| <!DOCTYPE html> |
| <!-- Generated by pkgdown: do not edit by hand --><html lang="en"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta charset="utf-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no"><meta name="description" content='Apache Arrow defines two formats for serializing data for interprocess communication (IPC): |
| a "stream" format and a "file" format, known as Feather. |
| RecordBatchStreamReader and RecordBatchFileReader are |
| interfaces for accessing record batches from input sources in those formats, |
| respectively. |
| For guidance on how to use these classes, see the examples section.'><title>RecordBatchReader classes — RecordBatchReader • Arrow R Package</title><!-- favicons --><link rel="icon" type="image/png" sizes="16x16" href="../favicon-16x16.png"><link rel="icon" type="image/png" sizes="32x32" href="../favicon-32x32.png"><link rel="apple-touch-icon" type="image/png" sizes="180x180" href="../apple-touch-icon.png"><link rel="apple-touch-icon" type="image/png" sizes="120x120" href="../apple-touch-icon-120x120.png"><link rel="apple-touch-icon" type="image/png" sizes="76x76" href="../apple-touch-icon-76x76.png"><link rel="apple-touch-icon" type="image/png" sizes="60x60" href="../apple-touch-icon-60x60.png"><script src="../deps/jquery-3.6.0/jquery-3.6.0.min.js"></script><meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no"><link href="../deps/bootstrap-5.2.2/bootstrap.min.css" rel="stylesheet"><script src="../deps/bootstrap-5.2.2/bootstrap.bundle.min.js"></script><!-- Font Awesome icons --><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.12.1/css/all.min.css" integrity="sha256-mmgLkCYLUQbXn0B1SRqzHar6dCnv9oZFPEC1g1cwlkk=" crossorigin="anonymous"><link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.12.1/css/v4-shims.min.css" integrity="sha256-wZjR52fzng1pJHwx4aV2AO3yyTOXrcDW7jBpJtTwVxw=" crossorigin="anonymous"><!-- bootstrap-toc --><script src="https://cdn.jsdelivr.net/gh/afeld/bootstrap-toc@v1.0.1/dist/bootstrap-toc.min.js" integrity="sha256-4veVQbu7//Lk5TSmc7YV48MxtMy98e26cf5MrgZYnwo=" crossorigin="anonymous"></script><!-- headroom.js --><script src="https://cdnjs.cloudflare.com/ajax/libs/headroom/0.11.0/headroom.min.js" integrity="sha256-AsUX4SJE1+yuDu5+mAVzJbuYNPHj/WroHuZ8Ir/CkE0=" crossorigin="anonymous"></script><script src="https://cdnjs.cloudflare.com/ajax/libs/headroom/0.11.0/jQuery.headroom.min.js" integrity="sha256-ZX/yNShbjqsohH1k95liqY9Gd8uOiE1S4vZc+9KQ1K4=" crossorigin="anonymous"></script><!-- clipboard.js --><script src="https://cdnjs.cloudflare.com/ajax/libs/clipboard.js/2.0.6/clipboard.min.js" integrity="sha256-inc5kl9MA1hkeYUt+EC3BhlIgyp/2jDIyBLS6k3UxPI=" crossorigin="anonymous"></script><!-- search --><script src="https://cdnjs.cloudflare.com/ajax/libs/fuse.js/6.4.6/fuse.js" integrity="sha512-zv6Ywkjyktsohkbp9bb45V6tEMoWhzFzXis+LrMehmJZZSys19Yxf1dopHx7WzIKxr5tK2dVcYmaCk2uqdjF4A==" crossorigin="anonymous"></script><script src="https://cdnjs.cloudflare.com/ajax/libs/autocomplete.js/0.38.0/autocomplete.jquery.min.js" integrity="sha512-GU9ayf+66Xx2TmpxqJpliWbT5PiGYxpaG8rfnBEk1LL8l1KGkRShhngwdXK1UgqhAzWpZHSiYPc09/NwDQIGyg==" crossorigin="anonymous"></script><script src="https://cdnjs.cloudflare.com/ajax/libs/mark.js/8.11.1/mark.min.js" integrity="sha512-5CYOlHXGh6QpOFA/TeTylKLWfB3ftPsde7AnmhuitiTX4K5SqCLBeKro6sPS8ilsz1Q4NRx3v8Ko2IBiszzdww==" crossorigin="anonymous"></script><!-- pkgdown --><script src="../pkgdown.js"></script><script src="../extra.js"></script><meta property="og:title" content="RecordBatchReader classes — RecordBatchReader"><meta property="og:description" content='Apache Arrow defines two formats for serializing data for interprocess communication (IPC): |
| a "stream" format and a "file" format, known as Feather. |
| RecordBatchStreamReader and RecordBatchFileReader are |
| interfaces for accessing record batches from input sources in those formats, |
| respectively. |
| For guidance on how to use these classes, see the examples section.'><meta property="og:image" content="https://arrow.apache.org/img/arrow-logo_horizontal_black-txt_white-bg.png"><meta property="og:image:alt" content="Apache Arrow logo, displaying the triple chevron image adjacent to the text"><meta name="twitter:card" content="summary_large_image"><meta name="twitter:creator" content="@apachearrow"><meta name="twitter:site" content="@apachearrow"><!-- mathjax --><script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js" integrity="sha256-nvJJv9wWKEm88qvoQl9ekL2J+k/RWIsaSScxxlsrv8k=" crossorigin="anonymous"></script><script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/config/TeX-AMS-MML_HTMLorMML.js" integrity="sha256-84DKXVJXs0/F8OTMzX4UR909+jtl4G7SPypPavF+GfA=" crossorigin="anonymous"></script><!--[if lt IE 9]> |
