blob: 367f41d86e81e1907d9709ed8a174aa462a8dff0 [file]
<!DOCTYPE html>
<html lang="en" data-content_root="../" data-theme="auto">
<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>Functions and table functions &#8212; Apache DataFusion in Python documentation</title>
<script data-cfasync="false">
document.documentElement.dataset.mode = localStorage.getItem("mode") || "auto";
document.documentElement.dataset.theme = localStorage.getItem("theme") || "auto";
</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" />
<link rel="stylesheet" type="text/css" href="../_static/mystnb.11b39860a7a0cbfd473a3ad8a317855267ff0bd372690045ca344a6b62be495e.css" />
<link rel="stylesheet" type="text/css" href="../_static/graphviz.css?v=4ae1632d" />
<link rel="stylesheet" type="text/css" href="../_static/copybutton.css?v=76b2166b" />
<link rel="stylesheet" type="text/css" href="../_static/theme_overrides.css?v=4af573bc" />
<!-- 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=9bcbadda"></script>
<script src="../_static/sphinx_highlight.js?v=dc90522c"></script>
<script src="../_static/clipboard.min.js?v=a7894cd8"></script>
<script src="../_static/copybutton.js?v=f281be69"></script>
<script>DOCUMENTATION_OPTIONS.pagename = 'extension-guide/functions';</script>
<script src="../_static/toc-toggle.js?v=36375f01"></script>
<link rel="icon" href="../_static/favicon.svg"/>
<link rel="index" title="Index" href="../genindex.html" />
<link rel="search" title="Search" href="../search.html" />
<link rel="next" title="Extension codecs" href="codecs.html" />
<link rel="prev" title="Providers and catalogs" href="table-providers.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="auto">
<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">
<img src="../_static/original.svg" class="logo__image only-light" alt="Apache DataFusion in Python"/>
<img src="../_static/original_dark.svg" class="logo__image only-dark pst-js-only" alt="Apache DataFusion in Python"/>
</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-internal" href="../user-guide/index.html">
User Guide
</a>
</li>
<li class="nav-item current active">
<a class="nav-link nav-internal" href="index.html">
Extension Guide
</a>
</li>
<li class="nav-item ">
<a class="nav-link nav-internal" href="../contributor-guide/index.html">
Contributor Guide
</a>
</li>
<li class="nav-item ">
<a class="nav-link nav-internal" href="../autoapi/index.html">
API Reference
</a>
</li>
<li class="nav-item ">
<a class="nav-link nav-internal" href="../links.html">
Links
</a>
</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"><ul class="navbar-icon-links"
aria-label="Icon Links">
<li class="nav-item">
<a href="https://github.com/apache/datafusion-python" title="GitHub" class="nav-link pst-navbar-icon" rel="noopener" target="_blank" data-bs-toggle="tooltip" data-bs-placement="bottom"><i class="fa-brands fa-github fa-lg" aria-hidden="true"></i>
<span class="sr-only">GitHub</span></a>
</li>
<li class="nav-item">
<a href="https://docs.rs/datafusion/latest/datafusion/" title="Rust API docs (docs.rs)" class="nav-link pst-navbar-icon" rel="noopener" target="_blank" data-bs-toggle="tooltip" data-bs-placement="bottom"><i class="fa-brands fa-rust fa-lg" aria-hidden="true"></i>
<span class="sr-only">Rust API docs (docs.rs)</span></a>
</li>
</ul></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-internal" href="../user-guide/index.html">
User Guide
</a>
</li>
<li class="nav-item current active">
<a class="nav-link nav-internal" href="index.html">
Extension Guide
</a>
</li>
<li class="nav-item ">
<a class="nav-link nav-internal" href="../contributor-guide/index.html">
Contributor Guide
</a>
</li>
<li class="nav-item ">
<a class="nav-link nav-internal" href="../autoapi/index.html">
API Reference
</a>
</li>
<li class="nav-item ">
<a class="nav-link nav-internal" href="../links.html">
Links
</a>
</li>
</ul>
</nav></div>
</div>
<div class="sidebar-header-items__end">
<div class="navbar-item"><ul class="navbar-icon-links"
aria-label="Icon Links">
<li class="nav-item">
<a href="https://github.com/apache/datafusion-python" title="GitHub" class="nav-link pst-navbar-icon" rel="noopener" target="_blank" data-bs-toggle="tooltip" data-bs-placement="bottom"><i class="fa-brands fa-github fa-lg" aria-hidden="true"></i>
<span class="sr-only">GitHub</span></a>
</li>
<li class="nav-item">
<a href="https://docs.rs/datafusion/latest/datafusion/" title="Rust API docs (docs.rs)" class="nav-link pst-navbar-icon" rel="noopener" target="_blank" data-bs-toggle="tooltip" data-bs-placement="bottom"><i class="fa-brands fa-rust fa-lg" aria-hidden="true"></i>
