow</span><span class="o">::</span><span class="n">OpenFile</span><span class="p">(</span><span class="n">input</span><span class="p">,</span><span class="w"> </span><span class="n">pool</span><span class="p">,</span><span class="w"> </span><span class="o">&amp;</span><span class="n">arrow_reader</span><span class="p">));</span>
 </span>
 <span class="c1">// Read entire file as a single Arrow table</span>
 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">arrow</span><span class="o">::</span><span class="n">Table</span><span class="o">&gt;</span><span class="w"> </span><span class="n">table</span><span class="p">;</span>
 <span class="hll"><span class="n">ARROW_RETURN_NOT_OK</span><span class="p">(</span><span class="n">arrow_reader</span><span class="o">-&gt;</span><span class="n">ReadTable</span><span class="p">(</span><span class="o">&amp;</span><span class="n">table</span><span class="p">));</span>
 </span></pre></div>
 </div>
 <p>Finer-grained options are available through the
 <a class="reference internal" href="api/formats.html#_CPPv4N7parquet5arrow17FileReaderBuilderE" title="parquet::arrow::FileReaderBuilder"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::FileReaderBuilder</span></code></a> helper class, which accepts the <a class="reference internal" href="api/formats.html#_CPPv4N7parquet16ReaderPropertiesE" title="parquet::ReaderProperties"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">ReaderProperties</span></code></a>
 and <a class="reference internal" href="api/formats.html#_CPPv4N7parquet21ArrowReaderPropertiesE" title="parquet::ArrowReaderProperties"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">ArrowReaderProperties</span></code></a> classes.</p>
 <p>For reading as a stream of batches, use the <a class="reference internal" href="api/formats.html#_CPPv4N7parquet5arrow10FileReader20GetRecordBatchReaderEPNSt10unique_ptrIN5arrow17RecordBatchReaderEEE" title="parquet::arrow::FileReader::GetRecordBatchReader"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">arrow::FileReader::GetRecordBatchReader()</span></code></a>
 method to retrieve a <code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::RecordBatchReader</span></code>. It will use the batch
 size set in <a class="reference internal" href="api/formats.html#_CPPv4N7parquet21ArrowReaderPropertiesE" title="parquet::ArrowReaderProperties"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">ArrowReaderProperties</span></code></a>.</p>
 <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="c1">// #include &quot;arrow/io/api.h&quot;</span>
 <span class="c1">// #include &quot;arrow/parquet/arrow/reader.h&quot;</span>

 <span class="n">arrow</span><span class="o">::</span><span class="n">MemoryPool</span><span class="o">*</span><span class="w"> </span><span class="n">pool</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">arrow</span><span class="o">::</span><span class="n">default_memory_pool</span><span class="p">();</span>

 <span class="c1">// Configure general Parquet reader settings</span>
 <span class="k">auto</span><span class="w"> </span><span class="n">reader_properties</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">ReaderProperties</span><span class="p">(</span><span class="n">pool</span><span class="p">);</span>
 <span class="n">reader_properties</span><span class="p">.</span><span class="n">set_buffer_size</span><span class="p">(</span><span class="mi">4096</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">4</span><span class="p">);</span>
 <span class="n">reader_properties</span><span class="p">.</span><span class="n">enable_buffered_stream</span><span class="p">();</span>

 <span class="c1">// Configure Arrow-specific Parquet reader settings</span>
 <span class="k">auto</span><span class="w"> </span><span class="n">arrow_reader_props</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">ArrowReaderProperties</span><span class="p">();</span>
 <span class="n">arrow_reader_props</span><span class="p">.</span><span class="n">set_batch_size</span><span class="p">(</span><span class="mi">128</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">1024</span><span class="p">);</span><span class="w">  </span><span class="c1">// default 64 * 1024</span>

 <span class="n">parquet</span><span class="o">::</span><span class="n">arrow</span><span class="o">::</span><span class="n">FileReaderBuilder</span><span class="w"> </span><span class="n">reader_builder</span><span class="p">;</span>
 <span class="n">ARROW_RETURN_NOT_OK</span><span class="p">(</span>
 <span class="w">    </span><span class="n">reader_builder</span><span class="p">.</span><span class="n">OpenFile</span><span class="p">(</span><span class="n">path_to_file</span><span class="p">,</span><span class="w"> </span><span class="cm">/*memory_map=*/</span><span class="nb">false</span><span class="p">,</span><span class="w"> </span><span class="n">reader_properties</span><span class="p">));</span>
 <span class="n">reader_builder</span><span class="p">.</span><span class="n">memory_pool</span><span class="p">(</span><span class="n">pool</span><span class="p">);</span>
 <span class="n">reader_builder</span><span class="p">.</span><span class="n">properties</span><span class="p">(</span><span class="n">arrow_reader_props</span><span class="p">);</span>

 <span class="n">std</span><span class="o">::</span><span class="n">unique_ptr</span><span class="o">&lt;</span><span class="n">parquet</span><span class="o">::</span><span class="n">arrow</span><span class="o">::</span><span class="n">FileReader</span><span class="o">&gt;</span><span class="w"> </span><span class="n">arrow_reader</span><span class="p">;</span>
 <span class="n">ARROW_ASSIGN_OR_RAISE</span><span class="p">(</span><span class="n">arrow_reader</span><span class="p">,</span><span class="w"> </span><span class="n">reader_builder</span><span class="p">.</span><span class="n">Build</span><span class="p">());</span>

