<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <link rel="stylesheet" href="../../static/styles.css?h=dff0aaad"> <link rel="stylesheet" href="../../static/pygments.css"> <link rel="shortcut icon" href="../../static/favicon.png?h=fa09bedd"> <title> | Lektor Static Content Management System</title> </head> <body class="default"> <nav class="navbar navbar-inverse navbar-static-top"> <div class="container"> <div class="navbar-header"> <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#navbar" aria-expanded="false" aria-controls="navbar"> <span class="sr-only">Toggle navigation</span> <span class="icon-bar"></span> <span class="icon-bar"></span> <span class="icon-bar"></span> </button> <a class="navbar-brand" href="../../">Lektor</a> </div> <div id="navbar" class="collapse navbar-collapse"> <ul class="nav navbar-nav"> <li><a href="../../downloads/">Download</a></li> <li><a href="../../docs/">Documentation</a></li> <li><a href="../../showcase/">Showcase</a></li> <li class="active"><a href="../">Plugins</a></li> <li><a href="../../community/">Community</a></li> <li><a href="../../blog/">Blog</a></li> </ul> </div> </div> </nav> <div class="body-wrapper"> <div class="page-banner page-banner-300" style="background-image: url(../header.jpg)"></div> <div class="container"> <!-- Place this tag in your head or just before your close body tag. --> <div class="plugin"> <div class="row"> <div class="col-sm-12"> <h1>Plugin – lektor-limit-dependencies 1.0.0</h1> </div> </div> <div class="row"> <div class="col-sm-1"></div> <div class="col-sm-11"> <p>Lektor plugin to limit dependencies created by queries<p> </div> </div> <div class="row"> <div class="col-sm-3 plugin-margin"> <h4>Project links</h4> <ul class="tree-nav"> <li><a href="https://pypi.org/project/lektor-limit-dependencies/" class="ext">Homepage</a></li> </ul> <div class="separator"> <h4>Meta</h4> </div> <p><strong>Version:</strong> 1.0.0</p> <p><strong>Author:</strong> <a href="mailto:dairiki@dairiki.org">Jeff Dairiki</a> </p> <div class="separator"> <h4>Tags</h4> </div> <a href="../tag/build-optimization/">build optimization</a>, <a href="../tag/Jinja-filters/">Jinja filters</a>, and <a href="../tag/setup-env/">setup-env</a> <p> View <a href="../tags/" class="ref">all tags</a>. </p> </div> <div class="col-sm-9 doc-styling"> <h2>Project Description</h2> <h1>Lektor Limit Dependencies</h1> <p><a href="https://pypi.org/project/lektor-limit-dependencies/" rel="nofollow"><img src="https://img.shields.io/pypi/v/lektor-limit-dependencies.svg" alt="PyPI version"></a> <a href="https://pypi.python.org/pypi/lektor-limit-dependencies/" rel="nofollow"><img src="https://img.shields.io/pypi/pyversions/lektor-limit-dependencies.svg" alt="PyPI Supported Python Versions"></a> <a href="https://github.com/dairiki/lektor-limit-dependencies/blob/master/LICENSE" rel="nofollow"><img src="https://img.shields.io/github/license/dairiki/lektor-limit-dependencies" alt="GitHub license"></a> <a href="https://github.com/dairiki/lektor-limit-dependencies" rel="nofollow"><img src="https://github.com/dairiki/lektor-limit-dependencies/workflows/Tests/badge.svg" alt="GitHub Actions (Tests)"></a></p> <p>This is an experimental <a href="https://www.getlektor.com/" rel="nofollow">Lektor</a> plugin which aims to provide tools (or, at least, a tool) to help keep Lektor’s dependency tracking under control.</p> <h2>Introduction</h2> <h3>Motivating Example</h3> <p>Suppose that you would like to list the three most recent blog posts in the sidebar of your Lektor-based site. This can be done by adding something like to your site base template:</p> <pre lang="html+jinja"><span class="p"><</span><span class="nt">h3</span><span class="p">></span>Recent Posts<span class="p"></</span><span class="nt">h3</span><span class="p">></span> <span class="p"><</span><span class="nt">ul</span><span class="p">></span> <span class="cp">{%</span> <span class="k">for</span> <span class="nv">post</span> <span class="k">in</span> <span class="nv">site.query</span><span class="o">(</span><span class="s1">'/blog'</span><span class="o">)</span><span class="nv">.order_by</span><span class="o">(</span><span class="s1">'-pub_date'</span><span class="o">)</span><span class="nv">.limit</span><span class="o">(</span><span class="m">3</span><span class="o">)</span> <span class="cp">%}</span> <span class="p"><</span><span class="nt">li</span><span