<span class="sr-only">Rust API docs (docs.rs)</span></a>
</li>
</ul></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="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 has-children"><a class="reference internal" href="../user-guide/index.html">User Guide</a><details open="open"><summary><span class="toctree-toggle" role="presentation"><i class="fa-solid fa-chevron-down"></i></span></summary><ul>
<li class="toctree-l2"><a class="reference internal" href="../user-guide/introduction.html">Introduction</a></li>
<li class="toctree-l2"><a class="reference internal" href="../user-guide/basics.html">Concepts</a></li>
<li class="toctree-l2"><a class="reference internal" href="../user-guide/data-sources.html">Data Sources</a></li>
<li class="toctree-l2 has-children"><a class="reference internal" href="../user-guide/dataframe/index.html">DataFrames</a><details><summary><span class="toctree-toggle" role="presentation"><i class="fa-solid fa-chevron-down"></i></span></summary><ul>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/dataframe/rendering.html">DataFrame Rendering</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/dataframe/execution-metrics.html">Execution Metrics</a></li>
</ul>
</details></li>
<li class="toctree-l2 has-children"><a class="reference internal" href="../user-guide/common-operations/index.html">Common Operations</a><details><summary><span class="toctree-toggle" role="presentation"><i class="fa-solid fa-chevron-down"></i></span></summary><ul>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/common-operations/views.html">Registering Views</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/common-operations/basic-info.html">Basic Operations</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/common-operations/select-and-filter.html">Column Selections</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/common-operations/expressions.html">Expressions</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/common-operations/joins.html">Joins</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/common-operations/functions.html">Functions</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/common-operations/spark-functions.html">Spark-Compatible Functions</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/common-operations/aggregations.html">Aggregation</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/common-operations/windows.html">Window Functions</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/common-operations/udf-and-udfa.html">User-Defined Functions</a></li>
</ul>
</details></li>
<li class="toctree-l2 has-children"><a class="reference internal" href="../user-guide/io/index.html">IO</a><details><summary><span class="toctree-toggle" role="presentation"><i class="fa-solid fa-chevron-down"></i></span></summary><ul>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/io/arrow.html">Arrow</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/io/avro.html">Avro</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/io/csv.html">CSV</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/io/json.html">JSON</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/io/parquet.html">Parquet</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/io/table_provider.html">Custom Table Provider</a></li>
</ul>
</details></li>
<li class="toctree-l2"><a class="reference internal" href="../user-guide/configuration.html">Configuration</a></li>
<li class="toctree-l2"><a class="reference internal" href="../user-guide/extensions.html">Using extension libraries</a></li>
<li class="toctree-l2 has-children"><a class="reference internal" href="../user-guide/distributing-work/index.html">Distributing work</a><details><summary><span class="toctree-toggle" role="presentation"><i class="fa-solid fa-chevron-down"></i></span></summary><ul>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/distributing-work/expressions.html">Shipping expressions to workers</a></li>
<li class="toctree-l3"><a class="reference internal" href="../user-guide/distributing-work/query-engines.html">Distributed query engines</a></li>
</ul>
</details></li>
<li class="toctree-l2"><a class="reference internal" href="../user-guide/sql.html">SQL</a></li>
<li class="toctree-l2"><a class="reference internal" href="../user-guide/upgrade-guides.html">Upgrade Guides</a></li>
<li class="toctree-l2"><a class="reference internal" href="../user-guide/ai-coding-assistants.html">Using AI Coding Assistants</a></li>
</ul>
</details></li>
<li class="toctree-l1 current active has-children"><a class="reference internal" href="index.html">Extension Guide</a><details open="open"><summary><span class="toctree-toggle" role="presentation"><i class="fa-solid fa-chevron-down"></i></span></summary><ul class="current">
