| |
| <!DOCTYPE html> |
| |
| |
| <html lang="en" data-content_root="../" > |
| |
| <head> |
| <meta charset="utf-8" /> |
| <meta name="viewport" content="width=device-width, initial-scale=1.0" /><meta name="viewport" content="width=device-width, initial-scale=1" /> |
| |
| <title>Scalar UDFs — Apache DataFusion Java documentation</title> |
| |
| |
| |
| <script data-cfasync="false"> |
| document.documentElement.dataset.mode = localStorage.getItem("mode") || ""; |
| document.documentElement.dataset.theme = localStorage.getItem("theme") || ""; |
| </script> |
| <!-- |
| this give us a css class that will be invisible only if js is disabled |
| --> |
| <noscript> |
| <style> |
| .pst-js-only { display: none !important; } |
| |
| </style> |
| </noscript> |
| |
| <!-- Loaded before other Sphinx assets --> |
| <link href="../_static/styles/theme.css?digest=8878045cc6db502f8baf" rel="stylesheet" /> |
| <link href="../_static/styles/pydata-sphinx-theme.css?digest=8878045cc6db502f8baf" rel="stylesheet" /> |
| |
| <link rel="stylesheet" type="text/css" href="../_static/pygments.css?v=8f2a1f02" /> |
| |
| <!-- So that users can add custom icons --> |
| <script src="../_static/scripts/fontawesome.js?digest=8878045cc6db502f8baf"></script> |
| <!-- Pre-loaded scripts that we'll load fully later --> |
| <link rel="preload" as="script" href="../_static/scripts/bootstrap.js?digest=8878045cc6db502f8baf" /> |
| <link rel="preload" as="script" href="../_static/scripts/pydata-sphinx-theme.js?digest=8878045cc6db502f8baf" /> |
| |
| <script src="../_static/documentation_options.js?v=5929fcd5"></script> |
| <script src="../_static/doctools.js?v=9a2dae69"></script> |
| <script src="../_static/sphinx_highlight.js?v=dc90522c"></script> |
| <script>DOCUMENTATION_OPTIONS.pagename = 'user-guide/scalar-udf';</script> |
| <link rel="index" title="Index" href="../genindex.html" /> |
| <link rel="search" title="Search" href="../search.html" /> |
| <link rel="next" title="Java table providers" href="table-provider.html" /> |
| <link rel="prev" title="Logical plans via datafusion-proto" href="proto-plans.html" /> |
| <meta name="viewport" content="width=device-width, initial-scale=1"/> |
| <meta name="docsearch:language" content="en"/> |
| <meta name="docsearch:version" content="" /> |
| </head> |
| |
| |
| <body data-bs-spy="scroll" data-bs-target=".bd-toc-nav" data-offset="180" data-bs-root-margin="0px 0px -60%" data-default-mode=""> |
| |
| |
| |
| <div id="pst-skip-link" class="skip-link d-print-none"><a href="#main-content">Skip to main content</a></div> |
| |
| <div id="pst-scroll-pixel-helper"></div> |
| |
| <button type="button" class="btn rounded-pill" id="pst-back-to-top"> |
| <i class="fa-solid fa-arrow-up"></i>Back to top</button> |
| |
| |
| <dialog id="pst-search-dialog"> |
| |
| <form class="bd-search d-flex align-items-center" |
| action="../search.html" |
| method="get"> |
| <i class="fa-solid fa-magnifying-glass"></i> |
| <input type="search" |
| class="form-control" |
| name="q" |
| placeholder="Search the docs ..." |
| aria-label="Search the docs ..." |
| autocomplete="off" |
| autocorrect="off" |
| autocapitalize="off" |
| spellcheck="false"/> |
| <span class="search-button__kbd-shortcut"><kbd class="kbd-shortcut__modifier">Ctrl</kbd>+<kbd>K</kbd></span> |
| </form> |
| </dialog> |
| |
| <div class="pst-async-banner-revealer d-none"> |
| <aside id="bd-header-version-warning" class="d-none d-print-none" aria-label="Version warning"></aside> |
| </div> |
| |
| |
| <header class="bd-header navbar navbar-expand-lg bd-navbar d-print-none"> |
| <div class="bd-header__inner bd-page-width"> |
| <button class="pst-navbar-icon sidebar-toggle primary-toggle" aria-label="Site navigation"> |
| <span class="fa-solid fa-bars"></span> |
| </button> |
| |
| |
| <div class="col-lg-3 navbar-header-items__start"> |
| |
| <div class="navbar-item"> |
| |
| |
| |
| |
| |
| <a class="navbar-brand logo" href="../index.html"> |
| |
| |
| |
| |
| |
| |
| <p class="title logo__title">Apache DataFusion Java documentation</p> |
| |
| </a></div> |
| |
| </div> |
| |
| <div class="col-lg-9 navbar-header-items"> |
| |
| <div class="me-auto navbar-header-items__center"> |
| |
| <div class="navbar-item"> |
| <nav> |
| <ul class="bd-navbar-elements navbar-nav"> |
| |
| <li class="nav-item "> |
| <a class="nav-link nav-external" href="https://github.com/apache/datafusion-java"> |
| GitHub Repository |
| </a> |
| </li> |
| |
| |
| <li class="nav-item "> |
| <a class="nav-link nav-external" href="https://github.com/apache/datafusion-java/issues"> |
| Issue Tracker |
| </a> |
| </li> |
| |
| |
| <li class="nav-item "> |
| <a class="nav-link nav-external" href="https://datafusion.apache.org/"> |
| Apache DataFusion |
| </a> |
| </li> |
| |
| |
| <li class="nav-item "> |
| <a class="nav-link nav-external" href="https://github.com/apache/datafusion/blob/main/CODE_OF_CONDUCT.md"> |
| Code of Conduct |
| </a> |
| </li> |
| |
| |
| <li class="nav-item current active"> |
| <a class="nav-link nav-internal" href="index.html"> |
| User Guide |