 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;::</span><span class="n">arrow</span><span class="o">::</span><span class="n">RecordBatchReader</span><span class="o">&gt;</span><span class="w"> </span><span class="n">rb_reader</span><span class="p">;</span>
 <span class="hll"><span class="n">ARROW_RETURN_NOT_OK</span><span class="p">(</span><span class="n">arrow_reader</span><span class="o">-&gt;</span><span class="n">GetRecordBatchReader</span><span class="p">(</span><span class="o">&amp;</span><span class="n">rb_reader</span><span class="p">));</span>
 </span>
 <span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">arrow</span><span class="o">::</span><span class="n">Result</span><span class="o">&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">arrow</span><span class="o">::</span><span class="n">RecordBatch</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">maybe_batch</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="o">*</span><span class="n">rb_reader</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
 <span class="w">  </span><span class="c1">// Operate on each batch...</span>
 <span class="p">}</span>
 </pre></div>
 </div>
 <div class="admonition seealso">
 <p class="admonition-title">See also</p>
 <p>For reading multi-file datasets or pushing down filters to prune row groups,
 see <a class="reference internal" href="dataset.html#cpp-dataset"><span class="std std-ref">Tabular Datasets</span></a>.</p>
 </div>
 <section id="performance-and-memory-efficiency">
 <h4>Performance and Memory Efficiency<a class="headerlink" href="#performance-and-memory-efficiency" title="Permalink to this heading">#</a></h4>
 <p>For remote filesystems, use read coalescing (pre-buffering) to reduce number of API calls:</p>
 <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="k">auto</span><span class="w"> </span><span class="n">arrow_reader_props</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">ArrowReaderProperties</span><span class="p">();</span>
 <span class="n">reader_properties</span><span class="p">.</span><span class="n">set_prebuffer</span><span class="p">(</span><span class="nb">true</span><span class="p">);</span>
 </pre></div>
 </div>
 <p>The defaults are generally tuned towards good performance, but parallel column
 decoding is off by default. Enable it in the constructor of <a class="reference internal" href="api/formats.html#_CPPv4N7parquet21ArrowReaderPropertiesE" title="parquet::ArrowReaderProperties"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">ArrowReaderProperties</span></code></a>:</p>
 <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="k">auto</span><span class="w"> </span><span class="n">arrow_reader_props</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">ArrowReaderProperties</span><span class="p">(</span><span class="cm">/*use_threads=*/</span><span class="nb">true</span><span class="p">);</span>
 </pre></div>
 </div>
 <p>If memory efficiency is more important than performance, then:</p>
 <ol class="arabic simple">
 <li><p>Do <em>not</em> turn on read coalescing (pre-buffering) in <a class="reference internal" href="api/formats.html#_CPPv4N7parquet21ArrowReaderPropertiesE" title="parquet::ArrowReaderProperties"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">parquet::ArrowReaderProperties</span></code></a>.</p></li>
 <li><p>Read data in batches using <a class="reference internal" href="api/formats.html#_CPPv4N7parquet5arrow10FileReader20GetRecordBatchReaderEPNSt10unique_ptrIN5arrow17RecordBatchReaderEEE" title="parquet::arrow::FileReader::GetRecordBatchReader"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">arrow::FileReader::GetRecordBatchReader()</span></code></a>.</p></li>
 <li><p>Turn on <code class="docutils literal notranslate"><span class="pre">enable_buffered_stream</span></code> in <a class="reference internal" href="api/formats.html#_CPPv4N7parquet16ReaderPropertiesE" title="parquet::ReaderProperties"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">parquet::ReaderProperties</span></code></a>.</p></li>
 </ol>
 <p>In addition, if you know certain columns contain many repeated values, you can
 read them as <a class="reference internal" href="../format/Glossary.html#term-dictionary-encoding"><span class="xref std std-term">dictionary encoded</span></a> columns. This is
 enabled with the <code class="docutils literal notranslate"><span class="pre">set_read_dictionary</span></code> setting on <a class="reference internal" href="api/formats.html#_CPPv4N7parquet21ArrowReaderPropertiesE" title="parquet::ArrowReaderProperties"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">ArrowReaderProperties</span></code></a>.
 If the files were written with Arrow C++ and the <code class="docutils literal notranslate"><span class="pre">store_schema</span></code> was activated,
 then the original Arrow schema will be automatically read and will override this
 setting.</p>
 </section>
 </section>
 <section id="streamreader">
 <h3>StreamReader<a class="headerlink" href="#streamreader" title="Permalink to this heading">#</a></h3>
 <p>The <a class="reference internal" href="api/formats.html#_CPPv4N7parquet12StreamReaderE" title="parquet::StreamReader"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">StreamReader</span></code></a> allows for Parquet files to be read using
 standard C++ input operators which ensures type-safety.</p>
 <p>Please note that types must match the schema exactly i.e. if the
 schema field is an unsigned 16-bit integer then you must supply a
 <code class="docutils literal notranslate"><span class="pre">uint16_t</span></code> type.</p>
 <p>Exceptions are used to signal errors.  A <a class="reference internal" href="api/support.html#_CPPv4N7parquet16ParquetExceptionE" title="parquet::ParquetException"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">ParquetException</span></code></a> is
 thrown in the following circumstances:</p>
 <ul class="simple">
 <li><p>Attempt to read field by supplying the incorrect type.</p></li>
 <li><p>Attempt to read beyond end of row.</p></li>
 <li><p>Attempt to read beyond end of file.</p></li>
 </ul>
 <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;arrow/io/file.h&quot;</span>
 <span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;parquet/stream_reader.h&quot;</span>

 <span class="p">{</span>
 <span class="w">   </span><span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">arrow</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">ReadableFile</span><span class="o">&gt;</span><span class="w"> </span><span class="n">infile</span><span class="p">;</span>

 <span class="w">   </span><span class="n">PARQUET_ASSIGN_OR_THROW</span><span class="p">(</span>
 <span class="w">      </span><span class="n">infile</span><span class="p">,</span>
 <span class="w">      </span><span class="n">arrow</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">ReadableFile</span><span class="o">::</span><span class="n">Open</span><span class="p">(</span><span class="s">&quot;test.parquet&quot;</span><span class="p">));</span>

 <span class="w">   </span><span class="n">parquet</span><span class="o">::</span><span class="n">StreamReader</span><span class="w"> </span><span class="n">stream</span><span class="p">{</span><span class="n">parquet</span><span class="o">::</span><span class="n">ParquetFileReader</span><span class="o">::</span><span class="n">Open</span><span class="p">(</span><span class="n">infile</span><span class="p">)};</span>

 <span class="w">   </span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="w"> </span><span class="n">article</span><span class="p">;</span>
 <span class="w">   </span><span class="kt">float</span><span class="w"> </span><span class="n">price</span><span class="p">;</span>
 <span class="w">   </span><span class="kt">uint32_t</span><span class="w"> </span><span class="n">quantity</span><span class="p">;</span>