<li class="toctree-l2"><a class="reference internal" href="why-ffi.html">Why FFI</a></li>
<li class="toctree-l2"><a class="reference internal" href="capsule-protocol.html">The capsule protocol</a></li>
<li class="toctree-l2"><a class="reference internal" href="table-providers.html">Providers and catalogs</a></li>
<li class="toctree-l2 current active"><a class="current reference internal" href="#">Functions and table functions</a></li>
<li class="toctree-l2"><a class="reference internal" href="codecs.html">Extension codecs</a></li>
<li class="toctree-l2"><a class="reference internal" href="bundles.html">Extension bundles</a></li>
<li class="toctree-l2"><a class="reference internal" href="query-planners.html">Query planners</a></li>
<li class="toctree-l2"><a class="reference internal" href="other-components.html">Optimizer rules and configuration</a></li>
<li class="toctree-l2"><a class="reference internal" href="sessions.html">Sessions, handles, and lifetimes</a></li>
<li class="toctree-l2"><a class="reference internal" href="checklist.html">Extension author checklist</a></li>
</ul>
</details></li>
<li class="toctree-l1 has-children"><a class="reference internal" href="../contributor-guide/index.html">Contributor Guide</a><details open="open"><summary><span class="toctree-toggle" role="presentation"><i class="fa-solid fa-chevron-down"></i></span></summary><ul>
<li class="toctree-l2"><a class="reference internal" href="../contributor-guide/introduction.html">Introduction</a></li>
<li class="toctree-l2"><a class="reference internal" href="../contributor-guide/pyo3-guidelines.html">PyO3 binding guidelines</a></li>
<li class="toctree-l2"><a class="reference internal" href="../contributor-guide/ffi-internals.html">FFI framing internals</a></li>
</ul>
</details></li>
<li class="toctree-l1 has-children"><a class="reference internal" href="../autoapi/index.html">API Reference</a><details open="open"><summary><span class="toctree-toggle" role="presentation"><i class="fa-solid fa-chevron-down"></i></span></summary><ul>
<li class="toctree-l2 has-children"><a class="reference internal" href="../autoapi/datafusion/index.html">datafusion</a><details><summary><span class="toctree-toggle" role="presentation"><i class="fa-solid fa-chevron-down"></i></span></summary><ul>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/catalog/index.html">datafusion.catalog</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/context/index.html">datafusion.context</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/dataframe/index.html">datafusion.dataframe</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/dataframe_formatter/index.html">datafusion.dataframe_formatter</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/expr/index.html">datafusion.expr</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/extensions/index.html">datafusion.extensions</a></li>
<li class="toctree-l3 has-children"><a class="reference internal" href="../autoapi/datafusion/functions/index.html">datafusion.functions</a><details><summary><span class="toctree-toggle" role="presentation"><i class="fa-solid fa-chevron-down"></i></span></summary><ul>
<li class="toctree-l4"><a class="reference internal" href="../autoapi/datafusion/functions/spark/index.html">datafusion.functions.spark</a></li>
</ul>
</details></li>
<li class="toctree-l3 has-children"><a class="reference internal" href="../autoapi/datafusion/input/index.html">datafusion.input</a><details><summary><span class="toctree-toggle" role="presentation"><i class="fa-solid fa-chevron-down"></i></span></summary><ul>
<li class="toctree-l4"><a class="reference internal" href="../autoapi/datafusion/input/base/index.html">datafusion.input.base</a></li>
<li class="toctree-l4"><a class="reference internal" href="../autoapi/datafusion/input/location/index.html">datafusion.input.location</a></li>
</ul>
</details></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/io/index.html">datafusion.io</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/ipc/index.html">datafusion.ipc</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/object_store/index.html">datafusion.object_store</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/options/index.html">datafusion.options</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/plan/index.html">datafusion.plan</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/record_batch/index.html">datafusion.record_batch</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/substrait/index.html">datafusion.substrait</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/unparser/index.html">datafusion.unparser</a></li>