| </a> |
| </li> |
| |
| <li class="nav-item dropdown"> |
| <button class="btn dropdown-toggle nav-item" type="button" |
| data-bs-toggle="dropdown" aria-expanded="false" |
| aria-controls="pst-nav-more-links"> |
| More |
| </button> |
| <ul id="pst-nav-more-links" class="dropdown-menu"> |
| |
| <li class=" "> |
| <a class="nav-link dropdown-item nav-internal" href="../contributor-guide/index.html"> |
| Contributor Guide |
| </a> |
| </li> |
| |
| </ul> |
| </li> |
| |
| </ul> |
| </nav></div> |
| |
| </div> |
| |
| |
| <div class="navbar-header-items__end"> |
| |
| <div class="navbar-item navbar-persistent--container"> |
| |
| |
| <button class="btn search-button-field search-button__button pst-js-only" title="Search" aria-label="Search" data-bs-placement="bottom" data-bs-toggle="tooltip"> |
| <i class="fa-solid fa-magnifying-glass"></i> |
| <span class="search-button__default-text">Search</span> |
| <span class="search-button__kbd-shortcut"><kbd class="kbd-shortcut__modifier">Ctrl</kbd>+<kbd class="kbd-shortcut__modifier">K</kbd></span> |
| </button> |
| </div> |
| |
| |
| <div class="navbar-item"> |
| |
| <button class="btn btn-sm nav-link pst-navbar-icon theme-switch-button pst-js-only" aria-label="Color mode" data-bs-title="Color mode" data-bs-placement="bottom" data-bs-toggle="tooltip"> |
| <i class="theme-switch fa-solid fa-sun fa-lg" data-mode="light" title="Light"></i> |
| <i class="theme-switch fa-solid fa-moon fa-lg" data-mode="dark" title="Dark"></i> |
| <i class="theme-switch fa-solid fa-circle-half-stroke fa-lg" data-mode="auto" title="System Settings"></i> |
| </button></div> |
| |
| </div> |
| |
| </div> |
| |
| |
| <div class="navbar-persistent--mobile"> |
| |
| <button class="btn search-button-field search-button__button pst-js-only" title="Search" aria-label="Search" data-bs-placement="bottom" data-bs-toggle="tooltip"> |
| <i class="fa-solid fa-magnifying-glass"></i> |
| <span class="search-button__default-text">Search</span> |
| <span class="search-button__kbd-shortcut"><kbd class="kbd-shortcut__modifier">Ctrl</kbd>+<kbd class="kbd-shortcut__modifier">K</kbd></span> |
| </button> |
| </div> |
| |
| |
| |
| <button class="pst-navbar-icon sidebar-toggle secondary-toggle" aria-label="On this page"> |
| <span class="fa-solid fa-outdent"></span> |
| </button> |
| |
| </div> |
| |
| </header> |
| |
| |
| <div class="bd-container"> |
| <div class="bd-container__inner bd-page-width"> |
| |
| |
| |
| <dialog id="pst-primary-sidebar-modal"></dialog> |
| <div id="pst-primary-sidebar" class="bd-sidebar-primary bd-sidebar"> |
| |
| |
| |
| <div class="sidebar-header-items sidebar-primary__section"> |
| |
| |
| <div class="sidebar-header-items__center"> |
| |
| |
| |
| <div class="navbar-item"> |
| <nav> |
| <ul class="bd-navbar-elements navbar-nav"> |
| |
| <li class="nav-item "> |
| <a class="nav-link nav-external" href="https://github.com/apache/datafusion-java"> |
| GitHub Repository |
| </a> |
| </li> |
| |
| |
| <li class="nav-item "> |
| <a class="nav-link nav-external" href="https://github.com/apache/datafusion-java/issues"> |
| Issue Tracker |
| </a> |
| </li> |
| |
| |
| <li class="nav-item "> |
| <a class="nav-link nav-external" href="https://datafusion.apache.org/"> |
| Apache DataFusion |
| </a> |
| </li> |
| |
| |
| <li class="nav-item "> |
| <a class="nav-link nav-external" href="https://github.com/apache/datafusion/blob/main/CODE_OF_CONDUCT.md"> |
| Code of Conduct |
| </a> |
| </li> |
| |
| |
| <li class="nav-item current active"> |
| <a class="nav-link nav-internal" href="index.html"> |
| User Guide |
| </a> |
| </li> |
| |
| |
| <li class="nav-item "> |
| <a class="nav-link nav-internal" href="../contributor-guide/index.html"> |
| Contributor Guide |
| </a> |
| </li> |
| |
| </ul> |
| </nav></div> |
| |
| |
| </div> |
| |
| |
| |
| <div class="sidebar-header-items__end"> |
| |
| <div class="navbar-item"> |
| |
| <button class="btn btn-sm nav-link pst-navbar-icon theme-switch-button pst-js-only" aria-label="Color mode" data-bs-title="Color mode" data-bs-placement="bottom" data-bs-toggle="tooltip"> |
| <i class="theme-switch fa-solid fa-sun fa-lg" data-mode="light" title="Light"></i> |
| <i class="theme-switch fa-solid fa-moon fa-lg" data-mode="dark" title="Dark"></i> |
| <i class="theme-switch fa-solid fa-circle-half-stroke fa-lg" data-mode="auto" title="System Settings"></i> |
| </button></div> |
| |
| </div> |
| |
| </div> |
| |
| <div class="sidebar-primary-items__start sidebar-primary__section"> |
| <div class="sidebar-primary-item"> |
| <nav class="bd-docs-nav bd-links" |
| aria-label="Section Navigation"> |
| <p class="bd-links__title" role="heading" aria-level="1">Section Navigation</p> |
| <div class="bd-toc-item navbar-nav"><ul class="current nav bd-sidenav"> |
| <li class="toctree-l1"><a class="reference internal" href="installation.html">Installation</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="quickstart.html">Quickstart</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="sessioncontext.html">SessionContext</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="dataframe.html">DataFrame and SQL</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="parquet.html">Parquet</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="proto-plans.html">Logical plans via datafusion-proto</a></li> |