 <span class="w">   </span><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="w"> </span><span class="o">!</span><span class="n">stream</span><span class="p">.</span><span class="n">eof</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">stream</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">article</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">price</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">quantity</span><span class="w"> </span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">EndRow</span><span class="p">;</span>
 <span class="w">      </span><span class="c1">// ...</span>
 <span class="w">   </span><span class="p">}</span>
 <span class="p">}</span>
 </pre></div>
 </div>
 </section>
 </section>
 <section id="writing-parquet-files">
 <h2>Writing Parquet files<a class="headerlink" href="#writing-parquet-files" title="Permalink to this heading">#</a></h2>
 <section id="writetable">
 <h3>WriteTable<a class="headerlink" href="#writetable" title="Permalink to this heading">#</a></h3>
 <p>The <a class="reference internal" href="api/formats.html#_CPPv4N7parquet5arrow10WriteTableERKN5arrow5TableEP10MemoryPoolNSt10shared_ptrIN5arrow2io12OutputStreamEEE7int64_tNSt10shared_ptrI16WriterPropertiesEENSt10shared_ptrI21ArrowWriterPropertiesEE" title="parquet::arrow::WriteTable"><code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">arrow::WriteTable()</span></code></a> function writes an entire
 <a class="reference internal" href="api/table.html#_CPPv4N5arrow5TableE" title="arrow::Table"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">::arrow::Table</span></code></a> to an output file.</p>
 <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="c1">// #include &quot;parquet/arrow/writer.h&quot;</span>
 <span class="c1">// #include &quot;arrow/util/type_fwd.h&quot;</span>
 <span class="k">using</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">ArrowWriterProperties</span><span class="p">;</span>
 <span class="k">using</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">WriterProperties</span><span class="p">;</span>

 <span class="n">ARROW_ASSIGN_OR_RAISE</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">arrow</span><span class="o">::</span><span class="n">Table</span><span class="o">&gt;</span><span class="w"> </span><span class="n">table</span><span class="p">,</span><span class="w"> </span><span class="n">GetTable</span><span class="p">());</span>

 <span class="c1">// Choose compression</span>
 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">WriterProperties</span><span class="o">&gt;</span><span class="w"> </span><span class="n">props</span><span class="w"> </span><span class="o">=</span>
 <span class="w">    </span><span class="n">WriterProperties</span><span class="o">::</span><span class="n">Builder</span><span class="p">().</span><span class="n">compression</span><span class="p">(</span><span class="n">arrow</span><span class="o">::</span><span class="n">Compression</span><span class="o">::</span><span class="n">SNAPPY</span><span class="p">)</span><span class="o">-&gt;</span><span class="n">build</span><span class="p">();</span>

 <span class="c1">// Opt to store Arrow schema for easier reads back into Arrow</span>
 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">ArrowWriterProperties</span><span class="o">&gt;</span><span class="w"> </span><span class="n">arrow_props</span><span class="w"> </span><span class="o">=</span>
 <span class="w">    </span><span class="n">ArrowWriterProperties</span><span class="o">::</span><span class="n">Builder</span><span class="p">().</span><span class="n">store_schema</span><span class="p">()</span><span class="o">-&gt;</span><span class="n">build</span><span class="p">();</span>

 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">arrow</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">FileOutputStream</span><span class="o">&gt;</span><span class="w"> </span><span class="n">outfile</span><span class="p">;</span>
 <span class="n">ARROW_ASSIGN_OR_RAISE</span><span class="p">(</span><span class="n">outfile</span><span class="p">,</span><span class="w"> </span><span class="n">arrow</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">FileOutputStream</span><span class="o">::</span><span class="n">Open</span><span class="p">(</span><span class="n">path_to_file</span><span class="p">));</span>

 <span class="hll"><span class="n">ARROW_RETURN_NOT_OK</span><span class="p">(</span><span class="n">parquet</span><span class="o">::</span><span class="n">arrow</span><span class="o">::</span><span class="n">WriteTable</span><span class="p">(</span><span class="o">*</span><span class="n">table</span><span class="p">.</span><span class="n">get</span><span class="p">(),</span>
 </span><span class="hll"><span class="w">                                               </span><span class="n">arrow</span><span class="o">::</span><span class="n">default_memory_pool</span><span class="p">(),</span><span class="w"> </span><span class="n">outfile</span><span class="p">,</span>
 </span><span class="hll"><span class="w">                                               </span><span class="cm">/*chunk_size=*/</span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="n">props</span><span class="p">,</span><span class="w"> </span><span class="n">arrow_props</span><span class="p">));</span>
 </span></pre></div>
 </div>
 <div class="admonition note">
 <p class="admonition-title">Note</p>
 <p>Column compression is off by default in C++. See <a class="reference internal" href="#parquet-writer-properties"><span class="std std-ref">below</span></a>
 for how to choose a compression codec in the writer properties.</p>
 </div>
 <p>To write out data batch-by-batch, use <a class="reference internal" href="api/formats.html#_CPPv4N7parquet5arrow10FileWriterE" title="parquet::arrow::FileWriter"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">arrow::FileWriter</span></code></a>.</p>
 <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="c1">// #include &quot;parquet/arrow/writer.h&quot;</span>
 <span class="c1">// #include &quot;arrow/util/type_fwd.h&quot;</span>
 <span class="k">using</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">ArrowWriterProperties</span><span class="p">;</span>
 <span class="k">using</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">WriterProperties</span><span class="p">;</span>

 <span class="c1">// Data is in RBR</span>
 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">arrow</span><span class="o">::</span><span class="n">RecordBatchReader</span><span class="o">&gt;</span><span class="w"> </span><span class="n">batch_stream</span><span class="p">;</span>
 <span class="n">ARROW_ASSIGN_OR_RAISE</span><span class="p">(</span><span class="n">batch_stream</span><span class="p">,</span><span class="w"> </span><span class="n">GetRBR</span><span class="p">());</span>

 <span class="c1">// Choose compression</span>
 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">WriterProperties</span><span class="o">&gt;</span><span class="w"> </span><span class="n">props</span><span class="w"> </span><span class="o">=</span>
 <span class="w">    </span><span class="n">WriterProperties</span><span class="o">::</span><span class="n">Builder</span><span class="p">().</span><span class="n">compression</span><span class="p">(</span><span class="n">arrow</span><span class="o">::</span><span class="n">Compression</span><span class="o">::</span><span class="n">SNAPPY</span><span class="p">)</span><span class="o">-&gt;</span><span class="n">build</span><span class="p">();</span>

 <span class="c1">// Opt to store Arrow schema for easier reads back into Arrow</span>
 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">ArrowWriterProperties</span><span class="o">&gt;</span><span class="w"> </span><span class="n">arrow_props</span><span class="w"> </span><span class="o">=</span>
 <span class="w">    </span><span class="n">ArrowWriterProperties</span><span class="o">::</span><span class="n">Builder</span><span class="p">().</span><span class="n">store_schema</span><span class="p">()</span><span class="o">-&gt;</span><span class="n">build</span><span class="p">();</span>

