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   <main id="main" class="col-md-9"><div class="page-header">
       <img src="" class="logo" alt=""><h1>ParquetFileReader class</h1>
       <small class="dont-index">Source: <a href="https://github.com/apache/arrow/blob/master/r/R/parquet.R" class="external-link"><code>R/parquet.R</code></a></small>
       <div class="d-none name"><code>ParquetFileReader.Rd</code></div>
     </div>

     <div class="ref-description section level2">
     <p>This class enables you to interact with Parquet files.</p>
     </div>


     <div class="section level2">
     <h2 id="factory">Factory<a class="anchor" aria-label="anchor" href="#factory"></a></h2>


 <p>The <code>ParquetFileReader$create()</code> factory method instantiates the object and
 takes the following arguments:</p><ul><li><p><code>file</code> A character file name, raw vector, or Arrow file connection object
 (e.g. <code>RandomAccessFile</code>).</p></li>
 <li><p><code>props</code> Optional <a href="ParquetArrowReaderProperties.html">ParquetArrowReaderProperties</a></p></li>
 <li><p><code>mmap</code> Logical: whether to memory-map the file (default <code>TRUE</code>)</p></li>
 <li><p><code>...</code> Additional arguments, currently ignored</p></li>
 </ul></div>
     <div class="section level2">
     <h2 id="methods">Methods<a class="anchor" aria-label="anchor" href="#methods"></a></h2>


 <ul><li><p><code>$ReadTable(column_indices)</code>: get an <code><a href="Table.html">arrow::Table</a></code> from the file. The optional
 <code>column_indices=</code> argument is a 0-based integer vector indicating which columns to retain.</p></li>
 <li><p><code>$ReadRowGroup(i, column_indices)</code>: get an <code><a href="Table.html">arrow::Table</a></code> by reading the <code>i</code>th row group (0-based).
 The optional <code>column_indices=</code> argument is a 0-based integer vector indicating which columns to retain.</p></li>
 <li><p><code>$ReadRowGroups(row_groups, column_indices)</code>: get an <code><a href="Table.html">arrow::Table</a></code> by reading several row
 groups (0-based integers).
 The optional <code>column_indices=</code> argument is a 0-based integer vector indicating which columns to retain.</p></li>
 <li><p><code>$GetSchema()</code>: get the <code><a href="Schema.html">arrow::Schema</a></code> of the data in the file</p></li>
 <li><p><code>$ReadColumn(i)</code>: read the <code>i</code>th column (0-based) as a <a href="ChunkedArray.html">ChunkedArray</a>.</p></li>
 </ul></div>
     <div class="section level2">
     <h2 id="active-bindings">Active bindings<a class="anchor" aria-label="anchor" href="#active-bindings"></a></h2>


 <ul><li><p><code>$num_rows</code>: number of rows.</p></li>
 <li><p><code>$num_columns</code>: number of columns.</p></li>
 <li><p><code>$num_row_groups</code>: number of row groups.</p></li>
 </ul></div>