| <li class="toctree-l1 current active"><a class="current reference internal" href="#">Scalar UDFs</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="table-provider.html">Java table providers</a></li> |
| <li class="toctree-l1"><a class="reference internal" href="api-reference.html">API Reference</a></li> |
| </ul> |
| </div> |
| </nav></div> |
| </div> |
| |
| |
| <div class="sidebar-primary-items__end sidebar-primary__section"> |
| <div class="sidebar-primary-item"> |
| <div id="ethical-ad-placement" |
| class="flat" |
| data-ea-publisher="readthedocs" |
| data-ea-type="readthedocs-sidebar" |
| data-ea-manual="true"> |
| </div></div> |
| </div> |
| |
| |
| </div> |
| |
| <main id="main-content" class="bd-main" role="main"> |
| |
| |
| <div class="bd-content"> |
| <div class="bd-article-container"> |
| |
| <div class="bd-header-article d-print-none"> |
| <div class="header-article-items header-article__inner"> |
| |
| <div class="header-article-items__start"> |
| |
| <div class="header-article-item"> |
| |
| <nav aria-label="Breadcrumb" class="d-print-none"> |
| <ul class="bd-breadcrumbs"> |
| |
| <li class="breadcrumb-item breadcrumb-home"> |
| <a href="../index.html" class="nav-link" aria-label="Home"> |
| <i class="fa-solid fa-home"></i> |
| </a> |
| </li> |
| |
| <li class="breadcrumb-item"><a href="index.html" class="nav-link">User Guide</a></li> |
| |
| <li class="breadcrumb-item active" aria-current="page"><span class="ellipsis">Scalar UDFs</span></li> |
| </ul> |
| </nav> |
| </div> |
| |
| </div> |
| |
| |
| </div> |
| </div> |
| |
| |
| |
| |
| <div id="searchbox"></div> |
| <article class="bd-article"> |
| |
| <!-- |
| Licensed to the Apache Software Foundation (ASF) under one |
| or more contributor license agreements. See the NOTICE file |
| distributed with this work for additional information |
| regarding copyright ownership. The ASF licenses this file |
| to you under the Apache License, Version 2.0 (the |
| "License"); you may not use this file except in compliance |
| with the License. You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, |
| software distributed under the License is distributed on an |
| "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| KIND, either express or implied. See the License for the |
| specific language governing permissions and limitations |
| under the License. |
| --> |
| <section id="scalar-udfs"> |
| <h1>Scalar UDFs<a class="headerlink" href="#scalar-udfs" title="Link to this heading">#</a></h1> |
| <p>A scalar UDF is a Java-implemented SQL function that operates one row at a time, |
| expressed in vectorised form: each invocation receives a batch of input columns |
| and returns either a per-row output column of the same length (<code class="docutils literal notranslate"><span class="pre">Array</span></code>) or a |
| single value broadcast to every row (<code class="docutils literal notranslate"><span class="pre">Scalar</span></code>).</p> |
| <section id="implement"> |
| <h2>Implement<a class="headerlink" href="#implement" title="Link to this heading">#</a></h2> |
| <p>Implement the <code class="docutils literal notranslate"><span class="pre">ScalarFunction</span></code> interface. The implementation declares its own |
| SQL name, argument fields, return field, and volatility, and supplies the |
| per-batch <code class="docutils literal notranslate"><span class="pre">evaluate</span></code> body:</p> |
| <div class="highlight-java notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span><span class="w"> </span><span class="nn">java.util.List</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.memory.BufferAllocator</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.IntVector</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.ArrowType</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.arrow.vector.types.pojo.Field</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.ColumnarValue</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.ScalarFunction</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.ScalarFunctionArgs</span><span class="p">;</span> |
| <span class="kn">import</span><span class="w"> </span><span class="nn">org.apache.datafusion.Volatility</span><span class="p">;</span> |
| |
| <span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">class</span> <span class="nc">AddOne</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ScalarFunction</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ArrowType</span><span class="w"> </span><span class="n">INT32</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">Int</span><span class="p">(</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">);</span> |
| |