 <span class="c1">// Create a writer</span>
 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">arrow</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">FileOutputStream</span><span class="o">&gt;</span><span class="w"> </span><span class="n">outfile</span><span class="p">;</span>
 <span class="n">ARROW_ASSIGN_OR_RAISE</span><span class="p">(</span><span class="n">outfile</span><span class="p">,</span><span class="w"> </span><span class="n">arrow</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">FileOutputStream</span><span class="o">::</span><span class="n">Open</span><span class="p">(</span><span class="n">path_to_file</span><span class="p">));</span>
 <span class="n">std</span><span class="o">::</span><span class="n">unique_ptr</span><span class="o">&lt;</span><span class="n">parquet</span><span class="o">::</span><span class="n">arrow</span><span class="o">::</span><span class="n">FileWriter</span><span class="o">&gt;</span><span class="w"> </span><span class="n">writer</span><span class="p">;</span>
 <span class="n">ARROW_ASSIGN_OR_RAISE</span><span class="p">(</span>
 <span class="hll"><span class="w">    </span><span class="n">writer</span><span class="p">,</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">arrow</span><span class="o">::</span><span class="n">FileWriter</span><span class="o">::</span><span class="n">Open</span><span class="p">(</span><span class="o">*</span><span class="n">batch_stream</span><span class="o">-&gt;</span><span class="n">schema</span><span class="p">().</span><span class="n">get</span><span class="p">(),</span>
 </span><span class="hll"><span class="w">                                             </span><span class="n">arrow</span><span class="o">::</span><span class="n">default_memory_pool</span><span class="p">(),</span><span class="w"> </span><span class="n">outfile</span><span class="p">,</span>
 </span><span class="hll"><span class="w">                                             </span><span class="n">props</span><span class="p">,</span><span class="w"> </span><span class="n">arrow_props</span><span class="p">));</span>
 </span>
 <span class="c1">// Write each batch as a row_group</span>
 <span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="n">arrow</span><span class="o">::</span><span class="n">Result</span><span class="o">&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">arrow</span><span class="o">::</span><span class="n">RecordBatch</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">maybe_batch</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="o">*</span><span class="n">batch_stream</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
 <span class="w">  </span><span class="n">ARROW_ASSIGN_OR_RAISE</span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="n">batch</span><span class="p">,</span><span class="w"> </span><span class="n">maybe_batch</span><span class="p">);</span>
 <span class="w">  </span><span class="n">ARROW_ASSIGN_OR_RAISE</span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="n">table</span><span class="p">,</span>
 <span class="w">                        </span><span class="n">arrow</span><span class="o">::</span><span class="n">Table</span><span class="o">::</span><span class="n">FromRecordBatches</span><span class="p">(</span><span class="n">batch</span><span class="o">-&gt;</span><span class="n">schema</span><span class="p">(),</span><span class="w"> </span><span class="p">{</span><span class="n">batch</span><span class="p">}));</span>
 <span class="hll"><span class="w">  </span><span class="n">ARROW_RETURN_NOT_OK</span><span class="p">(</span><span class="n">writer</span><span class="o">-&gt;</span><span class="n">WriteTable</span><span class="p">(</span><span class="o">*</span><span class="n">table</span><span class="p">.</span><span class="n">get</span><span class="p">(),</span><span class="w"> </span><span class="n">batch</span><span class="o">-&gt;</span><span class="n">num_rows</span><span class="p">()));</span>
 </span><span class="p">}</span>

 <span class="c1">// Write file footer and close</span>
 <span class="hll"><span class="n">ARROW_RETURN_NOT_OK</span><span class="p">(</span><span class="n">writer</span><span class="o">-&gt;</span><span class="n">Close</span><span class="p">());</span>
 </span></pre></div>
 </div>
 </section>
 <section id="streamwriter">
 <h3>StreamWriter<a class="headerlink" href="#streamwriter" title="Permalink to this heading">#</a></h3>
 <p>The <a class="reference internal" href="api/formats.html#_CPPv4N7parquet12StreamWriterE" title="parquet::StreamWriter"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">StreamWriter</span></code></a> allows for Parquet files to be written using
 standard C++ output operators, similar to reading with the <a class="reference internal" href="api/formats.html#_CPPv4N7parquet12StreamReaderE" title="parquet::StreamReader"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">StreamReader</span></code></a>
 class. This type-safe approach also ensures that rows are written without
 omitting fields and allows for new row groups to be created automatically
 (after certain volume of data) or explicitly by using the <code class="xref cpp cpp-type docutils literal notranslate"><span class="pre">EndRowGroup</span></code>
 stream modifier.</p>
 <p>Exceptions are used to signal errors.  A <a class="reference internal" href="api/support.html#_CPPv4N7parquet16ParquetExceptionE" title="parquet::ParquetException"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">ParquetException</span></code></a> is
 thrown in the following circumstances:</p>
 <ul class="simple">
 <li><p>Attempt to write a field using an incorrect type.</p></li>
 <li><p>Attempt to write too many fields in a row.</p></li>
 <li><p>Attempt to skip a required field.</p></li>
 </ul>
 <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;arrow/io/file.h&quot;</span>
 <span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;parquet/stream_writer.h&quot;</span>

 <span class="p">{</span>
 <span class="w">   </span><span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">arrow</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">FileOutputStream</span><span class="o">&gt;</span><span class="w"> </span><span class="n">outfile</span><span class="p">;</span>

 <span class="w">   </span><span class="n">PARQUET_ASSIGN_OR_THROW</span><span class="p">(</span>
 <span class="w">      </span><span class="n">outfile</span><span class="p">,</span>
 <span class="w">      </span><span class="n">arrow</span><span class="o">::</span><span class="n">io</span><span class="o">::</span><span class="n">FileOutputStream</span><span class="o">::</span><span class="n">Open</span><span class="p">(</span><span class="s">&quot;test.parquet&quot;</span><span class="p">));</span>

 <span class="w">   </span><span class="n">parquet</span><span class="o">::</span><span class="n">WriterProperties</span><span class="o">::</span><span class="n">Builder</span><span class="w"> </span><span class="n">builder</span><span class="p">;</span>
 <span class="w">   </span><span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">parquet</span><span class="o">::</span><span class="n">schema</span><span class="o">::</span><span class="n">GroupNode</span><span class="o">&gt;</span><span class="w"> </span><span class="n">schema</span><span class="p">;</span>

 <span class="w">   </span><span class="c1">// Set up builder with required compression type etc.</span>
 <span class="w">   </span><span class="c1">// Define schema.</span>
 <span class="w">   </span><span class="c1">// ...</span>