     <div class="section level2">
     <h2 id="ref-examples">Examples<a class="anchor" aria-label="anchor" href="#ref-examples"></a></h2>
     <div class="sourceCode"><pre class="sourceCode r"><code><span class="r-in"><span><span class="va">f</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/r/base/system.file.html" class="external-link">system.file</a></span><span class="op">(</span><span class="st">"v0.7.1.parquet"</span>, package <span class="op">=</span> <span class="st">"arrow"</span><span class="op">)</span></span></span>
 <span class="r-in"><span><span class="va">pq</span> <span class="op">&lt;-</span> <span class="va">ParquetFileReader</span><span class="op">$</span><span class="fu">create</span><span class="op">(</span><span class="va">f</span><span class="op">)</span></span></span>
 <span class="r-in"><span><span class="va">pq</span><span class="op">$</span><span class="fu">GetSchema</span><span class="op">(</span><span class="op">)</span></span></span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> Schema</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> carat: double</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> cut: string</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> color: string</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> clarity: string</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> depth: double</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> table: double</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> price: int64</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> x: double</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> y: double</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> z: double</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> __index_level_0__: int64</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> </span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> See $metadata for additional Schema metadata</span>
 <span class="r-in"><span><span class="kw">if</span> <span class="op">(</span><span class="fu"><a href="codec_is_available.html">codec_is_available</a></span><span class="op">(</span><span class="st">"snappy"</span><span class="op">)</span><span class="op">)</span> <span class="op">{</span></span></span>
 <span class="r-in"><span>  <span class="co"># This file has compressed data columns</span></span></span>
 <span class="r-in"><span>  <span class="va">tab</span> <span class="op">&lt;-</span> <span class="va">pq</span><span class="op">$</span><span class="fu">ReadTable</span><span class="op">(</span><span class="op">)</span></span></span>
 <span class="r-in"><span>  <span class="va">tab</span><span class="op">$</span><span class="va">schema</span></span></span>
 <span class="r-in"><span><span class="op">}</span></span></span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> Schema</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> carat: double</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> cut: string</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> color: string</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> clarity: string</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> depth: double</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> table: double</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> price: int64</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> x: double</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> y: double</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> z: double</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> __index_level_0__: int64</span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> </span>
 <span class="r-out co"><span class="r-pr">#&gt;</span> See $metadata for additional Schema metadata</span>
 </code></pre></div>
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	<main id="main" class="col-md-9"><div class="page-header">
	<img src="" class="logo" alt=""><h1>ParquetFileReader class</h1>
	<small class="dont-index">Source: <a href="https://github.com/apache/arrow/blob/master/r/R/parquet.R" class="external-link"><code>R/parquet.R</code></a></small>
	<div class="d-none name"><code>ParquetFileReader.Rd</code></div>
	</div>

	<div class="ref-description section level2">
	<p>This class enables you to interact with Parquet files.</p>
	</div>


	<div class="section level2">
	<h2 id="factory">Factory<a class="anchor" aria-label="anchor" href="#factory"></a></h2>



	<p>The <code>ParquetFileReader$create()</code> factory method instantiates the object and
	takes the following arguments:</p><ul><li><p><code>file</code> A character file name, raw vector, or Arrow file connection object
	(e.g. <code>RandomAccessFile</code>).</p></li>
	<li><p><code>props</code> Optional <a href="ParquetArrowReaderProperties.html">ParquetArrowReaderProperties</a></p></li>
	<li><p><code>mmap</code> Logical: whether to memory-map the file (default <code>TRUE</code>)</p></li>
	<li><p><code>...</code> Additional arguments, currently ignored</p></li>
	</ul></div>
	<div class="section level2">
	<h2 id="methods">Methods<a class="anchor" aria-label="anchor" href="#methods"></a></h2>


	<ul><li><p><code>$ReadTable(column_indices)</code>: get an <code><a href="Table.html">arrow::Table</a></code> from the file. The optional
	<code>column_indices=</code> argument is a 0-based integer vector indicating which columns to retain.</p></li>
	<li><p><code>$ReadRowGroup(i, column_indices)</code>: get an <code><a href="Table.html">arrow::Table</a></code> by reading the <code>i</code>th row group (0-based).
	The optional <code>column_indices=</code> argument is a 0-based integer vector indicating which columns to retain.</p></li>
	<li><p><code>$ReadRowGroups(row_groups, column_indices)</code>: get an <code><a href="Table.html">arrow::Table</a></code> by reading several row
	groups (0-based integers).
	The optional <code>column_indices=</code> argument is a 0-based integer vector indicating which columns to retain.</p></li>
	<li><p><code>$GetSchema()</code>: get the <code><a href="Schema.html">arrow::Schema</a></code> of the data in the file</p></li>
	<li><p><code>$ReadColumn(i)</code>: read the <code>i</code>th column (0-based) as a <a href="ChunkedArray.html">ChunkedArray</a>.</p></li>
	</ul></div>
	<div class="section level2">
	<h2 id="active-bindings">Active bindings<a class="anchor" aria-label="anchor" href="#active-bindings"></a></h2>