| <span class="w"> </span><span class="nd">@Override</span><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">name</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="s">"add_one"</span><span class="p">;</span><span class="w"> </span><span class="p">}</span> |
| <span class="w"> </span><span class="nd">@Override</span><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o"><</span><span class="n">Field</span><span class="o">></span><span class="w"> </span><span class="nf">argFields</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">List</span><span class="p">.</span><span class="na">of</span><span class="p">(</span><span class="n">Field</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="s">"x"</span><span class="p">,</span><span class="w"> </span><span class="n">INT32</span><span class="p">));</span><span class="w"> </span><span class="p">}</span> |
| <span class="w"> </span><span class="nd">@Override</span><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">Field</span><span class="w"> </span><span class="nf">returnField</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">Field</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="s">"y"</span><span class="p">,</span><span class="w"> </span><span class="n">INT32</span><span class="p">);</span><span class="w"> </span><span class="p">}</span> |
| <span class="w"> </span><span class="nd">@Override</span><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">Volatility</span><span class="w"> </span><span class="nf">volatility</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">Volatility</span><span class="p">.</span><span class="na">IMMUTABLE</span><span class="p">;</span><span class="w"> </span><span class="p">}</span> |
| |
| <span class="w"> </span><span class="nd">@Override</span> |
| <span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">ColumnarValue</span><span class="w"> </span><span class="nf">evaluate</span><span class="p">(</span><span class="n">BufferAllocator</span><span class="w"> </span><span class="n">allocator</span><span class="p">,</span><span class="w"> </span><span class="n">ScalarFunctionArgs</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="n">IntVector</span><span class="w"> </span><span class="n">in</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="n">IntVector</span><span class="p">)</span><span class="w"> </span><span class="n">args</span><span class="p">.</span><span class="na">args</span><span class="p">().</span><span class="na">get</span><span class="p">(</span><span class="mi">0</span><span class="p">).</span><span class="na">vector</span><span class="p">();</span> |
| <span class="w"> </span><span class="n">IntVector</span><span class="w"> </span><span class="n">out</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">IntVector</span><span class="p">(</span><span class="s">"add_one"</span><span class="p">,</span><span class="w"> </span><span class="n">allocator</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">out</span><span class="p">.</span><span class="na">allocateNew</span><span class="p">(</span><span class="n">in</span><span class="p">.</span><span class="na">getValueCount</span><span class="p">());</span> |
| <span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">in</span><span class="p">.</span><span class="na">getValueCount</span><span class="p">();</span><span class="w"> </span><span class="n">i</span><span class="o">++</span><span class="p">)</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">in</span><span class="p">.</span><span class="na">isNull</span><span class="p">(</span><span class="n">i</span><span class="p">))</span><span class="w"> </span><span class="n">out</span><span class="p">.</span><span class="na">setNull</span><span class="p">(</span><span class="n">i</span><span class="p">);</span> |
| <span class="w"> </span><span class="k">else</span><span class="w"> </span><span class="n">out</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="n">i</span><span class="p">,</span><span class="w"> </span><span class="n">in</span><span class="p">.</span><span class="na">get</span><span class="p">(</span><span class="n">i</span><span class="p">)</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span> |
| <span class="w"> </span><span class="p">}</span> |
| <span class="w"> </span><span class="n">out</span><span class="p">.</span><span class="na">setValueCount</span><span class="p">(</span><span class="n">in</span><span class="p">.</span><span class="na">getValueCount</span><span class="p">());</span> |
| <span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">ColumnarValue</span><span class="p">.</span><span class="na">array</span><span class="p">(</span><span class="n">out</span><span class="p">);</span> |
| <span class="w"> </span><span class="p">}</span> |
| <span class="p">}</span> |
| </pre></div> |
| </div> |
| <p>Each entry in <code class="docutils literal notranslate"><span class="pre">args.args()</span></code> is a <code class="docutils literal notranslate"><span class="pre">ColumnarValue</span></code> — either <code class="docutils literal notranslate"><span class="pre">ColumnarValue.Array</span></code> |