 <span class="w">   </span><span class="n">parquet</span><span class="o">::</span><span class="n">StreamWriter</span><span class="w"> </span><span class="n">os</span><span class="p">{</span>
 <span class="w">      </span><span class="n">parquet</span><span class="o">::</span><span class="n">ParquetFileWriter</span><span class="o">::</span><span class="n">Open</span><span class="p">(</span><span class="n">outfile</span><span class="p">,</span><span class="w"> </span><span class="n">schema</span><span class="p">,</span><span class="w"> </span><span class="n">builder</span><span class="p">.</span><span class="n">build</span><span class="p">())};</span>

 <span class="w">   </span><span class="c1">// Loop over some data structure which provides the required</span>
 <span class="w">   </span><span class="c1">// fields to be written and write each row.</span>
 <span class="w">   </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="k">auto</span><span class="o">&amp;</span><span class="w"> </span><span class="n">a</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="n">getArticles</span><span class="p">())</span>
 <span class="w">   </span><span class="p">{</span>
 <span class="w">      </span><span class="n">os</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">name</span><span class="p">()</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">price</span><span class="p">()</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">a</span><span class="p">.</span><span class="n">quantity</span><span class="p">()</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">EndRow</span><span class="p">;</span>
 <span class="w">   </span><span class="p">}</span>
 <span class="p">}</span>
 </pre></div>
 </div>
 </section>
 <section id="writer-properties">
 <span id="parquet-writer-properties"></span><h3>Writer properties<a class="headerlink" href="#writer-properties" title="Permalink to this heading">#</a></h3>
 <p>To configure how Parquet files are written, use the <a class="reference internal" href="api/formats.html#_CPPv4N7parquet16WriterProperties7BuilderE" title="parquet::WriterProperties::Builder"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">WriterProperties::Builder</span></code></a>:</p>
 <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;parquet/arrow/writer.h&quot;</span>
 <span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;arrow/util/type_fwd.h&quot;</span>

 <span class="k">using</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">WriterProperties</span><span class="p">;</span>
 <span class="k">using</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">ParquetVersion</span><span class="p">;</span>
 <span class="k">using</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">ParquetDataPageVersion</span><span class="p">;</span>
 <span class="k">using</span><span class="w"> </span><span class="n">arrow</span><span class="o">::</span><span class="n">Compression</span><span class="p">;</span>

 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">WriterProperties</span><span class="o">&gt;</span><span class="w"> </span><span class="n">props</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">WriterProperties</span><span class="o">::</span><span class="n">Builder</span><span class="p">()</span>
 <span class="w">   </span><span class="p">.</span><span class="n">max_row_group_length</span><span class="p">(</span><span class="mi">64</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="mi">1024</span><span class="p">)</span>
 <span class="w">   </span><span class="p">.</span><span class="n">created_by</span><span class="p">(</span><span class="s">&quot;My Application&quot;</span><span class="p">)</span>
 <span class="w">   </span><span class="p">.</span><span class="n">version</span><span class="p">(</span><span class="n">ParquetVersion</span><span class="o">::</span><span class="n">PARQUET_2_6</span><span class="p">)</span>
 <span class="w">   </span><span class="p">.</span><span class="n">data_page_version</span><span class="p">(</span><span class="n">ParquetDataPageVersion</span><span class="o">::</span><span class="n">V2</span><span class="p">)</span>
 <span class="w">   </span><span class="p">.</span><span class="n">compression</span><span class="p">(</span><span class="n">Compression</span><span class="o">::</span><span class="n">SNAPPY</span><span class="p">)</span>
 <span class="w">   </span><span class="p">.</span><span class="n">build</span><span class="p">();</span>
 </pre></div>
 </div>
 <p>The <code class="docutils literal notranslate"><span class="pre">max_row_group_length</span></code> sets an upper bound on the number of rows per row
 group that takes precedent over the <code class="docutils literal notranslate"><span class="pre">chunk_size</span></code> passed in the write methods.</p>
 <p>You can set the version of Parquet to write with <code class="docutils literal notranslate"><span class="pre">version</span></code>, which determines
 which logical types are available. In addition, you can set the data page version
 with <code class="docutils literal notranslate"><span class="pre">data_page_version</span></code>. It’s V1 by default; setting to V2 will allow more
 optimal compression (skipping compressing pages where there isn’t a space
 benefit), but not all readers support this data page version.</p>
 <p>Compression is off by default, but to get the most out of Parquet, you should
 also choose a compression codec. You can choose one for the whole file or
 choose one for individual columns. If you choose a mix, the file-level option
 will apply to columns that don’t have a specific compression codec. See
 <code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">::arrow::Compression</span></code> for options.</p>
 <p>Column data encodings can likewise be applied at the file-level or at the
 column level. By default, the writer will attempt to dictionary encode all
 supported columns, unless the dictionary grows too large. This behavior can
 be changed at file-level or at the column level with <code class="docutils literal notranslate"><span class="pre">disable_dictionary()</span></code>.
 When not using dictionary encoding, it will fallback to the encoding set for
 the column or the overall file; by default <code class="docutils literal notranslate"><span class="pre">Encoding::PLAIN</span></code>, but this can
 be changed with <code class="docutils literal notranslate"><span class="pre">encoding()</span></code>.</p>
 <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;parquet/arrow/writer.h&quot;</span>
 <span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;arrow/util/type_fwd.h&quot;</span>

 <span class="k">using</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">WriterProperties</span><span class="p">;</span>
 <span class="k">using</span><span class="w"> </span><span class="n">arrow</span><span class="o">::</span><span class="n">Compression</span><span class="p">;</span>
 <span class="k">using</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">Encoding</span><span class="p">;</span>