class="p">><</span><span class="nt">a</span> <span class="na">href</span><span class="o">=</span><span class="s">"</span><span class="cp">{{</span> <span class="nv">post</span><span class="o">|</span><span class="nf">url</span> <span class="cp">}}</span><span class="s">"</span><span class="p">></span><span class="cp">{{</span> <span class="nv">post.title</span> <span class="cp">}}</span><span class="p"></</span><span class="nt">a</span><span class="p">></</span><span class="nt">li</span><span class="p">></span> <span class="cp">{%</span> <span class="k">endfor</span> <span class="cp">%}</span> <span class="p"></</span><span class="nt">ul</span><span class="p">></span> </pre> <p>This is not without drawbacks, however. To sort the post query by date, Lektor iterates through <em><strong>all</strong></em> of the blog’s posts, then sorts them. In so doing, it records all of the blog posts as dependencies <em>of every page on which this most-recent-post query is used</em>. If this is in the sidebar of every page on your site, <em>now every page on your site will be rebuilt whenever any blog post at all</em> (not just one of the three most recent posts) <em>is edited</em>.</p> <p>Technically, it is true that all pages now depend on all posts. You might well edit the <code>pub_date</code> of one of your older posts, such that it should now appear in the most-recent listing. However, it is not true that all pages need to be rebuilt for <em>any</em> edit of any post. Unfortunately, Lektor’s dependency tracking system is not elaborate enough to be able to express details about <em>how</em> pages are dependent on other pages; it only records that they <em>are</em> dependent, so Lektor has no option but to rebuild everything.</p> <h3>A Solution?</h3> <p>This plugin introduces a Jinja filter, <code>limit_dependencies</code>. It expects, as input, a Lektor <a href="https://www.getlektor.com/docs/api/db/query/" title="Lektor documentation on the Query class" rel="nofollow">query</a> instance. It iterates through the input query, and returns a new query instance which will yield the same results. While it is doing its iteration, it — essentially — monkey-patches Lektor’s dependency tracking machinery to prevent it from recording any dependencies.</p> <p>At the end, <code>limit_dependencies</code> records one dependency on a <a href="https://www.getlektor.com/docs/api/db/obj/#virtual-source-objects" title="Lektor documentation on Virtual Source Objects" rel="nofollow">virtual source object</a> which depends only on the sequence of the identities of the records in the query result. (Lektor provides a means by which virtual source objects can report checksums. The dependency tracking mechanism records those checksums, and will trigger a rebuild should the checksum change. <code>Limit_dependencies</code> generates a virtual source object whose checksum depends on the sequence of identities in the query result.)</p> <p>In the above example, this is exactly what we want. We only want to trigger a rebuild if the order or composition of the most-recent three posts changes. (Or if any of their titles change. Note that this gets covered, too, since when the resulting query is iterated over in the <code>{% for %}</code> loop, dependencies will be recorded on the three most-recent posts.)</p> <p>Thus, the example above, if replaced by:</p> <pre lang="html+jinja"><span class="p"><</span><span class="nt">h3</span><span class="p">></span>Recent Posts<span class="p"></</span><span class="nt">h3</span><span class="p">></span> <span class="p"><</span><span class="nt">ul</span><span class="p">></span> <span class="cp">{%</span> <span class="k">for</span> <span class="nv">post</span> <span class="k">in</span> <span class="nv">site.query</span><span class="o">(</span><span class="s1">'/blog'</span><span class="o">)</span><span class="nv">.order_by</span><span class="o">(</span><span class="s1">'-pub_date'</span><span class="o">)</span><span class="nv">.limit</span><span class="o">(</span><span class="m">3</span><span class="o">)|</span><span class="nf">limit_dependencies</span> <span class="cp">%}</span> <span class="p"><</span><span class="nt">li</span><span class="p">><</span><span class="nt">a</span> <span class="na">href</span><span class="o">=</span><span class="s">"</span><span class="cp">{{</span> <span class="nv">post</span><span class="o">|</span><span class="nf">url</span> <span class="cp">}}</span><span class="s">"</span><span class="p">></span><span class="cp">{{</span> <span class="nv">post.title</span> <span class="cp">}}</span><span class="p"></</span><span class="nt">a</span><span class="p">></</span><span class="nt">li</span><span class="p">></span> <span class="cp">{%</span> <span class="k">endfor</span> <span class="cp">%}</span> <span class="p"></</span><span class="nt">ul</span><span class="p">></span> </pre> <p>will work in a much more efficient and sane manner. Pages will be rebuilt only if there are changes in the order, composition or content of the three most recent posts.