| (a per-row vector of length <code class="docutils literal notranslate"><span class="pre">args.rowCount()</span></code>) or <code class="docutils literal notranslate"><span class="pre">ColumnarValue.Scalar</span></code> (a |
| length-1 vector representing a single literal or folded constant). Access the |
| underlying Arrow vector with <code class="docutils literal notranslate"><span class="pre">.vector()</span></code>.</p> |
| <p>Allocate any new vectors — including the result — from the supplied |
| <code class="docutils literal notranslate"><span class="pre">BufferAllocator</span></code>. The input vectors are read-only views; do not close them. |
| Ownership of the returned vector transfers to the framework on return.</p> |
| </section> |
| <section id="declaring-argument-and-return-fields"> |
| <h2>Declaring argument and return fields<a class="headerlink" href="#declaring-argument-and-return-fields" title="Link to this heading">#</a></h2> |
| <p>Each argument and the return value are described as Arrow <code class="docutils literal notranslate"><span class="pre">Field</span></code>s. A <code class="docutils literal notranslate"><span class="pre">Field</span></code> |
| carries a name, a <code class="docutils literal notranslate"><span class="pre">FieldType</span></code> (Arrow type plus nullability and metadata), and a |
| list of child fields used by nested types.</p> |
| <p>For primitive types the <code class="docutils literal notranslate"><span class="pre">Field.nullable(name,</span> <span class="pre">arrowType)</span></code> and |
| <code class="docutils literal notranslate"><span class="pre">Field.notNullable(name,</span> <span class="pre">arrowType)</span></code> factories are the shortest form:</p> |
| <div class="highlight-java notranslate"><div class="highlight"><pre><span></span><span class="n">Field</span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Field</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="s">"x"</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">Int</span><span class="p">(</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">));</span> |
| <span class="n">Field</span><span class="w"> </span><span class="n">y</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Field</span><span class="p">.</span><span class="na">notNullable</span><span class="p">(</span><span class="s">"y"</span><span class="p">,</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">Int</span><span class="p">(</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">));</span> |
| </pre></div> |
| </div> |
| <p>Nested Arrow types — <code class="docutils literal notranslate"><span class="pre">List</span></code>, <code class="docutils literal notranslate"><span class="pre">Struct</span></code>, <code class="docutils literal notranslate"><span class="pre">Map</span></code>, <code class="docutils literal notranslate"><span class="pre">Union</span></code> — must declare their |
| element / member / key / value fields as children, because that information |
| does not live on the <code class="docutils literal notranslate"><span class="pre">ArrowType</span></code> itself. Use the |
| <code class="docutils literal notranslate"><span class="pre">new</span> <span class="pre">Field(name,</span> <span class="pre">FieldType,</span> <span class="pre">children)</span></code> constructor:</p> |
| <div class="highlight-java notranslate"><div class="highlight"><pre><span></span><span class="c1">// List<Int32></span> |
| <span class="n">ArrowType</span><span class="w"> </span><span class="n">INT32</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">Int</span><span class="p">(</span><span class="mi">32</span><span class="p">,</span><span class="w"> </span><span class="kc">true</span><span class="p">);</span> |
| <span class="n">Field</span><span class="w"> </span><span class="n">listOfInt</span><span class="w"> </span><span class="o">=</span> |
| <span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Field</span><span class="p">(</span> |
| <span class="w"> </span><span class="s">"vals"</span><span class="p">,</span> |
| <span class="w"> </span><span class="n">FieldType</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">List</span><span class="p">()),</span> |
| <span class="w"> </span><span class="n">List</span><span class="p">.</span><span class="na">of</span><span class="p">(</span><span class="n">Field</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="s">"item"</span><span class="p">,</span><span class="w"> </span><span class="n">INT32</span><span class="p">)));</span> |
| |
| <span class="c1">// Struct<a: Int32, b: Int32></span> |
| <span class="n">Field</span><span class="w"> </span><span class="n">structAB</span><span class="w"> </span><span class="o">=</span> |
| <span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">Field</span><span class="p">(</span> |
| <span class="w"> </span><span class="s">"ab"</span><span class="p">,</span> |
| <span class="w"> </span><span class="n">FieldType</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">Struct</span><span class="p">()),</span> |