<li class="toctree-l3"><a class="reference internal" href="../autoapi/datafusion/user_defined/index.html">datafusion.user_defined</a></li>
</ul>
</details></li>
</ul>
</details></li>
<li class="toctree-l1 has-children"><a class="reference internal" href="../links.html">Links</a><details open="open"><summary><span class="toctree-toggle" role="presentation"><i class="fa-solid fa-chevron-down"></i></span></summary><ul>
<li class="toctree-l2"><a class="reference external" href="https://github.com/apache/datafusion-python">GitHub and Issue Tracker</a></li>
<li class="toctree-l2"><a class="reference external" href="https://docs.rs/datafusion/latest/datafusion/">Rust API Docs</a></li>
<li class="toctree-l2"><a class="reference external" href="https://github.com/apache/datafusion/blob/main/CODE_OF_CONDUCT.md">Code of Conduct</a></li>
<li class="toctree-l2"><a class="reference external" href="https://github.com/apache/datafusion-python/tree/main/examples">Examples</a></li>
</ul>
</details></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">Extension Guide</a></li>
<li class="breadcrumb-item active" aria-current="page"><span class="ellipsis">Functions and table functions</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="functions-and-table-functions">
<span id="extension-functions"></span><h1>Functions and table functions<a class="headerlink" href="#functions-and-table-functions" title="Link to this heading">#</a></h1>
<p>Four hooks contribute functions written in Rust. Users can also define
functions in pure Python — see
<a class="reference internal" href="../user-guide/common-operations/udf-and-udfa.html"><span class="doc">User-Defined Functions</span></a> — and the two roads meet at
the same registration methods.</p>
<div class="pst-scrollable-table-container"><table class="table">
<thead>
<tr class="row-odd"><th class="head"><p>Hook</p></th>
<th class="head"><p>Contributes</p></th>
<th class="head"><p>Wrapped by</p></th>
<th class="head"><p>Registered with</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">__datafusion_scalar_udf__</span></code></p></td>
<td><p>scalar function</p></td>
<td><p><code class="xref py py-func docutils literal notranslate"><span class="pre">datafusion.udf()</span></code></p></td>
<td><p><code class="xref py py-meth docutils literal notranslate"><span class="pre">register_udf()</span></code></p></td>
</tr>
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">__datafusion_aggregate_udf__</span></code></p></td>
<td><p>aggregate function</p></td>
<td><p><code class="xref py py-func docutils literal notranslate"><span class="pre">datafusion.udaf()</span></code></p></td>
<td><p><code class="xref py py-meth docutils literal notranslate"><span class="pre">register_udaf()</span></code></p></td>
</tr>
<tr class="row-even"><td><p><code class="docutils literal notranslate"><span class="pre">__datafusion_window_udf__</span></code></p></td>
<td><p>window function</p></td>
<td><p><code class="xref py py-func docutils literal notranslate"><span class="pre">datafusion.udwf()</span></code></p></td>
<td><p><code class="xref py py-meth docutils literal notranslate"><span class="pre">register_udwf()</span></code></p></td>
</tr>
<tr class="row-odd"><td><p><code class="docutils literal notranslate"><span class="pre">__datafusion_table_function__</span></code></p></td>
<td><p>function returning a table</p></td>
<td><p><code class="xref py py-func docutils literal notranslate"><span class="pre">datafusion.udtf()</span></code></p></td>
<td><p><code class="xref py py-meth docutils literal notranslate"><span class="pre">register_udtf()</span></code></p></td>
</tr>
</tbody>
</table>
</div>
<p>All four are implemented in <a class="reference external" href="https://github.com/apache/datafusion-python/tree/main/examples/datafusion-ffi-example"><code class="docutils literal notranslate"><span class="pre">datafusion-ffi-example</span></code></a>, one per file.</p>
<section id="the-three-scalar-shaped-hooks">
<h2>The three scalar-shaped hooks<a class="headerlink" href="#the-three-scalar-shaped-hooks" title="Link to this heading">#</a></h2>
<p>The scalar, aggregate, and window getters take <strong>no argument</strong> beyond <code class="docutils literal notranslate"><span class="pre">py</span></code> —
they need no codec and no task-context provider, because a function is
identified by name and signature rather than by anything session-scoped:</p>
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="cp">#[pymethods]</span>