| <script src="https://oss.maxcdn.com/html5shiv/3.7.3/html5shiv.min.js"></script> |
| <script src="https://oss.maxcdn.com/respond/1.4.2/respond.min.js"></script> |
| <![endif]--><!-- Matomo --><script> |
| var _paq = window._paq = window._paq || []; |
| /* tracker methods like "setCustomDimension" should be called before "trackPageView" */ |
| /* We explicitly disable cookie tracking to avoid privacy issues */ |
| _paq.push(['disableCookies']); |
| _paq.push(['trackPageView']); |
| _paq.push(['enableLinkTracking']); |
| (function() { |
| var u="https://analytics.apache.org/"; |
| _paq.push(['setTrackerUrl', u+'matomo.php']); |
| _paq.push(['setSiteId', '20']); |
| var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0]; |
| g.async=true; g.src=u+'matomo.js'; s.parentNode.insertBefore(g,s); |
| })(); |
| </script><!-- End Matomo Code --></head><body> |
| <a href="#main" class="visually-hidden-focusable">Skip to contents</a> |
| |
| |
| <nav class="navbar fixed-top navbar-dark navbar-expand-lg bg-black"><div class="container"> |
| |
| <a class="navbar-brand me-2" href="../index.html">Arrow R Package</a> |
| |
| <span class="version"> |
| <small class="nav-text text-muted me-auto" data-bs-toggle="tooltip" data-bs-placement="bottom" title="">11.0.0</small> |
| </span> |
| |
| |
| <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbar" aria-controls="navbar" aria-expanded="false" aria-label="Toggle navigation"> |
| <span class="navbar-toggler-icon"></span> |
| </button> |
| |
| <div id="navbar" class="collapse navbar-collapse ms-3"> |
| <ul class="navbar-nav me-auto"><li class="nav-item"> |
| <a class="nav-link" href="../articles/arrow.html">Get started</a> |
| </li> |
| <li class="active nav-item"> |
| <a class="nav-link" href="../reference/index.html">Reference</a> |
| </li> |
| <li class="nav-item dropdown"> |
| <a href="#" class="nav-link dropdown-toggle" data-bs-toggle="dropdown" role="button" aria-expanded="false" aria-haspopup="true" id="dropdown-articles">Articles</a> |
| <div class="dropdown-menu" aria-labelledby="dropdown-articles"> |
| <h6 class="dropdown-header" data-toc-skip>Using the package</h6> |
| <a class="dropdown-item" href="../articles/read_write.html">Reading and writing data files</a> |
| <a class="dropdown-item" href="../articles/data_wrangling.html">Data analysis with dplyr syntax</a> |
| <a class="dropdown-item" href="../articles/dataset.html">Working with multi-file data sets</a> |
| <a class="dropdown-item" href="../articles/python.html">Integrating Arrow, Python, and R</a> |
| <a class="dropdown-item" href="../articles/fs.html">Using cloud storage (S3, GCS)</a> |
| <a class="dropdown-item" href="../articles/flight.html">Connecting to a Flight server</a> |
| <div class="dropdown-divider"></div> |
| <h6 class="dropdown-header" data-toc-skip>Arrow concepts</h6> |
| <a class="dropdown-item" href="../articles/data_objects.html">Data objects</a> |
| <a class="dropdown-item" href="../articles/data_types.html">Data types</a> |
| <a class="dropdown-item" href="../articles/metadata.html">Metadata</a> |
| <div class="dropdown-divider"></div> |
| <h6 class="dropdown-header" data-toc-skip>Installation</h6> |
| <a class="dropdown-item" href="../articles/install.html">Installing on Linux</a> |
| <a class="dropdown-item" href="../articles/install_nightly.html">Installing development versions</a> |
| <div class="dropdown-divider"></div> |
| <a class="dropdown-item" href="../articles/index.html">More articles...</a> |
| </div> |
| </li> |
| <li class="nav-item"> |
| <a class="nav-link" href="../news/index.html">Changelog</a> |
| </li> |
| </ul><form class="form-inline my-2 my-lg-0" role="search"> |
| <input type="search" class="form-control me-sm-2" aria-label="Toggle navigation" name="search-input" data-search-index="../search.json" id="search-input" placeholder="Search for" autocomplete="off"></form> |
| |
| <ul class="navbar-nav"></ul></div> |
| |
| |
| </div> |
| </nav><div class="container template-reference-topic"> |
| <div class="row"> |
| <main id="main" class="col-md-9"><div class="page-header"> |
| <img src="" class="logo" alt=""><h1>RecordBatchReader classes</h1> |