| <span class="w"> </span><span class="n">List</span><span class="p">.</span><span class="na">of</span><span class="p">(</span><span class="n">Field</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="s">"a"</span><span class="p">,</span><span class="w"> </span><span class="n">INT32</span><span class="p">),</span><span class="w"> </span><span class="n">Field</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="s">"b"</span><span class="p">,</span><span class="w"> </span><span class="n">INT32</span><span class="p">)));</span> |
| </pre></div> |
| </div> |
| <p>A UDF declared with <code class="docutils literal notranslate"><span class="pre">Field.nullable(...)</span></code> arguments is registered with an exact |
| nullability-bearing signature; calls whose argument types do not match exactly |
| are rejected. The declared <code class="docutils literal notranslate"><span class="pre">returnField</span></code>’s nullability is preserved end-to-end: |
| a non-nullable return field stays non-nullable in the result schema.</p> |
| </section> |
| <section id="returning-a-scalar"> |
| <h2>Returning a Scalar<a class="headerlink" href="#returning-a-scalar" title="Link to this heading">#</a></h2> |
| <p>Functions that yield a single value (nullary constants like <code class="docutils literal notranslate"><span class="pre">pi()</span></code>, or any |
| function that wants the framework to broadcast a result across the batch) can |
| return <code class="docutils literal notranslate"><span class="pre">ColumnarValue.scalar(...)</span></code> over a length-1 vector:</p> |
| <div class="highlight-java notranslate"><div class="highlight"><pre><span></span><span class="kd">public</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="kd">class</span> <span class="nc">JavaPi</span><span class="w"> </span><span class="kd">implements</span><span class="w"> </span><span class="n">ScalarFunction</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="kd">private</span><span class="w"> </span><span class="kd">static</span><span class="w"> </span><span class="kd">final</span><span class="w"> </span><span class="n">ArrowType</span><span class="w"> </span><span class="n">FLOAT64</span><span class="w"> </span><span class="o">=</span> |
| <span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">ArrowType</span><span class="p">.</span><span class="na">FloatingPoint</span><span class="p">(</span><span class="n">org</span><span class="p">.</span><span class="na">apache</span><span class="p">.</span><span class="na">arrow</span><span class="p">.</span><span class="na">vector</span><span class="p">.</span><span class="na">types</span><span class="p">.</span><span class="na">FloatingPointPrecision</span><span class="p">.</span><span class="na">DOUBLE</span><span class="p">);</span> |
| |
| <span class="w"> </span><span class="nd">@Override</span><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">String</span><span class="w"> </span><span class="nf">name</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="s">"java_pi"</span><span class="p">;</span><span class="w"> </span><span class="p">}</span> |
| <span class="w"> </span><span class="nd">@Override</span><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">List</span><span class="o"><</span><span class="n">Field</span><span class="o">></span><span class="w"> </span><span class="nf">argFields</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">List</span><span class="p">.</span><span class="na">of</span><span class="p">();</span><span class="w"> </span><span class="p">}</span> |
| <span class="w"> </span><span class="nd">@Override</span><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">Field</span><span class="w"> </span><span class="nf">returnField</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">Field</span><span class="p">.</span><span class="na">nullable</span><span class="p">(</span><span class="s">"p"</span><span class="p">,</span><span class="w"> </span><span class="n">FLOAT64</span><span class="p">);</span><span class="w"> </span><span class="p">}</span> |
| <span class="w"> </span><span class="nd">@Override</span><span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">Volatility</span><span class="w"> </span><span class="nf">volatility</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">Volatility</span><span class="p">.</span><span class="na">VOLATILE</span><span class="p">;</span><span class="w"> </span><span class="p">}</span> |
| |
| <span class="w"> </span><span class="nd">@Override</span> |
| <span class="w"> </span><span class="kd">public</span><span class="w"> </span><span class="n">ColumnarValue</span><span class="w"> </span><span class="nf">evaluate</span><span class="p">(</span><span class="n">BufferAllocator</span><span class="w"> </span><span class="n">allocator</span><span class="p">,</span><span class="w"> </span><span class="n">ScalarFunctionArgs</span><span class="w"> </span><span class="n">args</span><span class="p">)</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="n">org</span><span class="p">.</span><span class="na">apache</span><span class="p">.</span><span class="na">arrow</span><span class="p">.</span><span class="na">vector</span><span class="p">.</span><span class="na">Float8Vector</span><span class="w"> </span><span class="n">out</span><span class="w"> </span><span class="o">=</span> |