 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">WriterProperties</span><span class="o">&gt;</span><span class="w"> </span><span class="n">props</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">WriterProperties</span><span class="o">::</span><span class="n">Builder</span><span class="p">()</span>
 <span class="w">  </span><span class="p">.</span><span class="n">compression</span><span class="p">(</span><span class="n">Compression</span><span class="o">::</span><span class="n">SNAPPY</span><span class="p">)</span><span class="w">        </span><span class="c1">// Fallback</span>
 <span class="w">  </span><span class="o">-&gt;</span><span class="n">compression</span><span class="p">(</span><span class="s">&quot;colA&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Compression</span><span class="o">::</span><span class="n">ZSTD</span><span class="p">)</span><span class="w"> </span><span class="c1">// Only applies to column &quot;colA&quot;</span>
 <span class="w">  </span><span class="o">-&gt;</span><span class="n">encoding</span><span class="p">(</span><span class="n">Encoding</span><span class="o">::</span><span class="n">BIT_PACKED</span><span class="p">)</span><span class="w">         </span><span class="c1">// Fallback</span>
 <span class="w">  </span><span class="o">-&gt;</span><span class="n">encoding</span><span class="p">(</span><span class="s">&quot;colB&quot;</span><span class="p">,</span><span class="w"> </span><span class="n">Encoding</span><span class="o">::</span><span class="n">RLE</span><span class="p">)</span><span class="w">        </span><span class="c1">// Only applies to column &quot;colB&quot;</span>
 <span class="w">  </span><span class="o">-&gt;</span><span class="n">disable_dictionary</span><span class="p">(</span><span class="s">&quot;colB&quot;</span><span class="p">)</span><span class="w">             </span><span class="c1">// Never dictionary-encode column &quot;colB&quot;</span>
 <span class="w">  </span><span class="o">-&gt;</span><span class="n">build</span><span class="p">();</span>
 </pre></div>
 </div>
 <p>Statistics are enabled by default for all columns. You can disable statistics for
 all columns or specific columns using <code class="docutils literal notranslate"><span class="pre">disable_statistics</span></code> on the builder.
 There is a <code class="docutils literal notranslate"><span class="pre">max_statistics_size</span></code> which limits the maximum number of bytes that
 may be used for min and max values, useful for types like strings or binary blobs.
 If a column has enabled page index using <code class="docutils literal notranslate"><span class="pre">enable_write_page_index</span></code>, then it does
 not write statistics to the page header because it is duplicated in the ColumnIndex.</p>
 <p>There are also Arrow-specific settings that can be configured with
 <a class="reference internal" href="api/formats.html#_CPPv4N7parquet21ArrowWriterPropertiesE" title="parquet::ArrowWriterProperties"><code class="xref cpp cpp-class docutils literal notranslate"><span class="pre">parquet::ArrowWriterProperties</span></code></a>:</p>
 <div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span><span class="cp">#include</span><span class="w"> </span><span class="cpf">&quot;parquet/arrow/writer.h&quot;</span>

 <span class="k">using</span><span class="w"> </span><span class="n">parquet</span><span class="o">::</span><span class="n">ArrowWriterProperties</span><span class="p">;</span>