| <small class="dont-index">Source: <a href="https://github.com/apache/arrow/blob/master/r/R/record-batch-reader.R" class="external-link"><code>R/record-batch-reader.R</code></a></small> |
| <div class="d-none name"><code>RecordBatchReader.Rd</code></div> |
| </div> |
| |
| <div class="ref-description section level2"> |
| <p>Apache Arrow defines two formats for <a href="https://arrow.apache.org/docs/format/Columnar.html#serialization-and-interprocess-communication-ipc" class="external-link">serializing data for interprocess communication (IPC)</a>: |
| a "stream" format and a "file" format, known as Feather. |
| <code>RecordBatchStreamReader</code> and <code>RecordBatchFileReader</code> are |
| interfaces for accessing record batches from input sources in those formats, |
| respectively.</p> |
| <p>For guidance on how to use these classes, see the examples section.</p> |
| </div> |
| |
| |
| <div class="section level2"> |
| <h2 id="factory">Factory<a class="anchor" aria-label="anchor" href="#factory"></a></h2> |
| |
| |
| |
| <p>The <code>RecordBatchFileReader$create()</code> and <code>RecordBatchStreamReader$create()</code> |
| factory methods instantiate the object and |
| take a single argument, named according to the class:</p><ul><li><p><code>file</code> A character file name, raw vector, or Arrow file connection object |
| (e.g. <a href="InputStream.html">RandomAccessFile</a>).</p></li> |
| <li><p><code>stream</code> A raw vector, <a href="buffer.html">Buffer</a>, or <a href="InputStream.html">InputStream</a>.</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>$read_next_batch()</code>: Returns a <code>RecordBatch</code>, iterating through the |
| Reader. If there are no further batches in the Reader, it returns <code>NULL</code>.</p></li> |
| <li><p><code>$schema</code>: Returns a <a href="Schema.html">Schema</a> (active binding)</p></li> |
| <li><p><code>$batches()</code>: Returns a list of <code>RecordBatch</code>es</p></li> |
| <li><p><code>$read_table()</code>: Collects the reader's <code>RecordBatch</code>es into a <a href="Table.html">Table</a></p></li> |
| <li><p><code>$get_batch(i)</code>: For <code>RecordBatchFileReader</code>, return a particular batch |
| by an integer index.</p></li> |
| <li><p><code>$num_record_batches()</code>: For <code>RecordBatchFileReader</code>, see how many batches |
| are in the file.</p></li> |
| </ul></div> |
| <div class="section level2"> |
| <h2 id="see-also">See also<a class="anchor" aria-label="anchor" href="#see-also"></a></h2> |
| <div class="dont-index"><p><code><a href="read_ipc_stream.html">read_ipc_stream()</a></code> and <code><a href="read_feather.html">read_feather()</a></code> provide a much simpler interface |
| for reading data from these formats and are sufficient for many use cases.</p></div> |
| </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">tf</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/tempfile.html" class="external-link">tempfile</a></span><span class="op">(</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="fu"><a href="https://rdrr.io/r/base/on.exit.html" class="external-link">on.exit</a></span><span class="op">(</span><span class="fu"><a href="https://rdrr.io/r/base/unlink.html" class="external-link">unlink</a></span><span class="op">(</span><span class="va">tf</span><span class="op">)</span><span class="op">)</span></span></span> |
| <span class="r-in"><span></span></span> |
| <span class="r-in"><span><span class="va">batch</span> <span class="op"><-</span> <span class="fu"><a href="RecordBatch.html">record_batch</a></span><span class="op">(</span><span class="va">chickwts</span><span class="op">)</span></span></span> |
| <span class="r-in"><span></span></span> |
| <span class="r-in"><span><span class="co"># This opens a connection to the file in Arrow</span></span></span> |
| <span class="r-in"><span><span class="va">file_obj</span> <span class="op"><-</span> <span class="va">FileOutputStream</span><span class="op">$</span><span class="fu">create</span><span class="op">(</span><span class="va">tf</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="co"># Pass that to a RecordBatchWriter to write data conforming to a schema</span></span></span> |
| <span class="r-in"><span><span class="va">writer</span> <span class="op"><-</span> <span class="va">RecordBatchFileWriter</span><span class="op">$</span><span class="fu">create</span><span class="op">(</span><span class="va">file_obj</span>, <span class="va">batch</span><span class="op">$</span><span class="va">schema</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="va">writer</span><span class="op">$</span><span class="fu">write</span><span class="op">(</span><span class="va">batch</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="co"># You may write additional batches to the stream, provided that they have</span></span></span> |