| <span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">org</span><span class="p">.</span><span class="na">apache</span><span class="p">.</span><span class="na">arrow</span><span class="p">.</span><span class="na">vector</span><span class="p">.</span><span class="na">Float8Vector</span><span class="p">(</span><span class="s">"pi"</span><span class="p">,</span><span class="w"> </span><span class="n">allocator</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">out</span><span class="p">.</span><span class="na">allocateNew</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">out</span><span class="p">.</span><span class="na">set</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">Math</span><span class="p">.</span><span class="na">PI</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">out</span><span class="p">.</span><span class="na">setValueCount</span><span class="p">(</span><span class="mi">1</span><span class="p">);</span> |
| <span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">ColumnarValue</span><span class="p">.</span><span class="na">scalar</span><span class="p">(</span><span class="n">out</span><span class="p">);</span> |
| <span class="w"> </span><span class="p">}</span> |
| <span class="p">}</span> |
| </pre></div> |
| </div> |
| <p>The framework expands the scalar across <code class="docutils literal notranslate"><span class="pre">args.rowCount()</span></code> rows automatically.</p> |
| </section> |
| <section id="register"> |
| <h2>Register<a class="headerlink" href="#register" title="Link to this heading">#</a></h2> |
| <p>Wrap the implementation in a <code class="docutils literal notranslate"><span class="pre">ScalarUdf</span></code> and pass it to |
| <code class="docutils literal notranslate"><span class="pre">SessionContext.registerUdf</span></code>:</p> |
| <div class="highlight-java notranslate"><div class="highlight"><pre><span></span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="n">SessionContext</span><span class="w"> </span><span class="n">ctx</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">new</span><span class="w"> </span><span class="n">SessionContext</span><span class="p">())</span><span class="w"> </span><span class="p">{</span> |
| <span class="w"> </span><span class="n">ctx</span><span class="p">.</span><span class="na">registerUdf</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">ScalarUdf</span><span class="p">(</span><span class="k">new</span><span class="w"> </span><span class="n">AddOne</span><span class="p">()));</span> |
| |
| <span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">(</span><span class="n">DataFrame</span><span class="w"> </span><span class="n">df</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ctx</span><span class="p">.</span><span class="na">sql</span><span class="p">(</span><span class="s">"SELECT add_one(x) FROM t"</span><span class="p">);</span> |
| <span class="w"> </span><span class="n">ArrowReader</span><span class="w"> </span><span class="n">r</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">df</span><span class="p">.</span><span class="na">collect</span><span class="p">(</span><span class="n">allocator</span><span class="p">))</span><span class="w"> </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> |
| <p><code class="docutils literal notranslate"><span class="pre">ScalarUdf</span></code> mirrors DataFusion’s <code class="docutils literal notranslate"><span class="pre">ScalarUDF</span></code> struct; <code class="docutils literal notranslate"><span class="pre">ScalarFunction</span></code> mirrors |
| <code class="docutils literal notranslate"><span class="pre">ScalarUDFImpl</span></code>. Use <code class="docutils literal notranslate"><span class="pre">Volatility.IMMUTABLE</span></code> for pure functions, <code class="docutils literal notranslate"><span class="pre">STABLE</span></code> for |
| functions that are deterministic within a single query, and <code class="docutils literal notranslate"><span class="pre">VOLATILE</span></code> for |
| non-deterministic functions.</p> |
| </section> |
| <section id="errors"> |
| <h2>Errors<a class="headerlink" href="#errors" title="Link to this heading">#</a></h2> |
| <p>If the UDF throws, the exception class and message surface in the |
| <code class="docutils literal notranslate"><span class="pre">RuntimeException</span></code> raised from <code class="docutils literal notranslate"><span class="pre">collect()</span></code>. If the returned <code class="docutils literal notranslate"><span class="pre">ColumnarValue</span></code> is |
| <code class="docutils literal notranslate"><span class="pre">null</span></code>, an Array result’s vector length does not equal <code class="docutils literal notranslate"><span class="pre">args.rowCount()</span></code>, or |