<span class="k">impl</span><span class="w"> </span><span class="n">MyScalarUDF</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">fn</span><span class="w"> </span><span class="nf">__datafusion_scalar_udf__</span><span class="o">&lt;&#39;</span><span class="na">py</span><span class="o">&gt;</span><span class="p">(</span>
<span class="w"> </span><span class="o">&amp;</span><span class="bp">self</span><span class="p">,</span>
<span class="w"> </span><span class="n">py</span><span class="p">:</span><span class="w"> </span><span class="nc">Python</span><span class="o">&lt;&#39;</span><span class="na">py</span><span class="o">&gt;</span><span class="p">,</span>
<span class="w"> </span><span class="p">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">PyResult</span><span class="o">&lt;</span><span class="n">Bound</span><span class="o">&lt;&#39;</span><span class="na">py</span><span class="p">,</span><span class="w"> </span><span class="n">PyCapsule</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">udf</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">Arc</span><span class="p">::</span><span class="n">new</span><span class="p">(</span><span class="n">ScalarUDF</span><span class="p">::</span><span class="n">from</span><span class="p">(</span><span class="bp">self</span><span class="p">.</span><span class="n">clone</span><span class="p">()));</span>
<span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">ffi</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">FFI_ScalarUDF</span><span class="p">::</span><span class="n">from</span><span class="p">(</span><span class="n">udf</span><span class="p">);</span>
<span class="w"> </span><span class="n">PyCapsule</span><span class="p">::</span><span class="n">new_with_value</span><span class="p">(</span><span class="n">py</span><span class="p">,</span><span class="w"> </span><span class="n">ffi</span><span class="p">,</span><span class="w"> </span><span class="n">cr</span><span class="s">&quot;datafusion_scalar_udf&quot;</span><span class="p">)</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Aggregate and window follow identically with <code class="docutils literal notranslate"><span class="pre">FFI_AggregateUDF</span></code> /
<code class="docutils literal notranslate"><span class="pre">FFI_WindowUDF</span></code> and the matching capsule names.</p>
<p>Your users wrap the object once and register the result:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">datafusion</span><span class="w"> </span><span class="kn">import</span> <span class="n">udf</span>
<span class="n">ctx</span><span class="o">.</span><span class="n">register_udf</span><span class="p">(</span><span class="n">udf</span><span class="p">(</span><span class="n">my_library</span><span class="o">.</span><span class="n">MyScalarUDF</span><span class="p">()))</span>
</pre></div>
</div>
</section>
<section id="table-functions">
<h2>Table functions<a class="headerlink" href="#table-functions" title="Link to this heading">#</a></h2>
<p>A table function takes literal <code class="docutils literal notranslate"><span class="pre">Expr</span></code> arguments and returns a table provider,
so it needs the host’s logical codec the way a
<a class="reference internal" href="table-providers.html#extension-providers"><span class="std std-ref">table provider</span></a> does:</p>
<div class="highlight-rust notranslate"><div class="highlight"><pre><span></span><span class="k">fn</span><span class="w"> </span><span class="nf">__datafusion_table_function__</span><span class="o">&lt;&#39;</span><span class="na">py</span><span class="o">&gt;</span><span class="p">(</span>
<span class="w"> </span><span class="o">&amp;</span><span class="bp">self</span><span class="p">,</span>
<span class="w"> </span><span class="n">py</span><span class="p">:</span><span class="w"> </span><span class="nc">Python</span><span class="o">&lt;&#39;</span><span class="na">py</span><span class="o">&gt;</span><span class="p">,</span>
<span class="w"> </span><span class="n">session</span><span class="p">:</span><span class="w"> </span><span class="nc">Bound</span><span class="o">&lt;&#39;</span><span class="na">py</span><span class="p">,</span><span class="w"> </span><span class="n">PyAny</span><span class="o">&gt;</span><span class="p">,</span>
<span class="p">)</span><span class="w"> </span><span class="p">-&gt;</span><span class="w"> </span><span class="nc">PyResult</span><span class="o">&lt;</span><span class="n">Bound</span><span class="o">&lt;&#39;</span><span class="na">py</span><span class="p">,</span><span class="w"> </span><span class="n">PyCapsule</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">func</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="bp">self</span><span class="p">.</span><span class="n">clone</span><span class="p">();</span>