| <span class="r-in"><span><span class="co"># the same schema.</span></span></span> |
| <span class="r-in"><span><span class="co"># Call "close" on the writer to indicate end-of-file/stream</span></span></span> |
| <span class="r-in"><span><span class="va">writer</span><span class="op">$</span><span class="fu">close</span><span class="op">(</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="co"># Then, close the connection--closing the IPC message does not close the file</span></span></span> |
| <span class="r-in"><span><span class="va">file_obj</span><span class="op">$</span><span class="fu">close</span><span class="op">(</span><span class="op">)</span></span></span> |
| <span class="r-in"><span></span></span> |
| <span class="r-in"><span><span class="co"># Now, we have a file we can read from. Same pattern: open file connection,</span></span></span> |
| <span class="r-in"><span><span class="co"># then pass it to a RecordBatchReader</span></span></span> |
| <span class="r-in"><span><span class="va">read_file_obj</span> <span class="op"><-</span> <span class="va">ReadableFile</span><span class="op">$</span><span class="fu">create</span><span class="op">(</span><span class="va">tf</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="va">reader</span> <span class="op"><-</span> <span class="va">RecordBatchFileReader</span><span class="op">$</span><span class="fu">create</span><span class="op">(</span><span class="va">read_file_obj</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="co"># RecordBatchFileReader knows how many batches it has (StreamReader does not)</span></span></span> |
| <span class="r-in"><span><span class="va">reader</span><span class="op">$</span><span class="va">num_record_batches</span></span></span> |
| <span class="r-out co"><span class="r-pr">#></span> [1] 1</span> |
| <span class="r-in"><span><span class="co"># We could consume the Reader by calling $read_next_batch() until all are,</span></span></span> |
| <span class="r-in"><span><span class="co"># consumed, or we can call $read_table() to pull them all into a Table</span></span></span> |
| <span class="r-in"><span><span class="va">tab</span> <span class="op"><-</span> <span class="va">reader</span><span class="op">$</span><span class="fu">read_table</span><span class="op">(</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="co"># Call as.data.frame to turn that Table into an R data.frame</span></span></span> |
| <span class="r-in"><span><span class="va">df</span> <span class="op"><-</span> <span class="fu"><a href="https://rdrr.io/r/base/as.data.frame.html" class="external-link">as.data.frame</a></span><span class="op">(</span><span class="va">tab</span><span class="op">)</span></span></span> |
| <span class="r-in"><span><span class="co"># This should be the same data we sent</span></span></span> |
| <span class="r-in"><span><span class="fu"><a href="https://rdrr.io/r/base/all.equal.html" class="external-link">all.equal</a></span><span class="op">(</span><span class="va">df</span>, <span class="va">chickwts</span>, check.attributes <span class="op">=</span> <span class="cn">FALSE</span><span class="op">)</span></span></span> |
| <span class="r-out co"><span class="r-pr">#></span> [1] TRUE</span> |
| <span class="r-in"><span><span class="co"># Unlike the Writers, we don't have to close RecordBatchReaders,</span></span></span> |
| <span class="r-in"><span><span class="co"># but we do still need to close the file connection</span></span></span> |
| <span class="r-in"><span><span class="va">read_file_obj</span><span class="op">$</span><span class="fu">close</span><span class="op">(</span><span class="op">)</span></span></span> |
| </code></pre></div> |
| </div> |
| </main><aside class="col-md-3"><nav id="toc"><h2>On this page</h2> |
| </nav></aside></div> |
| |
| |
| <footer><div class="pkgdown-footer-left"> |
| <p></p><p><a href="https://arrow.apache.org/docs/r/versions.html">Older versions of these docs</a></p> |
| </div> |
| |
| <div class="pkgdown-footer-right"> |
| <p></p><p>Site built with <a href="https://pkgdown.r-lib.org/" class="external-link">pkgdown</a> 2.0.7.</p> |
| </div> |
| |
| </footer></div> |
| |
| |
| |
| |
| |
| </body></html> |
| |