</p> <h2>Installation</h2> <p>Add lektor-limit-dependencies to your project from command line:</p> <pre><code>lektor plugins add lektor-limit-dependencies </code></pre> <p>See <a href="https://www.getlektor.com/docs/plugins/" rel="nofollow">the Lektor plugin documentation</a> for more information.</p> <h2>Author</h2> <p>Jeff Dairiki <a href="mailto:dairiki@dairiki.org" rel="nofollow">dairiki@dairiki.org</a></p> <h2>Changelog</h2> <h3>Release 1.0.0 (2023-01-31)</h3> <p>No code changes from 1.0.0b1.</p> <p>Test under python 3.11.</p> <h3>Release 1.0.0b1 (2021-03-29)</h3> <p>Drop support for python<3.7 and lektor<3.3.</p> <h3>Release 0.1 (2021-02-05)</h3> <p>No code changes.</p> <p>Update development status classifier to "stable".</p> <p>Test under python 3.9. Stop testing under 3.5.</p> <h3>Release 0.1a1 (2020-05-19)</h3> <p>Initial release.</p> <div class="comment-box"> <h2>Comments</h2> <div id="disqus_thread"></div> <script> var disqus_config = function() { this.page.identifier = "/plugins/lektor-limit-dependencies"; this.page.url = "https://www.getlektor.com/plugins/lektor-limit-dependencies/"; }; (function() { var d = document, s = d.createElement('script'); s.src = '//lektordocumentation.disqus.com/embed.js'; s.setAttribute('data-timestamp', +new Date()); (d.head || d.body).appendChild(s); })(); </script> <noscript> Please enable JavaScript to view the <a href="https://disqus.com/?ref_noscript" rel="nofollow">comments powered by Disqus.</a> </noscript> </div> </div> </div> </div> </div> </div> <div class="bottomsummary"> <div class="container"> </div> </div> <footer> <div class="container"> <div class="row"> <div class="col-sm-4 icon-bar"> <a href="https://github.com/lektor/lektor/" title="Lektor on GitHub" ><i class="fa fa-github"></i></a> <a href="https://github.com/lektor/lektor/issues/" title="Report Issues for Lektor" ><i class="fa fa-bug"></i></a> <a href="https://twitter.com/getlektor" title="Find Lektor on Twitter" ><i class="fa fa-twitter"></i></a> <a href="https://gitter.im/lektor/lektor" title="Chat on Gitter" ><i class="fa fa-comment"></i></a> <a href="https://github.com/lektor/lektor-website/tree/master/content/plugins/lektor-limit-dependencies/contents.lr" title="View source for this page"><i class="fa fa-code"></i></a> </div> <div class="col-sm-8"> <a href="../../license/">License & Copyright</a> • <a href="../../contact/">Contact</a> • Made with <i class="fa fa-fw fa-heart" title="Heart"><span hidden>Heart</span></i> in Carinthia </div> </div> </div> </footer> <script type=text/javascript src="../../static/app.js?h=dcf26092" charset="utf-8"></script> <script> ((window.gitter = {}).chat = {}).options = { room: 'lektor/lektor', activationElement: null }; document.write('<button class="js-gitter-toggle-chat-button">Toggle Chat</button>'); var dnt = navigator.doNotTrack || window.doNotTrack || navigator.msDoNotTrack; if (dnt != "1" && dnt != "yes") { window.ga=window.ga||function(){(ga.q=ga.q||[]).push(arguments)};ga.l=+new Date; ga('create', 'UA-70822533-1', 'auto'); ga('set', 'anonymizeIp', true); ga('send', 'pageview'); } else { console.debug("Respecting Do-Not-Track, not running analytics."); } </script> <script async src='https://www.google-analytics.com/analytics.js'></script> <script async defer id="github-bjs" src="https://buttons.github.io/buttons.js"></script> <script>!function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0],p=/^http:/.test(d.location)?'http':'https';if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src=p+'://platform.twitter.com/widgets.js';fjs.parentNode.insertBefore(js,fjs);}}(document, 'script', 'twitter-wjs');</script> <script src="https://sidecar.gitter.im/dist/sidecar.v1.js" async defer></script> </body> </html>