 <span class="n">std</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o">&lt;</span><span class="n">ArrowWriterProperties</span><span class="o">&gt;</span><span class="w"> </span><span class="n">arrow_props</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ArrowWriterProperties</span><span class="o">::</span><span class="n">Builder</span><span class="p">()</span>
 <span class="w">   </span><span class="p">.</span><span class="n">enable_deprecated_int96_timestamps</span><span class="p">()</span><span class="w"> </span><span class="c1">// default False</span>
 <span class="w">   </span><span class="o">-&gt;</span><span class="n">store_schema</span><span class="p">()</span><span class="w"> </span><span class="c1">// default False</span>
 <span class="w">   </span><span class="o">-&gt;</span><span class="n">build</span><span class="p">();</span>
 </pre></div>
 </div>
 <p>These options mostly dictate how Arrow types are converted to Parquet types.
 Turning on <code class="docutils literal notranslate"><span class="pre">store_schema</span></code> will cause the writer to store the serialized Arrow
 schema within the file metadata. Since there is no bijection between Parquet
 schemas and Arrow schemas, storing the Arrow schema allows the Arrow reader
 to more faithfully recreate the original data. This mapping from Parquet types
 back to original Arrow types includes:</p>
 <ul class="simple">
 <li><p>Reading timestamps with original timezone information (Parquet does not
 support time zones);</p></li>
 <li><p>Reading Arrow types from their storage types (such as Duration from int64
 columns);</p></li>
 <li><p>Reading string and binary columns back into large variants with 64-bit offsets;</p></li>
 <li><p>Reading back columns as dictionary encoded (whether an Arrow column and
 the serialized Parquet version are dictionary encoded are independent).</p></li>
 </ul>
 </section>
 </section>
 <section id="supported-parquet-features">
 <h2>Supported Parquet features<a class="headerlink" href="#supported-parquet-features" title="Permalink to this heading">#</a></h2>
 <p>The Parquet format has many features, and Parquet C++ supports a subset of them.</p>
 <section id="page-types">
 <h3>Page types<a class="headerlink" href="#page-types" title="Permalink to this heading">#</a></h3>
 <table class="table">
 <thead>
 <tr class="row-odd"><th class="head"><p>Page type</p></th>
 <th class="head"><p>Notes</p></th>
 </tr>
 </thead>
 <tbody>
 <tr class="row-even"><td><p>DATA_PAGE</p></td>
 <td></td>
 </tr>
 <tr class="row-odd"><td><p>DATA_PAGE_V2</p></td>
 <td></td>
 </tr>
 <tr class="row-even"><td><p>DICTIONARY_PAGE</p></td>
 <td></td>
 </tr>
 </tbody>
 </table>
 <p><em>Unsupported page type:</em> INDEX_PAGE. When reading a Parquet file, pages of
 this type are ignored.</p>
 </section>
 <section id="compression">
 <h3>Compression<a class="headerlink" href="#compression" title="Permalink to this heading">#</a></h3>
 <table class="table">
 <thead>
 <tr class="row-odd"><th class="head"><p>Compression codec</p></th>
 <th class="head"><p>Notes</p></th>
 </tr>
 </thead>
 <tbody>
 <tr class="row-even"><td><p>SNAPPY</p></td>
 <td></td>
 </tr>
 <tr class="row-odd"><td><p>GZIP</p></td>
 <td></td>
 </tr>
 <tr class="row-even"><td><p>BROTLI</p></td>
 <td></td>
 </tr>
 <tr class="row-odd"><td><p>LZ4</p></td>
 <td><p>(1)</p></td>
 </tr>
 <tr class="row-even"><td><p>ZSTD</p></td>
 <td></td>
 </tr>
 </tbody>
 </table>
 <ul class="simple">
 <li><p>(1) On the read side, Parquet C++ is able to decompress both the regular
 LZ4 block format and the ad-hoc Hadoop LZ4 format used by the
 <a class="reference external" href="https://github.com/apache/parquet-mr">reference Parquet implementation</a>.
 On the write side, Parquet C++ always generates the ad-hoc Hadoop LZ4 format.</p></li>
 </ul>
 <p><em>Unsupported compression codec:</em> LZO.</p>
 </section>
 <section id="encodings">
 <h3>Encodings<a class="headerlink" href="#encodings" title="Permalink to this heading">#</a></h3>
 <table class="table">
 <thead>
 <tr class="row-odd"><th class="head"><p>Encoding</p></th>
 <th class="head"><p>Reading</p></th>
 <th class="head"><p>Writing</p></th>
 <th class="head"><p>Notes</p></th>
 </tr>
 </thead>
 <tbody>
 <tr class="row-even"><td><p>PLAIN</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td></td>
 </tr>
 <tr class="row-odd"><td><p>PLAIN_DICTIONARY</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td></td>
 </tr>
 <tr class="row-even"><td><p>BIT_PACKED</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td><p>(1)</p></td>
 </tr>
 <tr class="row-odd"><td><p>RLE</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td><p>(1)</p></td>
 </tr>
 <tr class="row-even"><td><p>RLE_DICTIONARY</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td><p>(2)</p></td>
 </tr>
 <tr class="row-odd"><td><p>BYTE_STREAM_SPLIT</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td></td>
 </tr>
 <tr class="row-even"><td><p>DELTA_BINARY_PACKED</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td></td>
 </tr>
 <tr class="row-odd"><td><p>DELTA_BYTE_ARRAY</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td></td>
 </tr>
 <tr class="row-even"><td><p>DELTA_LENGTH_BYTE_ARRAY</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td></td>
 </tr>
 </tbody>
 </table>
 <ul class="simple">
 <li><p>(1) Only supported for encoding definition and repetition levels,
 and boolean values.</p></li>
 <li><p>(2) On the write path, RLE_DICTIONARY is only enabled if Parquet format version
 2.4 or greater is selected in <code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">WriterProperties::version()</span></code>.</p></li>
 </ul>
 </section>
 <section id="types">
 <h3>Types<a class="headerlink" href="#types" title="Permalink to this heading">#</a></h3>
 <section id="physical-types">
 <h4>Physical types<a class="headerlink" href="#physical-types" title="Permalink to this heading">#</a></h4>
 <table class="table">
 <thead>
 <tr class="row-odd"><th class="head"><p>Physical type</p></th>
 <th class="head"><p>Mapped Arrow type</p></th>
 <th class="head"><p>Notes</p></th>
 </tr>
 </thead>
 <tbody>
 <tr class="row-even"><td><p>BOOLEAN</p></td>
 <td><p>Boolean</p></td>
 <td></td>
 </tr>
 <tr class="row-odd"><td><p>INT32</p></td>
 <td><p>Int32 / other</p></td>
 <td><p>(1)</p></td>
 </tr>
 <tr class="row-even"><td><p>INT64</p></td>
 <td><p>Int64 / other</p></td>
 <td><p>(1)</p></td>
 </tr>
 <tr class="row-odd"><td><p>INT96</p></td>
 <td><p>Timestamp (nanoseconds)</p></td>
 <td><p>(2)</p></td>
 </tr>
 <tr class="row-even"><td><p>FLOAT</p></td>
 <td><p>Float32</p></td>
 <td></td>
 </tr>
 <tr class="row-odd"><td><p>DOUBLE</p></td>
 <td><p>Float64</p></td>
 <td></td>
 </tr>
 <tr class="row-even"><td><p>BYTE_ARRAY</p></td>
 <td><p>Binary / other</p></td>
 <td><p>(1) (3)</p></td>
 </tr>
 <tr class="row-odd"><td><p>FIXED_LENGTH_BYTE_ARRAY</p></td>
 <td><p>FixedSizeBinary / other</p></td>
 <td><p>(1)</p></td>
 </tr>
 </tbody>
 </table>
 <ul class="simple">
 <li><p>(1) Can be mapped to other Arrow types, depending on the logical type
 (see below).</p></li>
 <li><p>(2) On the write side, <code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">ArrowWriterProperties::support_deprecated_int96_timestamps()</span></code>
 must be enabled.</p></li>
 <li><p>(3) On the write side, an Arrow LargeBinary can also mapped to BYTE_ARRAY.</p></li>
 </ul>
 </section>
 <section id="logical-types">
 <h4>Logical types<a class="headerlink" href="#logical-types" title="Permalink to this heading">#</a></h4>
 <p>Specific logical types can override the default Arrow type mapping for a given
 physical type.</p>
 <table class="table">
 <thead>
 <tr class="row-odd"><th class="head"><p>Logical type</p></th>
 <th class="head"><p>Physical type</p></th>