<span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">codec</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">ffi_logical_codec_from_pycapsule</span><span class="p">(</span><span class="n">session</span><span class="p">,</span><span class="w"> </span><span class="nb">None</span><span class="p">)</span><span class="o">?</span><span class="p">;</span>
<span class="w"> </span><span class="kd">let</span><span class="w"> </span><span class="n">provider</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">FFI_TableFunction</span><span class="p">::</span><span class="n">new_with_ffi_codec</span><span class="p">(</span><span class="n">Arc</span><span class="p">::</span><span class="n">new</span><span class="p">(</span><span class="n">func</span><span class="p">),</span><span class="w"> </span><span class="nb">None</span><span class="p">,</span><span class="w"> </span><span class="n">codec</span><span class="p">);</span>
<span class="w"> </span><span class="n">PyCapsule</span><span class="p">::</span><span class="n">new_with_value</span><span class="p">(</span><span class="n">py</span><span class="p">,</span><span class="w"> </span><span class="n">provider</span><span class="p">,</span><span class="w"> </span><span class="n">cr</span><span class="s">&quot;datafusion_table_function&quot;</span><span class="p">)</span>
<span class="p">}</span>
</pre></div>
</div>
<p>Only literal expressions are supported as arguments. The Python side is
described under
<a class="reference internal" href="../user-guide/common-operations/udf-and-udfa.html"><span class="doc">Table Functions</span></a>.</p>
</section>
<section id="serializing-functions">
<h2>Serializing functions<a class="headerlink" href="#serializing-functions" title="Link to this heading">#</a></h2>
<p>A function that appears in a plan leaving the process has to be reconstructible
on the far side. Functions are the one case where a codec often needs <strong>no
payload at all</strong>: the name is the whole encoding, <code class="docutils literal notranslate"><span class="pre">try_encode_udf</span></code> writes
nothing, and <code class="docutils literal notranslate"><span class="pre">try_decode_udf</span></code> rebuilds the function from <code class="docutils literal notranslate"><span class="pre">name</span></code>. See
<a class="reference internal" href="codecs.html#extension-codecs"><span class="std std-ref">Extension codecs</span></a> for how that works and for the one obligation it puts
on your decoder — with an empty payload there is no id to route on, so your
<code class="docutils literal notranslate"><span class="pre">try_decode_udf</span></code> can be called with a <code class="docutils literal notranslate"><span class="pre">name</span></code> belonging to another library.</p>
<p><code class="docutils literal notranslate"><span class="pre">NameOnlyUdfCodec</span></code> in <a class="reference external" href="https://github.com/apache/datafusion-python/tree/main/examples/datafusion-ffi-example"><code class="docutils literal notranslate"><span class="pre">datafusion-ffi-example</span></code></a> is the worked case.</p>
</section>
</section>
</article>
<footer class="prev-next-footer d-print-none">
<div class="prev-next-area">
<a class="left-prev"
href="table-providers.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">Providers and catalogs</p>
</div>
</a>
<a class="right-next"
href="codecs.html"
title="next page">
<div class="prev-next-info">
<p class="prev-next-subtitle">next</p>
<p class="prev-next-title">Extension codecs</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="#the-three-scalar-shaped-hooks">The three scalar-shaped hooks</a></li>
<li class="toc-h2 nav-item toc-entry"><a class="reference internal nav-link" href="#table-functions">Table functions</a></li>
<li class="toc-h2 nav-item toc-entry"><a class="reference internal nav-link" href="#serializing-functions">Serializing functions</a></li>
</ul>
</nav></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>
<!-- Based on pydata_sphinx_theme/footer.html -->
<footer class="footer mt-5 mt-md-0">
<div class="container">
<div class="footer-item">
<p>Apache Arrow DataFusion, Arrow DataFusion, Apache, the Apache feather logo, and the Apache Arrow DataFusion project logo</p>
<p>are either registered trademarks or trademarks of The Apache Software Foundation in the United States and other countries.</p>
</div>
</div>
</footer>
</body>
</html>