Make tags available as a map to scale better (minor)

[ge0ffrey]

I have use case pages such as "vehicleRouting.adoc" that define an attribute jbake-relatedTag=vehicle routing which is picked up by the useCaseTemplate.ftl to add a link to all related blog posts for that relatedTag.

Here's how that code looks like:

    <#assign relatedTags = tags?filter(tag -> tag.name == content.related_tag)>
    <#if relatedTags?size &gt; 0>
        <#assign relatedTag = relatedTags?first>
        <h2>Related blog posts</h2>
        <ul>
            <#list relatedTag.tagged_posts as blog>
                <li>
                    <div class="title">
                        <a href="${content.rootpath}${blog.uri}">${blog.title}</a>
                    </div>
                </li>
            </#list>
        </ul>
    </#if>

What's the problem with this? This part won't scale, as every single page executes it:

    tags?filter(tag -> tag.name == content.related_tag)?first

Given 1000 pages and 2000 tags, this causes 2 000 000 iterations. If the tags would be put into map by jbake at bootstrap, that would instead be:

    tags[content.related_tag]

which it would give 2000 iterations to create that map once, and then 1000 times a hash lookup. So 3000 iterations instead of 2 000 000.

[ge0ffrey]

That being said, I haven't seen this cause significant performance issues yet with our website with 105 pages.