| the result’s Arrow type differs from the declared return field, the runtime |
| raises a <code class="docutils literal notranslate"><span class="pre">RuntimeException</span></code> with a descriptive message. A Scalar result whose |
| vector is not length-1 is rejected at the <code class="docutils literal notranslate"><span class="pre">ColumnarValue.scalar</span></code> factory.</p> |
| </section> |
| <section id="threading"> |
| <h2>Threading<a class="headerlink" href="#threading" title="Link to this heading">#</a></h2> |
| <p>DataFusion may invoke a UDF concurrently from multiple worker threads. If the |
| implementation carries mutable state, the implementation must synchronize it.</p> |
| </section> |
| <section id="limitations-v1"> |
| <h2>Limitations (v1)<a class="headerlink" href="#limitations-v1" title="Link to this heading">#</a></h2> |
| <ul class="simple"> |
| <li><p>Scalar UDFs only — no aggregates, window functions, or table functions.</p></li> |
| <li><p>Exact-signature only — no variadic or polymorphic argument lists.</p></li> |
| <li><p>No nullable-argument short-circuiting; null inputs are passed through to the |
| UDF as nulls in the input vector.</p></li> |
| </ul> |
| </section> |
| </section> |
| |
| |
| </article> |
| |
| |
| |
| |
| |
| <footer class="prev-next-footer d-print-none"> |
| |
| <div class="prev-next-area"> |
| <a class="left-prev" |
| href="proto-plans.html" |
| title="previous page"> |
| <i class="fa-solid fa-angle-left"></i> |
| <div class="prev-next-info"> |
| <p class="prev-next-subtitle">previous</p> |
| <p class="prev-next-title">Logical plans via datafusion-proto</p> |
| </div> |
| </a> |
| <a class="right-next" |
| href="table-provider.html" |
| title="next page"> |
| <div class="prev-next-info"> |
| <p class="prev-next-subtitle">next</p> |
| <p class="prev-next-title">Java table providers</p> |
| </div> |
| <i class="fa-solid fa-angle-right"></i> |
| </a> |
| </div> |
| </footer> |
| |
| </div> |
| |
| |
| |
| <dialog id="pst-secondary-sidebar-modal"></dialog> |
| <div id="pst-secondary-sidebar" class="bd-sidebar-secondary bd-toc"><div class="sidebar-secondary-items sidebar-secondary__inner"> |
| |
| |
| <div class="sidebar-secondary-item"> |
| <div |
| id="pst-page-navigation-heading-2" |
| class="page-toc tocsection onthispage"> |
| <i class="fa-solid fa-list"></i> On this page |
| </div> |
| <nav class="bd-toc-nav page-toc" aria-labelledby="pst-page-navigation-heading-2"> |
| <ul class="visible nav section-nav flex-column"> |
| <li class="toc-h2 nav-item toc-entry"><a class="reference internal nav-link" href="#implement">Implement</a></li> |
| <li class="toc-h2 nav-item toc-entry"><a class="reference internal nav-link" href="#declaring-argument-and-return-fields">Declaring argument and return fields</a></li> |
| <li class="toc-h2 nav-item toc-entry"><a class="reference internal nav-link" href="#returning-a-scalar">Returning a Scalar</a></li> |
| <li class="toc-h2 nav-item toc-entry"><a class="reference internal nav-link" href="#register">Register</a></li> |
| <li class="toc-h2 nav-item toc-entry"><a class="reference internal nav-link" href="#errors">Errors</a></li> |
| <li class="toc-h2 nav-item toc-entry"><a class="reference internal nav-link" href="#threading">Threading</a></li> |
| <li class="toc-h2 nav-item toc-entry"><a class="reference internal nav-link" href="#limitations-v1">Limitations (v1)</a></li> |
| </ul> |
| </nav></div> |
| |
| <div class="sidebar-secondary-item"> |
| <div role="note" aria-label="source link"> |
| <h3>This Page</h3> |
| <ul class="this-page-menu"> |
| <li><a href="../_sources/user-guide/scalar-udf.md.txt" |
| rel="nofollow">Show Source</a></li> |
| </ul> |
| </div></div> |
| |
| </div></div> |
| |
| |
| </div> |
| <footer class="bd-footer-content"> |
| |
| </footer> |
| |
| </main> |
| </div> |
| </div> |
| |
| <!-- Scripts loaded after <body> so the DOM is not blocked --> |
| <script defer src="../_static/scripts/bootstrap.js?digest=8878045cc6db502f8baf"></script> |
| <script defer src="../_static/scripts/pydata-sphinx-theme.js?digest=8878045cc6db502f8baf"></script> |
| |
| <footer class="bd-footer"> |
| <div class="bd-footer__inner bd-page-width"> |
| |
| <div class="footer-items__start"> |
| |
| <div class="footer-item"> |
| |
| <p class="copyright"> |
| |
| © Copyright 2026, Apache Software Foundation. |
| <br/> |
| |
| </p> |
| </div> |
| |
| <div class="footer-item"> |
| |
| <p class="sphinx-version"> |
| Created using <a href="https://www.sphinx-doc.org/">Sphinx</a> 7.4.7. |
| <br/> |
| </p> |
| </div> |
| |
| </div> |
| |
| |
| |
| <div class="footer-items__end"> |
| |
| <div class="footer-item"> |
| <p class="theme-version"> |
| <!-- # L10n: Setting the PST URL as an argument as this does not need to be localized --> |
| Built with the <a href="https://pydata-sphinx-theme.readthedocs.io/en/stable/index.html">PyData Sphinx Theme</a> 0.16.1. |
| </p></div> |
| |
| </div> |
| |
| </div> |
| |
| </footer> |
| </body> |
| </html> |