 <th class="head"><p>Mapped Arrow type</p></th>
 <th class="head"><p>Notes</p></th>
 </tr>
 </thead>
 <tbody>
 <tr class="row-even"><td><p>NULL</p></td>
 <td><p>Any</p></td>
 <td><p>Null</p></td>
 <td><p>(1)</p></td>
 </tr>
 <tr class="row-odd"><td><p>INT</p></td>
 <td><p>INT32</p></td>
 <td><p>Int8 / UInt8 / Int16 /
 UInt16 / Int32 / UInt32</p></td>
 <td></td>
 </tr>
 <tr class="row-even"><td><p>INT</p></td>
 <td><p>INT64</p></td>
 <td><p>Int64 / UInt64</p></td>
 <td></td>
 </tr>
 <tr class="row-odd"><td><p>DECIMAL</p></td>
 <td><p>INT32 / INT64 / BYTE_ARRAY
 / FIXED_LENGTH_BYTE_ARRAY</p></td>
 <td><p>Decimal128 / Decimal256</p></td>
 <td><p>(2)</p></td>
 </tr>
 <tr class="row-even"><td><p>DATE</p></td>
 <td><p>INT32</p></td>
 <td><p>Date32</p></td>
 <td><p>(3)</p></td>
 </tr>
 <tr class="row-odd"><td><p>TIME</p></td>
 <td><p>INT32</p></td>
 <td><p>Time32 (milliseconds)</p></td>
 <td></td>
 </tr>
 <tr class="row-even"><td><p>TIME</p></td>
 <td><p>INT64</p></td>
 <td><p>Time64 (micro- or
 nanoseconds)</p></td>
 <td></td>
 </tr>
 <tr class="row-odd"><td><p>TIMESTAMP</p></td>
 <td><p>INT64</p></td>
 <td><p>Timestamp (milli-, micro-
 or nanoseconds)</p></td>
 <td></td>
 </tr>
 <tr class="row-even"><td><p>STRING</p></td>
 <td><p>BYTE_ARRAY</p></td>
 <td><p>Utf8</p></td>
 <td><p>(4)</p></td>
 </tr>
 <tr class="row-odd"><td><p>LIST</p></td>
 <td><p>Any</p></td>
 <td><p>List</p></td>
 <td><p>(5)</p></td>
 </tr>
 <tr class="row-even"><td><p>MAP</p></td>
 <td><p>Any</p></td>
 <td><p>Map</p></td>
 <td><p>(6)</p></td>
 </tr>
 <tr class="row-odd"><td><p>FLOAT16</p></td>
 <td><p>FIXED_LENGTH_BYTE_ARRAY</p></td>
 <td><p>HalfFloat</p></td>
 <td></td>
 </tr>
 </tbody>
 </table>
 <ul class="simple">
 <li><p>(1) On the write side, the Parquet physical type INT32 is generated.</p></li>
 <li><p>(2) On the write side, a FIXED_LENGTH_BYTE_ARRAY is always emitted.</p></li>
 <li><p>(3) On the write side, an Arrow Date64 is also mapped to a Parquet DATE INT32.</p></li>
 <li><p>(4) On the write side, an Arrow LargeUtf8 is also mapped to a Parquet STRING.</p></li>
 <li><p>(5) On the write side, an Arrow LargeList or FixedSizedList is also mapped to
 a Parquet LIST.</p></li>
 <li><p>(6) On the read side, a key with multiple values does not get deduplicated,
 in contradiction with the
 <a class="reference external" href="https://github.com/apache/parquet-format/blob/master/LogicalTypes.md#maps">Parquet specification</a>.</p></li>
 </ul>
 <p><em>Unsupported logical types:</em> JSON, BSON, UUID.  If such a type is encountered
 when reading a Parquet file, the default physical type mapping is used (for
 example, a Parquet JSON column may be read as Arrow Binary or FixedSizeBinary).</p>
 </section>
 <section id="converted-types">
 <h4>Converted types<a class="headerlink" href="#converted-types" title="Permalink to this heading">#</a></h4>
 <p>While converted types are deprecated in the Parquet format (they are superceded
 by logical types), they are recognized and emitted by the Parquet C++
 implementation so as to maximize compatibility with other Parquet
 implementations.</p>
 </section>
 <section id="special-cases">
 <h4>Special cases<a class="headerlink" href="#special-cases" title="Permalink to this heading">#</a></h4>
 <p>An Arrow Extension type is written out as its storage type.  It can still
 be recreated at read time using Parquet metadata (see “Roundtripping Arrow
 types” below).</p>
 <p>An Arrow Dictionary type is written out as its value type.  It can still
 be recreated at read time using Parquet metadata (see “Roundtripping Arrow
 types” below).</p>
 </section>
 <section id="roundtripping-arrow-types">
 <h4>Roundtripping Arrow types<a class="headerlink" href="#roundtripping-arrow-types" title="Permalink to this heading">#</a></h4>
 <p>While there is no bijection between Arrow types and Parquet types, it is
 possible to serialize the Arrow schema as part of the Parquet file metadata.
 This is enabled using <code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">ArrowWriterProperties::store_schema()</span></code>.</p>
 <p>On the read path, the serialized schema will be automatically recognized
 and will recreate the original Arrow data, converting the Parquet data as
 required (for example, a LargeList will be recreated from the Parquet LIST
 type).</p>
 <p>As an example, when serializing an Arrow LargeList to Parquet:</p>
 <ul class="simple">
 <li><p>The data is written out as a Parquet LIST</p></li>
 <li><p>When read back, the Parquet LIST data is decoded as an Arrow LargeList if
 <code class="xref cpp cpp-func docutils literal notranslate"><span class="pre">ArrowWriterProperties::store_schema()</span></code> was enabled when writing the file;
 otherwise, it is decoded as an Arrow List.</p></li>
 </ul>
 <section id="serialization-details">
 <h5>Serialization details<a class="headerlink" href="#serialization-details" title="Permalink to this heading">#</a></h5>
 <p>The Arrow schema is serialized as a <a class="reference internal" href="../format/Columnar.html#format-ipc"><span class="std std-ref">Arrow IPC</span></a> schema message,
 then base64-encoded and stored under the <code class="docutils literal notranslate"><span class="pre">ARROW:schema</span></code> metadata key in
 the Parquet file metadata.</p>
 </section>
 </section>
 <section id="limitations">
 <h4>Limitations<a class="headerlink" href="#limitations" title="Permalink to this heading">#</a></h4>
 <p>Writing or reading back FixedSizedList data with null entries is not supported.</p>
 </section>
 </section>
 <section id="encryption">
 <h3>Encryption<a class="headerlink" href="#encryption" title="Permalink to this heading">#</a></h3>
 <p>Parquet C++ implements all features specified in the
 <a class="reference external" href="https://github.com/apache/parquet-format/blob/master/Encryption.md">encryption specification</a>,
 except for encryption of column index and bloom filter modules.</p>
 <p>More specifically, Parquet C++ supports:</p>
 <ul class="simple">
 <li><p>AES_GCM_V1 and AES_GCM_CTR_V1 encryption algorithms.</p></li>
 <li><p>AAD suffix for Footer, ColumnMetaData, Data Page, Dictionary Page,
 Data PageHeader, Dictionary PageHeader module types. Other module types
 (ColumnIndex, OffsetIndex, BloomFilter Header, BloomFilter Bitset) are not
 supported.</p></li>
 <li><p>EncryptionWithFooterKey and EncryptionWithColumnKey modes.</p></li>
 <li><p>Encrypted Footer and Plaintext Footer modes.</p></li>
 </ul>
 </section>
 <section id="miscellaneous">
 <h3>Miscellaneous<a class="headerlink" href="#miscellaneous" title="Permalink to this heading">#</a></h3>
 <table class="table">
 <thead>
 <tr class="row-odd"><th class="head"><p>Feature</p></th>
 <th class="head"><p>Reading</p></th>
 <th class="head"><p>Writing</p></th>
 <th class="head"><p>Notes</p></th>
 </tr>
 </thead>
 <tbody>
 <tr class="row-even"><td><p>Column Index</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td><p>(1)</p></td>
 </tr>
 <tr class="row-odd"><td><p>Offset Index</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td><p>(1)</p></td>
 </tr>
 <tr class="row-even"><td><p>Bloom Filter</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td><p>(2)</p></td>
 </tr>
 <tr class="row-odd"><td><p>CRC checksums</p></td>
 <td><p>✓</p></td>
 <td><p>✓</p></td>
 <td></td>
 </tr>
 </tbody>
 </table>
 <ul class="simple">
 <li><p>(1) Access to the Column and Offset Index structures is provided, but
 data read APIs do not currently make any use of them.</p></li>
 <li><p>(2) APIs are provided for creating, serializing and deserializing Bloom
 Filters, but they are not integrated into data read APIs.</p></li>
 </ul>
 </section>
 </section>
 </section>


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