	<ul><li><p><code>$num_rows</code>: number of rows.</p></li>
	<li><p><code>$num_columns</code>: number of columns.</p></li>
	<li><p><code>$num_row_groups</code>: number of row groups.</p></li>
	</ul></div>

	<div class="section level2">
	<h2 id="ref-examples">Examples<a class="anchor" aria-label="anchor" href="#ref-examples"></a></h2>
	<div class="sourceCode"><pre class="sourceCode r"><code><span class="r-in"><span><span class="va">f</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/system.file.html" class="external-link">system.file</a></span><span class="op">(</span><span class="st">"v0.7.1.parquet"</span>, package <span class="op">=</span> <span class="st">"arrow"</span><span class="op">)</span></span></span>
	<span class="r-in"><span><span class="va">pq</span> <span class="op"><-</span> <span class="va">ParquetFileReader</span><span class="op">$</span><span class="fu">create</span><span class="op">(</span><span class="va">f</span><span class="op">)</span></span></span>
	<span class="r-in"><span><span class="va">pq</span><span class="op">$</span><span class="fu">GetSchema</span><span class="op">(</span><span class="op">)</span></span></span>
	<span class="r-out co"><span class="r-pr">#></span> Schema</span>
	<span class="r-out co"><span class="r-pr">#></span> carat: double</span>
	<span class="r-out co"><span class="r-pr">#></span> cut: string</span>
	<span class="r-out co"><span class="r-pr">#></span> color: string</span>
	<span class="r-out co"><span class="r-pr">#></span> clarity: string</span>
	<span class="r-out co"><span class="r-pr">#></span> depth: double</span>
	<span class="r-out co"><span class="r-pr">#></span> table: double</span>
	<span class="r-out co"><span class="r-pr">#></span> price: int64</span>
	<span class="r-out co"><span class="r-pr">#></span> x: double</span>
	<span class="r-out co"><span class="r-pr">#></span> y: double</span>
	<span class="r-out co"><span class="r-pr">#></span> z: double</span>
	<span class="r-out co"><span class="r-pr">#></span> __index_level_0__: int64</span>
	<span class="r-out co"><span class="r-pr">#></span> </span>
	<span class="r-out co"><span class="r-pr">#></span> See $metadata for additional Schema metadata</span>
	<span class="r-in"><span><span class="kw">if</span> <span class="op">(</span><span class="fu"><a href="codec_is_available.html">codec_is_available</a></span><span class="op">(</span><span class="st">"snappy"</span><span class="op">)</span><span class="op">)</span> <span class="op">{</span></span></span>
	<span class="r-in"><span> <span class="co"># This file has compressed data columns</span></span></span>
	<span class="r-in"><span> <span class="va">tab</span> <span class="op"><-</span> <span class="va">pq</span><span class="op">$</span><span class="fu">ReadTable</span><span class="op">(</span><span class="op">)</span></span></span>
	<span class="r-in"><span> <span class="va">tab</span><span class="op">$</span><span class="va">schema</span></span></span>
	<span class="r-in"><span><span class="op">}</span></span></span>
	<span class="r-out co"><span class="r-pr">#></span> Schema</span>
	<span class="r-out co"><span class="r-pr">#></span> carat: double</span>
	<span class="r-out co"><span class="r-pr">#></span> cut: string</span>
	<span class="r-out co"><span class="r-pr">#></span> color: string</span>
	<span class="r-out co"><span class="r-pr">#></span> clarity: string</span>
	<span class="r-out co"><span class="r-pr">#></span> depth: double</span>
	<span class="r-out co"><span class="r-pr">#></span> table: double</span>
	<span class="r-out co"><span class="r-pr">#></span> price: int64</span>
	<span class="r-out co"><span class="r-pr">#></span> x: double</span>
	<span class="r-out co"><span class="r-pr">#></span> y: double</span>
	<span class="r-out co"><span class="r-pr">#></span> z: double</span>
	<span class="r-out co"><span class="r-pr">#></span> __index_level_0__: int64</span>
	<span class="r-out co"><span class="r-pr">#></span> </span>
	<span class="r-out co"><span class="r-pr">#></span> See $metadata for additional Schema metadata</span>
	</code></pre></div>
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