Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>So I ran some tests based on @SWilk's advice. Here's how I did it :</p> <p>1) Set up a basic HTML page with an empty <code>&lt;style&gt;</code> tag in the <code>&lt;head&gt;</code> and the simple example he provided in a <code>&lt;script&gt;</code> tag at the bottom of the <code>&lt;body&gt;</code> :</p> <pre><code>&lt;!DOCTYPE html&gt; &lt;html&gt; &lt;head&gt; &lt;meta charset="utf-8" /&gt; &lt;title&gt;Performance test&lt;/title&gt; &lt;style&gt; /**/ &lt;/style&gt; &lt;/head&gt; &lt;body onload="onLoad()"&gt; &lt;div class="container"&gt;&lt;/div&gt; &lt;script&gt; function onLoad() { var now = new Date().getTime(); var page_load_time = now - performance.timing.navigationStart; console.log("User-perceived page loading time: " + page_load_time); } &lt;/script&gt; &lt;/body&gt; &lt;/html&gt; </code></pre> <p>2) Fill up the <code>div.container</code> with loaaads of HTML. In my case, I went to html-ipsum.com (no advertising intended), copied each sample, minified it all together, and duplicated it a bunch of times. My final HTML file was <strong>1.70 MB</strong>, and the <code>div.container</code> had <strong>33264</strong> descendants (direct or not ; I found out by calling <code>console.log(document.querySelectorAll('.container *').length);</code>).</p> <p>3) I ran this page 10 times in the latest Firefox and Chrome, <em>each time with an empty cache</em>.</p> <p><strong>Here are the results without the dreaded CSS ruleset (in ms) :</strong></p> <pre><code>Firefox : 1785 1503 1435 1551 1526 1429 1754 1526 2009 1486 Average : 1600 Chrome : 1102 1046 1073 1028 1038 1026 1011 1016 1035 985 Average : 1036 </code></pre> <p>(If you're wondering why there's such a difference between those two, I have much more extensions on Firefox. I let them on because I thought it would be interesting to diversify the testing environments even more.)</p> <p>4) Add the CSS we want to test in the empty <code>&lt;style&gt;</code> tag :</p> <pre><code>html:before, html:after, body:before, body:after, div:before, div:after, p:before, p:after, ul:before, ul:after, li:before, li:after, h1:before, div:after, strong:before, strong:after, em:before, em:after, code:before, code:after, h2:before, div:after, ol:before, ol:after, blockquote:before, blockquote:after, h3:before, div:after, pre:before, pre:after, form:before, form:after, label:before, label:after, input:before, input:after, table:before, table:after, thead:before, thead:after, tbody:before, tbody:after, tr:before, tr:after, th:before, th:after, td:before, td:after, dl:before, dl:after, dt:before, dt:after, dd:before, dd:after, nav:before, nav:after { content: ''; } </code></pre> <p>...and start again. Here I'm specifying every tag used in the page, instead of <code>*</code> (since it is counter-performant in itself, and we want to monitor the pseudo-element triggering only).</p> <p><strong>So, here are the results with all pseudo-elements triggered (still in ms) :</strong></p> <pre><code>Firefox : 1608 1885 1882 2035 2046 1987 2049 2376 1959 2160 Average : 1999 Chrome : 1517 1594 1582 1556 1548 1545 1553 1525 1542 1537 Average : 1550 </code></pre> <p>According to these numbers, <strong>we can conclude the page load is indeed slower (of about 400-500 ms) when declaring <code>content: ''</code> on every pseudo-element</strong>.</p> <p>Now, the remaining question now is : <strong>is the extra load time we can see here significative, given the relatively big test page that was used</strong> ? I guess it depends on the size of the website/project, but I'll let more web-performance-knowledgeable people give their opinion here, if they want to.</p> <p>If you run your own tests, feel free to post your conclusions here as well, as I'm very interested in reading them - and I think I won't be the only one.</p>
    singulars
    1. This table or related slice is empty.
    1. POIs declaring "content" property on :before and :after for every element a massive performance issue?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. This table or related slice is empty.
    1. USneemzy
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POIs declaring "content" property on :before and :after for every element a massive performance issue?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. COThe explanation that comes to mind is that this will insert a pseudo-element before and after every tag, including the ones that otherwise wouldn't need them (which, in this test, is every tag). It's basically tripling the number of elements on the page.
      singulars
      1. PO
      1. USuser1618143
    2. CO@user1618143 That's a good point, but my thoughts are that it could be browser-dependent, since the `*:before` and `*:after` rules are technically *just* styling rules, not pseudoelement creation rules (in theory). Perhaps some browsers always create the two hidden pseudoelements with every real element on the page, so the CSS rules wouldn't cause the issue you pointed out. On the other hand, other browsers may only reactively create the pseudoelements if style rules target them, in which case one indeed is creating excess pseudoelements on all real elements with those rules.
      singulars
      1. PO
      1. USajp15243
    3. COI also wonder if individual tag targeting (as opposed to using `*`) would not allow for certain optimizing assumptions to be made by the browser, since it now has to check each tag against the list of styles, rather than knowing a `*` rule will apply to any tag no matter what. Also, I think it would be more fair to FF if you did it without extensions/add-ons. There's no telling what kind of behind-the-scenes things the extensions do to the page, so your FF statistics may be muddied by them.
      singulars
      1. PO
      1. USajp15243
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload